Dissertations / Theses on the topic 'Sheep – Feeds'

Includes bibliographical references (leaves 290-309) Investigates aspects of the intake and utilization of barley grain and grain legume supplements by sheep fed low quality pasture hay and when grazing mature summer pastures.

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.

Two experiments determined the effects of flaxseed supplementation on reproductive parameters in sheep. In experiment one, 240 multiparous Rambouillet ewes were assigned to one of two treatments: basal ration alone or basal ration with a Flaxlic® Sheep Tub offered over 35 days. Serum was collected weekly for progesterone (P4). Flaxseed supplementation did not improve progesterone concentration or reproductive parameters (P ≥ 0.26). In experiment two, 120 Rambouillet ram lambs were assigned to one of two treatments: basal ration alone or basal ration with a Flaxlic® Sheep Tub offered over 112 days. Scrotal circumference measurements, serum for testosterone, and semen were collected on day 84 and 112. Day effects were found for select semen measurements, testosterone, weight, and scrotal circumference (P ≤ 0.05). There was no effect of treatment on testosterone concentration (P = 0.99) or any semen quality characteristics (P ≥ 0.33). Overall, tub supplementation did not alter reproductive ability.

Four studies were conducted to investigate some factors affecting milk fatty acid composition of dairy ewes. The first study was performed to determine the influence of freezing temperatures and storage time on ovine milk composition and cheese making. The other three experiments were conducted to examine the effects of dietary added fats with different profiles of fatty acids from canola, sunflower and flaxseeds on animal performance, nutrient utilization, milk yield and cheese making. The main emphasis was on fatty acid composition, particularly CLA and Omega-3 fatty acids, in milk and cheese. Results showed that: (1) feeding up to 8% of canola, sunflower and flaxseed had no adverse effects on dry matter intake and total tract digestibilities of dry matter, neutral detergent fiber, acid detergent fiber and crude protein, while the digestibilities of fatty acids and gross energy were increased with oilseed supplementation; (2) feeding flaxseed to lactating ewes up to 260g/ewe/d increased milk yield by up to 8.4%, and fat content by up to 14.3% without adversely affecting other milk components or cheese yield and composition; (3) Oilseed supplementation increased milk concentrations of long-chain and unsaturated fatty acids in the expenses of short-chain, medium-chain and saturated fatty acids. The concentrations of CLA and Omega-3 fatty acids were also increased by oilseed supplementation; (4) the manipulated fatty acids profiles can be reflected in cheese; (5) good quality cheese can be produced from ovine milk frozen at -15°C and -25°C for up to 6 months without influencing cheese content of fat and protein and fatty acid composition.
In conclusion, ovine milk with nutritionally healthy characteristics can be produced by feeding ewes diets with oilseeds, and freezing storage of milk for up to 6 months at -15°C or -25°C does not significantly affects milk composition including fatty acid composition. The characteristics of milk can be reflected in cheese.

This study was designed to provide information on some of the factors affecting voluntary consumption and digestibility of forages by sheep. A wet sieving procedure was used to determine particle size distribution in the reticulo-rumen, omasum and abomasum of sheep fed 100 % prebloom alfalfa or 100 % second-cut Altai wild ryegrass hays or mixtures of these with tall wheatgrass or Altai wild ryegrass straws. The study also compared second-cut Altai wild ryegrass and prebloom alfalfa as components in an all forage diet for sheep. Each diet was fed ad libitum to eight Romanov x Western whiteface wether lambs weighing 22 to 25 kg during the intake and digestibility trials. For the determination of particle size distribution, the animals were slaughtered at 12, 24, 36, and 48 hours after feed removal and the contents of the reticulo-rumen, omasum and abomasum sampled. Five different methods of describing digesta particle size distribution were compared as to their ability to predict voluntary intake and digestibility of the forages by sheep. The best method for expressing particle size distribution in the reticulo-rumen in terms of ability to predict dry matter digestibility (DMD) was the proportion of soluble dry matter in total dry matter (PSDM). A significant (P< 0.05) correlation (r = 0.84) between PSDM and dry matter digestibility, 12 hours after feed removal was obtained. PSDM in omasal digesta 24 hours after feed removal was also highly correlated with DMD and energy digestibility (r = 0.97, 0.91, respectively). Very high correlations were obtained between PSDM in abomasal digesta 24 hours after feed removal and digestibility of cellulose, NDF and ADF (r = 0.99, 0.97 and 0.97 respectively). The proportion of particles less than 1mm to the total particles (PIP) in the reticulo-rumen gave the most consistent correlations with intake of dry matter and energy. Voluntary intake of dry matter by the animals on the alfalfa-based diets were significantly higher (P< 0.05) than those on the second-cut Altai wild ryegrass-based diets. However, the apparent digestibility coefficients of the proximate fractions in the Altai wild ryegrass diets were significantly higher (P< 0.05) than those of diets containing alfalfa. Daily intake of digestible energy by animals on 100 % alfalfa was not significantly different from that of animals on 100 % second-cut Altai wild ryegrass. The difference between their respective combinations with tall wheatgrass and Altai wild ryegrass straws were also not significant. It was concluded that PIP and PSDM are indeces based on biologically significant fractions and may therefore have greater relevance than purely mathematical or statistical descriptions of particle size distribution in digesta. In this regard, the relationship between PSDM and digestibility and, PIP and intake are consistent with published theory and can be used in mathematical models to examine control processes in feed intake, rate of passage and digestion. The study also indicated that second-cut Altai wild ryegrass harvested at the prebloom stage can be used as a substitute for alfalfa in an all-forage diet for winter feeding of sheep.
Land and Food Systems, Faculty of
Graduate

Tydens embrio ontwikkeling groei weefsel deur selvermeedering, maar soos wat soogdiere volwassendheid nader vind groei net plaas deur sel vergroting. Volwassenheid word beskou as wanneer spiergroei ‘n maksimum bereik. Groei sluit die neerlegging van vet in, maar spiermassa is van primêre belang. Die groeikurwe (Fig 1) waarin massatoename teenoor ouderdom vergelyk word, volg ‘n sigmoidale kurwe (Owens et al, 1993). Onder ideale toestande is die groeitempo van lammers relatief konstant van kort na geboorte totdat die helfte van volwassemassa bereik word, waarna dit geleidelik afneem tot volwassenheid (Black, 1983). Die afname in groeitempo begin gewoonlik met die bereiking van puberteit (Owens et al, 1993).

Zugl.: Berlin, Freie Univ., Diss., 2007
"The aim of this work was to characterize the HCO₃⁻ Transport of the omasum and to look for possible alterations after the change from hay to concentrate feeding."

Linseed meal (LSM) was fed to ovariectomized ewes exposed to estradiol 17-? (E2) implants over time, and LSM was supplemented to beef cows during late gestation and early lactation to evaluate the estrogenic potential of the phytoestrogen secoisolariciresinol diglycoside (SDG) found in LSM. Forty-eight ovariectomized ewes were fed a diet containing 12.5% LSM for 0, 1, 7, or 14 d and implanted with estradiol-17? (E2) for 0, 6, or 24 h before tissue collection. Uterine cellular proliferation, vascularity, and the expression of the angiogenic factors and their receptors were recorded. There was an interaction of LSM and E2 on uterine mass (P = 0.05). At 24 h of E2 exposure, proliferation was reduced (P < 0.001) when ewes were fed for 14 d compared to being fed 0 or 1 days. There was a LSM x E2 interaction (P ? 0.03) on VEGF receptor-2 (KDR) and hasicfihrohlast growth factor receptor (FGFR2) decreasing by 24 h E2 exposure. Exposure of LSM and E2 may impact the estrogenic response of sensitive tissue. Two studies were conducted to examine the effects of supplementing beef cows with LSM during late gestation or early lactation on calf growth and development. In Experiment 1, multiparous cows received either LSM or a control (CON) supplement (approximately 10% diet dry matter) for the last 60 d of gestation. Offspring weights, ADG, heifer age at puberty, conception percentage and steer carcass characteristics were recorded. In Experiment 2, multiparous cows received LSM or CON supplements (approximately 10% diet dry matter) during the first 60 d of lactation, and only heifer calf development performance was observed and recorded. Heifer calf weight, average daily gain, and attainment of puberty were assessed. For both experiments, birth weight, weaning weight and ADG were not affected (P > 0.31) by LSM supplementation. While final body weights were heavier (P = 0.04) for steer calves in Experiment 1, there was no effect (P = 0.09) of supplementation on carcass characteristics. In Experiment 1 and 2, attainment of puberty in heifer calves was not influenced (P > 0.58) by supplement type. Linseed meal supplementation during late gestation or early lactation does not appear to have a negative impact on calf growth, onset of puberty in heifer calves, or steer carcass quality, implicating that it may make a good supplement choice in cattle.

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.

Experiments were conducted to investigate the effect of reducing dietary anion-cation balance (AC-balance), defined as meq $ sp circ$(Sodium + Potassium)-(Chloride + Sulfur) S, on calcium (Ca) metabolism. Reducing the dietary AC-balance from +314 to $-22$ (meq kg$ sp{-1}$ dry matter (DM)) did not affect plasma Ca level but reduced Ca retention mainly due to a 10-fold increase in urinary Ca excretion with similar rate of apparent absorption. It also decreased urine pH and titratable acidity. The response to induced hypocalcemia created by the infusion of 4.6% EDTA solution revealed that reducing dietary AC-balance from +354 to +37 (meq kg$ sp{-1}$DM) did not affect the volume of the compartment, within which there was rapid equilibration of free Ca but tended to increase the rate of Ca mobilization from it during the infusion. The Ca kinetic study with a four-compartment model indicated that reducing dietary AC-balance from +338 to $-127$ (meq kg$ sp{-1}$DM) during the eucalcemic period and from +429 to $-147$ (meq kg$ sp{-1}$DM) during an EGTA-infusion period (simulated lactational Ca loss) caused hypercalciuria and increased ionized form of plasma Ca. Increased true intestinal Ca absorption and reduced bone accretion were observed in the lowest AC-balance diet only during the EGTA-infusion period. There were no differences in the size of total exchangeable Ca pool but the amount of Ca movement between them tended to increase in reduced AC-balance diets during both periods. Results indicated that feeding reduced AC-balanced diet may have a beneficial role in preventing parturient paresis (milk fever) by increasing Ca flux through the exchangeable Ca pool and Ca mobilization capability.

Two experiments were conducted with sheep to determine the nutritional value of 'Lathco' flatpea (Lathyrus sylvestris) hay. In experiment 1, a finishing trial was conducted with 50 group fed crossbred lambs (25 ewes and 25 wethers) fed diets consisting of 70% chopped forage and 30% ground corn grain for 70 d. Five pens of five wethers and five pens of five ewes were selffed diets in which the forage consisted of 100:0, 75:25, 50:50, 25:75, and 0:100 proportions of alfalfa (Medicago sativa L.) and flatpea hay. Feed efficiencies decreased linearly (P<.05) as flatpea increased in the diet. Linear decreases (P<.05) were obtained in kidney and pelvic fat, backfat, leg conformation, and yield grade with increased flatpea in the diet. Blood urea-N (BUN), ruminal pH and NH3-N increased (P<.005) as proportion of flatpea increased. Total volatile fatty acid (VFA) and acetate concentration decreased linearly (P<.005) and propionate, isovalerate, and valerate levels increased linearly (P<.01) with increased proportions of flatpea hay. In experiment 2, 30 wether lambs were fed diets consisting of 100:0, 75:25, 50:50, 25:75 and 0:100 proportions of chopped alfalfa and flatpea hays in a digestion trial. Neutral detergent fiber (NOE), acid detergent fiber (ADE), cellulose, hemicellulose and energy digestibilities decreased linearly (P<.Ol) with increased levels of flatpea hay. Nitrogen retention was not different between sheep fed the different diets. Apparent absorbtion and retention of Ca decreased linearly (P<.05) with increased level of flatpea hay Ruminal pH and NHa-N, and BUN increased linearly (P<.OOl) as flatpea was increased in the diet. Ruminal total VEA, acetate and acetate to propionate ratio decreased linearly (P<.001) and propionate, isobutyrate, isovalerate, and valerate levels increased linearly (P<.001) as level of flatpea increased.

Master of Science

Three experiments were conducted with fresh caged layer waste collected within 24 h after excretion. The waste was stored uncovered for 42 d in polyethylene lined 210 liter metal drums. In the first experiment, waste was treated with no additive, 1 and 1.5% formaldehyde, 1.5 and 2% sodium metabisulfite and 1. 5 and 2% propionic/formic acid (1: 1, w/w). In the second experiment, the additives used were: none, 1% formaldehyde, 1.5% sodium metabisulfite, 1.5% propionic/formic (1: 1, w/w), 10% dry sugar cane molasses and 10% dry molasses plus 2% sodium chloride (salt). In this experiment, the wastes were ensiled with wheat straw (60:40, wet basis) in 4-liter cardboard containers double lined with polyethylene with the following additives: control, 10% dry molasses, silage inoculant or 10% dry molasses plus inoculant. In the third study, the preservatives were: untreated, 1% formaldehyde, 10% dry molasses or 10% dry molasses and 2% salt. After 42 d, treated wastes and straw (60:40) were ensiled with 10% dry molasses in 210 liter metal drums doubled lined with polyethylene. A metabolism trial was conducted with 30 crossbred wethers fed a basal diet alone or with silages containing the wastes which had been treated with the preservatives (1:1, dry basis). In all studies, putrefaction, maggot infestation and dark color were observed for untreated waste. The tops of the wastes treated with sodium metabisulfite and formaldehyde were covered with mold. Formaldehyde-treated waste maintained a stable pH, and water-soluble carbohydrate level. The higher level of propionic/formic acid was effective against visible deterioration. The pH of the silages containing molasses-treated waste was lower than for silages containing control or chemically-treated wastes. Adding molasses at ensiling reduced pH and increased lactic acid. Digestibilities of organic matter, crude protein and neutral detergent fiber were lower (P<.05) for the diet containing silage made from untreated waste, compared to diets containing silage made from treated waste. In all studies, putrefaction, maggot infestation and dark color were observed for untreated waste. The tops of the wastes treated with sodium metabisulfite and formaldehyde were covered with mold. Formaldehyde treated waste maintained a stable pH, and water-soluble carbohydrate level. The higher level of propionic/formic acid was effective against visible deterioration. The pH of the the silages containing molasses-treated waste was lower than for silages containing control or chemically-treated wastes. Adding molasses at ensiling reduced pH and increased lactic acid. Digestibilities of organic matter, crude protein and neutral detergent fiber were lower (P<.05) for the diet containing silage made from untreated waste, compared to diets containing silage made from treated waste.
Master of Science

The number of desert bighorn sheep (Ovis canadensis mexicana) in Pusch Ridge Wilderness (PRW), Santa Catalina Mountains, Arizona has declined to between 50 and 100 animals. Sheep have restricted movements to the southwest corner of PRW. I developed a model based on nitrogen (N) content of forage and forage quantity to measure seasonal changes in nutritional carrying capacity of sheep use areas in PRW. Forage based estimates of animals numbers were greater for April to September than for October to March. My study suggests that forage is not limiting desert bighorn sheep in PRW and illustrates the potential to support more desert bighorn sheep in PRW than the current population. Seasonal fluctuations in range productivity should be examined in relation to human disturbances proximal to desert bighorn sheep habitat and fire management programs for PRW.

The South African sheep industry has experienced an increase in the price of meat and wool over the past several years. This has led to an interest in intensification of sheep production off planted pastures. Due to this phenomenon an economic viability study was done on the intensification of sheep production on cultivated pastures under irrigation. When intensifying sheep production, certain management practices need to be incorporated in order to enhance the output obtained per hectare and to overcome the higher input cost of production. Management practices that could be included are creep feeding, accelerated breeding and feedlotting of lambs after weaning. In order to determine the economic viability of such a system, certain production parameters need to be obtained for producing sheep intensively from cultivated pastures. Three studies were conducted to obtain the required production parameters; these were then followed by an economic evaluation incorporating the parameters obtained from the studies. All the studies were conducted at Kromme Rhee and Langgewens, two research farms of the Department of Agriculture in the Western Cape.

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.

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico
O objetivo desse estudo foi avaliar o desempenho produtivo e a qualidade da carne de animais das raÃas Santa InÃs (SI), Somalis Brasileira (SO) e Morada Nova (MN), e de mestiÃos  Dorper x  Morada Nova (F1), terminados em pastagem cultivada irrigada. Foi realizada estaÃÃo de monta simultÃnea para as raÃas SI, SO e MN, sendo que metade das fÃmeas da raÃa Morada Nova foi cruzada com reprodutores da raÃa Dorper. Na fase de cria, matrizes e crias permaneceram em pastagem nativa. ApÃs o desmame, treze cordeiros da raÃa Santa InÃs, sete da raÃa Somalis Brasileira, seis da raÃa Morada Nova e sete do genÃtipo F1 foram alojados em piquetes de capim Panicum maximum cv. TanzÃnia em um sistema rotativo de pastejo sob um delineamento inteiramente casualizado. Semanalmente, os animais foram pesados e avaliados quanto ao escore corporal (ECC), grau FAMACHAÂ, nÃmero de ovos por grama de fezes (OPG), volume globular (VG) e proteÃna plasmÃtica total (PPT). Ao final do perÃodo experimental, os animais foram abatidos e avaliados quanto Ãs caracterÃsticas quantitativas e qualitativas da carcaÃa e dos cortes comerciais, assim como caracterÃsticas qualitativas da carne. As anÃlises estatÃsticas foram realizadas com auxÃlio do software SAS, por meio do procedimento GLM. A raÃa Morada Nova apresentou menor oscilaÃÃo nos valores referentes ao FAMACHA e VG ao longo do tempo, mesmo apresentando maior pico de OPG, indicando ser a raÃa com maior resiliÃncia quanto à infecÃÃo natural por verminose. Os grupos Santa InÃs e F1 apresentaram maiores ganhos de peso mÃdio diÃrio e melhor conformaÃÃo da carcaÃa. A raÃa Somalis Brasileira apresentou os melhores rendimentos de carcaÃa quente e fria e o melhor grau de acabamento. 15 Considerando os Ãndices de compacidade corporal, da carcaÃa e da perna, as raÃas Santa InÃs, Somalis Brasileira e o mestiÃo F1 apresentaram maior especializaÃÃo para produÃÃo de carne em comparaÃÃo ao Morada Nova. A Ãrea de olho de lombo foi similar entre os grupos Santa InÃs, F1 e Somalis Brasileira, sendo este Ãltimo tambÃm similar a raÃa Morada Nova. Pode-se concluir que para as condiÃÃes de manejo empregadas nesse estudo, os genÃtipos avaliados, oscilaram seus desempenhos em relaÃÃo Ãs caracterÃsticas analisadas, nÃo havendo um grupo superior nem inferior em tudo, o que denota que todos sÃo passÃveis de melhoramento. As boas caracterÃsticas de qualidade da carne apresentadas pelos grupos genÃticos Santa InÃs, Morada Nova, Somalis Brasileira e mestiÃo  Dorper x  Morada Nova, os tornam excelentes opÃÃes para abastecer um mercado mais exigente, nÃo havendo diferenÃas importantes entre eles.
The aim of this study was to evaluate the productive performance and meat quality of animals of Santa InÃs (SI), Somalis Brasileira (SO) and Morada Nova (MN) breeds and  Dorper x  Morada Nova crossbreds (F1) finished in irrigated cultivated pasture. Breeding season was done simultaneously for SI, SO and MN breeds and half of the Morada Nova females was crossed with Dorper rams. In lambing phase, ewes and lambs were raised in native pasture. After weaning, thirty-three males lambs (thirteen Santa InÃs, seven Somalis Brasileira, six Morada Nova and seven F1) were selected to be finished in irrigated cultivated pasture. The animals were housed in paddocks of Panicum maximum cv. Tanzania on a rotational system in a randomized design. Each week the animals were weighed and evaluated for body condition score (ECC), FAMACHA  degree, number of eggs per gram of faeces (OPG), packed cell volume (VG) and total plasma protein (PPT). At the end of the field trial the animals were slaughtered and evaluated for quantitative and qualitative traits of carcass and commercial cuts, as well as qualitative aspects of meat. Statistical analyses were performed by SAS software using the GLM procedure. The Morada Nova breed presented lower variation in the values of VG and FAMACHA  over time even with the highest peak of OPG, indicating this breed as more resilient to helminthic natural infection. For carcass traits Somalis Brasileira breed showed the best hot and cold carcass dressing and the greatest finishing degree. Genetic groups Santa InÃs and F1 showed a better carcass conformation. AOL was similar between Santa InÃs, Somalis 17 Brasileira and F1, the latter being also similar to Morada Nova. Considering the compactness indexes for body, carcass and leg, Santa InÃs, Somalis and Brazilian F1 group were similar showing greater specialization for meat production. It can be concluded that for the conditions of management employed in this study, the genotypes ranged their performances in relation to traits evaluated, since no group was superior or inferior for all traits, which shows that all groups can be improved. Good meat quality characteristics presented by genetic groups Santa InÃs, Morad Nova and Somalis Brasileira, and the crossbreed  Dorper x  Morada Nova, make them excellent choices to fill a more demanding market, with no significant differences between them

Bibliography: leaves 105-121. This study reports the first thorough investigation of palatability variation in Atriplex vesicaria Heward ex Benth. (bladder saltbush). Intensive small-plot dietary trials, supported by a paddock dietary experiment, cross-fence comparisons and cafeteria trials, showed that sheep preferentially grazed female saltbushes over male and bisexual ones. Sheep avoided male saltbushes due to a chemical deterrent, and used visual (male flower spike) and olfactory cues to detect male plants. The effect of this selective grazing was to reduce the size and reproductive output of female shrubs. Sheep also tended to return to shrubs they had grazed previously. In the semi-arid regions of South Australia, where bladder saltbush is grazed year-round, physical protection is recommended to maximise survival and reproductive output of heavily grazed shrubs.

Low and high endophyte infected stockpiled tall fescue was harvested, chopped and ensiled in 210 liter metal drums, double lined with polyethylene bags. Endophyte infection averaged 4 and 70%, respectively, for the low- and high-endophyte fescue. A metabolism trial was conducted with 24 wethers fed diets consisting of 100% low-endophyte fescue silage, 50% low-endophyte and 50% high-endophyte fescue silage, and 100% high-endophyte fescue silage. Chopped alfalfa hay was used as a control forage. Single samples were analyzed, so statistical treatment of chemical composition was not possible. However, certain numerical differences were recorded. Lignin was higher for the high-endophyte than the low-endophyte fescue. Dry matter, CP, and ash were similar for the fescue silages. The high-endophyte fescue silage was lower in P, Mg, S, K, Fe, Cu, Mn, Zn, and Al than the low-endophyte silage. Digestibilities of DM, NDF, and cellulose were higher (P<.01) for fescue silages than alfalfa hay. Level of endophyte infection did not affect digestibility of DM, NDF or cellulose. Among silage treatments, apparent absorption of N, expressed as g/d, showed a linear effect (P<.05), with the lowest value obtained for sheep fed 100% high-endophyte fescue silage. Apparent absorption and retention of Ca were higher for silages than alfalfa. Among the silage diets, apparent absorption of P decreased linearly (P<.01) with increased endophyte level. Apparent absorption of K decreased linearly (P<.01) with increased endophyte level, but the effect was related to intake. Serum prolactin concentrations of the wethers fed fescue silage showed a linear decrease (P<.05) with increased proportion of endophyte-infected fescue. Endophyte infection of fescue appears to affect N and mineral metabolism.
Master of Science

Thesis (MScAgric)--University of Stellenbosch, 2002.
ENGLISH ABSTRACT: The Dorper is numerically the second most abundent of all the sheep breeds in South Africa. It is the most numerous sheep breed in the dry arid areas of South Africa which make out a very big portion of the natural grazing in South Africa. In this study the feedlot performance was specifically investigated since so little research has been done in this regard. In the first study (Chapter 1), the production efficiency, body components and commercial yield of 13 Dorper and 12 Merino lambs were investigated. A pelleted diet was fed ad lib and the water intake per day was measured. Lambs were slaughtered at 30kg and at 40kg live weight and cut up according to the South African commercial cuts. The weights of the organs, head, feet, skin and carcass were also recorded. Results from the first study showed that Dorpers had a lower (P<0.05) water efficiency (285.97 mVkgO75/day) than the Merinos (240.07 mVkg075/day), but had a higher (P<0.05) nitrogen retention. The head, feet, skin, heart, lungs, kidneys and diaphragm of Merino lambs were heavier (P<0.05). Merinos had heavier (P<0.05) breast and shank and thick rib (only at 40kg live weight) cuts. But the Dorper had a significantly heavier hindquarter (buttock and loin) which is the high-priced cut of any carcass. It seems that the Dorper will do well under feedlot conditions, and would possibly make a better commercial meat producer than the Merino under all circumstances. In the second study (Chapter 2), the free-ranging Dorper on natural grazing were compared with 7 Dorper lambs in the feedlot study. The essential amino acids in the duodenal contents were compared. The free-ranging Dorpers were randomly slaughtered at 40 kg live weight and a duodenal sample was collected. The feedlot Dorpers were also slaughtered at 40 kg live weight and a duodenal sample was taken. The second study indicated no significant differences between the EAA composition of the duodenal samples, whether protein quantity was taken into account (gAA/100g crude protein (CP)) or not (expressed as % of lysine). The chemical scores indicated that the two most limiting amino acids in the duodenal digesta for whole empty body growth were: arginine and histidine. Excess levels of amino acids tend to be present in all three duodenal digesta samples (isoleucine, leucine, lusine, methionine, phenylalaline, threonine and valine). The whole empty body EAA composition (g AA/100 g crude protein) was as follows 7.10 arginine; 2.40 histidine; 3.31 isoleucine; 7.22 leucine; 6.61 lysine; 1.62 methionine; 3.91 phenylalanine; 3.77 threonine and 4.85 valine. The composition can serve as an example of the ideal EAA requirements for whole empty body growth between 30 and 40 kg live weight of Dorper ram lambs. The duodenal amino acid concentrations of the free-ranging Dorper compared well with those of the feedlot Dorpers which suggests that the microbial organisms have a big influence on the amino acid concentration which reaches the intestines.
AFRIKAANSE OPSOMMING: Die voerkraal prestasie en essentiele aminosuur behoeftes van groeiende Dorper lammers: The Dorper is getalgewys die tweede mees talryke skaapras in Suid-Afrika. Dit is die mees talryke skaapras wat in die drce woestynagtige gebiede van Suid-Afrika aangetref word. Die gebiede beslaan die grootste oppervlakte van Suid-Afrika se natuurlike weiveld. In die studie is voerkraal prestasie van die Dorper nagevors, spesifiek omdat daar so min navorsing op hierdie gebied gedoen is. In die eerste studie (Hoofstuk 1) is die produksie doeltreffendheid, liggaams komponente en kornrnersiele produksie van 13 Dorper- en 12 Merino lammers ondersoek. 'n Verpilde rantsoen is ad lib gevoer en die water inname per dag is ook gekontroleer. Die lammers is geslag op 30 en 40 kg lewende gewig en die karkasse is daarna opgesny volgens die Suid-Afrikaanse kornmersiele karkassnitte. Die resultate van die eerste studie het getoon dat Dorpers 'n laer water potentiaal (P<0.05) (285 97 mflkgO 75/dag) as die Merinos (240.07 mVkg075/dag) het. Dorper lammers het ook 'n hoer (P<0.05) stikstof retensie. Die kop, vel, pote, hart, longe, niere en diafragma van Merino lammers was swaarder (P<0.05). Merinos se brisket en dikrib snitte weeg ook swaarder (P<0.05). Die Dorper het 'n beduidende swaarder agterkwart (len de en boud) gehad, wat die duurste snit is van enige karkas. Die Dorper het baie goed gedoen in die voerkraal toestande en sal waarskynlik onder aile omstandighede 'n hcer vleisproduksie op die Merino lewer. In die tweede studie (Hoofstuk 2), is die vryweiende Dopers op natuurlike weiding vergelyk met die Dorpers in 'n voerkraal. Die twee groepe Dorpers se essensiele aminosuur samestelling in hul dunderms is bepaal en vergelyk om te bepaal of daar enige tekorte teenwoordig is. Die Dorpers in die veld en in die voerkraal is op 40 kg lewende gewig geslag en monsters van die dunderm inhoud is gekollekteer. Die monsters is ontleed om te bepaal of daar enige betekenisvolle verskille in die essensiele aminosure van die dunderm inhoud tussen die veld Dorpers en voerkraal Dorpers was. Die tweede studie het geen betekenisvolle verskille getoon tussen die dunderm monsters se essensiele aminosure, of die hoeveelheid proteien (gAA/100g) in aanmerking geneem is of nie (uitgedruk as % lisien). Die chemiese telling dui aan dat die twee mees beperkende aminosure in die dunderm inhoud vir lee liggaam groei arginien en histidien was. Oormaat vlakke van aminosure kom voor in al drie dunderm inhoud monsters (isoleusien, leusien, lisien, metionien, femielalanien, treonien en valien). Die totale lee liggaam essensiele aminosuursamestelling (g aminosuur/100g ruprotein) was soos volg: 7.10 arginien; 2.40 histidien; 3.31 isoleusien; 7.22 leusien; 6.61 lisien; 1.62 metionien; 3.91 fenielalanien; 3.77 treonien en 4.85 valien. Hierdie aminosuursamestelling kan as 'n aanduiding dien vir die ideale aminosuurbehoeftes van Dorper ram lammers vir totale lee liggaamsgroei vanaf 30 tot 40 kg lewende massa. Die dunderm aminosuur konsentrasie van die Dorper in die veld stem goed ooreen met die van die voerkraal Dorper. Dit toon waarskynlik dat die mikrobe organismes in die rumen In groot invloed het op die aminosuur samestelling wat die dunderm bereik.

The objectives of this study were to verify the potential benefits of growing green barley on anaerobic enzyme (ZAD) treated rice straw. In addition, the work intended to investigate the effect of this treatment on digestibility parameters in Ossimi sheep. A complete random design was used to distribute twelve mature male of Ossimi sheep (45.0 +0.5 Kg wt.) on the following treatments: Rice straw with grown barley (RSGB) without either ZAD or orange pulp (control, T1), RSGB plus ZAD (T2), RSGB plus orange pulp (T3) and RSGB + ZAD + orange pulp (T4). The obtained results could be summarized as follow 1- Significant decreases were observed in %CF from 38.09 for T1 to 32.01 and 30.02 for rations T4 and T2 respectively (P< 0.05). Percentage values of NDF were 70.01, 72.10 and 76.01 for rations T4, T2 and T1 respectively (P< 0.05); while %ADF values were 50.05, 52.10 and 58.10 for rations T4, T2 and T1 respectively (P< 0.05) and %ADL was 6.01for T4 versus 8.01for T1. And significant increases in %CP content to 7.96, 7.10, 7.95 for ration T4, T3, T2 respectively compared to the control ration was 5.75 (P< 0.05). 2- Adding ZAD to RSGB significantly increased (p< 0.05) %TDN to 55.02 and 59.02 for treatments T2 and T4 respectively and increased digestibility coefficients of CP to 72.43 and 77.70 respectively. 3- Rams fed rations T2, T3 and T4 had significantly higher values of ruminal ammonia-N 3 hrs. post feeding values were 25.41, 25.03, 25.96 mg/100ml respectively and total volatile fatty acids 3 hrs. post feeding were 8.20, 8.13 and 8.26 m.eq/100ml respectively. 4- Adding either ZAD, orange pulp or both to RSGB significantly increased (p<.05) plasma total protein values were 6.43, 6.23, 5.82 g/dl for treatments T4, T3, T2 respectively , while treating rations with ZAD reflected low level of GPT 6 hrs. post feeding values were 20.64 and 20.61 for treatments T2 and T4 respectively versus T1 (20.90 µ/l). It could be concluded that anaerobic enzyme matrix (ZAD) improved the nutritive value of soilless green barley and improved their digestibility coefficients in Ossimi sheep ZAD is a compound of enzymes are separated from anaerobic bacteria separated from the rumen, it contain a mixture of cellulase, hemicellulase, protease and alpha amylase enzymes.

[Truncated abstract] With the rapid development of multiple herbicide resistant weeds in crops, it is likely that an important role now exists for new grazing management strategies in farming systems to provide an integrated approach to weed management. In this thesis we examined the general hypothesis that sowing a legume of low preference by sheep relative to the target weeds of crops would improve the control of those weeds in a grazed pasture. To test this general hypothesis, legumes of low preference by Merino sheep were identified and a series of experiments conducted to determine the effect on pasture composition when these less preferred legumes were incorporated into a grazed pasture. We found a learned response that altered forage preference by sheep was important in determining the effectiveness of grazing to reduce seed set by weeds of crops. Investigations on this aspect of the grazing behaviour of sheep were a key part of this thesis. The short-term relative preference of Merino hoggets among 15 pasture legumes, 4 grain legumes and annual ryegrass was determined by offering adjacent monocultures of each of the forage genotypes to the sheep. The relative preference of the hoggets for each of the 20 forages was determined at three phases of plant growth from estimates of the amount of forage consumed. Sheep showed a low selective preference for Vetch (Vicia sativa L.), chickpea (Cicer arietinum L.), biserrula (Biserrula pelecinus L.), lotus (Lotus ornithopodioides L.) and snail medic (Medicago scutellata L.) cvs. Kelson and Sava at the vegetative phase of plant growth. An indoor method was also developed to test the relative preference of sheep among forages growing in pots. Using this method chickpea and snail medic, but not biserrula, were found to have a low relative preference by sheep at the vegetative phase.

To investigate the whole body metabolism of selenium (Se), isotope kinetic studies were undertaken in which indwelling catheters were implanted in the jugular veins of pregnant and nonpregnant ewes as well as the inferior vena cava and saphenous veins of 110-120 day (d) old ovine fetuses. A single injection of ⁷⁵Se-sodium selenite was administered and blood samples were obtained at various times. A 5 d Se balance trial, which commenced on the day of tracer experiment, was also undertaken. The plasma ⁷⁵Se specific activity data were used for determining the kinetic parameters of Se metabolism and the placental transfer rates. Using the Se balance and tracer data the net absorption and the fecal losses of Se were calculated. The fractional rate constants and T½ Se utilization in individual tissues were estimated by sacrificing the ewes and the fetuses at different times after the tracer injection and determining the tissue ⁷⁵Se specific activities. The effect of Se deficiency on the kinetics, placental transfer, net absorption and tissue metabolism was studied in a similar manner by feeding the ewes with Se deficient rations. The mean plasma Se concentrations in the positive nonpregnant and pregnant ewes were 142 187 ng/ml and were significantly higher than Se and the corresponding values (82 and 69 ng/ml) in the Se deficient ones respectively. The plasma Se levels in the Se positive fetuses (46 ng/ml) were not significantly different from the deficient ones (53 ng/ml). The irreversible disposal (ID) rates of Se were 7 ug/d/kg body weight (B.W.) in both nonpregnant and pregnant ewes, whereas, these values declined to 2 ug/d/kg B.W. under deficiency conditions. The ID values in the Se positive and deficient fetuses were 20 and 11 ug/d/kg B.W. respectively. These results indicated that the plasma Se turnover was lower in Se deficient animals than in the positive ones and that the fetuses had a higher turnover than adult ewes irrespective of the maternal Se status. Values for net Se absorption (% Se intake) and fecal Se losses (ug/d) in the Se positive nonpregnant ewes were 51% and 272 ug/d versus 97% and 25 ug/d in the Se deficient ones. The corresponding values for the Se positive pregnant ewes were 56% and 241 ug/d as against 84% and 27 ug/d in the deficient ones. These results suggested that the efficiency of net Se absorption expressed as the percent of Se intake decreased with increasing Se intakes and that the fecal route exerted a homeostatic control on Se metabolism in ewes. The tissue Se concentrations were significantly higher in the Se positive animals than in the deficient ones, whereas, the tissue fractional rate constant values were higher in the Se deficient animals than in the positive ones. These results implied that the tissue Se concentrations were significantly decreased under Se deficiency conditions and that the Se turnover was higher in tissues when the dietary Se intake was minimal. The placental transfer studies showed that there was a bidirectional exchange of Se across the placenta. The placental Se transfer rates from ewe to fetus declined from 53 ug/d in the positive ewes to 29 ug/d in the deficient ones. The rate of Se transfer from fetus to ewe also decreased from 24 ug/d in the positive ewes to 12 ug/d in the deficient ones. The net placental Se transfer was found to be reduced under conditions of decreased maternal dietary supply. The nutritional implications of Se status of the pregnant ewes on the availability of the trace mineral to the fetus have been discussed.
Land and Food Systems, Faculty of
Graduate

Feeds often contain molybdenum (Mo) and sulfur (S) in excess of recommended allowances for adequate copper (Cu) absorption by ruminant livestock. Two randomized-block experiments were conducted using lambs given a cereal-based diet (90% of dry matter (DM) intake), containing 8 mg Cu, 0.7 mg Mo and 2.1g S per kg DM, that was either unsupplemented or supplemented with ammonium molybdate or sodium sulfate alone or in combination, to determine the effects of Mo, S and Mo+S on growth, hematology, serum Cu and Mo concentrations and reproductive function. Short term intake (4 weeks) by rams, aged 18 and 20 weeks, of 26 mg Mo alone or in combination with 2g S per kg DM, had no effect on growth, hematology or the concentration of total Cu in serum (TCu). However, supplemented groups had lower (P<0.05) concentrations of serum Cu soluble in trichloroacetic acid (TCA-Cu), but the group given Mo+S had the highest (P<0.05) concentration of serum residual Cu (RCu). Luteinizing hormone (LH) peak amplitude was affected by age*diet interaction (P<0.05), because of high amplitude LH peaks in the serum of lambs, aged 24 wks, given Mo alone. Testosterone serum secretory profiles did not differ among diet groups, but testosterone peak frequency was higher (P<0.05) for older ram lambs. Long term intake (32-39 wks) by ewe, ram and wether lambs (gonadal influence) of 12 mg Mo, or 2g S alone or combined per kg DM also had no effect on hematology or TCu. Food intake and liver weights were higher (P<0.05), but TCA-Cu was lower (P<0.05) for groups given S. Serum concentrations of total Mo (TMo) were higher (P<0.05) for Mo-supplemented groups, but RCu was highest only for the Mo+S group. Growth was affected by Mo*S*gonadal influence*time interaction (P<0.05); until autumn, the body weight of Mo-supplemented groups were higher than those of ram and wether lambs given Mo+S. Ovarian or testicular functions were delayed more severely for Mo- than Mo+S-supplemented groups. Mean concentrations of LH were affected by Mo*S*gonadal influence*time interaction (P<0.05); the mean LH values of Mo-supplemented ram and ewe lambs were higher than the Mo+S-supplemented group, whereas a reverse trend was observed for wether lambs. The amplitude of LH peaks was affected by Mo*S*gonadal influence*time interaction (P<0.05); for ram lambs, LH peak amplitude was higher for Mo than Mo+S-supplemented groups, whereas for wether and ewe lambs the reverse trend was noted. Mean concentrations of serum Cortisol and Cortisol peak amplitude were affected by Mo*S interaction (P<0.05); the mean Cortisol concentration and peak amplitude for the Mo-supplemented group were higher than those for the Mo+S-supplemented group. The frequency of LH and Cortisol peaks did not differ (P>0.10) among diet groups. In conclusion, Mo supplementation of cereal-based diets containing a high concentration of Cu did not adversely affect lamb growth. However, the effect of high dietary Mo on reproductive function appears to depend on the dietary level of S and the induction of high serum RCu (thiomolybdate). Further investigations on the effects of Mo and thiomolybdate on endocrine function may provide a nutritional basis for improving reproductive efficiency in ruminants.
Land and Food Systems, Faculty of
Graduate

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

FERNANDES JÚNIOR, Gerardo Alves. Desempenho produtivo e qualidade da carne de ovinos terminados em pastagem irrigada no semiárido nordestino. 2010. 87 f. Dissertação (Mestrado em zootecnia)- Universidade Federal do Ceará, Fortaleza-CE, 2010.
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The aim of this study was to evaluate the productive performance and meat quality of animals of Santa Inês (SI), Somalis Brasileira (SO) and Morada Nova (MN) breeds and ½ Dorper x ½ Morada Nova crossbreds (F1) finished in irrigated cultivated pasture. Breeding season was done simultaneously for SI, SO and MN breeds and half of the Morada Nova females was crossed with Dorper rams. In lambing phase, ewes and lambs were raised in native pasture. After weaning, thirty-three males lambs (thirteen Santa Inês, seven Somalis Brasileira, six Morada Nova and seven F1) were selected to be finished in irrigated cultivated pasture. The animals were housed in paddocks of Panicum maximum cv. Tanzania on a rotational system in a randomized design. Each week the animals were weighed and evaluated for body condition score (ECC), FAMACHA © degree, number of eggs per gram of faeces (OPG), packed cell volume (VG) and total plasma protein (PPT). At the end of the field trial the animals were slaughtered and evaluated for quantitative and qualitative traits of carcass and commercial cuts, as well as qualitative aspects of meat. Statistical analyses were performed by SAS software using the GLM procedure. The Morada Nova breed presented lower variation in the values of VG and FAMACHA © over time even with the highest peak of OPG, indicating this breed as more resilient to helminthic natural infection. For carcass traits Somalis Brasileira breed showed the best hot and cold carcass dressing and the greatest finishing degree. Genetic groups Santa Inês and F1 showed a better carcass conformation. AOL was similar between Santa Inês, Somalis 17 Brasileira and F1, the latter being also similar to Morada Nova. Considering the compactness indexes for body, carcass and leg, Santa Inês, Somalis and Brazilian F1 group were similar showing greater specialization for meat production. It can be concluded that for the conditions of management employed in this study, the genotypes ranged their performances in relation to traits evaluated, since no group was superior or inferior for all traits, which shows that all groups can be improved. Good meat quality characteristics presented by genetic groups Santa Inês, Morad Nova and Somalis Brasileira, and the crossbreed ½ Dorper x ½ Morada Nova, make them excellent choices to fill a more demanding market, with no significant differences between them.
O objetivo desse estudo foi avaliar o desempenho produtivo e a qualidade da carne de animais das raças Santa Inês (SI), Somalis Brasileira (SO) e Morada Nova (MN), e de mestiços ½ Dorper x ½ Morada Nova (F1), terminados em pastagem cultivada irrigada. Foi realizada estação de monta simultânea para as raças SI, SO e MN, sendo que metade das fêmeas da raça Morada Nova foi cruzada com reprodutores da raça Dorper. Na fase de cria, matrizes e crias permaneceram em pastagem nativa. Após o desmame, treze cordeiros da raça Santa Inês, sete da raça Somalis Brasileira, seis da raça Morada Nova e sete do genótipo F1 foram alojados em piquetes de capim Panicum maximum cv. Tanzânia em um sistema rotativo de pastejo sob um delineamento inteiramente casualizado. Semanalmente, os animais foram pesados e avaliados quanto ao escore corporal (ECC), grau FAMACHA©, número de ovos por grama de fezes (OPG), volume globular (VG) e proteína plasmática total (PPT). Ao final do período experimental, os animais foram abatidos e avaliados quanto às características quantitativas e qualitativas da carcaça e dos cortes comerciais, assim como características qualitativas da carne. As análises estatísticas foram realizadas com auxílio do software SAS, por meio do procedimento GLM. A raça Morada Nova apresentou menor oscilação nos valores referentes ao FAMACHA© e VG ao longo do tempo, mesmo apresentando maior pico de OPG, indicando ser a raça com maior resiliência quanto à infecção natural por verminose. Os grupos Santa Inês e F1 apresentaram maiores ganhos de peso médio diário e melhor conformação da carcaça. A raça Somalis Brasileira apresentou os melhores rendimentos de carcaça quente e fria e o melhor grau de acabamento. 15 Considerando os índices de compacidade corporal, da carcaça e da perna, as raças Santa Inês, Somalis Brasileira e o mestiço F1 apresentaram maior especialização para produção de carne em comparação ao Morada Nova. A área de olho de lombo foi similar entre os grupos Santa Inês, F1 e Somalis Brasileira, sendo este último também similar a raça Morada Nova. Pode-se concluir que para as condições de manejo empregadas nesse estudo, os genótipos avaliados, oscilaram seus desempenhos em relação às características analisadas, não havendo um grupo superior nem inferior em tudo, o que denota que todos são passíveis de melhoramento. As boas características de qualidade da carne apresentadas pelos grupos genéticos Santa Inês, Morada Nova, Somalis Brasileira e mestiço ½ Dorper x ½ Morada Nova, os tornam excelentes opções para abastecer um mercado mais exigente, não havendo diferenças importantes entre eles.

The main hypothesis tested in this thesis was that poor animal production from saltbush pastures is due to the negative effects of high sodium chloride (NaCl) and potassium chloride (KCl) on the ruminal environment, and subsequent effects on microbial populations and products of rumen fermentation. This main hypothesis was tested in two experiments. In the first experiment (Chapter Four) the effects of saltbush and a formulated high-salt diet on the ruminal environment and microbial populations were measured over 24-hours following feeding. Feeding both the saltbush and high-salt diet increased the salinity of the rumen fluid, but the formulated high-salt diet caused a decrease in ruminal pH while the saltbush caused an increase. This resulted in differences in the composition of the ruminal microbial populations between the sheep fed different diets. In the second experiment (Chapter Five) the effects of saltbush and a formulated highsalt diet on rumen fermentation were measured. Sheep fed saltbush had inefficient rumen fermentation and this was only partially explained by the high salt content of the diet. Diets containing high levels of NaCl and KCl provided low levels of net energy to sheep, but sheep fed saltbush lost more energy as methane and faecal energy compared to sheep fed the formulated high-salt diet. Inefficient rumen fermentation could help to explain poor animal production from saltbush pastures. Energy supplements such as barley grain can improve the value of saltbush pastures as feed for sheep, but there is no information on how much supplement is required. A third experiment (Chapter Six) was designed to test the hypothesis that there would be an optimal amount of barley required to improve the efficiency of rumen fermentation in sheep fed saltbush. Barley and straw were combined in a pellet and substituted for saltbush at 0, 20, 40, 60, 80 and 100% of the maintenance ration. Feeding barley and straw improved the efficiency of rumen fermentation in sheep fed saltbush, with an optimal level of supplementation at 60% of the maintenance diet. This is likely to be lower (approximately 20% of maintenance) if barley is fed without straw.

Studies were conducted to determine the effects of feeding lasalocid and monensin upon mineral status of ruminants, changes in digestive and renal physiology which bring about altered mineral status, and the effects of dietary K upon the actions of ionophores. Two 84-d grazing trials were conducted with steers fed no ionophore, 200 mg lasalocid, or 150 mg monensin. Monensin tended to increase gain of steers, but lasalocid had no effect. Feeding supplemental lasalocid and monensin altered Ca, P, Mg, Na, K, Cu, Fe and Zn status of grazing steers, but effects were not consistent. Twenty-four crossbred steers were individually fed in a 147-d finishing trial to study a possible K x monensin interaction. Steers were fed diets ad libitum containing .4% or 2.3% K, with or without 23 ppm monensin, dry basis. Feeding monensin with low K increased serum Na, Mg, inorganic P, Cu and Zn, but monensin fed with high K had no effect or decreased these serum minerals. Fifteen wethers, fitted with abomasal and ileal cannulae, were fed a basal diet alone or supplemented with 23 ppm lasalocid or monensin; Apparent absorption of Mg, K and Fe increased when ionophores were fed. Magnesium flow through the small and large intestines was decreased by lasalocid and monensin. Effects of lasalocid and monensin differed for metabolism, digestive tract flow and (or) partial absorption of Ca, P, Cu, Fe and Zn. Twelve ewe lambs were used in a renal clearance experiment. Lambs were fed a basal diet with no ionophore, 23 ppm lasalocid, or 23 ppm monensin, dry basis. Ionophores were fed starting on d 1 of the experimental period. Serial collections of blood and urine were made during d 1 and d 5 of the experimental period. Monensin reduced urine flow rate at d 1 and d 5. Feeding monensin lowered serum clearance and urinary excretion rates of Na and K at d 5. Serum clearance and urinary excretion rates of Ca were lower in sheep fed ionophores at d 1. Feeding monensin decreased serum clearance and urinary excretion rates of Cu at d 1. At d 5, urinary excretion rates of Zn were greater when lasalocid was fed, and lower when monensin was fed, compared to feeding no ionophore. These studies indicate that dietary lasalocid and monensin can alter mineral status of ruminants, although their effects may differ. The effects of ionophores may be dependent upon dietary K levels.
Ph. D.

Includes bibliographical references (leaves 59-79) Examines the metabolism of volatile fatty acid and formic acid in fed sheep. Develops a method for analysing and qualifying volatile fatty acids with special reference to formic acid in biological fluids by High-Performance Liquid Chromatography.

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.

Conjugated linoleic acid (CLA) is produced in the rumen by isomerization of linoleic acid and has been shown to be anticarcinogenic. The objective of this study was to determine the effects of feeding dietary CLA to pre-ruminant lambs or linoleic acid-rich safflower oil to weaned ruminating lambs. Fat content, CLA content and fatty acid (FA) composition of diaphragm, leg, rib, subcutaneous (SC) adipose and liver tissues were determined. The triacylglycerol (TAG) fractions of the total lipid (TL) from the diaphragm, rib and SC adipose tissues were analyzed for FA composition and FA positional distribution. The phospholipid (PL) fractions of the TL were analyzed for FA composition. The positional (PL) fractions of the TL were analyzed for FA composition. The positional distribution of FAs of liver PL was determined. Tissue fat content was affected by diet only in SC adipose tissue. Dietary supplementation with safflower oil increased the fat content of the subcutaneous adipose tissue whereas CLA supplementation resulted in decreased (P<0.05) fat content. Dietary supplementation with safflower oil increased (P<0.05) the CLA content of tissues by more than 200% whereas dietary supplementation with CLA did not affect CLA content. Positional distribution analysis indicated that CLA tends was localized to the sn-1/3 positions of TAG and the sn-2 position of the liver PL.
xiii, 74 leaves : ill. ; 28 cm.

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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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O trabalho de pesquisa foi realizado com o objetivo de avaliar se há alteração no consumo, desempenho, comportamento ingestivo, digestibilidade, bem como a avaliação econômica do sistema, a qualidade da carne e característica de carcaça, dos cordeiros alimentados com dietas com silagens de milho advindas de cultivo exclusivo do milho e dos consórcios com Urochloa brizantha cv. Xaraés ou com Panicum maximum cv. Tanzânia produzidas em sistema de integração lavoura-pecuária sob plantio direto. As dietas foram compostas por 60% de volumoso e 40% de concentrado. Foram utilizados 24 cordeiros machos não castrados, 1⁄2 Dorper 1⁄2 Santa Inês, com aproximadamente 20 kg e 60 dias de idade, alojados em baias individuais com 1 m 2 . O consumo dos animais foi registrado diariamente com a obtenção do peso das sobras, onde foi permitido sobras de até 15%. Os animais foram pesados a cada 14 dias, a fim de se avaliar o desempenho, enquanto que o comportamento ingestivo foi realizado durante 24 horas, com observações a cada 5 minutos. No 14o dia do período experimental, os animais foram submetidos a coletas diárias de fezes para o ensaio de digestibilidade. A avaliação econômica utilizou como parâmetro principal a margem bruta da terminação dos cordeiros. Quando os animais atingiram o peso aproximado de 33 kg foram insensibilizados e abatidos. Durante o abate os componentes não-carcaça, assim como o sangue foram pesados para a obtenção dos rendimentos. Após o abate as carcaças foram pesadas e encaminhadas à câmara frigorífica, onde permaneceram por 24 horas. Percorrido este período as carcaças foram cortadas em meias carcaças e divididas em 5 cortes anatômicos para os cálculos de porcentagem dos cortes em relação a meia carcaça. Para as avaliações de qualidade da carne foi utilizado o músculo Longisimus lumborum, onde foi quantificada a capacidade de retenção de água, perda por cocção, cor e força de ...
The research work was conducted to evaluate if change in intake, performance, digestibility and intake behavior, as well as the economical evaluation of confined lambs system fed diets of corn silages; exclusive cultivation of corn and intercropped with Urochloa Brizantha [syn: Brachiaria brizantha] var. Xaraés or Panicum maximum var. Tanzania; from a crop-livestock integration under no-tillage system. The diets were composed of 60% roughage and 40% concentrate. 24 non-castrated lambs were, 1⁄2 Dorper 1⁄2 Santa Ines were used, with approximately 20 kg and 60 days of age, housed in individual pens of 1 m 2 . The feed intake by the animals was recorded daily weighting of the orts, accepting 15% of orts from feed offer. The animals were weighed every 14 days in order to evaluate performance, while the intake behavior was conducted over a period of 24 h, with observations every 5 minutes. On the 14 th day of the experimental period, the animals were subjected to daily fecal sampling for the digestibility trial. The economical evaluation used as main parameter to gross margin of finishing lambs. When the animals reached the approximate body weight of 33 kg were stunned and slaughtered. During slaughtering, non-carcass components and blood were weighed to obtain yields. After slaughter, the carcasses were weighed and sent to cold storage, where they remained for 24 hours. Subsequently, the carcasses were weighed and taken to the laboratory, where they were cut into half-carcasses and divided into 5 anatomical cuts for calculations of cuts percentage in relation to the half carcasses cuts. For meat quality evaluation the Longisimus lumborum muscles were used and quantified the ability to retain water, cooking loss, color and shear force. No significant differences of treatments on weight gain and feed conversion of lambs were observed, but the highest values of consumption in kg/day, body weight and metabolic weight were provided to diets ...

Orientador: Rafael Silvio Bonilha Pinheiro
Co-orientador: Marcelo Andreotti
Banca: Viviane Corrêa Santos
Banca: Cristiano Magalhães Pariz
Resumo: O trabalho de pesquisa foi realizado com o objetivo de avaliar se há alteração no consumo, desempenho, comportamento ingestivo, digestibilidade, bem como a avaliação econômica do sistema, a qualidade da carne e característica de carcaça, dos cordeiros alimentados com dietas com silagens de milho advindas de cultivo exclusivo do milho e dos consórcios com Urochloa brizantha cv. Xaraés ou com Panicum maximum cv. Tanzânia produzidas em sistema de integração lavoura-pecuária sob plantio direto. As dietas foram compostas por 60% de volumoso e 40% de concentrado. Foram utilizados 24 cordeiros machos não castrados, 1⁄2 Dorper 1⁄2 Santa Inês, com aproximadamente 20 kg e 60 dias de idade, alojados em baias individuais com 1 m 2 . O consumo dos animais foi registrado diariamente com a obtenção do peso das sobras, onde foi permitido sobras de até 15%. Os animais foram pesados a cada 14 dias, a fim de se avaliar o desempenho, enquanto que o comportamento ingestivo foi realizado durante 24 horas, com observações a cada 5 minutos. No 14o dia do período experimental, os animais foram submetidos a coletas diárias de fezes para o ensaio de digestibilidade. A avaliação econômica utilizou como parâmetro principal a margem bruta da terminação dos cordeiros. Quando os animais atingiram o peso aproximado de 33 kg foram insensibilizados e abatidos. Durante o abate os componentes não-carcaça, assim como o sangue foram pesados para a obtenção dos rendimentos. Após o abate as carcaças foram pesadas e encaminhadas à câmara frigorífica, onde permaneceram por 24 horas. Percorrido este período as carcaças foram cortadas em meias carcaças e divididas em 5 cortes anatômicos para os cálculos de porcentagem dos cortes em relação a meia carcaça. Para as avaliações de qualidade da carne foi utilizado o músculo Longisimus lumborum, onde foi quantificada a capacidade de retenção de água, perda por cocção, cor e força de ...
Abstract: The research work was conducted to evaluate if change in intake, performance, digestibility and intake behavior, as well as the economical evaluation of confined lambs system fed diets of corn silages; exclusive cultivation of corn and intercropped with Urochloa Brizantha [syn: Brachiaria brizantha] var. Xaraés or Panicum maximum var. Tanzania; from a crop-livestock integration under no-tillage system. The diets were composed of 60% roughage and 40% concentrate. 24 non-castrated lambs were, 1⁄2 Dorper 1⁄2 Santa Ines were used, with approximately 20 kg and 60 days of age, housed in individual pens of 1 m 2 . The feed intake by the animals was recorded daily weighting of the orts, accepting 15% of orts from feed offer. The animals were weighed every 14 days in order to evaluate performance, while the intake behavior was conducted over a period of 24 h, with observations every 5 minutes. On the 14 th day of the experimental period, the animals were subjected to daily fecal sampling for the digestibility trial. The economical evaluation used as main parameter to gross margin of finishing lambs. When the animals reached the approximate body weight of 33 kg were stunned and slaughtered. During slaughtering, non-carcass components and blood were weighed to obtain yields. After slaughter, the carcasses were weighed and sent to cold storage, where they remained for 24 hours. Subsequently, the carcasses were weighed and taken to the laboratory, where they were cut into half-carcasses and divided into 5 anatomical cuts for calculations of cuts percentage in relation to the half carcasses cuts. For meat quality evaluation the Longisimus lumborum muscles were used and quantified the ability to retain water, cooking loss, color and shear force. No significant differences of treatments on weight gain and feed conversion of lambs were observed, but the highest values of consumption in kg/day, body weight and metabolic weight were provided to diets ...
Mestre

Invitro synthesis and degradation capabilities and the cathepsin D activity of the skeletal muscles of experimentally induced Selenium-Vitamin E deficient lambs were investigated. Twenty-one Dorset x Coopworth x Suffolk lambs were blocked by weight and assigned to one of the following treatments: 1) a basal diet of 85% whole shelled corn and 15% mixed grass hay plus a mineral supplement that was low in Se and E (-Se-E), 2) the basal diet and deficient mineral mixture as fed in treatment 1 with the addition of a casein encapsulated fat supplement (-Se-E+fat), 3) the basal diet plus a mineral mixture which contained supplemental Se and E (+Se+E). Upon completion of the feeding trial, lambs which had been receiving the -Se-E treatment had the greatest body and individual muscle weights. The -Se-E+fat treatment had the lowest degradation rates and the highest synthesis rates. Cathepsin D activity was found to be lowest in the -Se-E+fat treatment. The -Se-E treatment was observed to have the highest degradation rate and the next highest synthesis rate indicating an increased rate of muscle turn-over. In all cases, the degradation rates were positively correlated with cathepsin D activity.
Master of Science

Thesis (M. Tech.) - Central University of Technology, Free State, 2010
The objective of this research study was to quantify the differences in average daily gain (ADG), back fat thickness (BFT), eye muscle area (EMA), fat thickness (FT) on different body parts, the feed conversion ratio (FCR) and body dimensions (by means of body measurements) of Dorper lambs exposed to supplemented light. For this study 120 Dorper lambs (115 ± 10 days old) weighing (29.76 ± 5.01kg) were used. The lambs were randomly divided into three homogeneous groups (20 castrated and 20 intact males). The three groups were then exposed to different levels of supplemented light at 145 lux (16h, 24h and normal photoperiod). The animals were fed ad libitum with pellets containing 9.5 MJ ME/kg DM and 12% CP in open pens. The animals were weighed every 7 days while ultrasound scanning of the EMA and the BFT was done at the beginning and the end of the 35 day trial. The ADG, FCR and feed intake (FI) were calculated at the end of the trial. Linear body measurements including shoulder height, body length and heart girth were taken at day 1 and day 35 respectively. All the animals were slaughtered at the end of the trail. The carcasses were then weighed, graded and the FT was measured with a caliper. The final results of the study showed that no significant differences between the three treatment groups (consisting of wethers and rams) in terms of body measurements, ultrasound scanning ADG and FCR could be detected. However, a significant difference was found between the wethers and the rams in the whole trial for ADG. The ADG of the rams exposed to 16 hours of supplemented light was significantly better than the normal photoperiod and the 24 hour light supplementation group.

The objective of this study was to determine sheep production practices, constraints, flock dynamics, body condition and weight variation in two ecologically different resource-poor communal farming systems of the Eastern Cape Province of South Africa. Mean sheep flock sizes per household were not significantly different between the two ecologically different areas (villages); Gaga (19.0±3.10) and Sompondo (18.3±3.10). Shortage of feed, disease and parasite were reported the most important constraints across the two villages. In both villages, sheep housing was poorly constructed using acacia brushwoods. Fewer farmers owned rams: the rams to ewes ratio for the two villages were 1:20, 1:19 for Gaga and Sompondo, respectively. The low ram: ewe ratios reported suggest that inbreeding might have been reducing productivity of their flocks. There was also uncontrolled breeding due to undefined and mating seasons. Gall sickness, heart water and footrot caused most of the sheep mortalities. Dohne Merinos were the common genotypes in the two villages. Total entrances for each flock were higher (p < 0.05) in hot-dry season and hot-wet season than in other seasons. Most of the entrances were lambs and were born in hot-dry season (September) and cool-dry season (June) for larger flocks (10.90 ± 3.02) and for small flocks (3.65 ± 3.02). High lamb mortalities were experienced in the post-rainy (April) and hot-wet (December) season. There was a significant interaction between season and flock size. Most of the sales occurred in the hot-wet season. Ecological area had significant effect on sheep production potential (p < 0.05) in both flock classes. The average sheep production efficiency (SPE) value for Gaga and Sompondo were 0.50 ± 0.116 and 0.50 ± 0.096 respectively. The SPE for large flock was higher (p < 0.05) by season and flock size. Large flocks had a higher (p < 0.05) SPE values and the SPE ranged from 1.11 ± 0.193 in April, a post-rainy season month to 1.55 ± 0.193 in December, a hot-wet season month. Lamb mortalities constituted the greater part of outflows. High lamb mortalities occurred in hot-wet (December), hot-dry (September) and post-rainy (April) seasons. There was a significant interaction between season and age of sheep on body weight of sheep. Highest (p < 0.05) body weights were recorded in the post-rainy and autumn season in both lambs and ewes. It is therefore very important to come up with affordable interventions which take into play ecological differences of the areas for improved nutritional status of sheep in communal areas which will lead to improved sheep productivity and the poor-resourced farmer human nutritional and livelihood.

Thesis (MScAgric)--Stellenbosch University, 2011.
ENGLISH ABSTRACT: The following study is to determine if a creep feed balanced for limiting essential amino acids (EAA) at a certain non structural carbohydrate (NSC) level will elicit greater responses than lambs reared on a commercial creep feed. Lysine, Threonine, Methionine, Isoleucine, Phenylalanine and Leucine were determined as the limiting amino acids for nursing lambs. These amino acids were incorporated into the creep feed treatments CF1 and CF2 representing 157 g CP/kg, 477 g NSC/kg and 179 g CP/kg, 508 g NSC/kg, respectively. A commercial creep feed with no optimisation for EAA is represented as CFC with 139 g CP/kg and 455 g NSC/kg. A negative control (CON) treatment represents lambs receiving no creep feed but with ad libitum access to suckle their dams while feeding on kikuyu pasture. A growth trial was conducted on Merino x Döhne-Merino cross twin lambs averaging a birth weight of 4.42 kg ± 0.11 for 60 days following with a digestibility trial towards the end of the trial. Half of the lamb crop was slaughtered at an average live weight of 23.6 kg ± 0.56. The M. longissimus dorsi was removed on both the left and right half of the carcass between the 2nd - 3rd last thoracic vertebrae and the 4th - 5th lumbar vertebrae. A sample from the rumen wall was taken at the rumino-reticular fold to determine development characteristics. Results indicate that the feed conversion ratio for the CFC lambs were better than CF1 (P = 0.052) but not more than CF2 (P = 0.307). The FCR was 0.88, 1.19 and 1.01 (kilogram feed required to gain 1 kg in bodyweight) for CFC, CF1 and CF2, respectively. Dressing percentage was higher for CF2 than for both CFC (P = 0.012) and CF1 (P = 0.077). Along with BUN data it was concluded that the high CP level of CF2 resulted in the higher fat deposition. The optimised creep feeds had higher nitrogen and energy balances than the commercial CFC, this implicates that the optimised creep feeds were more efficiently utilised. Optimised creep feed treatments had longer papillae than CON (P < 0.0001). Papillae of creep feed 2 was longer than CFC (P = 0.0537). Papillae width decreased as the NSC level increased thus it is surmised that higher NSC levels resulted in longer but thinner papillae. Rumen muscularization was equally developed between all the treatments and was ascribed to the lambs’ access to course roughage. Meat quality in terms of physical and chemical characteristics was found to be in range with that expected for lambs at higher slaughter weights (40 kg). In conclusion, the balancing of the limiting EAA increases the benefits of creep feeding while simultaneously being more efficiently utilised. Intensive sheep production systems may benefit from the feeding of such creep feeds provided it fits economically into their farming system.
AFRIKAANSE OPSOMMING: Die volgende studie is om te bepaal of 'n kruipvoer wat gebalanseerd is vir beperkende essensiële aminosure (EAA) by 'n vasgestelde nie-strukturele koolhidraat (NSK) vlak verbeterde groei sal ontlok teenoor lammers wat grootgemaak word op 'n kommersiële kruipvoer. Lisien, Treonien, Metionien, Isoleusien, Fenylalanien en Leusien is bepaal as die beperkende aminosure vir suipende lammers. Hierdie aminosure is opgeneem in die geoptimiseerde kruipvoer behandelings CF1 en CF2 wat 157 g RP/kg, 477 g NSK/kg en 179 g RP/kg, 508 g NSK/kg onderskeidelik verteenwoordig. 'n Kommersiële kruipvoer met geen optimalisering vir EAA is verteenwoordig as CFC met 139 g RP/kg en 455 g NSK/kg. 'n Negatiewe kontrole (CON) behandeling is verteenwoordig deur lammers wat geen kruipvoer ontvang het nie, maar wat ad libitum toegang tot hul ooi gehad het om te soog terwyl die ooi op ‘n kikoejoeveld wei. 'n Groei proef is uitgevoer met Merino x Döhne-Merino kruis tweelinglammers met ‘n gemiddelde geboorte gewig van 4,42 ± 0,11 kg vir 60 dae en 'n verteerbaarheids proef is na aan die einde van die studie uitgevoer. Helfte van die lam kudde is geslag by die lewende gewig van 23,6 ± 0, 56 kg. Die M. longissimus dorsi was op beide die linker-en regter helfte van die karkas tussen die 2de - 3de laaste torakale werwels en die 4de - 5de lumbale werwels verwyder. 'n Monster van die rumen wand is geneem langs die rumino retikulêre vou sodat die rumen ontwikkeling eienskappe daarmee bepaal kon word. Resultate dui daarop aan dat die voeromsetverhouding (VOV) vir CFC lammers beter was as vir CF1 (P = 0,052), maar nie meer as vir CF2 (P = 0,307) nie. Die VOV was 0,88 , 1,19 en 1,01 (kilogram voer wat nodig is om 1 kg liggaamsmassa aan te sit) vir CFC, CF1 en CF2 onderskeidelik. Uitslag persentasie vir CF2 was hoër as beide CFC (P = 0,012) en CF1 (P = 0,077). Saam met die bloed, urea en stikstofbalans data is daar tot die gevolgtrekking gekom dat die hoë RP inhoud van CF2 gelei het tot ‘n hoër vetneerlegging. Die geoptimaliseerde kruipvoere het ‘n hoër stikstof- en energiebalans gehad teenoor die kommersiële CFC behandeling wat dus impliseer dat die optimale kruipvoere doeltreffender benut was. Die geoptimaliseerde kruipvoer behandelings het langer papillae gehad as CON (P < 0,0001). Papillae lengte van die CF2 behandeling is langer as die van CFC (P = 0,0537). Papillae breedte het dunner geraak soos wat die NSK-vlak gestyg het dus word vermoed dat hoër NSK-vlakke langer maar dunner papillae tot gevolg het. Rumen bespiering is ewe ontwikkeld tussen al die behandelings en word toegeskryf aan die lammers se toegang tot growwe ruvoer. Vleis kwaliteit in terme van fisiese- en chemiese eienskappe was inlyn met wat verwag kan word vir lammers by hoër slaggewigte (40 kg). Ten slotte, die balansering van beperkende aminosure verhoog die voordele van kruipvoeding en word terselfdertyd doeltreffender benut. Intensiewe skaap produksie stelsels kan dus voordeel trek uit die voeding van sodanige kruipvoere mits dit ekonomies pas in die boerdery stelsel.

En zone tropicale, la production de lait et de viande par les ruminants est limitée par une faible disponibilité et une qualité médiocre des fourrages. A ces contraintes alimentaires s’ajoute l’impact environnemental lié en particulier aux émissions de méthane entérique par les ruminants. L’objectif de cette thèse était de comparer la production de méthane en milieu tempéré et en milieu tropical, puis de valoriser des fourrages tropicaux connus pour leur richesse en tanins dont les propriétés anti-méthanogènes sont reconnues, et qui peuvent réduire l’impact environnemental sans compromettre la productivité animale. Cette thèse comporte trois expérimentations distinctes. La première consistait en une étude in vivo visant à déterminer si les différences de digestibilité, de production de méthane, de fermentation et d’écosystème microbien du rumen observées entre les zones tempérées et tropicales proviennent de l’environnement (site d’expérimentation en milieu tempéré ou tropical), du fourrage (produit en zone tempérée ou tropicale), ou du génotype ovin (race de zone tempérée ou tropicale). Les résultats ont montré que les différences sont liées en priorité à la nature du fourrage, et sont influencées par les interactions entre génotype, caractéristiques du fourrage et environnement. La seconde expérience consistait à étudier l’effet de plantes riches en tanins condensés (feuilles de Gliricidia sepium, Leucaena leucocephala, Manihot esculenta) sur la production de méthane, l’ingestion et la digestibilité de la ration, les fermentations et l’écosystème microbien du rumen. Un essai in vivo a montré que l’incorporation de ces plantes à raison de 40% du régime d’ovins sous forme de granulés permettait de réduire le méthane entérique sans effets indésirables sur la digestibilité et la fermentation ruminale. Un essai in vitro a montré que le principal facteur de la réponse a été la dose de tanins condensés plutôt que la source. La troisième expérience consistait en l’étude in situ et in vitro du pouvoir anti-méthanogène et de la dégradation dans le rumen de plantes riches en tanins hydrolysables (feuilles et gousses d’Acacia nilotica) ou en tanins condensés (feuilles de Calliandra calothyrsus, Gliricidia sepium, Leucaena leucocephala, Manihot esculenta, Musa spp). Les résultats obtenus suggèrent que les tanins hydrolysables conviennent mieux à la réduction des émissions de méthane que les tanins condensés car ils inhibent fortement la production de méthane sans effets négatifs marqués sur la fermentation ruminale. Les effets des tanins sur la production de méthane et la fermentation dans le rumen ont été en partie expliqués par le devenir des différentes fractions des tanins (libres, associés aux protéines ou aux fibres) dans le rumen. L’association de plantes riches en tanins hydrolysables et en tanins condensés ne parvient pas à dégager de possibles synergies entre ces de types de molécules. Ce travail a permis de montrer qu’il était possible de réduire les émissions de méthane entérique par les ruminants en milieu tropical par la consommation de fourrages riches en tanins hydrolysables sans compromettre les processus digestifs dans le rumen ; la diminution de la méthanogenèse avec les tanins condensés présente plus de risque de réduire les fermentations
In tropical areas, dairy and meat production from ruminants is limited by low availability and poor quality of forages. In addition to this dietary constraint, the emission of enteric methane under these less productive conditions is proportionally larger than under temperate conditions. The aim of this work is i) to compare enteric methane production in tropical and temperate environments, and ii) to promote tropical forages rich in hydrolysable or condensed tannins having anti-methanogenic properties that could reduce the environmental impact without compromising animal productivity. This work includes three separate studies. The first one was an in vivo study aiming to determine the origin of the differences of digestibility, methane production, ruminal fermentation and microbial ecosystem between tropical and temperate countries using as variables: the site of the experiment (tropics or temperate area), the type of forage (grown in the tropics or in temperate areas); and the animal genotype (tropical or temperate). Results showed that differences are mainly due to forages, but with interactions between nature of forages, environment and genotype. The objective of the second study was to determine the effect of plants rich in condensed tannins (leaves of Gliricidia sepium, Leucaena leucocephala, and Manihot esculenta) on methane production, intake, digestibility, ruminal fermentation and microbial ecosystem. An in vivo trial demonstrated that the inclusion of 40% of these plants as pellets in sheep diet reduced enteric methane without compromising the nutritive value of the diet. An in vitro trial showed that the response to tannins was more due to tannin concentration than to the plant species. In the third study, plants rich in hydrolysable tannins (leaves and pods of Acacia nilotica) or in condensed tannins (leaves of Calliandra calothyrsus, Gliricidia sepium, Leucaena leucocephala, Manihot esculenta, Musa spp) were studied for their anti-methanogenic properties and their ruminal degradation in an in situ and an in vitro trial. Results suggest that hydrolysable tannins are more suitable than condensed tannins for mitigating methane emission because of a strong reduction in methane production without negatively affecting ruminal fermentation. These results have been partly explained by the fate of the different fractions of condensed tannins (free, protein-bound and fibre-bound) in the rumen. The association of plants rich in hydrolysable tannins with plants rich in condensed tannins failed to produce synergistic effects on methane mitigation. This work showed that enteric methane production by ruminants could be reduced in tropical areas by the inclusion of hydrolysable tannins without compromising digestive processes in the rumen; methane mitigation with condensed tannins may result in a reduction of the extent of fermentation

The objective of the present work was to elucidate some of the possible choice determinants involved in diet selection by sheep and goats. The first experiment investigated the ingestive and digestive responses of these two species to a range of forage chemical composition attributes (i.e. nitrogen and fibre content). Forage DM intake was positively associated with their nutritive quality. Goats had higher voluntary DM intakes (P<0.05) and lower apparent digestibility coefficients (P<0.001) for any given forage than sheep, but the intake of digestible DM was similar for the two species. When forages were offered in pairs in a preference trial, the two species ranked forages similarly by favouring those of higher nutritive quality. The second experiment investigated the effects of different staple lengths of a single hay on the ingestive and digestive responses of sheep and goats. Goats had higher voluntary DM intakes (P<0.05) and lower apparent digestibility coefficients (P<0.001) for any given length than sheep, but the intake of digestible DM was similar for the two species. Goats allocated less time (P<0.001) than sheep to chewing the feed consumed and the mean retention time of the undigested residues in the animals' digestive tract was significantly shorter (P<0.01) for goats than sheep. When staple lengths of the grass hay were offered in pairs none of them was favoured and the choices were not significantly different between goats and sheep. In a third experiment a new method of feed presentation was developed and compared with conventional feed-bins. Goats had higher voluntary intakes than sheep (P<0.05), whereas there was no effect of the feed presentation method on DM intake.

The selection on genetic values predicted from markers could substantially increase the rate of genetic gain in animals by increasing accuracy of prediction and reducing generation interval, especially for difficult to measure traits, such as feed efficiency. Feed efficiency is the most important trait in animal production due to its impacts on cost of production and environmental factors. Many metrics measure the feed efficiency, such as ratio of gain to feed (FER), the ratio of feed to gain (FCR) and residual feed intake (RFI). Nevertheless, in ovine, no study with the aim of understand the genetic variants or the accuracy of genomic estimated breeding value (GEBV) for feed efficiency traits was published yet. Moreover, before to apply the genomic information, it is necessary to understand and characterized the population structure, for instance, by linkage disequilibrium (LD). Both genome-wide association studies (GWAS) and genomic selection (GS) leverage LD between marker and causal mutation. Based on the above considerations, the aim of this study was to map LD in ovine, characterized by Brazilian Santa Inês sheep; to search genetic variants for feed efficiency traits (FER, FCR and RFI) through GWAS; and to verify the accuracy of GEBV for RFI. In total, 396 samples (animals) of Longissimus dorsi muscle were collect. A high-density panel of SNP (Illumina High-Density Ovine SNP BeadChip®) comprising 54,241 SNPs was used to obtain the genotyping data. The phenotype data was comprised of 387 animals. The average LD between adjacent markers for two LD metrics, r² and |D\'|, were 0.166 and 0.617, respectively. The degree of LD estimated was lower than reported in other species and it was characterized by short haplotype blocks. Consequently, for genomic analyses, high-density panels of marker are recommended. Many markers were associated to feed efficiency traits in GWAS, mainly to RFI trait. Few candidate genes were reported in this study, highlighting NRF-1 (nuclear respiratory factor 1), which controls mitochondrial biosynthesis, the most important process responsible by a great fraction of the produced energy. Finally, we verified the accuracy of GEBV for RFI using few Bayesian regression models, and we found low accuracy, ranging from 0.033 (BayesB with π=0.9912) to 0.036 (BayesA), which might be explained by the low relationship among animals and small training population.
A seleção com base nos valores genéticos genômicos preditos pode aumentar substancialmente a taxa de ganho genético em animais por meio do aumento da acurácia de predição e redução do intervalo de gerações, especialmente para características de difícil e/ou onerosa mensuração, como eficiência alimentar. A eficiência alimentar é uma das características mais importantes na produção animal devido principalmente aos seus impactos econômicos e ambientais. Muitas métricas representam a eficiência alimentar, por exemplo: a relação do ganho de peso e consumo alimentar (EA), a proporção do consumo alimentar e ganho de peso (CA) e o consumo alimentar residual (CAR). Em ovinos, nenhum estudo com o objetivo de buscar variantes genéticas ou verificar a acurácia do valor genético genômico estimado para eficiência alimentar foi publicado. Adicionalmente, antes de aplicar a informação genômica, é necessário compreender e caracterizar a estrutura da população, como por meio do desequilíbrio de ligação (LD). O estudo de associação genômica (GWAS) e seleção genômica (GS) consideram o LD entre marcador e a mutação causal. Com base nas considerações acima, o objetivo deste estudo foi mapear o LD em ovinos, caracterizado pela raça ovina Santa Inês; localizar variantes genéticas para as características de eficiência alimentar (EA, CA e CAR) utilizando a abordagem GWAS; e verificar a acurácia da estimação dos valores genéticos genômico para o CAR. No total, foram coletadas 396 amostras (animais) do músculo Longissimus dorsi, para posterior genotipagem utilizando o painel de alta densidade (Illumina High-Density Ovine SNP BeadChip®), compreendendo 54.241 SNPs. O banco fenotípico é composto por 387 animais. O LD médio entre marcadores adjacentes para duas métricas de LD, r² e |D\'|, foram 0,166 e 0,617, respectivamente. O grau de LD estimado foi menor que o relatado em outras espécies e foi caracterizado por blocos de haplótipos curtos. Consequentemente, para as análises genômicas são recomendados painéis de marcadores de alta densidade. No GWAS, foram encontrados muitos marcadores associados aos fenótipos, em especial, à característica CAR. Alguns genes candidatos foram relatados neste estudo, destacando-se o NRF-1 (fator respiratório nuclear 1), que controla a biossíntese mitocondrial, o processo mais importante responsável por grande parte da produção de energia. Finalmente, verificamos a acurácia do valor genético genômico estimado para o CAR usando modelos de regressão Bayesiana, e encontramos baixos valores para acurácia (0,033 a 0,036) o que pode ser explicado pelo baixo grau de relacionamento entre os indivíduos e tamanho reduzido da população de treinamento.

[Truncated abstract] Saltbush is one of the few types of forage that will grow on salt affected land but, sheep struggle to maintain weight when grazing saltbush mainly because of its high salt content. Therefore, a strategy to improve salt tolerance of sheep would be beneficial to the profitable use of revegetated saline land. This could be done by manipulating the dietary salt load of pregnant or lactating ewes which could 'program', or permanently alter the physiology of their offspring to allow them to cope better with a high-salt diet as adults. When rat dams consume a high amount of salt during pregnancy, the salt balance mechanisms of their offspring are 'programmed' due to suppression of the offspring's renin-angiotensin system in early development. If this occurs in offspring from ewes grazing saltbush, beneficial adaptations may be programmed in these offspring which could allow them to better cope with the high-salt content of saltbush. I tested the general hypothesis that offspring born to ewes that consumed a high-salt or saltbush diet from mid-pregnancy to early lactation would have an increased capacity to cope with salt that would allow them gain weight when grazing saltbush in later life. To test this hypothesis, I pair-fed ewes either a high-salt diet (14% NaCl) or control diet (2% NaCl) in an animal house from day 60 of gestation until day 21 of lactation. During the same period, I also conducted a field experiment where ewes grazed on saltbush (supplemented with barley) or on pasture (supplemented with lupins). ... This led to the high-salt offspring retaining more salt than control animals. In contrast, the renin activity of saltbush was consistently lower than pasture offspring which allowed them to excrete salt more rapidly. In experiment three, the saltbush offspring gained tissue weight after grazing saltbush for 8 weeks, whereas the offspring in the other three treatments lost weight. High-salt and saltbush offspring also had higher greasy fleece weights at 22 months of age than their respective control groups. Feeding saltbush to ewes from mid-pregnancy to early lactation induces physiological adaptations in their offspring that allow them to cope better with salt and gain weight when grazing saltbush as adults, supporting my hypothesis. However, contrary to expectations, the high-salt offspring did not gain weight when grazing saltbush because their physiological adaptations, such as salt retention, did not allow them to cope better with a salt load. The reason that saltbush offspring showed different adaptations to highsalt offspring is likely to be because saltbush contains not only NaCl but also high amounts of other minerals such as potassium, and other plant compounds, which may influence the adaptive responses of the offspring. This research has direct implications for farmers because it shows they could utilize otherwise unproductive saltland by grazing pregnant ewes on saltbush to 'program' their offspring to gain weight when they graze saltbush later in life.