Dissertations / Theses on the topic 'Romney and Merino sheep'

Ewes at two sites were fed to be either condition score 2 or 3 by Day 90 of pregnancy and then grazed on various levels of feed-on-offer (FOO) from Day 90 of pregnancy until weaning, to investigate whether nutrition of Merino ewes during pregnancy and lactation affected the muscle, fat and immunity to worms of their progeny. Eye muscle and fat depth at the C-site, and faecal worm egg counts (FWECs) of the progeny were measured between 7 - 27 months of age. Ewe condition score at day 90 of pregnancy did not impact largely on the eye muscle depth, fat depth or FWEC of the progeny. Increasing FOO available to ewes during the last 60 days of pregnancy and throughout lactation increased the eye muscle depth of progeny at one site and decreased the fat depth of progeny at the other site (P<0.05), but did not affect the majority of FWECs of the progeny at either site. The FWECs of the progeny were low, indicating a relatively low larval challenge, which limits the likelihood of differences in immunity to worms between the progeny being expressed. This Masters demonstrated that levels of nutrition available to Merino ewes typical of commercial grazing conditions had only small effects on the eye muscle and fat depth at the C-site, and on the faecal worm egg counts of their progeny

Bibliography: leaves 281-316. Presents investigations on pubertal development in South Australian merino ram lambs and examines the effect of active and passive immunizations against oestradiol-17ℓ or oestrone on testicular maturation.

Summary 1. The goals of this thesis were to determine whether Merino sheep use habitat at random. Specifically, this research was undertaken to identify areas of intensive use, determine daily activity patterns, explore habitat use between activities, between sheep, define home ranges and to explore the influence of weather on habitat use. 2. Sixteen Merino ewes were monitored using GPS collars recording locations every 15 minutes. A weather station was set up at 1380 m a.s.l. to record weather variables at the study site. 3. Merino ewes do not select and utilise habitat in proportion to its availability. Short tussock grassland was preferentially selected for despite having a low occurrence. Overall, ewes selected habitat that was within 400 metres of a water source, on slopes less than 30° and preferred easterly habitat. 4. Merino ewes utilised different habitat for different activities. The day was divided into grazing, resting and night camping, as determined from hourly movement, backed up by 10 days of visual observations. Grazing occurred mostly on flat to low slopes in short tussock grassland. Resting occurred mostly on the riverbed or on surrounding short tussock grassland. Night camping occurred at higher altitudes (~ 100 m higher) than the resting sites and was on steeper slopes, partly due to the U-shaped nature of the valley. Night camping occurred in tall tussock grassland and native mix habitat. Several night camps were used while a smaller number of grazing sites were used. 5. Sheep differed in their individual habitat use. Two sheep were explorers, one crossing the river to occupy adjacent land, and one sheep moved out of the original study area, passing through a narrow rocky gap. Some sheep stayed close to the main mobs, while others spread out in small groups. 6. Home ranges were affected by the presence of large mobs; those sheep in the main mob had smaller home ranges than those in smaller groups. Home ranges were also smaller in areas of higher quality forage. 7. Weather variables did affect sheep habitat use with rain having the most influence. One cold, wet, windy day resulted in sheep being less active while occupying the middle of the fan, so displayed a preference for grazing and resting at higher altitude than normal. Temperatures and wind had little effect on sheep habitat use.

Thesis (MScAgric)--Stellenbosch University, 2013.
ENGLISH ABSTRACT: The aim of the study was to determine the effect of increasing levels of Maize silage in finishing diets for Merino lambs on their feed intake, production performance, feed conversion ratio, digestibility and meat quality. Concerns exist regarding the intake of high moisture and fibre containing silage in sheep due to the physical fill effect thereof. To determine the efficiency of silage as feed ingredient for sheep, maize was cut at 27% dry matter (DM), compacted into 220 litre plastic drums, sealed and left to ferment for 60 days. The silage produced was analysed for fermentation end products and the nutritive value determined. The silage produced had an optimum pH, starch and water soluble carbohydrate (WSC) content. The crude protein (CP) content (112.2 g/kg DM) was higher than expected. Four diets containing, on a dry matter (DM) basis either, 0, 20, 50 or 70% maize silage was formulated on an iso-nutrient basis with exception of neutral detergent fibre (NDF). The aim was to establish the effect of increasing levels of silage on animal production with regard to dry matter intake, growth, digestibility and meat quality. Diets were formulated on an iso-nutrient basis to match the 70% silage diet and therefore had relatively low specifications due to the high inclusion of silage from the 70% silage diet. A growth study and an in vivo and in vitro digestibility study were conducted to determine the effect of the different diets on feedlot sheep production. Meat quality was also determined to establish whether the experimental diets had an effect on meat quality. Forty lambs in a completely randomised block design, with four treatments, were used in a 60-day finishing study. The dry matter intake (DMI) of lambs decreased as silage inclusion increased above the 20% silage inclusion level. At the 20% inclusion rate, the feed intake of the animals was stimulated. This resulted in significant differences found between the cumulative intake of the low and the high silage diets. Feed conversion ratio (FCR) was poorer, however, for the control and 20% silage diets. The poor FCR most likely was related to the quality of the feed ingredients used in the formulation of the control feed and the concentrate in the 20% silage diet rather than the silage itself. Significant differences were also found in the dressing percentage of the slaughtered animals where the 20 and 50% silage diets had a higher dressing percentage than the control and 70% silage diets. It was concluded that silage can be successfully incorporated into sheep diets, especially at low levels where its inclusion stimulates intake. Eight animals per group were used in an in vivo digestibility study to determine the apparent digestibility of the experimental diets. Feed, faeces and urine samples collected during the trial period were analysed for the respective nutrients. The 20% diet, even though having the best overall apparent digestibility, did not result in better production responses. Lambs on the 20% silage diet had the highest daily DM intake, which resulted in them having the highest energy intake. There were no differences in total energy excreted between the silage-based diets. This resulted in the 20% silage diet also having the best energy retention. Nitrogen retention was the highest for the control and 20% silage diets. This can be ascribed to the low quality of the concentrate part of the diet. The 20% silage diet, as previously stated, had the highest apparent DM and organic matter (OM) digestibility, while the control diet showed the lowest overall nutrient digestibility. The low nutrient digestibility of the control diet can be ascribed to the relatively poor quality ingredients used. There were no differences in the crude protein (CP) digestibility between the control and the 20% diet. Both proved to be higher than the CP digestibility of the 50 and 70% silage diet. As the neutral detergent insoluble nitrogen (NDIN) was higher for the 50 and 70% diets, this observation was not surprising. Fibre content of the silage-based diets increased as the inclusion level of the silage increased, which resulted in a decrease in overall fibre digestion. Three cannulated sheep were adapted on each experimental diet for two weeks before rumen fluid was collected for the in vitro digestibility study. No differences between the silage based diets were found for in vitro true digestibility (IVTD). The IVTD of the 20, 50 and 70% diets were higher, however, than the IVTD of the control diet confirming earlier observations on the choice of ingredients used in the control diet to formulate iso-nutrient diets. Degradability coefficients were determined for the DM and NDF fractions of the different experimental diets and fitted to the non-linear model; p = a + b (1 – e-ct). The amount of DM that disappeared in a certain time (t) is represented by p. Constant a represents the fraction that was rapidly soluble, b represents the potential degradable fraction and c is the rate at which b was degraded. There were no differences between experimental diets for the rapidly soluble fraction. The silage-based diets had a higher potential degradable fraction (b) but did not differ in the degradability rate (c) from the control diet. Silage-based diets had higher overall effective degradability than the control but did not differ between one another. Constant a was not determined for NDF degradability since the NDF fraction did not have a rapidly soluble fraction. The control diet had the lowest potential degradable NDF fraction with the rate also being lower than the silage based diets. Effective NDF degradability was highest for the 50% silage diet. Lambs used in the finishing study were slaughtered and meat samples taken for meat quality tests. The pH, colour, drip loss, cooking loss, shear force and fatty acid composition were determined on the Longissimus dorsi samples collected at Roelcor (Malmesbury, Western Cape, South Africa). Proximate analysis was also conducted on the meat samples. The experimental diets did not have a significant effect on the proximate chemical composition of the meat. Colour differences were found; however no clear pattern could be established. There were no differences in fatty acid composition. It can be concluded that up to 70% maize silage can be included in the finishing diets of Merino lambs with no adverse effects on the meat quality. The study showed that 20% maize silage can be included in the finishing diets of Merino lambs without negatively affecting intake, production, digestibility or meat quality. Future research is needed to optimise the 20% silage diet, however, and to again look at the effect that it will have on animal production, including the effect thereof on total methane emissions.
AFRIKAANSE OPSOMMING: Die doel van die studie was om te bepaal of mielie kuilvoer doeltreffend gebruik kan word as ‘n komponent in die afronding van Merino lammers. Gedurende die proses is mielies gesny teen 27% droë materiaal (DM), en saamgepers in 220 liter plastiek dromme. Dit is toegelaat om te fermenter vir 60 dae. Die kuilvoer wat daaruit geproduseer is, is geanaliseer vir fermentasie eindprodukte, en die voedingstofwaarde is bepaal. Vier diëte met onderskeidelik 0 (kontrole), 20, 50 en 70% kuilvoer is geformuleer op ‘n iso-nutriëntbasis met die uitsondering van vesel (NDF). ‘n Groeistudie, tesame met ‘n in vivo en in vitro verteerbaarheidstudie is uitgevoer om die effek van die verskillende diëte op diere produksie te toets. Vleiskwaliteit toetse is ook gedoen om te kyk of die verskillende diëte ‘n effek op vleiskwaliteit het. Veertig lammers, in ‘n ewekeurige blokontwerp, is gebruik in ‘n 60 dae afrondingstudie. Dit is opgemerk dat die DM inname (DMI) afgeneem het soos die kuilvoer insluiting bo die 20% vlak toegneem het. By die 20% insluitingskoers, is voerinname by die diere gestimuleer. Dit het veroorsaak dat beduidende verskille gevind is tussen die kumulatiewe inname van die lae en die hoë kuilvoer diëte. Die voeromsetkoers (VOK) was egter hoër vir die kontrole en 20% kuilvoer diëte. Beduidende verskille is ook gevind in die uitslagpersentasie van die diere, waar die 20% en 50% kuilvoer diëte ‘n hoër uitslagpersentasie as die kontrole en 70% kuilvoer diëte gehad het. Agt diere is per groep gebruik in ‘n in vivo verteerbaarheidstudie om die skynbare verteerbaarheid van die eksperimentele diëte te toets. Voer, feses en urien monsters is gedurende die proefperiode ingesamel en geanaliseer. Die 20% kuilvoer dieet het die hoogste DM en organiese materiaal skynbare verteerbaarheid teenoor die kontrole diet wat die laagste gehad het. Daar was geen verskille in die ru- proteien (RP) verteerbaarheid van die kontrole en 20% kuilvoer diet nie. Beide was hoër as die RP verteerbaarheid van die 50% en 70% kuilvoer dieet. Die veselinhoud van die kuilvoergebasseerde diëte het toegeneem soos die insluitingsvlak van die kuilvoer toegeneem het, wat ‘n afname in veselvertering veroorsaak het. Lammers op die 20% kuilvoer dieet het die hoogste daaglikse DM inname gehad, wat die hoogste energie inname tot gevolg gehad het. Daar was geen verskille in die totale energie inname van die kuilvoergebasseerde diëte – dit het veroorsaak dat die 20% kuilvoer dieet ook die beste energie retensie gehad het. Stikstof retensie was die hoogste vir die kontrole en 20% kuilvoer dieet. Drie gekannuleerde skape is vir twee weke op elke eksperimentele dieet aangepas voordat rumenvloeistof ingesamel is vir die in vitro verteerbaarheidstudie. Geen verskille is gevind vir die in vitro ware verteerbaarheid (IVWV) tussen die kuilvoergebasseerde diëte nie. Hulle was egter hoër as die IVWV van die kontrole dieet. Degradeerbaarheid koëffisiënte is bepaal vir die DM en NDF fraksies van die verskillende eksperimentele diëte en is gepas in die model p = a + b (1 – e-ct). Die hoeveelheid DM wat verdwyn het binne ‘n sekere tyd (t) word voorgestel deur p. Die konstante a verteenwoordig die fraksie wat vinnig oplosbaar is, b verteenwoordig die potensieel degradeerbare fraksie en c is die koers waarteen b gedegradeer is. Konstante a is nie bepaal vir die NDF degradeerbaarheid nie, aangesien die NDF fraksie nie ‘n vinnig oplosbare fraksie gehad het nie. Daar was geen verskille in die vinnig oplosbare fraksie tussen eksperimentele diete nie. Kuilvoer gebasseerde diete het ‘n hoër potensieel degradeerbare fraksie gehad, maar daar was geen verskille in koers van degradering nie. Die kuilvoergebasseerde diëte het ‘n hoër DM effektiewe degradeerbaarheid as die kontrole dieet. Effektiewe NDF degradeerbaarheid was die hoogste vir die 50% kuilvoer dieet. Lammers in die studie gebruik is geslag en vleismonsters is geneem vir vleiskwaliteit toetse, insluitende pH, kleur, drupverlies, kookverlies en taaiheid. Proksimale analise is ook uitgevoer op die vleismonsters. Die eksperimentele diëte het nie ‘n beduidende effek op die proksimale chemiese samestelling van die vleis gehad nie. Kleur verskille is wel gevind, maar geen duidelike patroon kon vasgestel word nie. Daar was geen verskille in die vetsuur samestelling nie. Daar kan dus tot die gevolgtrekking gekom word dat mielie kuilvoer ingesluit kan word in die afrondingsdiëte van Merino lammers, tot by 70%, sonder enige negatiewe effekte op die vleiskwaliteit. Daar is tot die gevolgtrekking gekom dat mielie kuilvoer suksesvol geïnkorporeer kan word in skaapdiëte, veral teen lae vlakke (20%) waar die gebruik nie net inname stimuleer nie, maar ook geen negatiewe effekte het op produksie en verteerbaarheid nie.
Dr. Francois van de Vyver, Cape Wools and NWGA for providing funding in the form of post graduate bursaries

A candidate gene approach was used to identify potential genetic markers associated with wool quality traits including mean fibre diameter (MFD), fibre diameter standard deviation (FDSD), coefficient of variation of fibre diameter (CVD), prickle factor, curvature, yellowness, brightness, staple strength, staple length, yield, greasy fleece weight (GFW) and clean fleece weight (CFW). Inheritance of potential genetic markers was studied in two half-sib Merino families and assessed for association with the wool quality traits. The sire for one of the half-sib families is referred to as MV144-58-00, and wool measurements from its progeny were taken at 12 (n = 131), 24 (n =128) and 36 (n = 37) months of age. The sire for the second half-sib family is referred to as Stoneyhurst, and wool measurements from its progeny (n = 35) were taken at 12 months of age. Genes that code for the keratin intermediate-filament proteins (KRTs) (KRT1.2, KRT2.10) and the keratin intermediate-filament-associated proteins (KAPs) (KAPl.1, KAPl.3, KAP3.2, KAP6.1, KAP 7, KAP8) were targeted for this investigation, along with the beta 3-adrenergic receptor (ADRB3) gene and microsatellites BfMS and OarFCB193. Polymerase chain reaction (PCR) was used to amplify specific DNA fragments from each locus and PCR- single strand conformational polymorphism (PCR-SSCP) analysis was used to detect polymorphism within the half-sib families for all the loci, except for the KAP1.1 gene, where length polymorphism was detected using agarose gel electrophoresis. Only the loci that were heterozygous for the sire (KAP1.1, KAP1.3, KRT1.2, ADRB3, KAP8) and hence were informative, were genotyped in the progeny. The total number of alleles observed at the KAP1.1, KAP1.3, KRT1.2, KAP8 and the ADRB3 loci were four, ten, six, five and six, respectively. Analysis of each of the informative loci revealed allelic associations with various wool traits. In the MV144-58-00 (genotypes KAP1.1 AB; KAP1.3 BD; KRT1.2 AB; ADRB3 CE) half-sib, inheritance of the KAP1.1 A allele was associated with a higher yield at 24 months of age (P = 0.037). This trend also observed at 36 months of age (P = 0.078). At 12 months of age, the KAP1.1 A allele tended to be associated with increased staple length (P = 0.08). At 36 months of age, the inheritance of the KAP1.1 B allele tended towards being associated with whiter wool (P = 0.080). The MV144-58-00 KAP1.3 D allele tended to be associated with increased yield at 24 and 36 months of age (P = 0.091 and 0.059, respectively), and with lower FDSD at 12 months of age (P = 0.055). The sire KAP1.3 B allele was associated with whiter wool colour at 36 months of age (P = 0.045). The inheritance of the MV144-58-00 KR T1.2 B allele was associated with or tended to be associated with a smaller FDSD (P = 0.040), an increase in staple strength (P = 0.025) and an increase in GFW (P = 0.069) at 12 months of age. At 24 months of age, the KR T1.2 B allele tended to be associated with increased yield (P = 0.057). At 36 months of age, the KRTl.2 A allele was associated with whiter wool (P = 0.019) and tended to be associated with increased crimp within the wool fibre (P = 0.089). In the Stoneyhurst (genotypes KAP1.1 BC; KAP1.3 CJ; KRT1.2 DE; ADRB3 CE) half-sib, inheritance of the KAP1.1 B allele was associated with longer staple length (P = 0.018) and a decrease in wool brightness (P = 0.039). In contrast, KAP1.1 C allele was associated with lowest staple length (P = 0.018) and brighter wool colour (P = 0.039). Associations observed with the inheritance of Stoneyhurst KAP 1.1 alleles were similar to the inheritance ofKAPl.3 alleles. Stoneyhurst KAP1.3 J allele was associated with longer staple length (P = 0.017) and a decrease in wool brightness (P = 0.010). In contrast, KAP1.3 C allele was associated with lowest staple length (P = 0.017) and brighter wool colour (P = 0.010). The Stoneyhurst KRT12 D allele was associated with longer staple length and a decrease in wool brightness (P = 0.033). In contrast, KRT1.2 E allele was associated with lowest staple length (P = 0.033) and brighter wool colour (P = 0.022). Sire alleles at the ADRB3 gene locus were associated with variation in staple strength (P = 0.025) for MV144-58-00's progeny, and with variation in yield (P = 0.023) for Stoneyhurst's progeny. The results obtained in this thesis are consistent with KAP1.1, KAP1.3 and KRT1.2 being clustered on one chromosome because both sires in this study passed on two major KAP1.1-KAP1.3-KRT1.2 haplotypes to their progeny, and the associations with wool traits were very similar for all the three loci. The major sire derived KAP1.1 – KAP1.3 - KRT1.2 haplotypes observed within the MV144-58-00 half-sib were: BBA (frequency of 43.4%; n = 43) and ADB (frequency of 44.4%; n = 44). Other minor haplotypes observed were: ADA (frequency of 4.0%; n = 4); BDA (frequency of 2.0%; n = 2); BBB (frequency of 3.0%; n = 3) and BDB (frequency of 3.0%; n = 3). In the Stoneyhurst half-sib, major sire-derived KAP 1.1 - KAP 1.3 - KR Tl.2 haplotypes observed were CCE (frequency of 53.1 %; n = 17) and BJD (frequency of 40.6%; n = 13). The minor haplotype BJE (frequency of 6.3%; n = 2) was also observed. Statistical analyses within the MVI44-58-00 half-sib showed that KAP1.1 AKAP1.3 D - KRT1.2 B haplotype was associated with increased yield (P = 0.023) and tended towards whiter wool colour (P = 0.059), smaller FDSD (P = 0.081) and stronger staple strength (P = 0.092). In the Stoneyhurst half-sib, the KAP1.1 B - KAP1.3 J - KRT1.2 D haplotype was associated with longer staple length (P = 0.010), while the KAP1.1 C - KAP1.3 C - KRT1.2 E haplotype showed a strong trend with increased wool brightness (P = 0.096). Result from this study indicated that the keratin genes on chromosome 11 are recombining relatively frequently at recombination "hotspots". A high rate of recombination among loci that impact on wool traits would make breeding for consistent wool quality very difficult. The results presented in this thesis suggest that genes coding for the KRTs and KAPs have the potential to impact on wool quality. KAP1.1, KAP1.3 and KRT1.2 could potentially be exploited in gene marker-assisted selection programmes within the wool industry to select for animals with increased staple length, 'increased staple strength, higher yield and brighter wool. This study was however limited to two half-sib families, and further investigation is required.

Thesis (PhD)--Stellenbosch University, 2015.
ENGLISH ABSTRACT: Reproduction and robustness traits are integral in ensuring sustainable, efficient and profitable sheep farming. Increases in genetic gain of reproduction and robustness traits are however, hampered by low heritability coupled with the difficulty in quantification of these traits for traditional selective breeding strategies. The aim of the current study was therefore to identify genomic regions underlying variation in reproduction traits and elucidate quantitative trait loci (QTL) and/or genes associated with reproductive traits. The Elsenburg Merino flock has been divergently selected for the ability to raise multiple offspring and has resulted in a High and a Low line that differ markedly with regard to reproductive output and other robustness traits. The flock thus served as an ideal platform to identify genomic regions subject to selection for reproductive traits. To pinpoint genomic regions subject to selection, a whole-genome genotyping platform, the OvineSNP50 chip, was selected to determine the genotype of more than 50 000 SNPs spread evenly across the ovine genome. The utility of the OvineSNP50 chip was determined for the Elsenburg Merino flock as well as additional South African Merino samples and three other important South African sheep breeds, the Blackheaded Dorper, South African Mutton Merino (SAMM) and the Namaqua Afrikaner. Although genotyping analysis of the Elsenburg Merino flock indicated some signs of poor genotype quality, the overall utility of the genotype data were successfully demonstrated for the South African Merino and the other two commercial breeds, the Dorper and SAMM. Genotyping results of the Namaqua Afrikaner and possibly other indigenous African breeds may be influenced by SNP ascertainment bias due to the limited number of indigenous African breeds used during SNP discovery. Analysis of pedigree, phenotypic records and SNP genotype data of the Elsenburg Merino cohort used in the current study, confirmed that the lines are phenotypically as well as genetically distinct. Numerous putative genomic regions subject to selection were identified by either an FST outlier approach or a genomic scan for regions of homozygosity (ROH) in the High and Low lines. Although annotated genes with putative roles in reproduction were identified, the exact mechanism of involvement with variation in reproduction traits could not be determined for all regions and genes. Putative ROH overlapped with QTL for several reproduction, milk, production and parasite resistance traits, and sheds some light on the possible function of these regions. The overlap between QTL for production and parasite resistance with putative ROH may indicate that several, seemingly unrelated traits add to the net-reproduction and may have been indirectly selected in the Elsenburg Merino flock. A SNP genotyping panel based solely on reproduction traits may therefore be ineffective to capture the variation in all traits influencing reproduction and robustness traits. A holistic selection strategy taking several important traits, such as robustness, reproduction and production into account may as such be a more effective strategy to breed animals with the ability to produce and reproduce more efficiently and thereby ensure profitable and sustainable sheep farming in South Africa.
AFRIKAANSE OPSOMMING: Reproduksie- en gehardheids-eienskappe is noodsaaklik om volhoubare, doeltreffende en winsgewende skaapboerdery te verseker. ‘n Toename in genetiese vordering in reproduksie- en gehardheids-eienskappe word egter bemoeilik deur lae oorerflikhede tesame met die probleme in kwantifisering van hierdie eienskappe vir tradisionele selektiewe diereteelt strategieë. Die doel van die huidige studie was dus om gebiede in die genoom onderliggend tot variasie in reproduksie-eienskappe te identifiseer en die rol van verwante kwantitatiewe eienskap loki (KEL) en/of gene met reproduktiewe eienskappe te bepaal. Die Elsenburg Merinokudde is uiteenlopend geselekteer vir die vermoë om meerlinge groot te maak en het gelei tot 'n Hoë en 'n Lae lyn wat merkbaar verskil ten opsigte van reproduksie-uitsette en ander gehardheids-eienskappe. Die kudde het dus gedien as 'n ideale platform om genomiese areas onderhewig aan seleksie vir reproduksie-eienskappe te identifiseer. Om vas te stel waar genomiese areas onderhewig aan seleksie gevind kan word, is ‘n heel-genoom genotiperingsplatform, die OvineSNP50 skyfie, gekies om die genotipes van meer as 50 000 enkel nukleotied polimorfismes (ENPs) eweredig versprei oor die skaap genoom, te bepaal. Die nut van die OvineSNP50 skyfie is bepaal vir die Elsenburg Merinokudde sowel as addisionele Suid-Afrikaanse Merinos en drie ander belangrike Suid-Afrikaanse skaaprasse, die Swartkop Dorper, Suid-Afrikaanse Vleismerino (SAVM) en die Namakwa Afrikaner. Hoewel genotipe resultate van die Elsenburg Merino kudde sommige tekens van swak genotipe gehalte getoon het, kon die algehele nut van die genotipering resultate vir die Suid-Afrikaanse Merino en die ander twee kommersiële rasse, die Dorper en SAVM, bevestig word. Genotipering resultate van die Namakwa Afrikaner en moontlik ook ander inheemse Afrika rasse kan deur ENP vasstellingspartydigheid beïnvloed word as gevolg van die beperkte aantal inheemse Afrika rasse gebruik tydens ENP ontdekking. Ontleding van stamboom inligting, fenotipe rekords en ENP genotipe data van die Elsenburg Merino-kohort gebruik in die huidige studie, het bevestig dat die lyne fenotipies asook geneties verskil. Talle vermeende genomiese areas onderhewig aan seleksie is geïdentifiseer deur 'n FST uitskieter benadering of deur ‘n genomiese skandering vir gebiede van homogositeit (GVH) in die Hoë en Lae lyne. Hoewel geannoteerde gene met potensiële rolle in reproduksie geïdentifiseer is, kan die presiese meganisme van betrokkenheid by variasie in reproduksie-eienskappe nie bevestig word vir al die gebiede en gene nie. Vermeende GVH oorvleuel met KEL vir 'n paar reproduksie-, melk-, produksie- en parasietweerstand-eienskappe, en werp daarom lig op die moontlike funksie van hierdie gebiede. Die oorvleueling tussen KEL vir produksie en parasietweerstand met vermeende GVH kan daarop dui dat 'n hele paar, skynbaar onverwante, eienskappe bydrae tot net-reproduksie, wat indirek geselekteer mag wees in die Elsenburg Merino-kudde. ‘n ENP genotiperingspaneel uitsluitlik gebaseer op reproduksie-eienskappe mag daarom onvoldoende wees om die variasie in alle eienskappe wat betrekking het op reproduksie- en gehardheids-eienskappe, in te sluit. ‘n Holistiese seleksie strategie wat verskeie belangrike eienskappe, soos gehardheid, reproduksie en produksie in ag neem, mag ‘n meer effektiewe strategie wees om diere te teel met die vermoë om in 'n meer doeltreffende manier te produseer en reproduseer en om daardeur winsgewende en volhoubare skaapboerdery in Suid-Afrika te verseker.

Thesis (MScAgric)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: The application of assisted reproductive biotechnologies in sheep flocks is hampered by the susceptability of ovine sperm to cryodamage. There is still considerable scope in the improvement of cryopreservation protocols for ovine sperm to minimize the degree of damage to sperm during the cryopreservation process. Pre-cryopreservation processing has a definite effect on the survivability, motility, and fertilizing ability of sperm. Little information is however available on the potential contribution of the genetic make-up of rams, divergently selected for fecundity, on the ability of sperm to offer resistance to the damage caused by cooling, cryopreservation and thawing. The study aimed to investigate the influence of genetic selection for prolificacy (i.e. High Merino Line and Low Merino Line in terms of fecundity) on the ability of ovine sperm to offer resistance to cryodamage. The study investigated the effect of pre-cryopreservation processing by comparing motility and morphometry traits recorded for fresh- and post-thaw Merino ejaculated and epididymal sperm samples obtained form the High and Low lines, respectively. The effect of different sperm concentrations, equilibration periods and the addition or omission of seminal plasma from cryopreserved samples on the viability and morphometrical traits were also investigated. Ejaculate samples were collected by means of the artificial vagina (AV) method from 8 High Line rams and 7 Low Line rams. Epididymal samples were collected from 6 rams of each of the High and Low lines respectively, by recovering the epididymal sperm via aspiration from the cauda epididymides post mortem. Ejaculate samples were subjected to macroscopic and microscopic evaluation, and epididymal samples only to microscopic evaluation, for which the Sperm Class Analyzer® program was used for the evaluation of motility and morphometric measurements. Sperm motility recordings were captured at 100 frames per second. From findings of the study, it was concluded that genotype had no positive influence on the conception rate of the ewes mated to the High or Low Line rams, even though the rams from the two lines differed significantly in terms of their serving capacity. When sperm morphometry was evaluated for fresh ejaculate samples, the two lines differed significantly in terms of the morphometric traits elongation and ellipticity. Epididymal and ejaculated sperm obtained from Low Line rams had broader and rounder heads, compared to sperm obtained from High Line rams. When morphometry was assessed for sperm samples between the two methods of sperm recovery (collected with an AV or recovery via aspiration from the cauda epididymides of sacrificed rams), no morphometrical differences were observed. Significant differences were reported for the majority of the sperm motility traits (i.e. percentage motile, rapid-, medium-, slow swimming, curvilinear velocity (VCL), straight line velocity (VSL), average path velocity (VAP), and amplitude of the lateral head displacement (ALH)) recorded for ejaculated and epididymal sperm. The motility traits ALH and beat-cross frequency (BCF) analysed for epididymal sperm differed significantly between the two lines. When epididymal sperm were evaluated post-thaw, it became evident that the sperm obtained from the High Line rams had a larger acrosome surface cover when compared to that of the Low Line ram sperm. The addition of seminal plasma to epididymal samples did not result in an improvement of the preservation of sperm motility. It is known from the literature that cryopreservation causes a decrease in sperm head size. Head width was unaffected by cryopreservation with the addition of seminal plasma in this study, indicating a potential benefit with the use of seminal plasma in the cryopreservation protocol of epididymal ram sperm. The study compared two pre-processing techniques, i.e. the more time consuming swim-up technique (SUT) with a more time-efficient ‘flush technique’ (FT) to optimize the pre-processing protocol for motility assessment of sperm samples before cryopreservation of ram sperm. Comparison of the SUT and FT indicated that almost all of the motility parameters measured using the FT compared favourably with those obtained using the SUT. The results indicated that the FT can be used a more time-efficient technique to use for determining the motility of a sperm sample prior to cryopreservation. In conclusion, line differences associated with reproduction were observed in terms of the serving capacity of the rams, with selection for fecundity influencing the morphometric traits elongation and ellipticity for sperm obtained from the two lines. Future studies should be aimed at investigating morphometric traits of ovine sperm, to correlate it with fertilizing ability of sperm post-thaw and ensure optimal cryopreservation processing.
AFRIKAANSE OPSOMMING: Die toepassing van ondersteunende reproduksie tegnieke in skaaptroppe word bemoeilik deur die onvermoë van ram sperme om weerstand teen bevriesingskade te bied. Daar is nog baie ruimte vir die verbetering van die bevriesingsprotokolle vir skaap sperm om die omvang van bevriesingskade te verminder. Voor-bevriesing verwerking het dan 'n besliste uitwerking op die oorlewing, beweeglikheid en bevrugtingsvermoë, van skaap sperme. Min inligting is beskikbaar oor die potensiële bydrae van die genetiese samestelling van ramme wat uiteenlopend op grond van vrugbaarheid geselekteer is, op die vermoë van skaap sperme om weerstand te bied teen die skade wat deur verkoeling, diepbevriesing en ontdooiing, veroorsaak word. Die doelwit van die studie was om die invloed van genetiese seleksie vir fekunditeit (d.i. Hoë Merino Lyn en Lae Merino Lyn in terme van fekunditeit) op die vermoë van skaap sperme om weerstand teen bevriesingskade te bied, te ondersoek. Die studie het getoets wat die bevriesing proses se effek op epididimale sperme is, deur sperm motiliteit en -morfometrie te vergelyk tussen vars gekollekteerde sperme en sperm monsters na ontdooiing. Die effek van verskillende sperm konsentrasies, ekwilibrasie tydperke en die byvoeging of uitsluiting van seminale plasma op die lewensvatbaarheid en morfometriese eienskappe van Merino ramsperme is ondersoek in die studie. Geëjakuleerde monsters is versamel met behulp van 'n kunsmatige vagina (AV) van 8 Hoë Lyn en 7 Lae Lyn ramme. Epididimale monsters is verkry van 6 ramme van elk van die Hoë en Lae Lyne, deur middel van aspirasie van die sperme uit die cauda epididimii nadoods. Geëjakuleerde sperm monsters is met behulp van makroskopiese en mikroskopiese metodes geëvalueer, en epididimale sperm monsters slegs mikroskopies geëvalueer, met behulp van die Sperm Class Analyzer® program wat vir die evaluasie van beweeglikheid en morfometriese afmetings gebruik is. Sperm beweeglikheids opnames is opgeneem teen 100 raampies per sekonde. Die resultate van die studie het aangedui dat genotipe geen effek het op besetting van die ooie gepaar met die Hoë of Lae Lyn ramme gehad het nie, terwyl die dekvermoë aansienlik tussen ramme van die twee lyne verskil het. Wanneer die morfometriese eienskappe van vars geëjakuleerde sperme vergelyk was, het die lyne beduidend in terme van die morfometriese eienskappe van verlenging (elongation) en elliptisiteit verskil het. Die epididimale en geëjakuleerde sperme verkry vanaf die Lae Lyn ramme het ʼn breër en ronder kopvorm getoon as sperme wat verkry is van die Hoë Lyn ramme. Wanneer die morfometriese eienskappe van sperme versamel met die twee verskillende metodes (d.i. kunsmatige vagina of aspirasie vanuit die cauda epididimides) vergelyk was, is geen morfometriese verskille waargeneem nie. Die meeste sperm beweeglikheidseienskappe (d.i. persentasie beweeglike, vinnig-, medium- en stadig-swemmende sperme, VCL, VSL, VAP en ALH) van geëjakuleerde en epididimale sperme het verskil. Die beweeglikheidseienskappe amplitude van die laterale verplasing van die spermkop (ALH) en frekwensie waarmee sperm sy eie pad kruis (BCF), soos bepaal vir epididimale sperme, het beduidend tussen die twee lyne verskil. Met die evaluering van epididimale sperme na ontdooiing was dit duidelik dat sperme verkry van die Hoë Lyn ramme 'n groter mate van akrosoom-oppervlak gehad het, in vergelyking met sperme van die Lae Lyn ramme. Die byvoeging van seminale plasma by epididimale monsters het nie bygedra tot 'n verbetering van spermbeweeglikheid nie. Bestaande literatuur dui aan dat diepbevriesing 'n afname in die kopgrootte van sperme veroorsaak. In hierdie studie het die byvoeging van seminale plasma ʼn verandering in kopgrootte voorkom, wat dui op ʼn potensiële voordeel om seminale plasma in die bevriesingsprotokol van epididimale ramsperme in te sluit. Die studie het twee beweeglikheid bepalingstegnieke vergelyk om te bepaal of die tydrowende “opswem” tegniek (SUT) vervang kan word met 'n meer tyd-doeltreffende "spoel tegniek” (FT) in die voorbevriesing verwerking protokolle van ram sperme. Vergelyking van die twee tegnieke het aangedui dat die meeste van die kinematiese eienskappe van die FT gunstig met die waardes soos verkry met die SUT, vergelyk het. Resultate het getoon dat die FT parameters goed vergelyk met die beweeglikheid parameters van die SUT, dus kan dit aangeneem word dat die FT ʼn meer tyd-doeltreffende tegniek is wat vergelykbare sperm beweeglikheidsinligting oor skaap sperm monsters voor bevriesing sal verskaf. In samevatting is verskille in terme van die dekvermoë en op morfometriese vlak, meer spesifiek die eienskappe van verlenging (elongation) en elliptisiteit, tussen die twee lyne waargeneem. In toekomstige studies moet die morfometriese eienskappe van skaapsperme verder bestudeer word, asook die korrelasie daarvan met die bevrugtingsvermoë na ontdooiing bepaal om sodoende die diepbevriesing protokolle van skaapsperme te optimaliseer.

The aim of this study was to characterise and cryopreserve semen of the indigenous Namaqua Afrikaner breed, and to compare it to that of Dorper and Dohne Merino sheep, whose semen is commercially frozen on a large scale. The study was conducted between January and August 2015. September 2013-born Namaqua Afrikaner (12), Dohne Merino (12) and Dorper (9) rams were used in the study. The rams were kept under kraal conditions with adequate shade, and they received a high protein, high energy diet. Originally it was envisaged to collect semen samples using the artificial vagina (AV) method, which proved to be problematic with the Namaqua Afrikaner rams. Semen samples were subsequently collected twice a week by either AV (Dohne Merino and Dorper) or electro-ejaculation (EE; all three breeds). Macroscopic sperm traits were assessed and sperm concentration determined immediately after collection. Each semen sample was diluted with Triladyl® (1:3) and subsequently frozen in liquid nitrogen vapour in straws. Frozen straws were thawed and evaluated at 7, 30 and 90 days after cryopreservation. A droplet (0.5 ml) from each thawed sample was assessed microscopically for post-thaw motility and percentage live sperm..

Thesis (MScAgric (Animal Sciences))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: The aim of this study was to investigate the effect of feedlot production on the growth and carcass characteristics, as well as the distribution of the main tissues (muscle, fat and bone) and meat quality of Merino, South African Mutton Merino (SAMM) and Dorper lambs. The Merino and SAMM 2008 outperformed (P<0.05) the 2007 SAMM and both Dorper production groups in terms of average daily gain, while the Merino and both SAMM production groups achieved the best feed conversion ratio (P<0.05). The highest percentage A2 graded carcasses was achieved after 42 days under feedlot conditions by the Merino and both Dorper production groups, but it took only 21 days in the feedlot for the SAMM lambs to achieve the same result. Slaughter weight, carcass weight and dressing percentage all increased significantly with an increase in the number of days under feedlot conditions for all three breeds, while a decrease in the percentage head, trotters and red offal was also documented. The fatter retail cuts (thick rib, flank, prime rib and loin) increased (P<0.05) in percentage with an increase in the number of days under feedlot conditions. A significant decrease in the percentage leaner retail cuts (raised shoulder and hind-quarters) was found when the amount of days under feedlot conditions increased. The highest profit is obtained by the prime rib, loin and hind-quarters in a lamb carcass. For the Merino and Dorper lambs these three cuts, or a combination of the three showed the highest combined percentages after 42 and 63 days under feedlot conditions, respectively. The late maturing SAMM lambs achieved the highest percentages for these three cuts after 63 and 84 days under feedlot conditions in 2007 and 2008 respectively. Visceral and renal fat deposition increased throughout the production period for all breeds. The Dorper lambs attained the highest subcutaneous fat depth, and also produced the heaviest, but fattest carcasses. For A2-graded carcasses, Dorper lambs had the highest dressing percentage and lowest subcutaneous fat depth, followed by the SAMM and then Merino breed. A decrease in the percentage muscle and bone was found with an increase in the number of days under feedlot conditions, whilst an increase in the percentage fat was found under the same conditions. Meat quality was mostly affected by the 48h post mortem pH. This pH value is affected by the cooling rate of the carcasses, which in turn is affected by the level of carcass fatness. Carcass fatness increased with an increase in the number of days under feedlot conditions, resulting in a low 48h post mortem pH. A low 48h post mortem pH is accompanied by higher percentages of cooking and drip loss, as well as a high a*-colour reading for all three breeds.
AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die effek van voerkraalproduksie op die groeivermoë, karkaseienskappe, verspreiding van spier, been en vet, en vleiskwaliteit van Merino, Suid-Afrikaanse Vleismerino (SAVM) en Dorperlammers te bepaal. Die Merino en SAVM 2008 produksiegroepe het hoër (P<0.05) gemiddelde daaglikse toenames getoon as die SAVM 2007 en beide Dorper groepe, terwyl die Merino en beide SAVM produksiegroepe die beste voeromset verhoudings bereik het (P<0.05). Die hoogste persentasie A2 gegradeerde karkasse is na 42 dae in die voerkraal deur die Merino en beide Dorper produksiegroepe geproduseer, terwyl dit slegs 21 dae onder dieselfde toestande vir die SAVM groepe geneem het om dieselfde resultaat te lewer. Daar is ‘n betekenisvolle verhoging in slagmassa, karkasmassa en uitslagpersentasie vir al drie die rasse gevind met ‘n toename in die aantal dae in die voerkraal, terwyl ‘n afname in die persentasie kop, pote en haarslag gevind was. Die persentasie vetter groothandelsnitte (dikrib, dunrib, ribtjop en lendesnit) het toegeneem (P<0.05) met ‘n toename in die aantal dae in die voerkraal. ‘n Betekenisvolle afname in die persentasie van die maerder groothandelsnitte (blad en boude) is gevind met ‘n toename in die aantal produksie dae in die voerkraal. Die hoogste inkomste van ‘n lamkarkas is afkomstige van die ribtjop, lende snit en boude. ‘n Kombinasie van hierdie drie snitte was die hoogste vir die lammers van die Merino en beide Dorper groepe na 42 en 63 dae in die voerkraal onderskeidelik. Die laat volwasse SAVM lammers het die hoogste persentasie van hierdie drie snitte bereik na 63 en 84 dae in die voerkraal vir die SAVM 2007 en SAVM 2008 onderskeidelik. Die neerlegging van pensvet en niervet het voortdurend toegeneem deur die produksieperiode vir al drie rasse. Die Dorperlammers het die hoogste onderhuidse vetneerlegging getoon, maar het ook die swaarste en vetste karkasse geproduseer. Dorperlammers het die hoogste uitslagpersentasie en laagste onderhuidse vetneerlegging vir A2 gegradeerde karkasse gehad, gevolg deur die SAVM en Merino. ‘n Afname in die persentasie spier en been in karkasse is waargeneem namate die lammers langer in die voerkraal was, terwyl ‘n toename in die persentasie vet onder dieselfde omstandighede waargeneem is. Die 48h post mortem karkas pH affekteer die meeste vleiskwaliteit eienskappe. Hierdie pH waarde word weer deur die tempo van karkasafkoeling beϊnvloed, wat op sy beurt deur die vetheidsgraad van die karkas bepaal word. Die vetheid van karkasse het toegeneem met ‘n toename in die aantal dae in die voerkraal, wat ‘n lae pH waarde 48h post mortem tot gevolg gehad het. ‘n Lae 48h post mortem pH waarde het gelei tot hoër persentasies kook- en dripverliese en hoë a* kleurlesings vir al drie rasse.

The primary objective of this research project was to determine whether area-selective grazing, by Dorper and Merino wethers, took place in small grazing camps as governed by differences in vegetal cover. The main research techniques employed were the descending-point method for the determination of botanical composition, sub-division of the camps into gridblocks to trace sheep movement in relation to vegetation patterning, fistulated animals to determine diet selection, the electronic theodolite for micro-topography, and few minor techniques. The result have shown that area- patch- and species selective grazing are prevalent in small grazing camps under "normal" stocking densities, and that different breeds of stock (Merino and Dorper sheep) have different grazing patterns and diet selection . Climax and sub-climax areas were those primarily select ed for grazing. There is little or no correlation between botanical composition and diet selected as per fistula ted animal. The average distances travelled by Dorpers and Merinos was 2 km / day and 3.1 km/day respectively. Plant phenology did not have a detectable influence in the choice of diet.

Thesis (MSc)--Stellenbosch University, 2000.
ENGLISH ABSTRACT: South Africa, like many other developing countries throughout the world, has a rapidly growing human population, resulting in a consequent increased demand for food. Ironically, this increased food supply has to be produced on a smaller area of available agricultural land, which means that agricultural production processes have to become more efficient. Furthermore, the majority of the people in these countries are unschooled and poverty is a common phenomenon. Therefore, animal scientists are faced with the challenge and the responsibility to provide affordable, high quality food to these people. One way of reaching this objective is to improve the utilisation of low-quality, high roughage feedstuffs like crop residues and dry natural grass pastures. In the winter rainfall area of South Africa alone, about 460 000 ha of wheat straw are annually available. The ruminant animal has the ability to utilise the relatively unavailable energy (cellulose, hemi-cellulose and pectin) in the fibre component of these low-quality forages. Unfortunately, various factors, of which a N deficiency is the pre-dominant one, limit the utilisation of these feedstuffs. If the ability of the ruminant to utilise low-quality, fibrous energy sources is improved, these abundantly available and relatively inexpensive crop residues and natural pastures can be converted into high quality protein food for human consumption. Therefore, in order to rectify the N deficiency caused by these low-quality forages, the supplemental N requirement to optimise the fermentation and digestive processes of the ruminant animal has to be determined. The first study was conducted to determine the supplemental rumen degradable protein (RDP) requirement, to maximise the digestible organic matter intake (DOMI) of Dohne Merino sheep fed wheat straw. Keeping the high cost of natural protein supplementation in mind, the purpose of the second study was to determine the amount of true protein that can be replaced by nonprotein nitrogen (NPN) in RDP supplements fed to Dohne Merino sheep consuming wheat straw. In both trials animals had ad libitum access to low-quality wheat straw (3.2% CP; 74.2% NDF) and water. In the first trial, RDP (calsium caseinate: 90% CP; 100% rumen degradable) was intraruminally administered at 07hOOand 19hOO,at the following levels: 0, 40,80, 120 and 160 gld. Intake, fermentation and digestion were monitored to determine the RDP requirement to maximise DOM!. Digestible organic matter (OM) intake displayed a quadratic increase with elevated amounts of RDP (P < .01), and was maximised at an estimated 3.15 g RDPlkg BW·75 or 11.6% of DOM. Forage OM intake tended to increase quadratically (P = .15) with higher RDP levels. Microbial nitrogen (MN) flow to the duodenum and microbial efficiency increased quadratically (P ~ .04) and fluid dilution rate tended to increase in a quadratic manner (P = .15) with increased RDP supplementation levels. Rumina! ammonia nitrogen (NH3-N) and total volatile fatty acid (VFA) concentrations increased linearly (P ~ .07), while rumen pH exhibited a variable response to increased RDP levels (cubic; P = .08). Increasing RDP supplementation to Dohne Merino wethers consuming wheat straw, generally enhanced forage utilisation and DOM!. In the second trial, urea replaced different levels of casein N on an isonitrogenous basis, ranging from 0 - 100%. Since true protein is much more expensive than urea, the purpose of this study was to determine the maximum natural protein level that can be replaced by urea in RDP supplements, without adversely affecting intake and/or fermentation and digestive processes. The control treatment provided all of the RDP in the form of calcium caseinate (90% CP; 100% rumen degradable). The percentages of supplemental RDP from urea in the other treatments were 25, 50, 75 and 100%. The 100% urea treatment was balanced with maize starch to contain 40% CP and all other treatments received the same amount (150 gld) of starch. Intake of forage OM showed a weak decreasing trend (linear; P = .16) with increasing urea levels. Ruminal digestibilities of OM and NDF were not affected (P ;;::.:18) by urea level. Increasing urea levels resulted in linearly reduced total tract OM and NDF digestibilities (P ~ .10). As a result, DOMI declined (linear; P < .01) with increasing proportions of urea. Effects of increasing urea proportions on duodenal N flow, microbial efficiency and fluid dilution rate were minimal. Ruminal NH3-N tended to increase quadratically with increasing urea levels (P = .l4). Total VFA concentration decreased linearly (P = .03), while rumen pH increased in a linear manner (P = .08) with increasing urea proportions. Branched-chain volatile fatty acids (BCVFA's) and valerate decreased linearly (P ~ .05) with increasing urea levels, while other VFA's and the acetate:propionate ratio were generally not affected by treatment (P ;;:::.16). It appears as though ruminal and total tract OM and NDF digestibility criteria, as well as DOMI reached maximum values at substituting 25% of casein for urea. It is therefore concluded that replacing 25% of casein with urea in RDP supplements, will maintain effective utilisation of low-quality forages by sheep.
AFRIKAANSE OPSOMMING: Ontwikkelende lande, insluitend Suid-Afrika, word gekenmerk deur 'n vmmge bevolkingsaanwas. Dit lei tot 'n verhoogde vraag na voedsel, wat op 'n gevolglik kleinerwordende beskikbare kommersiële lanbbou-area geproduseer moet word. Die doeltreffendheid van produksieprosesse in die landbousektor moet dus noodgedwonge verbeter word. Die oorgrootte meerderheid van die bevolkings in ontwikkelende lande is ongeletterd en armoede en hongersnood is soms 'n algemene verskynsel. Veekundiges word dus gekonfronteer met die uitdaging en verantwoordelikheid om bekostigbare, hoë kwaliteit voedsel aan hierdie mense te voorsien. Een van die mees doeltreffende metodes om hierdie probleem aan te spreek, is om die benutting van lae kwaliteit, hoë-vesel voerbronne, bv. oesreste en droë grasweidings te verhoog. In die winterreënstreek van Suid-Afrika alleen, is 460 000 ha koringstrooi jaarliks beskikbaar. Herkouers beskik oor die besondere vermoë om die relatief onbeskikbare energie (sellulose, hemi-sellulose en pektien) in die veselkomponent van hierdie lae kwaliteit voere te benut. Verskeie faktore, waarvan 'n N-tekort die mees prominente is, beperk egter die benutting van hierdie voerbronne. Die uitdaging is dus om die herkouer se vermoë om hierdie voere te benut, te optimaliseer. Sodoende word 'n geredelik beskikbare, onderbenutte en relatief goedkoop voerbron omgeskakel in hoë kwaliteit proteïen vir menslike gebruik. Die N-aanvullingsbehoefte om die fermentasie- en verteringsprosesse van die herkouerdier te optimaliseer moet dus bepaal word, sodat die N-tekort in herkouers, wat soortgelyke weidings benut, reggestel kan word. Gevolglik was die doel met die eerste proef om die behoefte aan rumen degradeerbare proteïen-(RDP)-aanvulling, vir die maksimum inname van verteerbare organiese materiaal (VOM) van Dohne Merino skape wat koringstrooi ontvang, te bepaal. Weens die hoë koste van natuurlike proteïenaanvulling, was die doel met die tweede proef om die hoeveelheid ware proteïen in RDP-aanvullings, vir Dohne Merino skape wat koringstrooi ontvang, wat met nie-proteïen stikstof (NPN) vervang kan word, te bepaal. In beide eksperimente het die diere ad libitum toegang tot koringstrooi (3.2% RP; 74.2% NBV) en water gehad. In die eerste proefis RDP (kalsiumkaseïnaat; 90% RP; 100% rumen degradeerbaar) teen 07hOOen 19hOOintraruminaal toegedien, teen die volgende peile: 0, 40, 80, 120 en 160 gld. Inname, fermentasie en vertering is gemonitor om die RDP behoefte vir die maksimum inname van VOM te bepaal. Verteerbare OM-inname het 'n stygende kwadratiese tendens (P < .01) getoon met verhoogde RDP-peile en het 'n maksimum bereik by 'n aanvullingspeil van 3.15 g RDPlkg metaboliese liggaamsmassa (LM·75 ) of 11.6% van VOM. Organiese materiaalinname vanaf koringstrooi het geneig om kwadraties toe te neem (P = .15) met verhoogde RDP-peile. Mikrobiese stikstof-(MN)-vloei na die duodenum en mikrobiese effektiwiteit het kwadraties toegeneem (P :::;.;04) en vloeistof deurvloeitempo het 'n neiging vir 'n kwadratiese toename (P = .15) met verhoogde RDPpeile getoon. Rumen-ammoniakstikstof (NH3-N) en vlugtige vetsuur-(VVS)-konsentrasies het lineêr toegeneem (P :::;.;07), terwyl rumen pH 'n wisselende reaksie (kubies; P = .08) met stygende RDP-peile getoon het. Verteerbare OM-inname en benutting van koringstrooi is verbeter deur stygende peile van RDP aanvulling by Dohne Merino hamels. In die tweede proef is kaseïen op 'n iso-stikstof basis met verskillende ureumpeile, vanaf o - 100%, vervang. Omdat ureum baie goedkoper is as natuurlike proteïen, was die doel van die tweede proef om die hoeveelheid natuurlike proteïen in RDP-aanvullings te bepaal wat met ureum vervang kan word, sonder om inname, fermentasie en vertering te benadeel. Die kontrolebehandeling het 100% van die RDP in die vorm van kalsiumkaseïnaat (90% RP; 100% rumen degradeerbaar) voorsien, terwyl ureum in die ander behandelings onderskeidelik 25, 50, 75 en 100% van die kaseïen-N vervang het. Die 100% ureumbehandeling is met mieliestysel tot 40% RP gebalanseer en dieselfde hoeveelheid stysel (150 gld) is by al die ander behandelings ingesluit, om moontlike effekte van stysel op rumenfermentasie te elimineer. Organiese materiaalinname vanafkoringstrooi het 'n swak dalende tendens getoon met stygende ureum insluitingsvlakke (lineêr; P = .16). Rumenverteerbaarheid van OM en neutraal bestande vesel (NBV) is nie deur die ureumpeil beïnvloed nie (P ;;:: .18). Toenemende ureumpeile het gelei tot 'n lineêre afname in totale kanaal OM en NBVverteerbaarheid (P ~ .10). Gevolglik het VOM inname lineêr afgeneem (P < .01) met stygende ureum insluitingspeile. Die effek van behandeling op duodenale N-vloei, mikrobiese effektiwiteit en vloeistof deurvloeitempo was minimaal. Rumenammoniakstikstof-( NH3-N)-konsentrasie het 'n stygende kwadratiese tendens getoon (P = .14) met toenemende ureum peile. Totale vlugtige vetsuur-(VVS)-konsentrasies het lineêr gedaal (P = .03), terwyl rumen pH lineêr toegeneem het (P = .08) met stygende ureum insluitingsvlakke. Vertakte ketting VVS' e en valeriaansuurkonsentrasies het lineêr gedaal (P ~ .05) met stygende ureumpeile, terwyl die ander VVS' e en die asynsuur:propioonsuurverhouding oor die algemeen nie deur behandeling beïnvloed N; nie (P ;;:: .16). Dit blyk asof VOM inname, sowel as rumen- en totale kanaal verteerbaarheidsmaatstawwe, by 25% vervanging van kaseïen-N met ureum-N 'n maksimum bereik het. Die gevolgtrekking is gemaak dat die doeltreffende benutting van lae kwaliteit ruvoere deur skape, gehandhaaf sal word deur 25% van die ware proteïen in RDP-aanvullings met ureum te vervang.

Bibliography : leaves 120-133. Defines the sources of reproductive wastage in FecB FecÊ Booroola Merino x South Australian Merino ewes and examines factors associated with the survival of embryos, fetuses and lambs with the aim of improving net reproduction efficiency. Experiments were conducted to define the problem; to examine factors affecting embryonic and fetal loss; and, to investigate factors influencing wastage at lambing.

Thesis (MScAgric (Animal Sciences))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: The objective of this study was to evaluate Dohne Merino sheep and Boer goats in terms of the degradable parameters of a high-fibre diet, a low-fibre diet and two vegetable protein sources commonly used in South Africa. Differences between species were evaluated following the potential differences within species. The feedstuffs used were those for the following diets: low-fibre diet (LF); high-fibre diet (HF); sunflower meal (SFM) oilcake; and soybean meal (SBM) oilcake. In the first trial, the digestible characteristics of the HF and LF diets were determined by means of a digestibility study. A 6 × 6 Latin square design was used to determine whether Dohne Merino sheep or Boer goat wethers differ regarding the digestibility characteristics of low- and high-fibre diets. The diets were fed once daily at 1.24 kg to all the wethers, which had ad libitum access to fresh water. Each period consisted of 10 days of adaptation and seven days of faecal and urinary sampling. The results indicated that the intake and digestibility characteristics of nutrients did not differ between sheep and goats. However, the different diets differed in terms of the nutrient intake and digestibility range of sheep and goats. The second trial was an in sacco degradability trial to determine the dry matter (DM) and crude protein (CP) degradability of the LF, HF, SBM and SFM diets. Six Dohne Merino and six Boer goat wethers were fitted with rumen cannulae so that they could be used in the trial. All wethers received the same basal diet. The samples were incubated in the rumen in polyester Dacron bags, with the bags being removed at intervals of 0h, 3h, 9h, 12h, 24h, 48h, 72h, and 96h for the LF and HF diets. All the oilcake was removed at intervals of 0h, 2h, 4h, 8h, 12h, 16h, 24h, 36h and 48h. The sheep and goats were found not to differ from one another in terms of effective degradability of any of the feedstuffs concerned. However, within species differences were observed. To establish a fully integrated outcome of degradability, the study described in the current thesis was structured in such a way that the in vitro trial ran parallel with the in sacco trial, being performed with the aid of a Daisy Incubator (ANKOM Technology Corp., Fairport, NY). Such a procedure was only adopted in relation to the SFM and SBM diets in order to evaluate their in vitro data in relation to the in sacco data. The same oilcake was tested in the case of both trials, with the composite sample of rumen liquid of four sheep or goats, which was used in the in sacco trial, also being used in the in vitro study. In the study, DM disappearance values were determined and fitted to a single-compartment model by means of an iterative least-square procedure in order to determine the DM and CP degradability parameters. The DM used in vitro or in sacco was compared, using the actual values obtained after 8h incubation, due to only a limited amount of residue being left after incubation. In the study, the in vitro method overestimated the digestibility of SBM by 37% to 39% and the digestibility of SFM by 17% to 20% compared with that found to occur in the in sacco method. In vitro DM disappearance values for all SBM samples were found to be higher than those that were detected in the SFM samples. The percentage of in vitro true digestibility parameters was also calculated. No significant differences were found between species for effective degradability, though differences were observed within species between the two substrates concerned. In conclusion, the sheep and goats used in the study were not found to differ in terms of digestion parameters when they were compared on different types of roughage or protein sources. However, within species differences were, indeed, found to occur. Sheep and goats digested the SBM better than they did the SFM.
AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om te bepaal of Dohne Merino skape verskil van Boerbokke in terme van degradeerbaarheidsparameters van ‘n hoë vesel-, ‘n lae veseldieët en twee plantaardige proteïenbronne wat algemeen in Suid-Afrika gebruik word. Die verskille tussen spesies is ge-evalueer en daarna die potensiële verskille binne spesies. Die volgende grondstowwe is geëvalueer: ‘n laevesel-dieët (LF), ‘n hoëvesel-dieët (HF), sonneblom-oliekoekmeel (SFM) en sojaboon-oliekoekmeel (SBM). In die eerste proef is die degradeerbaarheidsparameters van die HF dieët en die LF dieët met behulp van ‘n verteerbaarheidstudie bepaal. Dohne Merino hamels of Boerbok kapaters was gebruik om te bepaal of skape en bokke verskil in terme van inname en degradeerbaarheid van voedingstowwe wanneer hul hoë- en lae vesel voere gevoer word. Al die hamels en kapaters het ad libitum toegang tot vars water gehad en hul was een keer per dag (1.24 kg) gevoer. Elke periode het bestaan uit ‘n 10 dag aanpassingsperiode en ‘n toegelate 7 dae vir mis- en urienmonster versameling. Die resultate het aangedui dat die inname- en degradeerbaarheidsparameters van nutriënte beinvloed word deur verskillende diëte binne spesies. Geen verskille is gevind tussen spesies wanneer daar hoë- en lae kwaliteit voere gevoer is nie. Die tweede proef was ‘n in sacco-degradeerbaarheidsstudie om te bepaal wat die droë materiaal (DM) en ruproteïen (RP) verteerbaarheidsparameters van die HF dieët, die LF dieët, die SBM en die SFM is. Ses Dohne Merino’s en ses Boer bokke met rumen kanullas is in die studie gebruik en al die diere het dieselfde basale dieët ontvang. Die monsters is in die rumen geïnkubeer in poliester dakronsakkies en die sakkies is verwyder na onderskeidelik 0 uur, 3 uur, 9 uur, 12 uur, 24 uur, 48 uur, 72 uur en 96 uur intervalle. Laasgenoemde intervalle was geldig vir die lae vesel- en hoëveseldieët. Die oliekoeke se intervalle het verskil en is verwyder na 0 uur, 2 uur, 4 uur, 8 uur, 12 uur, 16 uur, 24 uur, 36 uur en 48 uur. Daar was geen verskille tussen spesies in effektiewe degradeerbaarheid nie, alhoewel verskille voorgekom het binne spesies. Skape verteer veselagtige grondstowwe meer effektief terwyl bokke weer hoë proteïn bevattende grondstowwe beter verteer. Om ‘n volkome geïntegreede uitkoms van degradeerbaarheid te bewerkstellig is die in vitro proef en die in sacco proef gelyktydig gedoen. Die in vitro-degradeerbareheidstudie is met behulp van ‘n ANKOM Daisy Inkubeerder uitgevoer (ANKOM Tegnologie Korp., Fairport, NY) vir net die oliekoek behandelings. Gedurende die studie is dieselfde oliekoeke gebruik. ‘n Saamgestelde monster van die rumenvloeistof van vier van die skape of bokke wat vir die in sacco-studie gebruik was, is gebruik vir die in vitro-inkubasie van die monsters. DM verdwyningparameters is bereken en dan met ‘n interaktiewe kleinste kwadraat prosedure op ‘n een-kompartement model gepas om die in sacco DMdegradeerbaarheidsparameters te bepaal. Die DM verdwyning, na 8h inkubasie, was gebruik om die in vitro en die in sacco metodes met mekaar te vergelyk, weens ‘n beperkte residu na die afloop van die elke inkubasiestudie. Tydens die studie het die in vitro metode degradering oorskat in vergelyking met die in sacco metode. DM verdwyningswaardes vir al die SBM monsters was hoër in vitro as die SFM monsters. In die studie is die persentasie in vitro ware degradeerbaarheidswaardes bereken. Geen verskille is opgemerk tussen spesies vir effektiewe degradeerbaarheid nie. Daar was wel verskille binne spesies. Om af te sluit het dit voorgekom dat skape en bokke nie verskil aan degradeerbaarheidswaardes wanneer daar ‘n vergelyking was tussen verskillende vesels- en proteϊenbronne nie, alhoewel verskille voorgekom het binne spesies. Skape en bokke het SBM effektief beter verteer as SFM.

Thesis (MScAgric)--Stellenbosch University, 2013.
ENGLISH ABSTRACT: Genetic (co)variances for body weight, clean fleece weight and fibre diameter were estimated for the South African Dohne Merino using data transformed as proportions of contemporary group means. The data analysed included body weight, clean fleece weight and fibre diameter records for 282 513 animals, evaluated between 1992 and 2011. There were 5 698 sires, 105 886 dams and 6 291 contemporary groups in the data. A three-trait animal model was fitted, where the random variables were the direct additive genetic effects, as well as the sire-flock-season (SFS) interaction, while the fixed effects included contemporary groups (FYSSM) (6 291 classes), birth status (single, twins or triplets), age of dam (1 to 3 years), which was plotted as a linear regression as well as age at performance measurement, which was fitted as a polynomial. The direct heritability estimates (SE) for body weight, clean fleece weight and fibre diameter were 0.265 (0.005), 0.210 (0.004) and 0.437 (0.005), respectively. Genetic correlations for body weight with clean fleece weight and fibre diameter were 0.035 (0.015) and 0.139 (0.011), respectively, while the genetic correlation between clean fleece weight and fibre diameter was 0.169 (0.012). Body weight had phenotypic correlations of 0.327 (0.002) and 0.150 (0.002), respectively, with clean fleece weight and fibre diameter, which had a phenotypic correlation of 0.190 (0.002) with clean fleece weight. The moderate to high heritability estimates suggests that there is substantial genetic variation, which may result in genetic improvement if selection is applied on these traits. Genetic correlations were generally low, suggesting that progress in all these traits was possible in a scientific selection program. Genetic trends derived during the study supported the contention that genetic progress in all traits was attainable in a well-constructed breeding programme. Transformation of the data to percentages of contemporary groups resulted in adjustments to breeding values. The breeding values for sires originating from flocks maintained in limiting environments (Low group; 180 sires) were adjusted upwards, while those of sires originating from a non-limiting production environment (High group; 146 sires) were adjusted downwards. These effects were markedly obvious for the quantitative traits (body weight and clean fleece weight), but to a much lesser extent for fibre diameter. This transformation resulted in the genetic trends for the Low groups being adjusted to be comparable to those in the High group for body weight and Fibre diameter. It was concluded that sire breeding values derived from transformed data would be more robust across the typical diverse environments supporting local Dohne Merino production. The genetic value of animals entering the recorded population from a commercial base (F4 animals) was below the fully recorded part of the population. The inclusion of phantom parent groups in the genetic analysis rendered genetic trends in F4 animals comparable to that of the pedigreed portion of animals in the analyses. It was concluded that animals from a commercial base (which are alleged to have advantages in terms of fitness and robustness) were more likely to perform satisfactorily for selection with the inclusion of phantom groups than without it. It was recommended that data in the national Dohne Merino analysis be transformed proportion of contemporary group means to account for heterogeneous contemporary group variances. Phantom parent groups should also be applied to the analysis to increase the probability of those animals entering the breeding flock from a commercial base being selected.
AFRIKAANSE OPSOMMING: Genetiese kovariansies vir liggaamgewig, skoonvaggewig en veseldikte is vir die SA Dohne Merino bevolking in Suid-Afrika beraam nadat data getransformeer as ‘n proporsie van die kontemporêre groep gemiddelddes uitgedruk is. Die data het rekords in van liggaamsgewig, skoonvaggewig en veseldikte van 282 513 diere oor die tydperk van 1992 tot 2011 ingesluit. Die data sluit rekords van 5 698 vaars, 105 886 moers en 6 291 kontemporêre groepe in. 'n Meer-eienskapdieremodel met 'n additiewe diere-effekte sowel as 'n vaar-kudde-seisoen (SFS) interaksie is as ewekansige effekte gemodelleer, bykomstig tot die vaste effekte van kontemporêre groep (FYSSM) (6 291 klasse), geboortestatus (enkelling, tweeling of drieling), ouderdom van moer (1 tot 3 jaar) gepas as 'n lineêre regressive, sowel as ouderdom by prestasie meting as ‘n polinoom gepas. Die beraamde direkte oorerflikheid (SF) van liggaamgewig, skoonvaggewig en veseldikte van die meereienskap dieremodel was onderskeidelik 0,265 (0,005), 0,210 (0,004) en 0,437 (0,005). Die genetiese korrelasies van liggaamsgewig met skoonvaggewig en veseldikte was 0,035 (0.015) en 0,139 (0.011) onderskeidelik, terwyl die genetiese korrelasie tussen skoonvaggewig en veseldikte 0,169 (0.012) beloop het. Liggaamsgewig het onderskeie fenotipiese korrelasies van 0,327 (0.002) en 0.150 (0.002) met skoonvaggewig en veseldikte gehad, terwyl skoonvaggewig ‘n fenotipiese korrelasie van 0.190 (0.002) met veseldikte gehad het. Die medium tot hoë oorerflikheidhede dui daarop dat daar aansienlike genetiese variasie voorkom, wat kan aanleiding gee tot genetiese vordering as seleksie op die eienskappe toegepas word. Genetiese korrelasies was oor die algemeen laag wat daarop dui dat vordering in al die eienskappe deur ‘n wetenskaplike seleksie program moontlik is. Die aanspraak is deur genetiese tendense in die studie bevestig. Die transformasie van data na proporsies van kontemporêre groep gemiddeldes het daartoe gelei dat teelwaardes aangepas word. Die teelwaardes van vaars uit kuddes met ‘n omgewing wat beperk word (Lae groep:180 vaars), is opwaarts aangepas. Daarenteen is vaars uit 'n nie-beperkende produksie omgewing (Hoë groep:146 vaars) se teelwaardes afwaarts aangepas. Hierdie effekte was veral ooglopend vir die kwantitatiewe eienskappe, liggaamgewig en skoonvaggewig, maar tot 'n mindere mate vir veseldikte. Die transformasie het daartoe gelei dat die genetiese tendense for die Lae groep aangepas word om vergelykbaar te wees met die Hoë groep vir liggaamsgewig en skoonvaggewig. Die gevolgtrekking was gemaak dat meer toepaslike vaar teelwaardes, bereken vanaf getransformeerde data, verkry word vir regoor die diverse omgewings wat produksie van plaaslike Dohne Merinos ondersteun. Die genetiese waarde van diere wat die aangetekende populasie uit ‘n kommersiële agtergrond (F4 diere) binnekom was laer as die volledig aangetekende gedeelte van die populasie. Die insluiting van skimgroepe in die genetiese ontleding het tot genetiese tendense gelei wat die F4 diere vergelykbaar gemaak het met diere in die ontleding wat wel stamboekinligting het. Die gevolgtrekking is gemaak dat diere van ‘n kommersiële agtergrond (wat aanvaar word om voordele in te hou in terme van fiksheid en robuustheid) meer geredelik geselekteer sal word vir die stoet met die insluiting van skimgroepe as daarsonder. Dit word aanbeveel dat die data in die Nasionale Dohne Merino na proporsies van die kontemporêre groepgemiddeldes getrensformeer word om vir heterogene kontemporêre groep variansies voorsiening te maak. Skimgroepe moet ook gepas word in die ontleding om die waarskynlikheid te verhoog dat diere vanuit 'n kommersiële basis, ook geselekteer sal word.

Wool from Merino sheep is an important component of the Australian economy. However, little is known of the mechanisms within the wool follicle that regulate fibre production. The aim of the research described here was to identify and characterise some of the genes expressed in the follicle.A highly expressed gene has been identified from skin and sequenced. The information obtained on this gene suggests that it might be of use in future transgenic studies. Two cDNA libraries were constructed. The first was constructed using small amounts of total RNA from skin and PCR methodology, following a published method. A second cDNA library was then produced from adult mid-flank skin using a commercially available kit. A pool of 420 potential wool follicle specific transcripts were identified from this adult mid-flank skin cDNA library using a combination of differential and subtractive screening. Clone 1-25 was chosen as the focus for the remaining work described in this thesis. Expression of clone 1-25 was detected at all stages of wool follicle development and was localised to the wool follicle bulb, inner root sheath, outer root sheath, epidermis, but not the dermis or dermal papilla. The function of clone 1-25 is as yet unknown. However, from its expression in the wool follicle, and studies by other groups, it appears that it may play a role in inducing differentiation
Doctor of Philosophy (PhD) (Biological Sciences)

Muscular dystrophies (MDs) are neuromuscular disorders characterised by chronic, usually progressive, skeletal muscle weakness. Individuals often lose walking ability and can suffer terminal cardiorespiratory complications. Determining the genetics of a disease helps provide diagnosis, prognosis, genetic counselling, and the basis for rational therapeutic design. A naturally occurring sheep model of autosomal recessive congenital MD was identified in WA in the 1950’s and preserved as a research colony. The pathological features and distribution of this MD is novel. A sheep model of MD is incredibly valuable; sheep have similar skeletal muscle mass to humans, representing a significant improvement over smaller mammals in which to trial therapies. Successfully characterising the causative gene(s) would enable a possible target for new therapies and may open new lines of investigation into better understanding and treatment of MD in humans. This project utilised a two-pronged approach to investigate the genetics of this ovine MD. First, bioinformatics analysis of SNP genotyping for multiple individuals in the flock by a 50,000 SNP array in combination with the latest sheep genome reference build released by the International Sheep Genome Consortium, enabling homozygosity mapping, genetic linkage and association mapping. Second, molecular biological approaches further explored the identified prime candidate gene by cDNA sequencing. This research project identified ROCK2 as the prime candidate gene most likely harbouring a mutation causing the muscular dystrophy in this internationally unique ovine model. It also demonstrated for the first time in sheep the existence of ROCK2m, an isoform of ROCK2 preferentially expressed in skeletal muscle. This work has set the stage for further investigations into ROCK2m and the ovine MD which will hopefully pinpoint the causative disease mutation.

Thesis (PhD)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: This study describes: • the comparison of the enzymatic activities of the two ovine cytochrome P450 17 - hydroxylase/17,20-lyase (CYP17) isoforms expressed in non-steroidogenic COS-1 cells. The Km and Vmax values for the metabolism of pregnenolone and progesterone were determined, while time-dependent metabolism of pregnenolone, 17-hydroxypregenolone, progesterone and 17-hydroxyprogesterone was also reported. The cloning and sequencing of ovine cytochrome b5 is reported and was co-expressed with CYP17. The results showed that the wild type 1 (WT1) isoform of ovine CYP17 produce more cortisol precursors than the wild type 2 (WT2) isoform; • the analysis of the frequency distribution of the CYP17 genotypes within a South African Merino population, which were divergently selected for (H-line) or against (L-line) the ability of a ewe to rear multiple offspring per birthing opportunity. It was observed that the CYP17 frequency distribution was the same within the H- and L-line, with 78.3 % heterozygous WT1/WT2 and 21.7 % homozygous WT1/WT1. No homozygous WT2/WT2 individuals were identified; • the development of a UPLC-MS/MS method for the separation and quantification of all thirteen adrenal steroids that are produced in the adrenal gland; • the relative contribution of the CYP17 genotypes in the total steroidogenic output in adult adrenocortical cells from the adrenal glands of H- and L-line sheep, with particular emphasis on cortisol production. The adrenocortical cells from the H-line sheep showed a marked higher cortisol production than the L-line, while adrenocortical cells from homozygous WT1/WT1 sheep also produced more cortisol than heterozygous WT1/WT2 sheep; • the blood cortisol responses upon the stimulation of the HPA axis by insulin induced hypoglycaemia of the H- and L-line sheep with known CYP17 genotypes. It was observed that the CYP17 genotype and selection line are important factors affecting the cortisol responses of sheep, where L-line heterozygous WT1/WT2 sheep showed the lowest cortisol response and glucose recovery; • the association of the CYP17 genotype with behavioural responses of H- and L-line sheep to flock isolation stress, as well as the association of the CYP17 genotype with ewe reproduction and lamb output. While reproduction seemed to be unaffected by the CYP17 genotype, the behavioural stress responses of sheep to flock isolation correlated with the CYP17 genotype, where the heterozygous WT1/WT2 genotype was associated with a wilder nature.
AFRIKAANSE OPSOMMING: Hierdie studie ondersoek: • die vergelyking van die ensiemaktiwiteite vir twee isoforme van skaap sitochroom P450 17 -hidroksilase/17,20-liase (CYP17), wat uitgedruk was in nie-steroïed genererende COS- 1 selle. Die Km and Vmax waardes was bepaal vir die metabolisme van pregnenoloon en progesteroon, terwyl die tyd-afhanklike metabolisme van pregnenoloon, 17- hidroksiepregnenoloon, progesteroon en 17-hidroksieprogesteroon ook gerapporteer word. Die klonering en volgorde bepaling van skaap sitochroom b5 was gedoen en gevolglik was sitochroom b5 saam met CYP17 uitgedruk in COS-1 selle. Die resultate het gewys dat wilde tipe 1 (WT1) meer voorlopers van kortisol produseer as wilde tipe 2 (WT2); • die frekwensie distrubusie van die CYP17 genotipes in ‘n Suid-Afrikaanse Merino populasie, waar skape in teenoorgestelde rigtings geselekteer was vir (H-lyn) of teen (L-lyn) die vermoë van ‘n ooi om geboorte te gee aan veelvoudige lammers per lamgeleentheid. Die frekwensie distrubusie van CYP17 was dieselfde in beide die H- en L-lyn, waar 78.3 % van die populasie heterosigoties WT1/WT2 en 21.7 % homosigoties WT1/WT1 was. Geen homosigote WT2/WT2 individue was geïdentifiseer nie; • die ontwikkeling van ‘n UPLC-MS/MS metode vir die skeiding en kwantifisering van al dertien steroïede wat natuurlik geproduseer word in die bynier van die skaap; • die relatiewe bydrae van die CYP17 isoforme tot die totale steroïedale uitsette vanuit die bynier kortex selle, vanaf die byniere van H- en L-lyn skape, waar klem geplaas word op die produksie van kortisol. Die bynierselle van die H-lyn skape het aansienlik meer kortisol produseer as die L-lyn, terwyl die bynierselle van die homosigotiese WT1/WT1 skape ook meer kortisol produseer het as heterosigotiese WT1/WT2 skape; • die bloed kortisol in reaksie tot die stimulering van die hipotalamus-hipofise-adrenale aksis, deur insulien geïnduseerde hipoglisemiese stress, in skape van die H- en L-lyne met bekende CYP17 genotipes. Dit was gevind dat die kortisol reaksie geaffekteer word deur beide die CYP17 genotipe en seleksie lyn, waar L-lyn heterosigotiese WT1/WT2 skape die minste kortisol geproduseer het en die stadigste herstel van glukose vlakke getoon het; • die assosiasie tussen die CYP17 genotipe en die gedrags reaksies op trop-isolasie, sowel as ooi-reproduksie en lamuitset, van die H- en L-lyn skape. Die reproduksie parameters was onafhanklik van die CYP17 genotipe, terwyl ‘n sterk assosiasie gevind was tussen die CYP17 genotipe en gedrags reaksies op trop-isolasie. Die heterosigotiese WT1/WT2 skape het ‘n wilder natuur getoon gedurende trop-isolasie in vergelyking met homosigotiese WT1/WT1 skape.

Thesis (MScAgric)--University of Stellenbosch, 2002.
ENGLISH ABSTRACT: An experiment was conducted to determine the effect of the frequency of supplementary feeding on the production of South African Mutton Merino (SAMM) ewes grazing wheat stubble. One hundred and sixty ewes were randomly divided into two groups that consisted of four groups each. Eight camps were grazed for 138 days during which lambing occurred. Four groups of 25 ewes each grazed a 17 ha camp at a stocking density of 5.8 ewes/ha and four groups of 15 ewes each grazed a 12 ha camp at a stocking density of 5.0 ewes/ha. A combination energy/protein supplement was made available to the ewes as a lick. Two of the groups received no supplementary feed (control), two groups received 200 g/ewe/day, two groups received 400 g/ewe every second day and two groups received 600 g/ewe every third day. The smallest decrease in weight during the feeding period was observed in the ewe group that received supplementation every day as well as the ewe group that received supplementation every second day, but no significant differences were observed between these two groups. The smallest decrease in weight over the total feeding period was observed in the three ewe groups that received supplementation (P < 0.1), while the ewes that received none (control groups) lost the most weight during the same period. All supplemented groups performed significantly better than the unsupplemented control group in terms of the liveweight change over the feeding as well as the total period. No significant differences occurred in the lambing percentage, weaning percentage, birthweight, 42-day weight and survival rate of the lambs due to the different feeding regimes. It was concluded that supplementation to ewes every third day or every second day is an economically feasible option and will reduce labour and transport costs. In the second study the effect of stocking density on canola stubble composition and subsequently the production of SAMM ewes on this type of stubble was investigated. Forty-eight ewes were randomly divided into four groups that grazed canola stubble at a stocking density of approximately 1.5, 3.5, 5.5 and 7.5 ewes/ha for 152 days. The ewes did not receive any supplementation and were weighed every 14 days. Parturition occurred during the last week in March 1997 until the first week in May 1997, and the lambs were weighed at birth, and every 14 days thereafter. Stubble samples were collected from the paddocks during the first part of the trial (January and February) and at the end of the trial (April and May) by cutting ten replicate quadrates per paddock and were analysed for dry matter (DM), crude protein (CP), acid detergent fibre (ADF), neutral detergent fibre (NDF) and in vitro digestibility of organic matter (IVDOM). The live weight of the ewes at a stocking density of 5.5 ewes/ha decreased significantly, while the ewes at a stocking density of 1.5 ewes/ha gained weight. The ewes at a stocking density of 3.5 ewes/ha had the lowest weight loss (P = 0.01). Stocking density did not affect the birthweight of the lambs significantly. The CP concentration of the stubble decreased with an increase in stocking density, while the ADF and NDF concentration of samples were significantly higher at the higher stocking density. In the third study the supplementation of rumen inert fat or starch on the production of ewes grazing wheat stubble, was investigated. Fifty-six SAMM ewes were randomly divided into four groups of 14 ewes each, grazing the wheat stubble at a stocking density of 4.6 ewes/ha. Each group was supplemented with 250 gJewe daily for the last six weeks of pregnancy, which was increased to 360 gJewe during the first four weeks of lactation. Supplementation was supplied on Mondays, Wednesdays and Fridays for a 70-day period. The CP concentration of the supplement varied between 16.7 % and 19.6 %, while the total digestible nutrient (TDN) content varied between 52.0 % and 76.7 %. No significant difference (P > 0.05) occurred between the live weights of ewes during the last six weeks of pregnancy, the first four weeks of lactation, or the total feeding period. The ewes in the 50 % fat plus 50 % maizemeal group lost less weight (P :s; 0.08) during lactation than the ewes that received maizemeal as their main energy source. The study indicated that there was no significant advantage in the live weight change of the ewes during the experimental period, when compared to the group that received wheat bran (control group). In the fourth study the economic advantage of supplementation to SAMM ewes grazing wheat- or oat stubble were studied. Three hundred and sixteen ewes were divided into four flocks, of which two grazed oat stubble and two wheat stubble. Each of these four flocks was again subdivided into four subdivisions of which two subdivisions received supplementation and two none. Four subdivisions received 200 g/d for 83 days, and the other four subdivisions received 200 g/d for 44 days after which it was increased to 300 g/d for 37 days (81 days in total). The ewes were weighed monthly. The final bodyweight of the ewes that received supplementation was significantly higher than those that received none. Over the feeding period, the ewes that received supplementation had a significant lower weight loss in comparison to the ewes that did not receive supplementation. The 42-day weight of the lambs improved significantly due to supplementation, but no significant increase was indicated in the birthweight, weaning weight and survival rate of the lambs whose mothers received supplementation. In the fifth study the influence of supplementary feeding to ewes and creep feeding of their lambs on the production of both the ewes and lambs were studied. One hundred and sixty eight ewes were divided into two groups of 68 and 100 ewes that grazed a 12.9 and 18 ha camp respectively. Each of these ewe groups was subdivided into four groups of which two ewe groups received supplementation and two none. Within each ewe group two groups of lambs received creep feeding and two received none. A two (supplementation of ewes) by two (creep feeding of lambs) factorial design was used. Supplementation was supplied at 200 g/d for the first 69 days and 300 g/d for the next 120 days to ewes. Lambs received an average ofO.58 kg creep feed per day for 96 days. It was concluded that the live weight change (LWC) of the ewes during the experimental period was not affected significantly by creep feeding of their lambs. Ewes that received supplementation maintained higher live weights than their counterparts for most of the feeding period, although final weights at the end of the experimental period did not differ significantly. The average daily gain (ADG) of the lambs whose mothers received supplementation tended to be higher than that of mothers that received no supplementation, while the ADG of the lambs that received creep feeding was significantly higher than the lambs that received none. In the sixth study the carry-over effect of supplementation in the previous year on the production of the ewes in the following year was studied. Three hundred and sixteen ewes were divided into four flocks, of which two grazed oat stubble and two wheat stubble. Each of these four flocks was again subdivided into four subdivisions of which two subdivisions received supplementation and two none. Four subdivisions received 200 g/d for 83 days, and the other four subdivisions received 200 g/d for 44 days after which it was increased to 300 g/d for 37 days (81 days in total). The ewes were weighed monthly. Results indicated that birth status (lambs born per ewes mated) of lambs showed a tendency to increase in 1999 due to supplementation in 1998, while weaning status was not significantly affected. Due to multiple births in the supplemented groups, the birthweight and weaning weight of lambs was negatively affected by supplementation. The study concluded that supplementary feeding in the previous year did not have significant carry-over effects in the following year. However, the effect may have been influenced by the fact that mature animals were used in the study, while the pasture availability during the non-productive stage will also affect possible carry-over effects.
AFRIKAANSE OPSOMMING: 'n Eksperiment is uitgevoer om te bepaal wat die invloed van die frekwensie van byvoeding op die produksie van Suid-Afrikaanse Vleismerino (SAVM) ooie wat koringstoppel bewei, sal wees. Eenhonderd-en-sestig ooie is ewekansig in twee groepe verdeel wat bestaan het uit vier groepe elk. Die agt kampe is vir 138 dae bewei waartydens die ooie ook gelam het. Vier groepe bestaande uit 25 ooie het 'n 17 ha kamp teen 'n weidigtheid van 5.8 ooie/ha bewei en die ander vier groepe bestaande uit 15 ooie het 'n 12 ha kamp teen 'n weidigtheid van 5.0 ooie/ha bewei. 'n Kombinasie energie/proteïen aanvulling in die vorm van 'n lek is aan die ooie beskikbaar gestel. Twee van die groepe het geen aanvullende voeding ontvang nie (kontrole), twee groepe het 200 g/dag/ooi ontvang, twee groepe het 400 glooi elke tweede dag ontvang en twee groepe het 600 glooi elke derde dag ontvang. Die kleinste daling in liggaamsgewig tydens die voerperiode is waargeneem in die ooie wat elke dag sowel as elke tweede dag byvoeding ontvang het, alhoewel geen betekenisvolle verskille tussen dié twee groepe waargeneem is nie. Die kleinste daling in gewig tydens die totale voerperiode is waargeneem in die drie groepe wat byvoeding ontvang het (P < 0.1) terwyl die groepe wat geen byvoeding ontvang het nie (kontrole) die meeste gewig tydens dieselfde periode verloor het. Al die groepe wat byvoeding ontvang het, se liggaamsmassa verandering oor die voerperiode asook die totale periode was betekenisvol beter as die kontrole groep Geen betekenisvolle verskille is gevind by lampersentasie, speenpersentasie, geboortegewig, 42-dae gewig en oorlewing van lammers nie. Daar is bevind dat die byvoeding aan ooie elke derde of elke tweede dag ekonomies geregverdig is en 'n moontlike afname in arbeid- en vervoerkostes mag meebring. In die tweede studie is die invloed van weidigtheid op die samestelling van kanolastoppel en die produksie van SAVM-ooie op hierdie tipe stoppelondersoek. Agt-en-veertig ooie is ewekansig in vier groepe verdeel en het kanolastoppel teen 'n weidigtheid van ongeveer 1.5, 3.5, 5.5 en 7.5 ooie/ha vir 152 dae bewei. Die ooie het geen byvoeding ontvang nie en is elke 14 dae geweeg. Die ooie het gelam vanaf die laaste week in Maart 1997 tot die eerste week in Mei 1997. Die lammers is met geboorte geweeg en daarna elke 14 dae. Stoppelmonsters van die kampe is versamel gedurende die eerste deel van die studie (Januarie en Februarie) asook aan die einde van die studie (April en Mei) deur tien kwadrate per kamp te sny en is daarna ontleed vir droë materiaal (DM), ruproteïen (RP), suur bestande vesel (SBV), neutraal bestande vesel (NBV) en in vitro verteerbaarheid van organiese materiaal (lVVOM). Die liggaamsgewig van die ooie teen 'n weidigtheid van 5.5 ooie/ha het betekenisvol afgeneem, terwyl die ooie teen die weidigtheid van 1.5 ooie/ha toegeneem het in massa. Die ooie teen 'n weidigtheid van 3.5 ooie/ha het die kleinste gewigsverlies getoon (P = 0.01). Die geboortegewig van die lammers is nie betekenisvol deur weidigtheid beïnvloed nie. Die RP-konsentrasie van die stoppel het afgeneem met 'n toename in weidigtheid, terwyl die SBV en NBV -konsentrasie van die monsters betekenisvol hoër was by die hoër weidigtheid. In die derde studie is die byvoeding van rumen inerte vet of stysel aan ome wat koringstoppel bewei ondersoek. Ses-en-vyftig SAVM ooie is ewekansig in vier groepe van 14 elk verdeel en het koringstoppel teen 'n weidigtheid van 4.6 ooielha bewei. Elke groep het daagliks byvoeding teen 250 glooi tydens die laaste ses weke van dragtigheid ontvang, waarna dit vermeerder is tot 360 glooi tydens die eerste vier weke van laktasie. Byvoeding is op Maandae, Woensdae en Vrydae vir 70 dae voorsien. Die RP-konsentrasie van die byvoeding het gevarieer tussen 16.7 % en 19.6 % terwyl die totale verteerbare voedingstof (TVV) konsentrasie gevarieer het tussen 52.0 % en 76.7 %. Daar was geen betekenisvolle verskille (P > 0.05) tussen die liggaamsmassa van die ooie gedurende die laaste ses weke van dragtigheid, die eerste vier weke van laktasie, of die totale voerperiode nie. Die ooie in die 50 % vet plus 50 % mieliemeel groep het minder gewig (P ~ 0.08) gedurende laktasie verloor as die ooie wat mieliemeel as hulle hoof energiebron ontvang het. Die studie het getoon dat daar geen betekenisvolle toename in die liggaamsgewig van die ooie tydens die eksperimentele periode was in vergelyking met die groep wat koringsemels (kontrole) ontvang het nie. In die vierde studie is die ekonomiese voordeel van byvoeding vir SAVM ooie wat koringof hawerstoppel bewei het ondersoek. Driehonderd-en-sestien ooie is in vier groepe verdeel,waarvan twee hawerstoppel en twee koringstoppel bewei het. Elk van hierdie vier groepe is herverdeel in vier subdivisies waarvan twee byvoeding ontvang het en twee geen. Vier subdivisies het 200 gld vir 83 dae ontvang, terwyl die ander vier subdivisies 200 gld vir 44 dae ontvang het, waarna dit verhoog is na 300 gld vir 37 dae ('n totaal van 81 dae). Die ooie is maandeliks geweeg. Die finale liggaamsgewig van die ooie wat byvoeding ontvang het betekenisvol hoër was as die ooie wat geen byvoeding ontvang het nie. Tydens die voerperiode het die ooie wat byvoeding ontvang het 'n betekenisvolle laer gewigsverlies getoon in vergelyking met die ooie wat geen byvoeding ontvang het nie. Die 42-dae gewig van die lammers het ook betekenisvol toegeneem, maar geen verskil is waargeneem in die geboortegewig, speengewig en oorlewingstempo van lammers wie se moeders byvoeding ontvang het nie. In die vyfde studie is die invloed van byvoeding aan ooie en kruipvoeding aan hulle lammers op die produksie van beide die ooie en lammers bestudeer. Eenhonderd-agt-en-sestig ooie is onderskeidelik in twee groepe van 68 en 100 verdeel wat twee kampe van 12.9 en 18 ha respektiewelik bewei het. Elkeen van hierdie groepe is onderverdeel in vier groepe waarvan twee groepe byvoeding ontvang het en twee groepe geen. Binne elke ooi groep het twee groepe lammers kruipvoeding ontvang en twee geen. 'n Twee (byvoeding aan ooie) by twee (kruipvoeding aan lammers) faktoriaal ontwerp is gebruik. Byvoeding aan die ooie is verskaf teen 200 gld vir die eerste 69 dae en 300 gld vir die volgende 120 dae. Lammers het 0.58 kg kruipvoer per dag vir 96 dae ontvang. Daar is bepaal dat die liggaamsgewig-verandering van die ooie gedurende die eksperimentele periode nie betekenisvol beïnvloed is deur kruipvoeding van die lammers nie. Ooie wat byvoeding ontvang het het 'n hoer liggaamsgewig vir die grootste deel van die voerperiode gehandhaaf, alhoewel die finale gewigte aan die einde van die eksperimentele periode nie betekenisvol verskil het nie. Die gemiddelde daaglikse toename (GDT) van die lammers wie se moeders byvoeding ontvang het, het geneig om hoër te wees as die lammers wie se moeders geen byvoeding ontvang het nie, terwyl die GDT van die lammers wat kruipvoeding ontvang het was betekenisvol hoër as die lammers wat geen kruipvoeding ontvang het nie. In die sesde studie is die oordrageffek van byvoeding in die vorige jaar op ooie se produksie in die opvolgende jaar ondersoek. Driehonderd-en-sestien ooie is in vier groepe verdeel,waarvan twee hawerstoppel en twee koringstoppel bewei het. Elk van hierdie vier groepe is herverdeel in vier subdivisies waarvan twee byvoeding ontvang het en twee geen. Vier subdivisies het 200 gld vir 83 dae ontvang, terwyl die ander vier subdivisies 200 gld vir 44 dae ontvang het, waarna dit verhoog is na 300 gld vir 37 dae ('n totaal van 81 dae). Die ooie is maandeliks geweeg. Resultate het aangedui dat die geboortestatus (lammers gebore/ ooie gepaar) van lammers 'n tendens getoon het om toe te neem in 1999 as gevolg van byvoeding in 1998, terwyl speenstatus nie betekenisvol beïnvloed is nie. Byvoeding in 1998 het die geboortegewig en speengewig van lammers verlaag omdat dit 'n groter aantal meerlinggeboortes veroorsaak het. Die studie het bevind dat byvoeding in die vorige jaar nie 'n betekenisvolle oordrageffek in die volgende jaar teweeg gebring het nie. Die resultate mag egter beïnvloed gewees het deurdat volwasse diere in die studie gebruik is, terwyl die beskikbaarheid van weiding tydens die stadium wanneer die ooie nie gereproduseer het nie ook die moontlike oordrageffek kon beïnvloed het.

A fasciolose, causada por Fasciola hepatica, um trematode zoonótico globalmente distribuído, é uma parasitose hepática responsável por importantes perdas económicos na produção ovina. O estudo teve por objetivo determinar a prevalência e possíveis fatores de risco associados à infeção por F. hepatica em ovinos das raças Merina Branca e Merina Preta da região do Alentejo. Para tal, foram analisadas amostras de fezes e sangue colhidas de 423 ovinos da raça Merina Branca e 252 ovinos da raça Merina Preta provenientes de 28 explorações. O exame coprológico, pelo método de sedimentação natural modificada, revelou uma prevalência de 2,1%. A análise serológica, utilizando kits comerciais ELISA (IDEXX© Fasciolosis Verification Test), mostrou uma seroprevalência de 4,4% (IC95%=3,1%-6,3%). Apenas a variável “Pastoreio em regadio” foi identificada como fator de risco. Com base nos resultados, os ovinos das raças Merina Branca e Merina Preta da região estudada apresentaram uma baixa prevalência de F. hepatica; Prevalence and risk factors associated with Fasciola hepatica infection in White Merino and Black Merino sheep Abstract: Fasciolosis, caused by Fasciola hepatica, a globally distributed zoonotic trematode, is a hepatic parasitosis responsible for important economic losses in sheep production. The aim of the present study was to determine the prevalence and possible risk factors associated with F. hepatica infection in White Merino and Black Merino sheep from the Alentejo region. For this purpose, faecal and blood samples collected from 423 White Merino sheep and 252 Black Merino sheep from 28 farms were analysed. The coprological exam, using a modified natural sedimentation method, obtained a prevalence of 2.1%. Serological analysis, using commercial ELISA kits (IDEXX© Fasciolosis Verification Test), revealed a seroprevalence of 4.4% (IC95%=3.1%-6.3%). The only variable identified as a risk factor was “Grazing in irrigated pasture”. Based on the results, White Merino and Black Merino sheep from the studied region showed a low prevalence of F. hepatica.

Alexandra Flocke Untersuchung von Stoffwechselparametern und Lipoproteinen im Blutserum von einlings- und zwillingsträchtigen Merino- und Schwarzköpfigen Fleischschafen im peripartalen Zeitraum Medizinische Tierklinik, Veterinärmedizinische Fakultät, Universität Leipzig Eingereicht im Februar 2012 (94 Seiten, 15 Abbildungen, 8 Tabellen, 199 Literaturangaben, 12 Tabellen im Anhang) Schlüsselwörter: Lipoproteine, Schaf, Stoffwechsel, Endotoxin, Ketose Problemstellung: Der Lipoproteinstatus in der kritischen Phase der Hochträchtigkeit wurde beim Schaf bisher nur wenig untersucht. Die Fähigkeit der Lipoproteine, sowohl Lipide zu transportieren und im Körper umzuverteilen, als auch ihre Rolle in der Endotoxinneutralisation machen sie zu einem wichtigen Parameter in stoffwechselbelasteten Situationen. Das Ziel dieser Arbeit ist es, den Lipoproteinstatus zweier verschiedener Leistungsrassen zu analysieren und zu prüfen, ob und inwiefern peripartal Unterschiede bei Ein- und Zwillingsträchtigkeiten bestehen. Zusätzlich werden die Endotoxine der Tiere bestimmt und mögliche Zusammenhänge mit der Stoffwechselsituation und dem Lipoproteinstatus evaluiert. Tiere, Material und Methoden: Untersucht wurden gesunde einlingsträchtige Merinofleischschafe (MFS1), zwillingsträchtige Merinofleischschafe (MFS2) sowie zwillingsträchtige Schwarzköpfige Fleischschafe (SKF2). Im Abstand von je sieben Tagen wurden den Tieren im Zeitraum von der 5. Woche a.p. bis eine Woche p.p. Blutproben aus der V. jugularis externa entnommen. Aus dem Serum wurden die Konzentrationen von β-Hydroxybutyrat (BHB), Glucose, Freie Fettsäuren (FFS), Triacylglycerol (TG), Cholesterol, Bilirubin, Gesamtprotein (alle Hitachi 912), Insulin (RIA-Kit, Firma IBL, Hamburg), α- und β-Lipoproteine (LIPIDOPHOR All In12®, - ohne prä-β-Lipoproteine), freies Endotoxin (LAL-Test) und Anti-Lipid A Antikörper (ALAAK; ELISA) bestimmt. Ergebnisse: Die α-Lipoproteinkonzentration stieg bei den MFS1 vor dem Ablammen signifikant an und erreichte eine Konzentration von = 208,0 ± 40,1 mg/dl (1. Woche a.p.). Die MFS2 wiesen vor dem Lammen einen konstanten Verlauf zwischen = 180,4 ± 31,1 mg/dl (5. Woche a.p.) und = 196,1 ± 42,1 mg/dl (3. Woche a.p.) auf. Die SKF2 zeigten in der 5. Woche a.p. mit = 206,5 ± 39,0 mg/dl eine größtenteils signifikant höhere Konzentration gegenüber den folgenden Untersuchungszeitpunkten. Bei beiden Rassen ließ sich bei den Zwillingsmuttern nach dem Lammen ein signifikanter Abfall der α-Lipoproteinkonzentration auf = 144,3 ± 46,1 mg/dl (MFS2) bzw. = 170,2 ± 48,8 mg/dl (SKF2) feststellen. Es bestand eine gesicherte Korrelation zu Cholesterol. Die β-Lipoproteinkonzentration lag in der 1. Woche p.p. bei den Zwillingsmuttern (MFS2 und SKF2) signifikant niedriger als vor dem Lammen. Die SKF2 wiesen in der 5. und 4. Woche a.p. signifikant niedrigere Konzentrationen als die MFS1 auf. Gesicherte Korrelationen bestanden zu TG, Cholesterol und ALAAK (MFS1). Für die α-Lipoproteinkonzentration wurde ein Referenzbereich von 144,3 – 208,0 mg/dl und für die β-Lipoproteinkonzentration von 13,6 – 28,0 mg/dl bei Muttertieren der beschriebenen Rassen ermittelt. Ausgenommen die Insulinkonzentration in der 1. Woche a.p. bestanden keine signifikanten Differenzen zwischen MFS1 und MFS2. Im Vergleich der Rassen zeigten sich signifikante Differenzen in der Glucosekonzentration in der 2. Woche a.p. und in der Konzentration von Bilirubin in der 3. und 1. Woche a.p.. Die BHB-Konzentration zeigte einen konstanten Verlauf und stieg bei den MFS1 bis auf = 0,96 ± 0,36 mmol/l eine Woche p.p., bei den MFS2 auf = 0,73 ± 0,35 mmol/l und bei den SKF2 auf = 0,63 ± 0,14 mmol/l eine Woche a.p. signifikant an. Gesicherte Korrelationen bestanden zu FFS (MFS2) und Insulin (MFS2; SKF2). Die Glucosekonzentration zeigte sich bei den Zwillingsmuttern nach zunächst abfallenden Konzentrationen in der Hochträchtigkeit eine Woche p.p. signifikant höher ( = 3,63 ± 0,59 mmol/l; MFS2 und = 3,28 ± 0,42 mmol/l; SKF2) als vor dem Lammen. Gesicherte Korrelationen ließen sich zu FFS (MFS1; MFS2), BHB (MFS2) und dem Zeitpunkt der Untersuchung (MFS2; SKF2) feststellen. Die FFS-Konzentration stieg bei den SKF2 zur 1. Woche a.p. auf = 265 ± 131 μmol/l an, fiel eine Woche p.p. signifikant auf = 128 ± 95 μmol/l ab und korrelierte gesichert mit TG. Die TG-Konzentration fiel von der 1. Woche a.p. bis zur 1. Woche p.p. signifikant auf = 0,19 mmol/l (MFS1; SKF2) bzw. = 0,18 ± 0,05 mmol/l (MFS2) ab und korrelierte mit Gesamtprotein (MFS1), Cholesterol (MFS1; MFS2), β-Lipoproteinen (MFS1; MFS2) und freiem Endotoxin (MFS1). Die Cholesterolkonzentration fiel eine Woche p.p. bei den Zwillingsmuttern signifikant ab, bei den MFS1 war der Verlauf konstant. Die Bilirubinkonzentration stieg eine Woche p.p. signifikant an (MFS1; MFS2) und korrelierte mit der Konzentration von freiem Endotoxin. Das Gesamtprotein sank zum Zeitpunkt des Ablammens hin signifikant ab, erreichte jedoch eine Woche p.p. wieder seine Ausgangskonzentration. Eine gesicherte Korrelation konnte mit ALAAK festgestellt werden (MFS2; SKF2). Freies Endotoxin konnte zu jedem Zeitpunkt der Untersuchungsreihe nachgewiesen werden. Dabei lagen die festgestellten Konzentrationen bei x̃ = 0,06 – 1,30 EU/ml. Eine gesicherte Korrelation fand sich mit der Konzentration der ALAAK (MFS2). ALAAK konnten ebenfalls zu jedem Zeitpunkt in Konzentrationen von x̃ = 22,2 - 56,8 (OD-Wert) nachgewiesen werden. Fazit: Die Lipoproteinkonzentrationen in den einzelnen Gruppen zeigten sich a.p. zunächst regulativ den erhöhten peripartalen Belastungen des Lipidstoffwechsels angepasst, p.p. demonstrierte auch die Abnahme der Lipoproteinkonzentrationen das Ende der lipolytischen Aktivität bei den Schafen. Die vorliegenden Ergebnisse der Stoffwechselparameter lassen auf eine stärkere Belastung der Zwillingsmuttern schließen, welche auch die Lipoproteine mit einbezieht. Freies Endotoxin konnte auch bei gesunden Schafen zwar zu jedem Zeitpunkt nachgewiesen, eine gesicherte Korrelation mit der Lipoproteinkonzentration jedoch nicht festgestellt werden
Alexandra Flocke Evaluation of metabolic parameters and lipoproteins in the serum of merino and blackhead sheep for meat production with one or two lambs in the peripartal period Large Animal Clinic for Internal Medicine, Faculty of Veterinary Medicine, University of Leipzig Submitted in February 2012 (94 pages, 15 figures, 8 tables, 199 references, 12 tablets in the appendix) Keywords: lipoproteins, sheep, metabolism, endotoxin, ketosis Objective: The lipoprotein status in the critical phase of the peripartal period of sheep has been few reviewed. The ability of lipoproteins to transport and redistribute lipids in the organism and their capacity for endotoxinneutralisation makes them a considerable parameter in metabolic bonded situations. The objective of this research is to show the lipoprotein status of two competitive breeds and to proof if and to what extend differences between ewes with one and two lambs exist. Additionally, the endotoxic situation is assigned and possible correlations with the metabolic system and the lipoprotein status are evaluated. Animals, materials and methods: The research contains healthy merino sheep with one lamb (MFS1), merino sheep with two lambs (MFS2) and blackhead sheep with two lambs (SKF2). At intervals of seven days, blood samples out of the V. jugularis externa were taken from the animals in a period from the 5th week a.p. to one week p.p.. Concentrations in the serum of the following parameters were defined: β-hydroxybutyrat (BHB), glucose, free fatty acids (FFS), triacylglycerol (TG), cholesterol, bilirubin, total protein (all Hitachi 912), insulin (RIA-kit, IBL, Hamburg), α- and β-lipoprotein (LIPIDOPHOR All In12® - without pre-β-lipoprotein), free endotoxin (LAL-test) and anti-lipid A antibodies (ALAAK). Results: The concentration of α-lipoproteins of the MFS1 increased significantly before parturition and finally reached 208,0 ± 40,1 mg/dl (1st Week a.p.). The group of MFS2 showed a constant deviation between = 180,4 ± 31,1 mg/dl (5th Week a.p.) and = 196,1 ± 42,1 mg/dl (3rd week a.p.) before parturition. The SKF2 evidenced with a concentration of = 206,5 ± 39,0 mg/dl in the 5th week a.p. a predominantly significant higher result as during following points in time. Both groups carrying twins showed a significant decrease of the α-lipoprotein concentration down to = 144,3 ± 46,1 mg/dl (MFS2) or = 170,2 ± 48,8 mg/dl (SKF2) after parturition. There were statistically reliable correlations between the α-lipoprotein concentration and cholesterol. The β-lipoprotein concentration from both twin pregnant groups had been significantly lower one week after parturition than before parturition. The results of the SKF2 in week 5 and 4 a.p. were significantly lower than those of the MFS1. Reliable correlations could be determined with TG, cholesterol and ALAAK (MFS1). An α-lipoprotein reference range for ewes of the introduced breeds could be determined from 144,3 - 208,0 mg/dl and for β-lipoproteins from 13,6 - 28,0 mg/dl. There were no significant differences between MFS1 and MFS2 except the concentration of insulin in the 1st week a.p.. In the comparison of the different breeds, significant differences in the concentration of glucose (2nd week a.p.) and bilirubin (3rd week a.p. and 1st week a.p.) could be shown. The concentration of BHB showed a constant deviation and increased significantly to = 0,96 ± 0,36 mmol/l (MFS1; 1st week p.p.), = 0,73 ± 0,35 mmol/l (MFS2, 1st week a.p.) or = 0,63 ± 0,14 mmol/l (SKF2, 1st week a.p.), respectively. Reliable correlations existed with FFS (MFS2) and insulin (MFS2; SKF2). The concentration of glucose of the twin pregnant ewes decreased initially before parturition and increased significantly again in the 1st week p.p. ( = 3,63 ± 0,59 mmol/l; MFS2 and = 3,28 ± 0,42 mmol/l; SKF2). Reliable correlations had been determined with FFS (MFS1; MFS2), BHB (MFS2) and the time of sampling (MFS2; SKF2). Concentrations of FFS increased in the group of SKF2 to = 265 ± 131 μmol/l in the 1st week a.p., decreased again significantly to = 128 ± 95 μmol/l one week p.p. and showed a correlation with TG. The TG concentration decreased significantly from one week a.p. to one week p.p. down to = 0,19 mmol/l (MFS1; SKF2) and = 0,18 ± 0,05 mmol/l (MFS2), respectively. A reliable correlation existed between TG and total protein (MFS1), cholesterol (MFS1; MFS2), β-lipoproteins (MFS1; MFS2) and free endotoxin (MFS1). Both twin pregnant groups had a significant decrease in the cholesterol concentration one week after parturition, in contrast the group of MFS1 showed a constant deviation. The concentration of bilirubin increased significantly one week p.p. (MFS1; MFS2) and showed a reliable correlation with the concentration of free endotoxin. Total protein decreased significantly towards parturition, but reached its initial concentration again one week p.p.. A statistically reliable correlation could be determined with ALAAK (MFS2; SKF2). Free endotoxin could be detected at any point of the exploration. The observed concentrations ranged from x̃ = 0,06 – 1,30 EU/ml. A reliable correlation could be shown with the concentration of ALAAK (MFS2). ALAAK was detected as well in concentrations from x̃ = 22,2 - 56,8 (OD-value) in any taken sample. Conclusion: The lipoprotein concentrations in each group appeared a.p. initially adapted to the peripartal bonds of the increased lipid metabolism. After parturition, the decrease in lipoprotein concentrations, too, demonstrated the end of the lipolytic activity of the ewes. The results of the metabolic parameters lead to the conclusion of a stronger liability of the ewes with twins. This is also valid for the lipoproteins. Free endotoxin could be detected in healthy sheep at any time, but a reliable correlation with the concentration of lipoproteins was not visible

Thesis (MScAgric)--University of Stellenbosch, 2001.
ENGLISH ABSTRACT: One of the reasons why meat supply does not meet human demand is that man has concentrated on utilising relatively few animal species as a source of meat. Development of unconventional livestock, such as goats, is advocated as a means of increasing global meat production and consumption. Although South Africa possesses large numbers of domestic ruminants, meat consumption has been limited mainly to sheep and cattle. Goats are used to a lesser extent. This is partly attributed to a general belief that goat meat is inferior to mutton and beef. Numerous contradictions regarding comparative goat and sheep growth, carcass characteristics and meat composition exist in literature. Concepts involved with most of the contradictions includes average daHy gain (ADG), dressing percentage, carcass weight distribution and organoleptic characteristics, especially tenderness, juiciness and flavour, particularly as pertaining to animals reared/grown under intensive/feedlot conditions. Therefore this project was undertaken to obtain more information on the growth, carcass and organoleptic characteristics, as well as meat chemical compositions of Boer goat (BG) kids in comparison with South African Mutton merino (MM) lambs, reared under feedlot conditions. Thirty-two BG kids and 32 MM lambs were used for this investigation. All the animals were castrated and weaned before entering the feedlot. Two pelleted diets (fed to 16 animals/species) with either a low (LE; 8.9 MJ/kg OM) or a high (HE, 10.9 MJ/kg OM) metabolisabie energy level were fed individually, ad lib for either 28 or 56 days. Feed and water intake, ADG and feed conversion efficiencies (FCE) were monitored. During the last week of the feeding trial, 12 BG kids and 12 MM lambs were used to evaluate the digestibility of the two diets. After either 28 or 56 days, the animals were slaughtered and the carcasses dissected into South African commercial cuts. The m. semimembranosus and 8-9-10-rib cut of each carcass was dissected for determination of chemical composition, drip loss, cooking loss, shear force values and colour measurement. The m. gracilis was dissected from the hind leg of the carcass and used for sensory evaluation. MM's had significantly higher AOG's than BG's (e.g. MMHE56: 0.281; BGHE56: 0.162 kg/day). Within a diet there was no difference (P>0.05) in FCE between BG's and MM's and only the MM's FCE differed between the LE and HE diet (e.g. BGLE28: 7.65; BGHE28: 6.37; MMLE28: 8.73; MMHE28: 5.56 kg feed/kg weight gain). BGLE digested dry matter (OM), crude protein (CP) and energy more efficiently and had a higher energy retention than MMLE. The two diets had the same ME-value for the goats, which confirms that goats perform equally well on a lower quality feed as their contemporaries on a higher quality feed. Neither species, nor diet affected nitrogen retention. The BG had a 49 % lower (P<0.01) water intake per kg weight gain than the MM on both the high and low energy diets. Both species had a lower (P<0.01) water intake on the high than on the low energy diet. Furthermore, the BG had a daily water intake of only 171 ml/kgo.75 compared to the 302 ml/kgo.75 of the MM. The weight of the liver, empty stomach, head and feet (as a percentage of empty body weight) were higher in goats than in sheep. The MM's had significantly heavier skins, probably due to wool growth. Both kidney fat and gastro-intestinal tract (GIT) fat increased with age. The animals slaughtered after 56 days in the feedlot had significantly longer and deeper carcasses than their contemporaries slaughtered after 28 days. Within a diet and slaughter age, the MM had significantly broader and deeper carcasses than the BG's. BG's had significantly less weight per unit carcass length, and thus more slender carcasses than MM's. Diet had no significant influence on the carcass weight distribution of the goats. However, MM's had heavier carcasses (LE: 19.87 vs. 15.28 kg; HE: 24.01 vs. 17.05 kg) and proportionally heavier ribs and buttocks than BG's. Neither diet nor slaughter age influenced the proximate analysis of the m. semimembranosus, but MM's had significantly lower moisture values than BG's. In the 8-9-10-rib cuts BG's had significantly more moisture and protein and lower fat and energy values than MM's. OM, fat and energy values increased with an increase in slaughter age in both species. BG's had significantly higher concentrations of 11 of the 18 measured essential amino acids in their 8-9- 10-rib cuts than the MM's. Gaat carcasses had higher Ca, K, Mg, Na and P-Ievels than sheep carcasses, regardless of the diet fed. There was a tendency for goat's m. semimembranosus to have a lower Fe-content than that of sheep. BG carcasses had a lower carcass cholesterol content than that of lamb (66.77 vs. 99.28 mg/100g, respectively). Palmitic (C16:0), stearic (C18:0) and oleic (C18:1 n9) acid comprised the greatest proportions of fatty acids in both the m. semimembranosus and 8-9-10-rib cut for both species. On a LE-diet there was no significant difference between the saturated fatty acid (SFA) to unsaturated fatty acid (UFA) ratio of goat meat and lamb. However, on the HEdiet, lamb had a significantly higher SFA:UFA ratio than chevon (m. semimembranosus: 0.842 vs. 0.689; 8-9-10-rib cut: 1.407 vs. 0.892). Organoleptically, a difference was noted between chevon and lamb. Each has a specific species flavour, which was not influenced by energy level of the diet. BG meat was perceived to be stringier than that of the MM, but there was no significant difference in Warner-Bratzler shear force values. Tenderness declined with age in both species and there was also a tendency for goat meat to be less juicy than lamb. Chevon had a more pronounced aftertaste than lamb. No objective differences could be distinguished between the colour of the cooked chevon and lamb. There was a tendency for fresh lamb to have a higher a*-value (redness) than chevon. Although diet did not influence drip loss, drip loss increased with an increase in slaughter age. Only after 56 days did the MM's m. semimembranosus have a significantly higher drip loss than the BG's (LE: 4.84 vs. 3.43%; HE: 4.72 vs. 3.32%). In the m. semimembranosus of both species, cooking loss increased with an increase in slaughter age. Since diet did not influence the growth, carcass weight distribution, water holding capacity, colour, shear force values or organoleptic qualities of chevon, BG's may be finished on a diet with a lower ME-value than that usually formulated for sheep, without a reduction in performance. This may render a direct economic advantage for BG feedlot finishing. Meat from young feedlot goats is not inferior to that of lamb and it has a higher protein percentage and lower fat percentage. Therefore, it can be considered as a healthy food commodity, especially among low-income groups or people wishing to consume a low calorie diet.
AFRIKAANSE OPSOMMING: 'n Vergelykende analise van nutriëntverbruik en vleiskwaliteisparameters van Boerbokke en Suid-Afrikaanse Vleismerino's: Een van die hoofredes waarom die vraag na vleis die aanbod oorskrei, is die feit dat die mens tot op hede net op 'n paar dierspesies as bron van vleis gekonsentreer het. Benutting van niekonvensionele spesies, soos bokke, kan aanbeveel word ten einde die globale vleisproduksie en -verbruik te verhoog. Ten spyte van die feit dat Suid-Afrika oor baie gedomestikeerde herkouerspesies beskik, is vleisverbruik in die verlede tot hoofsaaklik skape en beeste beperk. Bokke is tot 'n mindere mate gebruik. Dit kan gedeeltelik toegeskryf word aan die algemene siening dat bokvleis ondergeskik aan skaap- en beesvleis is. Verskeie teenstrydighede ten opsigte van vergelykings tussen bokke en skape se groei, karkaseienskappe en vleissamestelling bestaan in die literatuur. Teenstrydige resultate ten bpsigte van gemiddelde daaglikse toename (GOT), uitslagpersentasie, karkasgewigverspreiding en organoleptiese eienskappe (veral taaiheid, sappigheid en geur) van diere afgerond onder intensiewe/voerkraal-toestande, kom veral voor. Hierdie projek is vervolgens uitgevoer ten einde meer inligting ten opsigte van die groei, karkas- en organoleptiese eienskappe, sowel as die chemiese samestelling van die vleis van Boerbok (BB) lammers in vergelyking met Suid-Afrikaanse Vleismerino (VM) lammers, onder voerkraal-toestande grootgemaak, te verkry. Twee-en-dertig BB lammers en 32 VM lammers is vir hierdie studie gebruik. AI die diere is gekastreer en gespeen voor hulle in die voerkraal geplaas is. Twee verpilde diëte (gevoer aan 16 diere/spesie) met óf 'n lae (LE, 8.9 MJ/kg DM) óf 'n hoë (HE, 10.9 MJ/kg DM) metaboliseerbare energievlak is individueel, ad lib, vir óf 28 óf 56 dae aan die diere gevoer. Voer- en waterinname, GOT en voeromsettingsdoeltreffendheid (VOD) is gemonitor. Gedurende die laaste week van die voedingsproef is 12 BB'e en 12 VM's gebruik ten einde die verteerbaarheid van die twee diëte te bepaal. Na 28 of 56 dae is die diere geslag en die karkasse in Suid-Afrikaanse kommersiële snitte verdeel. Die m. semimembranosus en 8-9-10-rib snit van elke karkas is verwyder vir bepaling van chemiese samestelling, drupverlies, kookverlies, skeurwaardes en kleurbepaling. Die m. gracilis is uit die agterbeen uitgehaal en vir sensoriese evaluering gebruik. VM's het betekenisvolle hoër GOT's as BB'e (bv. VMHE56: 0.281; BBHE56: 0.162 kg/dag) gehad. Binne 'n dieet was daar geen verskille (P>0.05) in VOD tussen BB'e en VM's nie en net die VM's se VOD het tussen die LE- en HE-dieet verskil (bv. BBLE28: 7.65; BBHE28: 6.37; VMLE28: 8.73; VMHE28: 5.56 kg voer/kg gewigstoename). BBLE het die droë materiaal (DM), ruproteïen (RP) en energie meer effektief verteer en het 'n hoër energieretensie as VMLE gehad. Die twee diëte het dieselfde ME-waarde vir die bokke gehad, wat bevestig dat bokke net so goed op 'n laer kwaliteit voer presteer as op 'n dieet van 'n hoër kwaliteit. Stikstofretensie is nie deur spesie of dieet beïnvloed nie. Die BB het 'n 49% laer (P<0.01) waterinname per kg massatoename op beide die HE- en LE-dieet gehad. Beide spesies het 'n laer (P<0.01) waterinname op die hoë as die lae energie dieet gehad. Verder het die BB ook 'n daaglikse waterinname van slegs 171 ml/kg075 gehad in vergelyking met die 302 ml/kgO.75van die VM. Die gewig van die lewer, leë pens, kop en pote (as persentasie van leë liggaamsgewig) was hoër vir bokke as vir skape. Die VM's se velle was betekenisvol swaarder, waarskynlik as gevolg van wolgroei. Beide niervet en kanaalvet het toegeneem met 'n toename in slagouderdom. Die diere wat na 56 dae in die voerkraal geslag is, het betekensivol langer en dieper karkasse gehad as dié na 28 dae. Binne 'n dieet en slagouderdom, het die skape breër en dieper (P<0.05) karkasse as die bokke gehad. BB'e het betekenisvol minder gewig per eenheid karkaslengte en dus maerder karkasse as VM's gehad. Dieet-energievlak het geen betekenisvolle effek op die verspreiding van karkasgewig by bokke gehad nie. VM's het egter swaarder karkasse (LE: 19.87 vs. 15.28 kg; HE: 24.01 vs. 17.05 kg) en proporsioneel swaarder ribbes en boude as BB'e gehad. Dieet of slagouderdom het nie 'n betekenisvolle effek op die chemiese samestelling (vog, vet, proteïen en as) van die m. semimembransous gehad nie, maar VM's het laer (P<0.05) vogwaardes as BB'e gehad. In die 8-9-10-rib snit het BB'e betekenisvolle hoër vog en proteïen, maar laer vet- en energiewaardes as VM's gehad. In beide spesies het DM, vet en energiewaardes toegeneem met 'n toename in slagouderdom. BG'e het 'n betekenisvolle hoër konsentrasie in 11 van die 18 gemete essensiële aminosure in hul 8-9-10-rib snitte gehad in vergelyking met VM's. Bokkarkasse het ook hoër Ca, K, Mg, N en P-vlakke as skaapkarkasse gehad, ongeag die dieet. Daar was 'n neiging vir die bok m. semimembranosus om 'n laer Fe-inhoud as dié van die skaap te hê. BB-karkasse het 'n laer cholesterol-inhoud as skaapkarkasse (66.77 vs. 99.28 mg/100g, onderskeidelik) gehad. Palmitiensuur (C16:0), steariensuur (C18:0) en oleïensuur (C18:1n9) het die grootste proporsies van die vetsure in beide die m. semimembranosus en 8-9-10-rib snit van beide spesies uitgemaak. Op 'n LE-dieet was daar geen verskil tussen die versadigde (SFA) tot onversadigde (UFA) vetsuur-verhouding van bok- en skaapvleis nie. Op 'n HE-dieet het skaapvleis egter 'n betekenisvol hoër SFA:UFA-verhouding as bokvleis gehad (m. semimembranosus: 0.842 vs. 0.689; 8-9-10-rib snit: 1.40 vs. 0.892, onderskeidelik). Organolepties is 'n verskil tussen bok- en skaapvleis gevind. Elkeen het 'n spesifieke spesiegeur, wat onafhanklik van die dieet was. Bokvleis is waargeneem as meer veselrig as skaapvleis, maar daar was geen verskil in Warner-Bratzler skeurwaardes nie. In beide spesies het sagtheid afgeneem met 'n toename in ouderdom en daar was 'n neiging vir bokvleis om minder sappig as lamsvleis te wees. Bokvleis het ook 'n meer pertinente nasmaak as lam gehad. Geen objektiewe verskil kon tussen die kleur van gekookte skaapen bokvleis onderskei word nie. Daar was egter 'n tendens vir vars lamsvleis om 'n hoër a*- waarde (rooiheid) as bokvleis te hê. Alhoewel dieet nie 'n invloed op drupverlies gehad het nie, het drupverlies toegeneem met 'n toename in slagouderdom. Slegs na 56 dae het die VM se m. semimembranosus 'n hoër (P>0.05) drupverlies as dié van die BB getoon (LE: 4.84 vs. 3.43%; HE: 4.72 vs. 3.32%, onderskeidelik). In die m. semimembranosus van beide spesies het kookverlies toegeneem met 'n toename in slagouderdom. Aangesien dieet nie 'n effek op die groei, karkasgewig-verspreiding, waterhouvermoë, kleur, skeurwaardes of organoleptiese eienskappe van bokvleis gehad het nie, kan BB'e op 'n dieet met 'n laer ME-waarde as wat normaalweg vir skape geformuleer word, afgerond word, sonder om 'n verlaging in produksie te verwag. Dit mag 'n direkte ekonomiese voordeel vir afronding van BB'e in die voerkraal inhou. Vleis van jong voerkraalbokke is nie minderwaardig teenoor die van skape nie e-n dit het 'n hoër proteren- en laer vetpersentasie. Dus kan bokvleis as 'n gesonde voedselbron gesien word, veralonder lae-inkomste groepe of mense wat 'n lae kalorie-dieet wil inneem.

Includes bibliographical references (leaves 276-2970. Investigations presented involve 18 hour to 5 day old South Australian merino lambs. Some twin lambs were available for comparative studies. Examines the relationship between the strength of ewe-lamb bond and the lamb's ability to follow the mother, the energy availability and usage in the lamb, particularly for locomotion, and the metabolic and cardiorespiratory responses to locomotion.

Thesis (MSc Food Sc (Food Science))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: The aim of this study was to investigate the impact of an extensive (free-range) and intensive (feedlot) production system on the consumer’s intrinsic preference cues (physical attributes, chemical composition, fatty acid profile, aroma, flavour, initial juiciness, sustained juiciness, first bite, residue, instrumental tenderness) for three muscles (Biceps femoris, Longissimus dorsi, Semimembranosus) of Dohne Merino lambs (8 months). Secondly to investigate the effect of natural exercise (grazing, extensive production systems) or restrictive movement (intensive production systems), on the muscle fiber type composition of the same lamb muscles and the subsequent effect on the meat quality characteristics. Intensively raised lambs produced carcasses with a significantly higher dressing percentage, thicker subcutaneous fat layer (13th rib and 3rd/4th lumbar vertebra) and a greater fat ratio (carcass composition). Meat of intensively raised lambs had a higher (p < 0.050) Homo-glinolenic (C20:3n6), Eicosapentaenoic (C20:5n3), Docosapentaenoic acid (C22:5n3) content and n3:n6 ratio. Extensively reared lambs had a higher (p < 0.050) slaughter weight, cold carcass weight and the meat of these lambs had a higher myoglobin content. Results of this study indicate that intensively reared lambs produced meat with more favourable sensory characteristics compared to the extensive production system as well as a significant increase in sensory tenderness for Biceps femoris muscle. Overall the Biceps femoris muscle was the muscle that was primarily affected by the treatment (production systems). The Biceps femoris from intensively raised lambs contained significantly more intramuscular fat and type IIB muscle fibers whereas the Bicpes femoris of the lambs from the extensive production system contained more (p < 0.050) insoluble collagen and type I muscle fibers. During texture profile analysis (instrumental tenderness test) the Longissimus dorsi and Semimembranosus of extensively raised lambs required a higher (p < 0.050) compression force during the first cycle of compression, indicating that these muscles are tougher. The results of this study provided valuable insight into the impact of production systems on lamb meat quality and that the application of intensive production systems will increase the sensory characteristics of the selected muscles from Dohne Merino lambs, especially the tenderness of the Biceps femoris, which has a high retail value. On the other hand health conscious consumers will prefer extensively produced meat due to the favourable n3:n6 ratio, intramuscular fat content and the presences of less visible fat (subcutaneous).
AFRIKAANSE OPSOMMING: Hierdie studie was tweedoelig en is uitgevoer op die Biceps femoris, Longissimus dorsi en Semimembranosus spiere van Dohne Merino lammers (8 maande oud). Die eerste doel van die studie was om te bepaal wat die effek van ‘n ekstensiewe (weiding) en intensiewe produksie sisteem sal wees op vleis verbruikers se algemene kwaliteit voorkeure (fisiese eienskappe, chemiese samestelling, vetsuur profile, aroma, smaak, sappigheid, taaiheid,). Tweedens om te bepaal tot watse mate natuurlike oefening, verkry deur weiding asook beperkte beweging as gevolg van voerkraal omstandighede, die spier vesel tipe samestelling sal verander en die direkte impak van die samestelling op kwaliteit eienskappe van vleis. Lammers van die intensiewe produksie sisteem het ‘n betekenisvolle verhoging in uitslagpersentasie, onderhuidse vet dikte (13de rib en 3de/4de lende werwel) en vet ratio (karkas samestelling) getoon. Die vleis van die lammers het meer (p < 0.050) C20:3n6, C20:5n3 en C22:5n3 vetsure bevat asook ‘n hoër n3:n6 ratio gehad. Lammers van die ekstensiewe produksie sisteem het ‘n betekenisvolle hoër slag en koue karkas gewig gehad. Die vleis van die lammers het meer (p < 0.050) mioglobien bevat as intensiewe lammers. Resultate van die studie dui aan dat die vleis van lammer van die intensiewe produksie sisteem meer gunstige sensories karakteristiek produseer in vergelyking met lammers van die ekstensiewe produksie sisteem, asook ‘n betekenisvolle verhoging in sensoriese sagtheid van die Biceps femoris spier. Die Biceps femoris was die spier in die studie wat die meeste geaffekteer was deur die behandeling (produksie sisteme). Die Biceps femoris spier van intensiewe lammers het meer intramuskulêre vet en tipe IIB spier vesels bevat teenoor die Biceps femoris van ekstensiewe lammers wat meer onoplosbare kollageen en tipe I spier vesels bevat het. Gedurende die tekstuur profiel analise (instrumentele sagtheid toets) het die Longissimus dorsi en Semimembranosus van ekstensiewe lammers a hoër kompressie krag vereis, wat aandui dat die spiere taaier is as die ooreenstemmende spiere van intensiewe lammers. Die resultate van die studie voorsien ons met waardevolle insig in die inpak van verskeie produksie sisteme op die kwaliteit van lams vleis. Die afleiding kan gemaak word dat die implementering van intensiewe produksie sisteem die sensoriese kwaliteit van die spiere van Dohne Merino lammers verbeter, veral die sagtheid van die Biceps femoris spier, wat ‘n hoë kommersiële waarde het. Laastens, gesondheidsbewus verbruikers sal verkies om vleis te koop van ekstensiewe lammers weens die gunstige n3:n6 ratio, spier vetinhoud en die minder sigbare vet (onderhuidse vet) op die vleis.

‘Targeted selective treatment’ (TST) is the concept of targeting anthelmintic treatments to individual animals that will benefit from treatment, rather than giving whole flock treatments. The purpose of TST is to delay the onset of anthelmintic resistance in nematode populations. Two key issues that have delayed the utilization of TST are; a) the need for a convenient and reliable method for identifying animals less likely to cope with nematode challenge; and b) the risk that some animals will be left with nematode burdens sufficient to cause sub-clinical disease that compromises production and welfare. To investigate these issues, this thesis tested the hypothesis that body condition can indicate the ability of mature sheep to better cope with nematodes (and therefore remain untreated), thereby providing a convenient selection method for TST strategies in a Mediterranean climate, where Trichostrongylus spp. and Teladorsagia circumcincta are the predominant nematode parasites. The risk of loss of production and welfare by leaving some animals untreated was examined by modelling simulations, based on data derived from field studies, and on computer models, with various proportions of the flock remaining untreated to determine the threshold proportions of sheep to leave untreated. This approach indicated the trade-offs between delaying anthelmintic resistance with production loss and animal welfare associated with nematode burdens resultant from leaving animals untreated. Further to this, an investigation of Western Australian sheep producers (farmers) identified factors associated with the acceptance of sustainable nematode control practices, especially those likely to facilitate the adoption of TST and act as the basis for the development of communication strategies to producers. The findings of this research provide evidence-based recommendations for the sheep industry regarding sustainable nematode management strategies utilising TST in Mediterranean environments and the facilitation of adoption of TST strategies. In conclusion, the general hypothesis was shown to be applicable, that a body condition score-based TST control program can be practical to implement and will delay anthelmintic resistance in adult Merino sheep in a Mediterranean environment.

The aim of this study was to evaluate the Small Ruminant Nutrition System (SRNS) model’s performance predictions for lambs under South African conditions using growth and body composition data of early- (Dorper) and late-maturing (South African Mutton Merino), indigenous sheep breeds. The Cornell Net Carbohydrate and Protein System (CNCPS) biological model has consistently been modified to include recent information. This has led to the development of the SRNS model, but up to now the SRNS model has only been validated with European sheep breeds under European conditions. Thirty two Dorper, 16 male and 16 female lambs, and 36 South African Mutton Merino, 18 male and 18 female lambs, were fed a grower diet for the experimental period of 60 days. Three groups of lambs of each breed were slaughtered as the lambs reached pre-determined target weights. The first group of 24 animals (slaughter group 1) was slaughtered at the onset of the experiment at a live weight of 20 kg. With the second group (slaughter group 2) the South African Mutton Merinos were slaughtered at an average weight of 35 kg and the Dorpers at an average weight of 30 kg. The last group (slaughter group 3) had an average weight of 50 kg for the South African Mutton Merinos and 40 kg for the Dorpers at slaughter. Using the data from this trial, predictions of the average daily gain (ADG), feed intake (DMI), empty body gain and the composition of the empty body gain were used to evaluate the model. The animals were divided into three slaughter groups, based on growth stage, for the determination of body composition data. Energy value of gain (EVG), fat and protein content on a shrunk and empty body weight basis were compared with the corresponding values predicted by the SRNS. Growth composition of the lambs was determined by dividing them into two growth periods. Average daily gain and DMI were evaluated in the experiment, and results compared to the mean ADG and DMI predictions obtained from the SNRS model. Two different equations were compared to estimate EVG and two sets of coefficients were also compared for the EVG. Five different equations were compared to estimate the efficiency of conversion of metabolisable energy (ME) to net energy (NE) for gain, kg. The correction factor to adjust for the increase in the size of the visceral organs as nutrient intake increases and the coefficient for the effect of gender on maintenance requirements were tested for relevance of use in the SRNS. Overall, based on these evaluations it appears that the original SRNS model gave the best predictions when compared to any of the modifications tested. With regards to ADG the model over-predicts the requirements of the lambs in the early growth stage and under-predicts the requirements of the lambs in the later growth stage. The DMI predictions that were made using the original SRNS were accurate. The evaluation of the SNRS predictions in relation to the composition of gain indicated that this model over-predicted both the fat and the protein content of gain. The predictions were accurate, however the precision was low. The low precision was probably due to the lack of variation in the measured range of fat and protein content of gain. Before field application further studies and adjustments to the SRNS model is required, especially with regard to predictions on the fat and protein content of gain and over or under predictions of ADG during different growth stages of Dorper and South African Mutton Merino lambs.
Dissertation (MSc)--University of Pretoria, 2013.
gm2014
Animal and Wildlife Sciences
unrestricted

Sheep farming is practiced extensively in South Africa for its significant contributions to the livestock, wool and meat industries. The sheep farming sector in the country has approximately 13,800 farmers with commercial and communal sheep farmers making up 58 percent and 42 percent of the entire work force (Directorate of Agricultural Information Services, 2008). An estimate of 28.8 million sheep and flock size ranging between ≤ 50 and ≥ 1800 exist in various South African provinces. Although the national herd size is unevenly distributed provincially most of the herds are found in the Eastern Cape (30 percent) followed by the Northern Cape (25 percent), Free State (20 percent) and the Western Cape (11 percent) respectively (Agriculture, Forestry and Fisheries, 2011). Over twenty indigenous and locally developed sheep breeds are managed where about 69 percent of the land area is available for their grazing nation-wide (Campher et al., 1998; Palmer and Ainslie, 2006). Common among the indigenous breeds are the Afrikaner, Blackhead Persian, Blackhead Speckled Persian, Blinkhaar Ronderib, Damara, Karakul, Namaqua Afrikaner, Pedi, Redhead Persian, Redhead Speckled, Swazi and Zulu. The locally developed breeds include Dorper, Van Rooy and Merinos. The local breeds developed from Merinos consist of the Afrino, Dormer, Dohne Merino and South African mutton Merino (Hammond, 2000; Pranisha, 2004; Hinton, 2006; Sorma et al., 2012). All these sheep breeds are best suited for providing by-products such as wool, meat, hide, milk or a combination of products (Dave and Meadowcroft, 1996; Jensen, 2009). The indigenous and locally developed sheep were bred to meet the growing demand for its by-products (Peters et al., 2010). Expectedly, sheep farmers therefore, make use of the products from these sheep as a means of livelihood and sustenance of a viable local society (Cloete and Olivier, 2010).

This thesis presents a comprehensive set of results, obtained through an innovative experimental methodology, that have important and extensive implications for the fields of integrative biology and complex systems. The main objective of the thesis is to study the inter-individual interactions involved during the initiation and coordination of movement in gregarious vertebrates, and in particular in the sheep Merinos d’Arles (Ovis aries). Key questions are, when an individual initiates a movement, what information is taken into account by conspecifics, how is this information spread across the group, and what mechanisms underlie the collective decision processes? To answer these questions, we created an experimental paradigm to trigger, in a standardized way, the movement of trained individuals that were then placed in a group of naïve conspecifics. Using two types of stimuli, a sound (public) and a vibration (private), we could evaluate the individual response of followers, and the effect of the behavioural state on this response. An additional set of experiments also provided recordings of spontaneous initiations of movement.

Our results suggest that every individual in a group can initiate a collective movement. Our quantitative analysis then showed that, in Mérinos sheep, the individual decision to follow depends on a double mimetic effect; individuals take into account both the number of already departed individuals and the number of individuals which have not yet departed. A comparison between three experimental situations reveals that the decision rule is unique and that the behavioural state of potential followers only slightly affects the collective dynamics.

Our approach, a combination of experimentation and modelling, provides original results that contribute to the understanding of individual and collective decision-making processes, and of the mechanisms involved during collective movement. The experimental paradigm that was proposed here, and the mathematical tools that were used, open interesting perspectives for new experimental studies and for the generalization of the behavioural rules exposed in this thesis.

Doctorat en Sciences
info:eu-repo/semantics/nonPublished

Methodology is developed for Quantitative Trait Loci (QTL) analysis in F₂ and backcross designed experiments between outbred lines using a mixed model framework through the modification of segment mapping techniques. Alleles are modelled in the F₁ and parental generations allowing the estimation of individual additive allele effects while accounting for QTL segregation within lines as well as differences in mean QTL effects between lines.

Initially the theory, called F₁ origin mapping, is developed for a single trait scenario involving possible multiple QTL and polygenic variation. Additive genetic variances are estimated via Restricted Maximum Likelihood (REML) and allele effects are modelled using Best Linear Unbiased Prediction (BLUP). Simulation studies are carried out comparing F₁ origin mapping with existing segment mapping methods in a number of genetic scenarios. While there was no significant difference in the estimation of effects between the two methods the average CPU time of one hundred replicates was 0.26 seconds for F₁ origin mapping and 3.77 seconds for the segment mapping method. This improvement in computation efficiency is due to the restructuring of IBD matrices which result in the inversion and REML iteration over much smaller matrices.

Further theory is developed which extends F₁ origin mapping from single to multiple trait scenarios for F₂ crosses between outbred lines. A bivariate trait is simulated using a single QTL with and without a polygenic component. A single trait and bivariate trait analysis are performed to compare the two approaches. There was no significant difference in the estimation of QTL effects between the two approaches. However, there was a slight improvement in the accuracy of QTL position estimates in the multiple trait approach. The advantage of F₁ origin mapping with regard to computational efficiency becomes even more important with multiple trait analysis and allows the investigation of interesting biological models of gene expression.

F₁ origin mapping is developed further to model the correlation structure inherent in repeated measures data collected on F₂ crosses between outbred lines. A study was conducted to show that repeated measures F₁ origin mapping and multiple trait F₁ origin mapping give similar results in certain circumstances. Another simulation study was also conducted in which five regular repeated measures where simulated with allele breed difference effects and allele variances increasing linearly over time. Various polynomial orders of fit where investigated with the linear order of fit most parsimoniously modelling the data. The linear order of fit correctly identified the increasing trend in both the additive allele difference and allele variance. Repeated measures F₁ origin mapping possesses the benefits of using the correlated nature of repeated measures while increasing the efficiency of QTL parameter estimation. Hence, it would be useful for QTL studies on measurements such as milk yield or live weights when collected at irregular intervals.

Theory is developed to combine the data from QTL studies involving F₂ and backcross designed experiments. Genetic covariance matrices are developed for random QTL effects by modelling allele variation in the parental generation instead of the offspring generation for an F₂ and backcross between outbred lines. The result is a general QTL estimation method called parental origin mapping. Phenotypes and genotypes from such a study involving Romney and Merino sheep are analysed providing evidence for a QTL affecting adult and hogget fibre diameter.

By coupling these new methods with computer software programs such as ASREML, F₁ origin mapping and parental origin mapping provide powerful and flexible tools for QTL studies with the ability to efficiently handle single traits, multiple traits and repeated measures.

"May 2002"
Includes bibliographical references (leaves 148-164)
xi, 164 leaves : ill. ; 30 cm.
Describes a series of novel experiments designed to enhance our understanding of nutrient utilisation for growth of wool and the whole body.
Thesis (Ph.D.)--University of Adelaide, Dept. of Animal Science, 2002

Primary wool follicles are initiated in the skin of sheep foetuses at approximately day 50 of gestation as the result of complex reciprocal molecular interactions between the mesenchyme and overlying epithelium. The lifetime wool production potential and fibre diameter of the Merino sheep is dependent on the total number of follicles initiated in utero. Understanding the molecular events that surround primary wool follicle initiation may provide approaches to enhance or manipulate this process in order to maximise the profitability of wool production enterprises. In order to study the morphological and molecular changes occurring during early wool follicle development, a foetal skin series spanning primary follicle initiation was generated. Foetal skin was sampled from the shoulder, midside and rump of four foetuses at 8 time points between day 43 and day 68 of gestation. Histological characterisation of the shoulder skin samples revealed that primary epidermal placodes emerged at around day 53, dermal condensates were visible from day 57 and downgrowth of the follicle began at day 68. An equation relating age of the foetus (day of gestation post AI) and crown-rump length, specific to Merino foetuses, was developed for use in future studies of this nature. Molecular markers of fibroblast migration, epidermal and dermal stem cells and cell proliferation were selected to test the hypothesis that dermal condensates are initiated at discrete sites beneath the epidermis as a result of a combination of migration and arrangement of multipotent pre-papilla cells. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) analysis of RAC1 and RHOa (migration markers), β1-integrin and alkaline phosphatase (stem cell markers), proliferative nuclear cell antigen and cyclinB1 (proliferation markers), patched-1, selected tumor necrosis factor (TNF) signalling molecules and eleven reference genes was conducted using midside and rump skin samples from each of four foetuses from the 8 time points. geNorm analysis of the reference and target genes revealed that the migration markers RAC1 and RHOa along with GAPDH were the most stably expressed genes in this sample series. Significant changes in mRNA expression were detected for β1-integrin, alkaline phosphatase, patched-1 and the TNF members EDA, EDAR, TROY and TRAF6. Many of these significant differences in expression coincided with key morphological events. Significant differences in expression were also detected between the midside and rump samples for numerous transcripts. Laser capture microdissection (LCM) was implemented for analysis of the target transcripts within particular structures of foetal sheep skin. Frozen tissue sectioning, staining, LCM, RNA extraction and cDNA synthesis were optimised for qRT-PCR analysis of endogenous controls and selected TNF transcripts. Several RNA extraction methods and reverse transcription approaches were trialled to ensure optimum extraction and reverse transcription efficiency for this tissue type. Exogenous mRNA transcripts were also incorporated prior to RNA extraction and reverse transcription to track reaction efficiency between samples. A comparison of different slide types revealed that laser pressure catapulting from membrane slides was an absolute requirement for foetal skin tissue studies. Follicle regions (including the epidermal placode and dermal condensate) and the adjacent non-follicle regions were laser captured from foetal skin, and the mRNA expression levels of patched-1 and selected TNF members was compared. Preliminary qRT-PCR analysis using this technique revealed that EDAR, TROY and PTCH1 mRNA levels were higher in the follicle regions than the non-follicle regions. The TNF signalling pathway appears to play an important role in primary wool follicle initiation and patterning at different sites on the body. Spatial differences in expression of some of these regulators may be involved in initiating different types of follicles. The molecular events surrounding primary wool follicle initiation also show a high degree of conservation between sheep, humans, and mice. Considering the high degree of DNA sequence conservation as well as the histological, signalling and cycling similarities between sheep and humans, sheep may represent a better model for the study of human hair follicle initiation and disease than the currently used mice and rat models.
http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1523639
Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2010

The Elsenburg Merino flock has been divergently selected for the ability of ewes to rear multiple offspring since 1986. Updated genetic trends for reproduction are reported for the Elsenburg Merino resource flock. The objective was to determine whether genetic trends estimated previously for the Elsenburg Merino Resource flock changed significantly with the introduction of genetic material from the industry to the high (H) line. All analyses included the full pedigree file, consisting of 6547 individuals. Heritability estimates were 0.08 ± 0.02 for number of lambs weaned and 0.11 ± 0.02 for corrected weight of lamb weaned. The ewe permanent environment variance was estimated at 0.09 ± 0.02 and 0.11 ± 0.02 for number of lambs weaned and for corrected weight of lamb weaned, respectively. Genetic trends for the H and low (L) lines were divergent (P < 0.05) for all reproduction traits during the period prior to the observed breakpoints. Progress for number of lambs weaned in the H line stabilised after 1999 while a decline in response for weight of lamb weaned in the H line occurred after 2003. The change points may result from reduced selection intensity during the formation of reciprocal crossbred lines, or the introduction of unrelated industry sires in the H line. The pedigree was analysed and inbreeding trends computed for the H and L lines with the aim to test the significance of inbreeding within the lines. The software packages used for the statistical analyses were ENDOG v4.8 and POPREP web analysis software. The average inbreeding coefficients (F) were 1.47% and 0.73% for the divergently selected H and L lines. The rate of inbreeding (ΔF) per generation was 0.5% for the H line and 0.6% in the L line. The overall rates of inbreeding per generation were different in the H and L lines but within acceptable levels. The L line, however, showed an unwanted recent increase in inbreeding that will need to be considered in future. Since 2003, part of the Elsenburg Merino breeding flock was subjected to structured reciprocal within-breed crossing. Lamb survival traits and ewe reproductive performance of purebred (H and L) and reciprocal crosses (HxL and LxH) were evaluated using least squares analyses. Levels of heterosis were also assessed. The mean survival of the two crossbred lines was notably superior to the midparent value in absolute terms, although the contrast did not reach statistical significance (P = 0.098). Further research is required to establish whether this within breed heterosis for lamb survival can be exploited to decrease lamb losses. Reproduction, number of lambs born (NLB) and number of lambs weaned (NLW) in the H line was higher than in the L line (P < 0.05) while the two crossbred lines were intermediate and different from both the H line and the L line (P < 0.05) from the analyses of annual reproduction and overall “lifetime” reproduction across three lambing opportunities. Individual heterosis for annual reproduction was estimated at 2.2% for NLB, 13.8% for NLW and 8.5% for corrected weight of lamb weaned (TWW), with the estimate for NLW reaching significance (P < 0.05). Corresponding estimates for total production over three lambing opportunities were 8.7% for TNLB, 19.1% for TNLW and 13.8% for TTWW, with the estimate for NLW reaching significance (P < 0.05). Ten RAPD markers were used to study molecular divergence between the H and L lines. Phenotypic data on the lifetime reproduction of ewes born in 1999 and 2000 indicated that reproduction in the H line ewes was markedly higher than that of L line contemporaries (P < 0.01). The RAPD assay, conducted on 15 ewes from each line, used eight primers and produced 87% polymorphic loci. The mean coefficient of genetic differentiation between lines (Gst) was estimated to be 0.25. In conclusion, the H and L lines were shown to be divergent for genetic trends and levels of inbreeding. The derived estimates of heterosis may also be used to infer divergence between the lines and significant molecular divergence proven using RAPD assays.
Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.

Copies of author's previously published works inserted. Includes bibliographical references (leaves 222-258). Researches the occurence and inheritance of isolated melanin pigmented wool fibres and macroscopic pigmentation in Merino sheep. The mode of inheritance of key indicators (pigmented leg fibres and pigmented birthcoat halo-hair) of isolated pigmented wool fibres is investigated and confirms an association between isolated pigmented fibres in hogget Merino fleeces and the presence and degree of types of remnant macroscopic fibre pigmentation. These associations could be exploited to improve wool quality in relation to dark fibre risk.

Bibliography: leaves 325-341. Skin and fleece measurements were recorded at different ages for both male and female sheep from the Turretfield Merino Resource Flock and used to estimate the heritability of each trait and the phenotypic and genetic correlations among and between the skin and fleece traits. Generally, the heritability of each trait was high, which indicates that both the fleece and skin traits should respond well to selection.

"October 2005"
Bibliography: leaves 171-200.
xv, 200 leaves [14] : ill. 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Thesis (Ph.D.)--University of Adelaide, School of Agriculture and Wine, Discipline of Animal Science, 2005