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Since birth type showed only a low association with weaning type and preweaning gain, it is of no practical interest whether or not type at birth can be expressed by certain body proportions, which themselves are not high enough correlated with the two weaning traits to be of any predictive value. The high association between birth weight and the linear body measurements suggests that birth weight is as good a measure of a calf's merit at birth as any other birth observation. Birth weight should be considered a useful selection criterion for Angus and possibly Hereford calves, but not for Shorthorns, except that extremely small calves should not be kept as breeding stock. Neither body measurements nor type at birth can be recommended as selection criteria as their use would not be likely to result in an improvement of the more important weaning traits. / Master of Science

The purpose of this study was to investigate the effect of prepartum and postpartum nutrition on milk production of commercial beef cows. Forty-three Angus or Angus X Holstein females, ranging in age from 2 to 6 yr, were randomly assigned by age and percentage Holstein within age to one of two prepartum grazing treatments (PRE). All females, regardless of PRE, were assigned at calving to receive the same post-calving nutritional energy. Females were assigned at calving by age, percentage Holstein within age, prepartum nutritional treatment and calving date to one of two milking groups. Milk weight (grams), milk composition (fat, protein, lactose, solids-not-fat, somatic cell count), dam body condition score (1 to 9), dam body weight, dam backfat thickness, loineye area, calf weaning weight and postpartum interval to estrus were all evaluated. Milk removal occurred biweekly by vacuum milking machine after intravenous injection of 20 IU of oxytocin. Samples were weighed and taken for milk analysis and determination of milk components. At 76± 10 d post-calving, females were assigned by age, percentage Holstein within age, prepartum nutritional treatment, and calving date to receive one of two postpartum nutritional treatments (POST). Females continued to be milked by machine biweekly until calves were weaned 199 ± 10 d. Differences in grazing level prior to calving significantly effected calf birth weights, with dams on the prepartum restricted grazing being lighter in weight at birth, 36.69 ± .68 and 38.95 ± .81 kg for PRE-L and PRE-H groups, respectively, however grazing differences did not effect calf weaning weight, calf gain or calf average daily gain. POST nutritional treatments significantly effected all calf performance traits with 37.10±.70, 38.54±.88; 196.89±4.9, 213.33±6.2; 159.79±4.8, 174.78±6.0; .809±.024, .888±.030; for birth weight, weaning weight, calf gain and calf average daily gain from cows on the POST -M or POST -H nutritional treatments, respectively. Pre-partum nutrition effected milk production (P < .001) with dams from the PRE-L grazing group producing less milk, 5622 ± 75 vs 6888 ±80 g. Postpartum energy also effected milk production with dams on the POST-H energy level producing more milk than dams from the POST-M group. Percentages of fat, protein, lactose and solids-not-fat were not different between the prepartum or postpartum diets (P>. 10). Somatic cell count was negatively correlated with dam milk production (P< .03). Postpartum interval to estrus was shorter for the PRE-L group than for the PRE-H, 43 ± 4 vs 53 ± 4 d. / Master of Science

Six Angus steers were used in a series of three metabolism trials to study the effect of energy concentration on nitrogen metabolism and digestibility. The experimental design consisted of two randomly selected 3 x 3 Latin squares. Three fattening rations were ted which contained 1133, 1164 and 1222 kcal. digestible energy per lb. feed and 12.18, 12.51 and 12.29% crude protein, respectively. The rations were composed of 10% grass hay, shelled corn, corn cobs and cottonseed meal. An attempt was made to equalize calcium and phosphorus contents. Vitamins A and D were added at the rate or 30,000 I.U. and 3750 I.U. per steer per day, respectively. Energy concentration was varied by changing the proportions of shelled corn and corn cobs. Digestible and metabolizable energy and TDN were all significantly increased with each increase in energy concentration. Digestible energy concentration of feed had no significant effect on nitrogen retention. Biological value waa higher for the medium energy ration than for the low or high energy rations. The quadratic effect was significant (P < .05). The apparent digestibilities of crude protein and ether extract were not influenced by energy concentration. Digestibility of' dry matter, organic matter and NPE significantly increased and digestibility of crude fiber significantly decreased with each increase in energy concentration. / Master of Science

The objective of these experiments was to determine the effects of and/or interactions among estrous synchronization treatments, reproductive status, and stage of the estrous cycle on estrous response (ER), first service conception rates (CR), pregnancy rates (PR), and embryonic mortality (EM) after 25 d of gestation. Angus or Angus crossbred cattle (n=391) at two locations were assigned to receive either melengestrol acetate for 7 d (MGA-PGF; .5 mg/hd/d, n=136) or progesterone releasing intravaginal device for 7 d (PRID-PGF; n=139) or to serve as untreated controls (n=116). All animals in MGA and PRID treated groups coincidentally received 25 mg prostaglandin F₂α (PGF) on the final day of treatment. Real time, B-mode, ultrasound with a 7.5 mHz linear-array transducer was used to conduct three ovarian scans at 7-d intervals beginning 7 d prior to initiation of treatment. Jugular blood samples were collected at each scanning period. Serum was harvested and stored at 4°C until radioimmunoassayed for progesterone (P4). Serum P4 levels in conjunction with ovarian scans were used to determine cycling status and stage of the estrous cycle at initiation of treatment. Cattle treated with PRID-PGF exhibited a greater synchronized ER (P < .06) than MGA-treated cattle. Cycling animals had a greater ER than noncycling animals, regardless of treatment (P < .01). Anestrous postpartum cows and prepubertal heifers treated with PRID-PGF exhibited a greater ER (P < .05) within 7 d than either MGA-treated or untreated control animals. Conception rates of cattle treated with PRID-PGF beginning late (> Day 16) in the estrous cycle were improved over those of MGA-treated cattle (P < .13) at the same stage. Pregnancy rate at 21 d was higher in PRID-treated cattle than untreated controls (P < .01). Ultrasound scans for embryonic viability were conducted at 25, 45, and 65 d of gestation. Calving data was collected to characterize EM between 65 d and term. The majority of embryonic loss occurring after 25 d of pregnancy occurred before 45 d. Synchronization treatment had no effect on the extent of EM occurring after 25 d of gestation. Embryonic mortality occurring between d 45 and 65 (2%) and between d 65 and term (3%) when combined were similar in magnitude to EM occurring between 25 and 45 d of gestation (4.8%). In conclusion, PRID for 7 d combined with PGF was a superior synchronization treatment for the mixed group of cyclic and anestrous cattle. / Master of Science

Variation among sires in daughters' reproductive performance was analyzed using data on 4,360 cows from nine herds obtained from the American Simmental Association. Cows were required to have at least 50% Simmental breeding, to have calved first at 2 yr of age and to have been born and subsequently calved in the same herd and season. Traits analyzed included first and second calving dates, first calving interval and the percentage of cows that returned to calve in the same season as 3-yr-olds. Data were adjusted for effects of percentage Simmental and first-calf calving ease score. At second calving, purebred Simmentals calved 1.7 &#177; 1.2 d later than 75% Simmental cattle and 5.1 &#177; 1.4 d later than 50% Simmental cattle. When compared to cows that calved without assistance at first calving, cows experiencing easy pulls were 1.7 &#177; 1.4% less likely to calve as 3-yr-olds and had 4.9 &#177; 1.0 d longer calving intervals. Cows with hard pulls were 9.0 &#177; 2.1% less likely to return and had 6.5 &#177; 1.6 d longer calving intervals. Cows requiring Cesarean section were 23.1&#177; 2.5% less likely to return and had 19.6 &#177; 2.4 d longer calving intervals. Heritability estimates were .17 &#177; .04 for first calving date, .07 &#177; .06 for second calving date, .04:105 for calving interval and .11 &#177; .04 for percent return. Calving interval does not appear to be a useful selection criterion to improve reproduction. Phenotypic and genetic correlations of first calving date with calving interval were -.58 and -.83 &#177; .37, respectively. The genetic correlation between first and second calving dates was .66 &#177; .41. Given current data recording procedures, calving date appears to be the most useful potential selection criterion to improve reproductive fitness. / Master of Science

Thie experiment was conducted by the Virginia Agricultural Experiment Station for the purpose of comparing the values of several feeds for wintering beef steers with especial regard for local conditions. 1st. 28 lbs. silage and 1 lb. cottonseed meal will maintain 1000-pound steers during the winter without a loss of more than 25 lbs. per head. 2nd. 38 lbs. silage per steer per day will give about the same results as above. 3rd. Steers will change from grass to silage and from silage to grass again with practically no loss in weight. 4th. Steers fed silage alone, and stover and corn meal during the winter were the only steers to average 2 pounds gain per day on grass. 5th. Steers fed on silage alone made greatest total gain at the lowest cost per 100 pounds gain. 6th. Steers fed on stover and corn meal made the least total gain at the greatest cost per 100 pounds gain. 7th. Silage is a very economical feed for wintering steers, while stover and corn meal is a very costly feed. 8th. One pound of cottonseed meal will replace ten pounds of silage and it may be advisable to make this substitution when silage is scarce, or cottonseed meal cheap, or both, although cottonseed meal is not absolutely necessary. 9th. Winter steers so that they will not lose more than 25 pounds each during the winter months, for greater losses cannot be overcome during the grazing season. / Master of Science

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 + 1.0 IU 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.

Master of Science / Department of Agronomy / Clenton E. Owensby / Currently there are no model inputs for eastern gamagrass [Tripsacum dactyloides (L.) L] for use in the National Research Council's (NRC) beef cattle model. This study was conducted to determine model inputs for two eastern gamagrass varieties for use with the forage database of the NRC model. Cattle producers in the Midwestern US will be able to evaluate eastern gamagrass in a forage system and estimate net energy for maintenance (NEm), metabolizable protein (MP), and degradable intake protein (DIP) balance for various production scenarios. Eastern gamagrass varieties 'Iuka' and 'Pete' were arranged in a split-plot randomized complete block experiment with four replications. Varieties were whole plots with harvest maturities as split plots. Plant tissue was harvested from both varieties at four maturities: vegetative/early elongation, anthesis, seed shattering and dormancy. Various compositional attributes were determined on forage samples to enable the determination of model inputs for predicting energy and protein balances. A slight difference between varieties was found for crude protein concentration (p<0.05). Differences (p<0.05) due to maturity were found for all analyses used in the model, corroborating the decline in nutritive value of eastern gamagrass with advancing maturity. Neutral detergent fiber (NDF) ranged from 593 g kg-1 at the vegetative/early elongation stage of maturity to 731 g kg-1 at dormancy. Assumed animal and environmental inputs were used for beef cattle at two stages: nonlactating 160 d prepartum and 60 d peak lactation. Energy and protein balance were estimated using level I of the model. The vegetative/early elongation stage of development supplied the greatest amount of MP. Digestible intake protein declined as plant tissue matured. All but the vegetative/early elongation stage of maturity were limited in DIP for cows in both stages of production. Soybean meal was used as a protein supplement in amounts ranging from 0.8 kg to 1.4 kg to meet nutritional demands of cattle grazing eastern gamagrass at anthesis, seed shattering and dormancy. In the simulations conducted, eastern gamagrass would be an acceptable forage source for beef cattle provided that appropriate protein supplementation was given when the forage was at more advanced stages of maturity.

Thesis (MScAgric (Animal Sciences))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The aim of this study was to evaluate the Simbra breed of cattle for certain non-genetic as well as genetic parameters influencing live weight traits in the breed. Live weight traits included birth weight (BW), weaning weight at 200 days of age (WW), yearling weight at 400 days of age (YW) and 600 day weight. The Simmental and Simbra Breeders’ Society of Southern Africa availed 148751 records for analysis from the year 1987 till 2009. Due to deficiencies of various kinds in the data and the restrictions imposed for the purposes of the analysis, 56.44% of the records were discarded for BW, 76.55% for WW, 91.54% for YW and 96.32% for 600-day weight. Non-genetic parameters affecting BW, WW, YW and 600-day weight were analysed using the General Linear Models procedure of the Statistical Analysis System (SAS, 2004) software. During this procedure sex of calf, breed composition of calf, breeder of calf, month of birth, year of birth and dam age were fitted in the models. BW, WW, YW and Mature Cow Weight (MCW) were fitted as covariates where possible. It was determined that the fixed effects of sex, dam age, breeder, year and month had a significant (P < 0.05) effect of BW and WW while dam age was not significant (P > 0.05) for YW or 600-day weight. Breed was found non significant for YW. Breeder of the calf accounted for the most variation in BW, WW, YW as well as 600-day weight with a contribution of 17.55%, 25.77%, 18.35% and 10.71% respectively. Tukey’s multiple range tests were performed for testing differences between least square means. Results indicated male calves to be significantly heavier than females for all four traits measured. Breed composition differences were found significant until WW. Calves with higher Brahman percentage weighted more at birth while calves with higher Simmental percentage weighed more at weaning. Middle-aged dams were found to account for heavier calves at both BW and WW while very young dams and very old dams produced lighter calves for the two live weight traits. A number of years showed a significant difference from each other for all the traits measured as well as month of birth. (Co) variance components and the resulting genetic parameters were estimated using single-traits and three-traits analysis by means of Restricted Maximum Likelihood procedures (Gilmour et al., 2002). Appropriate models were selected by means of Log likelihood ratios tests and implemented to estimate genetic parameters for each of the traits studied. Direct additive heritabilities for BW, WW, YW and 600-day weight in the Simbra were respectively 0.56 ± 0.08, 0.67 ± 0.09, 0.70 ± 0.11 and 0.10 ± 0.03 when the most suitable animal model was fitted in single-trait analyses for each trait. Single traits analysis also included maternal additive as well as the correlation between direct additive and maternal additive for BW, WW and YW. Maternal additive heritability estimates of 0.24 ± 0.07, 0.33 ± 0.06 and 0.38 ± 0.07 was obtained for BW, WW and YW. Correlation estimates between direct additive and maternal additive were -0.75 ± 0.07, -0.93 ± 0.07 and -0.85 ± 0.08 for BW, WW and YW respectively. Furthermore, dam permanent environment was included as an additional random effect that increased the log likelihood value significantly. A value of 0.04 ± 0.05 was obtained for dam permanent environment estimate for WW. When a three traits analysis was done for the same traits, but using a significantly smaller data set, direct additive heritabilities of 0.24 ± 0.07 for BW, 0.33 ± 0.06 for WW and 0.38 ± 0.07 for YW were obtained. Genetic and environmental correlation estimates of 0.18 ± 0.16 and 0.09 ± 0.06 between BW and WW; 0.27 ± 0.16 and 0.07 ± 0.06 between BW and YW; as well as 0.52 ± 0.10 and 0.45 ± 0.05 between WW and YW were obtained during the three-trait analysis. The magnitude of the heritabilities obtained in this study indicates that the opportunity exists to make genetic progress through proper selection objectives. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die Simbra bees ras te evalueer op grond van sekere niegenetiese so wel as genetiese parameters wat lewende gewig beïnvloed. Gereelde en akkurate opnames van lewende gewig, is ‘n goeie indikasie van groei potensiaal en is ‘n minimim vereiste vir meeste beesras telings genootskappe. Lewende gewigs eienskappe sluit in geboorte gewig (BW), speen gewig gemeet op 200 dae (WW), jaaroue gewig gemeet op 400 dae (YW) en finale gewig gemeet op 600-dag gewig. Die Simmentaler en Simbra genootskap van Suid Afrika het 148751 rekords beskikbaar gestel vir evaluasie vanaf die jaar 1987 tot 2009. Daar was egter groot tekort komings aan die gewewe data en dus is daar 56.44% van die rekords vir BW nie gebruik nie, 76.55% vir WW, 91.54% vir YW en 96.32% vir 600-dag gewig. Nie-genetiese parameters wat die onderskeie lewende gewigte beïnvloed het, is geanaliseer deur Algemene Lineêre Modelle met behulp van die Statistiese Analitiese Sisteem (SAS, 2004) sagteware. Gedurende die analise is geslag van die kalf, ras samestelling, teler van die kalf, maand van geboorte, jaar van geboorte asook moeder ouderdom gepas in die modelle vir die onderskeie gewigte. Geboorte gewig, speen gewig, jaaroue gewig asook volwasse koei gewig is gepas in elk van die modelle as ko-variate. Volgens die resutate is daar vasgestel dat geslag van die kalf, moeder ouderdom, teler, jaar, maand en volwasse koei gewig almal ‘n betekenisvolle (P < 0.05) invloed gehad het op BW en WW. Die moederouderdom was nie betekenisvol (P > 0.05) vir YW of 600-dag gewig nie. Die ras samestelling was ook nie betekenisvol gevind vir YW. Teler van die kalf was verantwoordelik vir die meeste variasie in BW, WW, YW asook 600-dag gewig met ‘n bydrae van 17.55%, 25.77%, 18.35% en 10.71% onderskeidelik. Tukey se veelvuldige vergelykings toets is gebruik om onderskeid te tref tussen “least square means”. Resultate het aangedui dat manlike diere swaarder weeg as vroulike diere tot en met finale gewig. Ras samestelling vir BW en WW was betekenisvol verskillend vir die diere. Kalwers met ‘n hoër Brahmaan persentasie het swaarder BW opgelewer as dié met ‘n hoër Simmentaler persentasie, terwyl kalwers met ‘n hoër Simmentaler persentasie swaarder geweeg het met speen en dus ideal is vir speen kalwer produksie stelsels. Middel-jarige moeders het swaarder kalwers geproduseer met geboorte en speen as baie jong en - ou moeders. Sommige jare waarin van die kalwers gebore is, het ook betekenisvol van mekaar verskil asook die maand waarin die kalf gebore is. Ko) variansie faktore en opeenvolgende genetiese parameters is bepaal met behulp van enkeleienskap analises asook meervuldige-eienskap analises deur middel van die “Restricted Maximum Likelihood” prosedure (Gilmour et al., 2002). Modelle is opgestel vir elk van die gewigte deur die geskikte genetiese terme toe te voeg en te toets met behulp van “Log likelihood tests” om sodoende die onderskeie genetiese parameters te bepaal. Direkte genetiese oorerflikhede bepaal deur enkeleienskap analises vir die Simbra ras was as volg, 0.56 ± 0.08 vir BW, 0.67 ± 0.09 vir WW, 0.70 ± 0.11 vir YW en 0.10 ± 0.03 vir 600-dag gewig. Die direkte maternale genetiese oorerflikhede tydens dieselfde enkel-eienskap analise vir die onderkeie gewigte was 0.24 ± 0.07 vir BW, 0.33 ± 0.06 vir WW en 0.38 ± 0.07 vir YW. Korrelasies tussen direkt genetiese en direk maternale eienskappe was sterk negatief. ‘n Waarde van -0.75 ± 0.07 is bepaal vir BW, -0.93 ± 0.07 vir WW en -0.85 ± 0.08 vir YW. ‘n Adisionele faktor was ook ingelsuit vir WW, naamlik die permanente omgewing van die moeder, wat ‘n waarde opgelewer het van 0.04 ± 0.05. Tydens die veelvuldige-eienskap analise het die oorerflikhede merkwaardig verminder vir die betrokke gewigte en kan ook waargeneem word as die meer korrekte genetiese weergawe. Direkte genetiese oorerflikhede van 0.24 ± 0.07 vir BW, 0.33 ± 0.06 vir WW en 0.38 ± 0.07 vir YW was bepaal. Hierdie matig tot hoë parameters dui op genetiese vordering deur middel van korrekte seleksie prosedures. Genetiese- en omgewing korrelasies is ook bepaal tydens die analise en het positiewe waardes opgelewer. ‘n Genetiese korrelasie waarde van 0.18 ± 0.16 tussen BW en WW is bepaal asook ‘n waarde van 0.27 ± 0.16 tussen BW en YW en ‘n waarde van 0.52 ± 0.10 tussen WW en YW. Hierdie korrelasies dui daarop dat na-speengewigte vermeerder kan word deur te selekteer vir verhoogde WW sonder om BW dramties te vermeerder. Omgewings korrelasie waardes van 0.09 ± 0.06 tussen BW en WW, 0.07 ± 0.06 tussen BW en YW asook ‘n waarde van 0.45 ± 0.05 tussen WW en YW is gevind. Genetiese neigings is bepaal vir die onderskeie gewigte deur die gemiddelde voorspelde teelwaardes aan te teken teenoor elke jaar wat bereken was tydens die enkel-eienskap analises vir die onderskeie gewigte. Groot variasie asook negatiewe tendense vir WW en YW is ondervind van jaar tot jaar en dui daarop dat die seleksie doelwitte vir lewendige gewig nie in plek gestel is nie en is dit nodig om te her evalueer.