Rozprawy doktorskie na temat „Bees Feeding and feeds”

In the community of Tunshi San Nicols of the Licto parish in the Province of Chimborazo, an evaluation was done on the effect of an energetic supplementary feeding of bees (Italian-mestizas) during the dry season (September 23 to February 20). These supplements consisted of carrot juice (T1), orange juice (T2) and sugar cane juice (T3). These supplements were also compared to a control group (T0). The experimental units consisted of 16 standard beehives distributed randomly with the 4 treatments and 4 repetitions of each treatment. The results showed that sugar cane juice (T3) obtained the best results in the consumption of the supplementary feeding because it was the only treatment where its consumption increased as the nectar sources in the zone decreased. At the end of the evaluation, 17,312.50 ml. of sugar cane juice were consumed. On the other hand, only 1,486.25 ml. of carrot juice were consumed, which was the least amount out of all of the treatments. Similarly, sugar cane juice presented the least weight loss, with 1.050 kg. per beehive. In addition, sugar cane juice also presented the greatest number of breeding frames (6.950 frames per beehive), as well as the best benefit/cost index (1.15) at the end of the study.

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 (PhD (Agric))--University of Stellenbosch, 2005.
ENGLISH ABSTRACT: It is generally accepted that feed intake and growth (gain) are the most important economic components when calculating profitability in a growth test or feedlot. Feeding cost of animals is a major determinant of profitability in livestock production enterprises. Genetic selection to improve feed efficiency aims to reduce the cost of feeding in beef cattle production and thereby improve profitability. The objective of this study was to define a clear selection objective to enable South African beef breeders and especially the feedlot industry to select for post-weaning growth or feedlot performance and to identify factors influencing profitability in a feedlot environment. Because of the recording of individual feed intake and weight gain values in the South African Agricultural Research Councils' centralized growth tests, it was also possible to calculate a phenotypic value for feedlot profitability (R-value) for each bull tested in a centralized growth test. (Co)variances, using multitrait as well as random regression models, for and between feedlot profitability, weaning weight and other production, reproduction and efficiency traits were estimated. Residual feed intake (RFI) and feed conversion ratio (FCR) as efficiency traits were also compared to growth (average daily gain (ADG), weaning weight (WW) and shoulder height (SHD)), reproductive (scrotum circumference (SCR)) and profitability (feedlot profitability) traits measured in growth tests of young Bonsmara bulls. Consequently, a single post-weaning growth selection index value based on the economic and breeding values of different selection criteria related to feedlot profitability was composed. (Co)variance components, heritabilities and genetic correlations for and between initial weight (lW), final weight (FW), total feed intake (FI) and shoulder height (SHD) were estimated through the use of multitrait restricted maximum likelihood (REML) procedures. These breeding values (EBV s) were then used in a selection index to calculate a single economical value for each animal. This economical value is an indication of the gross profitability value or gross test value (GTV) of the animal in a post-weaning growth test. The heritability estimate of 0.36 for R-value, obtained from the multitrait analysis, shows that this trait is genetically inherited and that it can be selected for. The heritability for R-value obtained from the single trait random regression model varied between 0.57 and 0.62. The genetic correlations between the R-value and the other traits, obtained from the multitrait analysis, varied from negligible to high. The heritability estimated for FCR was 0.34 and for RFl 0.31 with a genetic correlation estimate of 0.75 between the traits. The estimated genetic correlation between profitability (R-value) and FCR and RFl were -0.92 and -0.59, respectively. The genetic correlation estimate of -0.92 between FCR and R-value is largely due to the part-whole relationship between these two traits. This is also shown in their genetic trends. The genetic correlations and expected correlated responses between RFl and FCR with R-value suggest that indirect selection for R-value through the direct selection for FCR and/or RFl will result in slower genetic progress in Rvalue than direct selection for R-value. However, where the R-value cannot be calculated and/or where direct selection for R-value is not possible, it would be better to select indirectly for R-value through the use of FCR rather than RF!. Consequently, a regression equation was developed (with an R2 of 0.82) to estimate a feed intake value for all performance-tested Bonsmara bulls which were group fed and whose feed intakes were unknown. These predicted feed intake values made it possible to calculate a feedlot or post-weaning growth profitability value (R-value) for all tested bulls even where individual feed intakes were unknown. Subsequently, an R-value for each bull was calculated in a favourable economic environment (FEE), an average economic environment (AEE) and in an unfavourable economic environment (VEE). The high Pearson and Spearman correlations between the EBV s based on AEE and the other two environments suggested that the average economic environment could be used to calculate EBVs for R-value or feedlot growth profitability. It is therefore not necessary to change the carcass, weaner or feed price on a regular basis to account for possible re-rankings based on R-value EBVs. Heritabilities for lW, FW, Fl and SHD were 0.41, 0.40, 0.33 and 0.51, respectively. The highest genetic correlations between these traits were the 0.78 (between lW and FW) and 0.70 (between Fl and FW). GTV values varied between -R192.l7 and R231.38, with an average of R9.31. The Pearson correlations between EBVs (for production and efficiency traits) and GTV range from -0.51 to 0.68. The lowest correlation (closest to zero) was 0.26 between the Kleiber ratio (KLB) and GTV. Correlations of 0.68 and -0.51 were estimated between average daily gain (ADG) and GTV and feed conversion ratio (FCR) and GTV, respectively. The heritabilities of the different traits included in the selection index suggest that it is possible to select for a GTV. The selection index can benefit feedlotting In selecting offspring of bulls with high GTV values to maximize profitability. The Pearson and Spearman correlations between the R-value EBVs and the index values (GTV) were very high (0.97). This high correlation of 97% indicates that it is not important which method is used to calculate a genetic post-weaning growth of feedlot profitability value. The selection index value is, however, more simplified than the feedlot profitability with less assumption. Therefore, it is recommended that the post-weaning selection index value be used as a selection objective in breeding programmes to improve post-weaning growth profitability rather than the more complex feedlot profitability value.
AFRIKAANSE OPSOMMING: 'N GENETIESE ANALIESE VAN DIE BIOLOGIESE EN EKONOMIESE DOELTREFFENTHEID VAN NASPEENSE GROEI IN VLEISBEESTE IN DIE VOERKRAAL: Dit word algemeen aanvaar dat voerinname en groei die twee ekonomies mees belangrike komponente in die berekening van 'n naspeense groei- of voerkraalwinsgewindheidswaarde is. Voerkostes is 'n bepalende faktor van winsgewindheid in enige lewendehawe boerderypraktyk. Seleksie om voerdoeltreffendheid te verbeter, verminder dus die voerkostes in vleisbeesproduksie en gevolglik 'n verhoging in die winsgewindheid. Die doelwit van die studie was om faktore te identifiseer wat 'n invloed op winsgewindheid in die voerkraaiomgewing het asook om 'n duidelike seleksiedoelwit te formuleer wat die Suid- Afrikaanse vleisbeesteiers en veral die voerkraalbedryf instaat sal kan stelom vir naspeense groeidoeltreffendheid ofvoerkraalwinsgewindheid te selekteer. As gevolg van die aantekening en rekordhouding van weeklikse individuele voennnames en gewigstoenames van alle prestasiegetoetsde bulle, in 'n gesentraliseerde groeitoets deur die Suid- Afrikaanse Landbou Navorsingsraad getoets, was dit moontlik om vir elk van hierdie bulle 'n fenotipiese voerkraalwinsgewindheidswaarde (R-waarde) te kon bereken. (Ko)variansies is vir en tussen voerkraalwinsgewindheid, speengewig en ander produksie-, reproduksie- en doeltreffendheidseienskappe bereken deur van meereienskap en ewekansige regressie modelle gebruik te maak. Twee doeltreffendheidseienskappe naamlik residuele voerinname (RFI) en voeromsetverhouding (FCR) is ook met groei (gemiddelde daaglikse toename (ADG), speengewig (WW) en skouerhoogte (SHD)), reproduksie (skrotumomvang (SCR)) en winsgewindheidseienskappe (voerkraalwinsgewindheid (R-waarde)) vergelyk, om sodoende te bepaal watter een die mees geskikte eienskap is om indirek vir voerkraalwinsgewindheid of groei, gebaseer op teeltwaardes en ekonomiese waardes vir die verskillende eienskappe, wat 'n invloed op naspeense groei winsgewindheid het, gestruktueer. (Ko)variansiekomponente, oorerflikhede en genetiese korrelasies vir en tussen begingewig (lW), eindgewig (FW), voerinname (FI) en skouerhoogte (SHD) is bereken deur van 'n meereienskap (REML) ontleding gebruik te maak. Hierdie teelwaardes (EBVs) is vervolgens in 'n seleksie-indeks gebruik om 'n enkele ekonomies of voerkraal-winsgewindheids seleksie-indekswaarde (GTV) vir elke dier te bereken. Hierdie ekonomiese waarde is 'n aanduiding van die bruto winsgewindheidswaarde ofbruto toetswaarde (GTV) van die dier in 'n naspeentoets. Die oorerflikheid, vanuit die meereienskapontleding vir R-waarde beraam, was 0.36. Hierdie oorerflikheid dui daarop dat die eienskap oorerflik is en dat dit wel moontlik is om daarvoor te selekteer. Die ooreflikhede van R-waarde, voorspel vanuit die enkeleienskap ewekansige regressieontleding varieer tussen 0.57 en 0.62. Die genetiese korrelasie tussen R-waarde en ander eienskappe, vanuit die meereienskap ontleding beraam, varieer tussen weglaatbaar klein tot hoog. Die oorerflikheid van FeR was 0.34 en van RFI 0.31 met 'n genetiese korrelasie van 0.75 tussen die twee eienskappe. Die genetiese korrelasie tussen R-waarde en FeR, en R-waarde en RFI was onderskeidelik -0.92 en -0.59. Die rede vir die hoë negatiewe genetiese korrelasie tussen R-waarde en FeR van -0.92 is omdat dieselfde komponente in die berekening van die twee eienskappe gebruik is. Dit word ook in die genetiese tendense weerspeël. Die genetiese korrelasies en verwagte gekorreleerde responsies tussen R-waarde en FeR, en tussen R-waarde en RFI dui daarop dat stadiger genetiese vordering verkry sal word in R-waarde deur direkte seleksie vir beide FeR en RFI as wat verkry sal word deur die direkte seleksie vir R-waarde. Wanneer 'n R-waarde egter nie bereken kan word nie of waar dit nie moontlik is om direk vir R-waarde te selekteer nie, sal vinniger genetiese vordering in R-waarde gemaak word deur die direkte seleksie vir FeR as vir RF!. 'n Regressievergelyking is geformuleer (met 'n R2 van 0.82) om vir alle prestasiegetoetsde bulle, waar bulle in 'n groep gevoer is en individuele voerinnames onbekend is, 'n voerinnamewaarde te voorspel. Hierdie voorspelde voerinnames maak dit moontlik om vir elke prestasiegetoetsde bul ,'n naspeengroei- of voerkraalwinswaarde (R-waarde) te bereken, al is hulle individuele voerinnames onbekend. Vervolgens is drie verskillende R-waarde vir vleisproduksie vir elke bul bereken naamlik, in 'n gunstige ekonomiese omgewing (FEE), 'n gemiddelde ekonomiese omgewing (AEE) en 'n ongunstige ekonomiese omgewing (VEE). Die hoë Pearson en Spearman korrelasies tussen die EBVs vir R-waarde, bereken in die AEE en die EBVs in die ander twee ekonomiese omgewings, dui daarop dat die AEE gebruik kan word om EBVs vir naspeense groeiof voerkraalwins te bereken. Dit is dus nie nodig om op 'n gereelde grondslag die karkasprys, lewendige speenkalfprys of die voerprys te verander nie. Oorerflikhede, vanuit die meereienskap ontledings VIr lW, FW, FI en SHD verkry, was onderskeidelik 0.41, 0.40, 0.33 en 0.51. Die hoogste genetiese korrelasies tussen die eienskappe was 0.78 tussen lW en FW en 0.70 tussen FI en FW. GTV indekswaardes varieer tussen -Rl92.17 en R231.38 met 'n gemiddelde waarde van R9.31. Die Pearson korrelasies tussen die EBVs van produksie- en doeltreffenheidseienskappe en GTV het tussen -0.51 en 0.68 gevarieer. Die korrelasie naaste aan zero, van 0.26, was die korrelasie tussen GTV en die Kleiber-verhouding. Die korrelasies tussen GTV en ADG, en GTV en FeR was onderskeidelik 0.68 en -0.51. Die oorerflikhede van die verskillende eienskappe wat in die seleksie-indeks ingesluit is, dui daarop dat die indekswaarde weloorerflik is en dat seleksie hiervoor wel moontlik is. Hierdie indekswaarde kan deur die voerkraaiindustrie gebruik word om nageslag van diere met hoë GTV waardes te selekteer om sodoende maksimum wins uit die voerkraai te genereer. Die Pearson en Spearman korrelasies tussen R-waarde EBVs en die indekswaardes (GTV) was besonder hoog (0.97). Hierdie hoë korrelasie dui daarop dat dit geen verskil sal maak watter een van die twee metodes gebruik word in die berekeninge van 'n naspeense groei- of voerkraalwinswaarde nie. Die seleksie-indeks metode is egter minder gekompliseerd met minder aannames as in die geval van die rekeningkundige fenotipiese benadering (R-waarde). As gevolg hiervan, word die naspeense seleksie-indeks waardes (GTV) aanbeveel om te gebruik as 'n teeldoelwit in telingsprogramme om naspeense groei- of voerkraaiwins geneties te verbeter, eerder as die meer gekompliseerde fenotipiese voerkraaiwins (R-waardes) metode.

Sugar intake is linked to developmental programming of obesity and diabetes. We hypothesized that supplementing ground beef in place of sugar during pregnancy would reduce fetal and offspring developmental programming. Gestating sows were fed 1 of 4 isocaloric supplements: control, ground beef, granulated sugar, or beef plus sugar. In the fetal study supplements were fed from d 40 to 110 of gestation and in the offspring study from d 40 until weaning. Gene expression differences in fetal liver and muscle were observed for IGF2 (P = 0.04), FBPase (P = 0.03), and IGF2R (P = 0.02). Differences were also seen in offspring back fat (sex by day interaction, P = 0.01), longissimus dorsi muscle area (treatment by sex, P = 0.001), body weight (sex, P = 0.0006; sex by day interaction, P < 0.0001), and plasma insulin concentrations (treatment by sex, P = 0.0002).
North Dakota Beef Commission
Topigs Norsvin
North Dakota. State Board of Agricultural Research and Education

Thesis (MScAgric)--University of Stellenbosch, 2001.
ENGLISH ABSTRACT: The purpose of this study was to determine the essential amino acid requirements of beef cattle under feedlot conditions through evaluation of the duodenal and whole empty body essential amino acid compositions. To define the ideal protein required for growth, the whole empty body essential amino acid compositions of 8 beef steers (Simmental and Hereford crosses) was investigated. The amino acid composition of the components (carcass, metabolic organs and residual fraction), was pooled relative to their respective mass and protein contribution, resulting in the calculated whole empty body amino acid composition: arginine 6.81; histidine 2.69; isoleucine 4.02; leucine 6.96; lysine 7.43; methionine 2.01; phenylalanine 4.03; threonine 4.01; valine 5.30; tryptophan 0.82. Variations in profiles were found between scientific reports, either indicating that ratios change with growth and implants or possibly through genotype. The present study's body amino acid ratios were used to estimate dietary amino acid requirements through evaluation of the duodenal essential amino acid compositions from three different maize based feedlot diets. Although there was a general increase in the biological value of protein after rumen fermentation, the duodenal essential amino acids in comparison with the whole empty body recorded deficient/unbalanced profiles of essential amino acids for growth. The chemical scores suggested that the first-to-thirdlimiting amino acids in the duodenal digesta of beef cattle, that received three different commercially available feedlot diets, were: histidine, lysine, methionine/arginine (Diet 1), histidine, arginine, lysine (Diet 2) and arginine, methionine, histidine (Diet 3). Thedisproportionate duodenal amino acid concentrations obtained from the three diets, emphasise the necessity to enhance the intestinal delivery of amino acid profiles through different undegradable protein sources, with the objective to maximise protein utilisation and obtain the genetic potential for optimal growth in feedlot cattle. When amino acid requirements and flows to the duodenum were simulated using the Cornell Net Carbohydrate and Protein system (CNCPS), predictions indicated that lysine amino acid flow was limiting the metabolizable allowable average daily gain in Diet 1 and 3. Predicted profiles indicated that the order of limitation was: lysine, arginine, histidine (Diet 1), lysine, arginine, histidine, methionine (Diet 2) and lysine, arginine, histidine (Diet 3). The predicted profiles were in accordance with observed duodenal values, except for methionine that was observed limiting in Diet 1 and 3; however, the sequence and extent of limitation varied. Results indicate that prediction models have potential in predicting requirements; however there are still limitations for use to accurately define requirements for particular EAA's. From the present study, it is clear that the protein accretion was constrained by quantity and/or disproportionality of amino acids available for absorption. Further research should therefore be directed towards obtaining a more desirable array of amino acids to the lower digestive tract that is digestible, absorbable and an economically viable option for the feedlot operator.
AFRIKAANSE OPSOMMING: Aminosuurbehoeftes van Voerkraalbeeste Volgens die Duodenale en Totale Lee Liggaam Essensiele Aminosuur Profiel: Die doel van hierdie studie was om die essensiele aminosuur vereistes van vleisbeeste onder voerkraal toestande te bepaal deur die evaluering van die duodenale en totale lee liggaam essensiele aminosuursamesteilings. Om die idea Ie proteiene wat vir groei benodig word te definieer, is 'n ondersoek ingestel na die totale lee liggaam essensiele aminosuursamesteilings van 8 vleisbees osse (Simmetailer en Hereford kruise). Die aminosuursamesteiling van die komponente (karkas, metaboliese organe en residuele fraksie), se massa en proteien bydrae is gebruik om die totale lee liggaam aminosuursamestelling 5005 volg te bereken: arginien 6.81; histidien 2.69; isoleusien 4.02; leusien 6.96; lisien 7.43; metionien 2.01; fenielalanien 4.03; treonien 4.01; valien 5.3; triptofaan 0.82. Variasies in profiele tussen wetenskaplike verslae is gevind. Dit dui daarop dat groei en inplantings of moontlik genotipe 'n invloed op profiele kan he. Die huidige studie se liggaam aminosuurverhoudings is gebruik om die dieet aminosuurbehoeftes te skat deur evaluering van die duodenale essensiele aminosuursamesteilings van drie verskiilende mielie-gebaseerde voerkraal diete. Alhoewel daar 'n algemene toe name in die biologiese waarde van die proteien na rumen fermentasie was, het die duodenale essensiele aminosure in vergelyking met die totale lee liggaam, ongebalanseerde profiele van essensiele aminosure vir groei getoon. Die chemiese teilings toon aan dat die eerste-tot-derde-beperkende aminosure in die duodenale inhoud van vleisbeeste wat drie verskillende kommersieel beskikbare voerkraal diete ontvang het, soos volg is: histidien, lisien, metionieniarginien (Dieet 1), histidien, arginien, lisien (Dieet 2) en arginien, metionien, histidien (Dieet 3). Die ongebalanseerde aminosuur konsentrasies wat in die duodenum van die drie dlete verkry is, beklemtoon die noodsaaklikheid om die intestinale lewering van aminosuurprofiele te verbeter deur verskillende nie-degradeerbare proteien bronne te voer. Die doelwit moet wees om proteien verbruik te optimaliseer en daardeur die genetiese potensiaal vir optimale groei in voerkraalbeeste te bereik. Met die simulering van aminosuurbehoeftes en vloei na die duodenum van die drie standaard voerkraal diete met behulp van die "Cornell Net Carbohydrate and Protein System" (CNCPS), het voorspellings gewys dat lisien aminosuurvloei die metaboliseerbare toelaatbare gemiddelde daaglikse toename in Dieet 1 en 3 beperk het. Voorspelde profiele wys dat die volgorde van beperking soos volg sou wees: lisien, arginien, histidien (Dieet 1), lisien, arginien, histidien, metionien (Dieet 2)' en lisien arginien, histidien (Dieet 3). Die voorspelde profiele was in ooreenstemming met die waargeneemde duodenale waardes, behalwe vir metionien wat beperkend was in Dieet 1 en 3; die volgorde en mate van beperking was egter verskillend. Resultate wys dat voorspellingsmodelle die potensiaal het om behoeftes te voorspel. Vir die akkurate definisie van behoeftes vir spesifieke essensiele aminosuure is daar egter nog beperkinge. Uit die huidige studie, is dit duidelik dat protetenneerleqqinq deur die hoeveelheid en/of oneweredigheid van geabsorbeerde aminosure beperk is. Verdere navorsing moet dus fokus op die verkryging van In meer geskikte profiel van aminosure wat verteerbaar, opneembaar en 'n ekonomiese lewensvatbare opsie vir die voerkraalbestuurder is.

Diets were based on steam-flaked milo and contained chopped alfalfa hay in the control diet. At the 65% concentrate level, cottonseed hulls or chopped wheat straw replaced half the alfalfa hay. At the 90% concentrate level, roughage sources were chopped alfalfa hay, cottonseed hulls, or wheat straw. Six growing steers and three mature, rumen-cannulated steers per concentrate level were used in separate Latin square experiments. Total tract digestion coefficients, particulate passage rates, liquid turnover rates, and rumination time were measured in the intact steers. In situ digestion, rumen pH, and rumen dry matter distribution were evaluated in the cannulated steers. Competition between rates of passage and digestion were used to calculate apparent extent of ruminal digestion (AED). At the 65% concentrate level, total tract digestion coefficients for the wheat straw vs alfalfa hay diet were not different, apparently due to increased milo and alfalfa hay neutral detergent fiber (NDF) digestion in the wheat straw diet. Milo and alfalfa hay AED for NDF were higher (P<.10). Dietary AED for DM, NDF, and cell solubles were highest (P<.05) for the alfalfa hay diet. Differences between diets were minimal, indicating roughage source in 90% concentrate diets does not substantially influence milo digestion or passage as it does in 65% concentrate diets.

Total tract digestion coefficients for dry matter (DM) and neutral detergent fiber (NDF), passage rates for grain and roughage components of diets and liquid turnover were measured for 65 and 90% concentrate diets in separate 4 x 4 Latin square experiments using intact growing steers. Kinetics of in situ digestion for DM and NDF in diet ingredients, rumen pH, volume and DM distribution were determined in mature, rumen cannulated steers. Rates of passage and digestion were combined to calculate apparent extent of ruminal digestion (AERD) for diet ingredients. Diets were based on steam flaked milo. The control roughage was chopped alfalfa hay (AH). In 65% concentrate diets, chopped wheat straw (WS), bermudagrass straw (BS) or cottonseed hulls (CSH) replaced 50% of the AH. In 90% concentrate diets, all of the AH was replaced by WS, BS or CSH. Total tract starch digestion was not influenced by source of roughage at either concentrate level. In 65% concentrate diets, total tract digestion of DM and NDF was not adversely affected by substitution of WS for 50% of the AH. Digestion of these fractions was lower (P<.05) for BS and CSH diets, but the severity of depression was greatest (P<.05) for the CSH diet. Reduced digestibility of the CSH diet was attributed to lower digestibility of CSH in comparison with AH. Although WS and BS were also less digestible than AH, their inclusion in the diet improved (P<.05) AERD of DM and NDF from milo and AH. Improved AERD for NDF appeared to be related to the raft-forming properties of WS and BS, and their ability to maintain rumen pH in a more desirable range for NDF digestion. In 90% concentrate diets, effects of roughage source on utilization of milo were minimal. Total tract digestion of DM and NDF was lower (P<.05) for WS, BS and CSH diets than for the AH diet, because of dilution of the more digestible AH by these roughages. Wheat straw had a tendency to moderate ruminal pH and consequently might be more useful in high concentrate diets than roughages such as CSH and BS.

Genetic parameters were estimated using 8086 weaning weight records of Mashona cattle from commercial herds in Zimbabwe, through Derivative-free Restricted Maximum Likelihood (DFREML) procedure fitting an individual animal model. All known additive relationships among animals were incorporated and all sires were assumed to have been bred by unknown parents. A simulation study was carried out to estimate the amount of bias in the estimated genetic parameters caused by the failure to account for the true relationships among the breeding animals.
Genetic differences between the weaning weights of Mashona cattle in commercial herds and in small holder herds were estimated using performance records of progeny from 2 reference bulls, 3 bulls from commercial herds, 14 bulls from Makoholi Research Station and 20 bulls from small holder farms. The findings from this study were used as a basis for simulating different strategies of improving the weaning weights of Mashona cattle through the creation of nucleus herds. Estimates ($ pm$s.e) of direct heritability (h$ sb{ rm A} sp2$), maternal heritability (h$ sb{ rm M} sp2$) and the correlation between direct and maternal genetic effects (r$ sb{ rm AM}$) were 0.243 $ pm$ 0.046, 0.392 $ pm$ 0.031 and $-$0.282 $ pm$ 0.081, respectively. When a permanent environmental effect of the dam (c$ sp2$) was fitted, the estimates of h$ sb{ rm A} sp2$, h$ sb{ rm M} sp2$, r$ sb{ rm AM}$ and c$ sp2$ were 0.281 $ pm$ 0.026, 0.113 $ pm$ 0.022, $-$0.269 $ pm$ 0.106 and 0.228 $ pm$ 0.023, respectively. No significant trends were observed in direct breeding values but there was a decline in maternal breeding values. The simulation study indicated that the bias in h$ sb{ rm A} sp2$ and h$ sb{ rm M} sp2$ resulting from the lack of sire pedigrees was trivial if the correlation between direct and maternal genetic effects was high and a large proportion of dams had known pedigrees.
The progeny test showed that both the mean breeding values of the reference sires and the bulls from commercial farms were significantly higher than the mean breeding values of small holder bulls for birth weight (by 1.6 and 1.7 kg, respectively) and weaning weight (by 10.4 and 11.0 kg, respectively). The strategies that selected breeding animals on their maternal genetic values resulted in the highest responses for weaning weight.
It was concluded that maternal genetic values of Mashona cattle should be improved to allow this breed to compete favourably as a maternal breed in commercial agriculture.

The effect of selenium (Se) supplementation, by ad libitum salt-mineral mixture (SMM) and/or Se injection, on bovine immune response was evaluated in three experiments. Sixty weaned beef calves, with marginal blood Se (67 μg Se/1), were allotted to one of six Se treatment groups in a 70-day experiment. Antibody responses to lysozyme were lower in calves fed 20 ppm Se salt-mineral mixture (SMM) ad libitum as compared to calves fed 20 ppm Se SMM and injected with 0.1 mg Se + 1.0IU vitamin E/kg body weight, IM, or with calves ad libitum fed 80, 120, 160, or 200 ppm Se SMM. Blood Se on day 70 was higher in calves fed 80, 120, 160, or 200 ppm Se SMM than calves fed 20 ppm Se and injected with 0.1 mg Se + 1.01IU vitamin E/kg of body weight, IM. An ad libitum 120 ppm Se SMM was compared to Se injection in 80 mid-gestation beef cows that were Se-deficient (50 μg Se/l blood). Supplementation with 120 ppm Se SMM increased blood Se in cows and calves to > 100 μg/l, increased IgG concentrations in colostrum, and increased IgG concentrations in serum of post-suckle calves. Calves from Se-adequate dams had higher Se concentrations in blood and higher average daily gains at 60 days than Se-deficient calves injected with Se at birth. An ad libitum 120 ppm Se SMM was compared to Se injection in 60 Se-deficient (41 μg Se/l blood) weaned beef calves in a 56-day experiment. Calves fed 120 ppm Se SMM and unsupplemented control calves had higher antibody responses to lysozyme than calves injected with 0.1 mg Se + 1.0 IU vitamin E/kg body weight. Blood Se concentrations increased in calves fed 120 ppm Se SMM, did not change in calves injected with 0.1 mg Se/kg body weight, and decreased in control calves. Se treatment did not affect IgA response in tears of calves.
Ph. D.

Leafy spurge (Euphorbia esula L.) is a costly noxious weed to manage in the Northern Great Plains; it invades rangelands and displaces native and desirable vegetation. Our first objective was to test the recommended full rate and half rate of selected herbicides applied in September following a spring burn on a leafy spurge invaded plant community. Our second objective was to determine if raffinate (desugared beet molasses) applied to leafy spurge invaded rangeland would attract cattle to consume leafy spurge. The aminocyclopyrachlor with chlorosulfuron treatment had the best leafy spurge control at the full rate, with stem density reductions of 95 percent for both sites nine and twelve months after treatment. The salt block treatment had the best success at reducing leafy spurge stem density. Herbicides can be the most common and effective type of management; however, manipulating livestock to graze noxious weeds converts a weed into a useable forage.

Excessive dietary protein may affect MP use because of energetic costs of excreting excess N. Amino acids also may influence post-ruminal digestion. Therefore, two experiments were designed to evaluate the effects of MP intake and post-ruminal flow of AA on growth performance and pancreatic digestive enzymes. In experiment 1, treatments supplied different amounts of MP intake to cattle and the effects on growth performance and feeding behavior were evaluated. In experiment 2, duodenal infusion of glutamate or casein was examined and the effects on pancreatic enzymes were measured. Experiment 1 suggests that feeding steers 906 g MP/d in finishing diets supplied enough MP for the greatest growth performance and carcass characteristics. Interestingly, MP intake caused different responses on feeding behavior with greater effects on steers fed 626 and 1444 g MP/d. In experiment 2, casein infusion increased α-amylase activity but not trypsin activity. Glutamate did not influence pancreatic digestive enzymes.

Orientador: Rafael Silvio Bonilha Pinheiro
Coorientador: Marcos Chiquitelli Neto
Banca: João Batista Alves
Banca: Jane Maria Bertocco Ezequiel
Resumo: O objetivo do trabalho foi verificar a influência de teores de concentrado na emissão de metano e de dióxido de carbono, no desempenho e digestibilidade de bovinos Guzerá terminados em confinamento. Foram utilizados trinta e seis bovinos da raça Guzerá, com peso médio de 464 kg e idade de 30 meses e alojados em baias individuais de 10m2 . O delineamento experimental foi inteiramente casualizado, com três tratamentos 30, 50 e 70% de concentrado na dieta e 12 repetições por tratamento para o desempenho e digestibilidade. Para obtenção dos dados referentes à produção de metano, pH e a degradação ruminal, o delineamento foi em blocos casualizados com 3 períodos de incubação totalizando 21 repetições por ingrediente. O ganho de peso diário foi de 0,99 kg, 1,33kg e 1,22kg respectivamente, para dieta com 30, 50 e 70%, evidenciando que houve diferença (P<0,01) entre os tratamentos. O consumo de matéria seca foi menor à medida que aumentou o nível de concentrado com médias de 11,04, 10,75 e 7,67 kg/dia respectivamente para dietas com 30, 50 e 70%. A melhor conversão alimentar foi observada no tratamento de 70% de concentrado (6,73%), a qual também apresentou melhor digestibilidade entre os tratamentos. A produção de metano na dieta com 50% de concentrado apresentou as maiores médias. Na produção de gases em 12 e 24 horas foram observados que níveis maiores de concentrado apresentaram maior nível de dióxido de carbono em relação ao metano. Sendo assim as dietas com 50 e 70% de concentrado apresentaram melhor desempenho; a dieta com 70% de concentrado apresentou menor produção de metano, maior digestibilidade, menor conversão alimentar e ganho de peso em relação as dietas dos demais tratamentos
Abstract: Not available
Mestre

Thesis (MScAgric)--University Stellenbosch, 2001.
ENGLISH ABSTRACT: The aim of this study was to estimate genetic parameters as well as to evaluate the influence of some genetic factors on preweaning growth traits in a multi breed beef cattle population. These preweaning growth traits were birth weight (BW), weaning weight (WW) and average daily gain (ADG). Three aspects were addressed in this particular study; namely the Estimation of (co)variance components and genetic parameters, the effect of sire breeds and dam genotypes and the contribution of Charolais and Angus breeding levels on weaning traits in a multibreed beef cattle herd. Variance components and resulting genetic parameters of BW, WW and ADG in the population were estimated by Restricted Maximum Likelihood (REML) procedures. Four different unitrait and multitrait animal models were fitted ranging from a simple model with the animal direct effects as the only random effect to the model allowing for both genetic and permanent maternal environmental effects. The model that included directgenetic and permanent maternal environmental effects generally best described the data analysed. The simple model ignoring maternal effects most likely inflated direct heritability estimates. Direct heritability estimates were 0.11, 0.19, and 0.15 for BW, WW and ADG, respectively, fitting a multitrait model that comprised of both the genetic and maternal environmental effects. Under this comprehensive model, maternal heritabilties were low under both analyses, ranging from 0.02 to 0.10. Permanent maternal environmental effects were more important than maternal additive genetic effects for WW and ADG. Direct and maternal genetic correlations range from 0.42 to 0.44 for BW, -0.22 to -0.25 for WW and -0.17 to -0.23 for ADG, while the corresponding estimates ofunitrait analysis varied from 0.58 to 0.61 for BW, -0.43 to-0.53 for WW and -0.49 to -0.79 for ADG. The effect of Charolais and Hereford sires and dam breed genotypes on BW and WW in calves of Hereford, F I, two and three breed rotational as well as terminal crosses among the Charolais, Hereford, Angus and Bonsmara breeds were investigated. BW and WW of the Charolais sired calves were significantly (PAFRIKAANSE OPSOMMING: Die doel van die studie was om genetiese parameters in 'n meerras vleisbeeskudde te beraam, sowel as om die invloed van sekere genetiese faktore te evalueer. Die voorspeense groei-eienskappe het geboortegewig (BW), speengewig (WW) en gemiddelde daaglikse toename (ADG) ingesluit. Drie aspekte is in dié betrokke studie ondersoek, naamlik; die beraming van (ko )variansiekomponente en genetiese parameters, die invloed van ras van vader en moedergenotipe en die invloed van Charolais en Angus bydrae op speeneienskappe in 'n meerras vleisbeeskudde. Variansiekomponente en afgeleide genetiese parameters vir BW, WW en ADG in die kudde is met behulp van die Beperkte Maksimum Waarskynlikheidsprosedure (REML) beraam. Vier verskillende enkel- en meereienskapmodelle is gepas, wat vanaf 'n eenvoudige model wat slegs die direkte effek as enigste toevallige effek, tot dié model waarin beide die genetiese en permanente mateme omgewingseffekte ingesluit is. Die model wat beide die direkte en permanente mateme effekte ingesluit het, het die data die beste gepas. Die eenvoudige model, wat die mateme effekte nie insluit nie, het in alle waarskynlikheid die direkte oorerflikhede oorberaam. Die direkte oorerflikheidsberamingsas onderskeidlik 0.11, 0.19 en 0.15 vir BW, WW en ADG met dié meereienskapmodel wat beide genetiese en mateme effekte ingesluit het. Met die omvattende model was die mateme oorerflikhede laag en het van 0.02 tot 0.10 gewissel. Die permanente mateme omgewingseffekte was belangriker as die direkte mateme effekte vir WW en ADG. Die genetiese korrelasies tussen direkte en mateme effekte het vir BW tussen 0.42 en 0.44, vir WW tussen -0.22 en -0.25 en vir ADG tussen -0.49 en -0.79 gewissel. Die invloed van Charolais en Hereford bulle en moederrasgenotipes op BW en WW van Hereford, F 1, twee- en drieras rotasie sowel as terminale kruisings tussen die Charolais, Hereford, Angus en Bonsmara is ondersoek. BW en WW van kalwers van Charolais bulle was betekenisvol (P