Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 159-170). Also available via the Internet.

Call number: LD2668 .T4 1985 K74 / Master of Science

Data from 946 Angus and 351 Simmental females were used to quantify relationships between calfhood and early-life traits of females with fertility in the first two breeding seasons, and with calf production in the first, in three and in eleven years of life. These traits were used to develop prediction equations for fertility using logistic regression methodology. For productive performance, three methodologies were compared: least squares, ridge regression and principal components regression. For heifers of both breeds, fertility was associated with birth date, weaning weight ratio and weaning-yearling relative growth rate (RGR). The only calfhood trait that consistently affected fertility in the second breeding season was birth weight of the cow. Fertility of first parity Simmentals was also associated with birth-yearling RGR. First calving season traits explained a higher proportion of variation in second breeding season fertility than calfhood traits of the cow. Among these traits, calving date, calving ease score and sex of the calf were the most important. The combination of birth date and weaning-yearling RGR produced the best models to predict heifer fertility for both breeds. Fertility in the second breeding season was best predicted for Angus cows when calving date, calving ease score and sex of the calf were used as regressors. For Simmental cows, fertility in the second breeding season was best predicted from birth weight of the calf and calving ease score. The regression of weaning weight of the first calf on pre-selected calfhood traits was used to evaluate models produced by least squares, ridge regression and principal components regression. Although biased, the regression coefficient estimates produced by ridge and principal components regression had smaller variances than estimates obtained from least squares. Between the two alternatives to least squares, ridge regression produced better results than principal components regression. Ridge and least squares regression were quite similar in their regression coefficient estimates, in prediction sum of squares (PRESS)-like statistics and, to a lesser extent, in conceptual predictive criteria (C_p)-like statistics. For prediction, the performance of models produced by least squares and by ridge regression were very similar. For analyses of the production traits, least squares regression models for all possible combinations of pre-selected regressor variables were fit. Birth date of the female was negatively associated with the weaning weight of the first calf, and with number of calves weaned, total weaning weight of calves produced and average weaning weight of calves in the first three years of productive life. Age of the dam affected early-life production traits of daughters, as well as the average weaning weight of calves produced per year of productive life and calf survival in eleven years. Heavier females at birth tended to produce smaller number of calves and lower calf weaning weight through their lives than females lighter at birth. Overall female productivity was consistently more positively associated with yearling than with weaning growth traits. Among traits observed in the first calving season, calving date, calving ease score, sex and weaning weight of the calf were associated with subsequent production. Weaning weight of the first calf was always positively associated and it was the most important variable to predict female production, except for survival rate. Prediction equations for production in three years included birth date, birth weight of the female, calving ease in the first parturition, sex of the calf and weaning weight of the first calf. This latter variable was the only one useful to predict production in eleven years. Average calf weaning weights in the first three years of production were best predicted using yearling weight ratio or weaning-yearling ADG and first calf weaning weight. Models including age of the female’s dam best predicted weaning weight of calves per year of productive life in eleven years and calf survival. / Ph. D.

Thesis (MScAgric)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: The objective of this study was to obtain more information regarding the characterisation of Afrikaner (A), Hereford (H) and Simmentaler (S) breeds in an initial crossbreeding programme and subsequent composite development. This involves the estimation of breed additive effects, breed maternal, individual heterotic effects and maternal heterotic effects in the initial crossbreeding phase and the estimation of genetic parameters and prediction of breeding values in later generations for birth weight (BW), weaning weight (WW) and cow efficiency (CE; WW/dam weight" 75 x 100) in an intensive environment under high stocking rates. In the analysis of the initial crossbreeding phase, the S breed direct effects, expressed as deviation from the general mean, were positive (P :s; 0.01) for both BW and WW. Hereford and A breed direct effects were negative (P :s; 0.01) for both BW and WW. Afrikaner direct maternal effects were positive (P :s; 0.01) for both BW and WW. The H direct maternal effect was negative (P :s; 0.05) (- 2.8%) for WW. Simmentaler maternal effect was negative (P :s; 0.01) for BW but non-significant (P ;:::0:.05) for WW. Individual heterotic effects for BW were significant (P:S; 0.01) in H x S (3.5%) and S x A (11.0%) only. Individual heterotic effects were positive (P :s; 0.01) for WW, with that of the H x A (9.8%) and S x A (6.7%) crosses exceeding the H x S (3.1%) cross. Maternal heterotic effects were non-significant (P ;:::0:.05) for both BW and WW. Investigations of the contributions of the A, Hand S during composite development in later generations, respectively, were made to estimate direct heritabilities (h2 a) and maternal heritabilities (h2 m) for BW and WW of the calf and CE of the dam. Calves were born between 1968 and 1993 (n = 52628). Calves of this composite population had varying levels of A, Hand S genes ranging from o to 75%, 0 to 100% and 0 to 96.9%, with an average of 4.3,19.3 and 33.4%, respectively. For the A, direct heritabilities fitting unitrait models were 0.67, 0.53 and 0.19 for BW, WW and CE, respectively, with corresponding estimates of h2mbeing 0.22, 0.36 and 0.58. Genetic correlations between direct and maternal effects (ram)were negative for all three traits, varying from -0.32 to - 0.62. Direct breeding values for BW increased and reached a maximum value at 0.11 proportion of A. The maternal breeding values for BW decreased linearly between 1.6 to 37.5% A proportion and increased linearly between 37.5 to 75% A proportion. For WW, the direct breeding values decreased linearly with increasing A proportion, while the maternal breeding values were not affected by proportion of A. Cow efficiency was unaffected by an increase in proportion of A. For the H, direct heritabilities fitting unitrait models were 0.67,0.52 and 0.21 for BW, WW and CE, respectively, with corresponding estimates of h2mbeing 0.22, 0.36 and 0.60. Genetic correlations between direct and maternal effects (ram)were negative for all three traits, varying from -0.32 to - 0.64. Direct breeding values and maternal breeding values for BW and WW decreased with increasing proportion of H. Direct breeding value for CE increased, while the maternal breeding value for CE reached minimum value at 0.62 proportion ofH. For the S, direct heritabilities fitting unitrait models were 0.66, 0.53 and 0.21 for BW, WW and CE, respectively, with corresponding estimates of h2m being 0.22, 0.36 and 0.59. Genetic correlations between direct and maternal effects (ram)were negative for all three traits, varying from -0.32 to - 0.63. Direct breeding values for BW and WW decreased and maternal breeding values increased with increasing proportion of S. Cow efficiency was unaffected by an increase in proportion of S. The study suggests that in the initial crossbreeding phase, purebred S breeding seems to be the best breeding practice for this environment and that during composite development, high A and H contributions could lead to low BW and WW (except the maternal contribution of the A for BW and WW). The advantage of the S lies more in the maternal contribution than in the direct contribution suggesting that the S is a large-framed maternal line rather than a terminal sire line. / AFRIKAANSE OPSOMMING: 'N WAARDEBEP ALING VAN DIE BYDRAE VAN DIE AFRIKANER, SIMMENTALER EN HEREFORD TYDENS KOMPOSIETE RASONTWIKKELING BY VLEISBEESTE: Die doel van die studie was om inligting aangaande die karakterisering van die Afrikaner (A), Hereford (H) en Simmentaler (S) rasse tydens die oorspronklike aanvangsfase van kruisteling en daaropvolgende komposiet ontwikkeling te verkry. Dit het die beraming van direkte additiewe, individuele heterose, direkte materne en materne heterotiese effekte tydens die aanvangsfase van die kruisteeltprogram, die beraming van genetiese parameters en die voorspelling van die teeltwaardes in latere generasies behels. Die eienskappe wat ingesluit is, is geboortegewig (BW), speengewig (WW) en koeidoeltreffendheid (CE; WW/koeigewigo.75 ). Hierdie kudde is in 'n intensiewe maar onder 'n hoë weidingsdruk omgewing aangehou. Tydens die ontleding van die eerste kruisteeltfase is die direkte additiewe effekte vir die S, uitgedruk as afwyking van die algemene gemiddelde, vir beide BW en WW positief (P ~ 0.01). Direkte additiewe effekte vir die H en A was vir beide BW en WW negatief (P ~ 0.01). Afrikaner materne effekte was vir beide BW en WW (P ~ 0.01) positief. Die H direkte materne effekte was negatief (-2.8%) (P ~ 0.05) vir WW. Simmentaler maternal effekte was ook vir BW negatief (P ~ 0.01), maar nie-betekenisvol (P 20.05) vir WW. Individuele heterose was slegs betekenisvol (P ~ 0.01) vir kombinasies van H x S (3.5%) en S x H (11.0%) vir BW. Individuele heterose was positief (P ~ 0.01) vir WW waar H x A (9.8%) en S x A (6.7%) kruisings dié van die H x S (3.1%) kruising oortrefhet. Materne heterose was vir beide BW en WW nie-betekenisvol (P 2 0.05). Die relatiewe bydraes van die A, H en S is ook tydens komposiet-ontwikkeling bereken. Direkte additiewe oorerflikhede (h2 a) en materne oorerflikhede (h2m) is vir BW en WW van die kalf en CE van die koei beraam. Kalwers in die komposiet kudde, gebore tussen 1968 en 1993 (n = 52628), het variërende vlakke van A, H en S gene. Die samestelling het gevarieer van 0 - 75%, 0 - 100% en 0 - 96.9%, met 'n gemiddeld van 4.3, 19.3 en 33.4%. Vir die A was die direkte erfbaarhede (h2 a), soos deur die passing van 'n enkeleienskapmodel beraam, 0.67, 0.53 en 0.19 vir onderskeidelik BW, WW en CE, met ooreenstemmende beramings van 0.22, 0.36 en 0.58 vir h2 rn- Genetiese korrelasies tussen direkte en mateme effekte (ram)was almal negatief en het tussen -0.32 en -0.62 gewissel. Direkte teelwaardes vir BW het met toenemende A-bydrae gestyg en het 'n maksimum waarde by 0.11 bereik. Die mateme teelwaardes vir BW het lineêr gedaal tussen 1.6 en 37.5% A-bydrae en het weer lineêr tussen 37.5 en 75% Abydrae gestyg. Vir WW het die direkte teelwaardes lineêr met toenemende A-bydrae gestyg, terwyl die mateme teelwaardes nie deur A-bydrae beïnvloed was nie. Koeidoeltreffendheid was nie deur 'n toename in A-bydrae beïnvloed nie. Vir die H was die direkte erfbaarhede (h2 a), soos deur die passing van 'n enkeleienskapmodel beraam 0.67, 0.52 en 0.21 vir onderskeidelik BW, WW en CE, met ooreenstemmende beramings van 0.22, 0.36 en 0.60 vir h2 rn- Genetiese korrelasies tussen direkte en mateme effekte (ram)was almal negatief en het tussen -0.32 en -0.64 gewissel. Direkte teelwaardes en mateme teelwaardes vir BW en WW het met toenemende H-bydrae gedaal. Direkte teelwaarde vir CE het ook met toenemende If-bydrae gedaal, terwyl die mateme teelwaarde 'n minimum waarde by 0.62 H-bydrae bereik het. Vir die S was die direkte erfbaarhede (h2a), soos deur die passing van 'n enkeleienskapmodel beraam 0.66, 0.53 en 0.21 vir onderskeidelik BW, WW en CE, met ooreenstemmende beramings van 0.22, 0.36 en 0.59 vir h2 m- Genetiese korrelasies tussen direkte en mateme effekte (ram)was almal negatief en het tussen -0.32 en -0.63 gewissel. Direkte teelwaardes vir BW en WW het gedaal, terwyl die mateme teelwaardes met toenemende S-bydrae gestyg het. Koeidoeltreffendheid was nie deur 'n toename in S-bydrae beïnvloed nie. Die bevinding was dat tydens die ontleding van die eerste kruisteeltfase die teling van suiwer S aanbeveel word en dat tydens komposiete-ontwikkeling toenemende A- en H-bydraes neig om aanleiding te gee tot afnames in BW en WW (behalwe die mateme bydrae van die A vir BW en WW). Die S-bydrae se voordeel is meer in die mateme bydrae as in die direkte bydrae geleë en dui dus aan dat die S as 'n mateme grootraam lyn i.p.v. as 'n terminale bullyn gebruik moet word.

The thesis goal was to evaluate the effect of selected breeding methods in Simmental cattle herd on chosen indicators calf birth weight, weight in the age of 120 and 210 days. The thesis deals with the evaluation of differences between sex and the comparison of calving seasons 2014 and 2015 and also shortly focus on the comparison of chosen sires and the evaluation of its effect on selected indicators. Proposal of measures in specific breeding based collected and statistically evaluated data in part of this thesis. As the first, using a linear model, analysed the effect of individual factors which can affect observed indicators was analysed. Afterwards the evaluation of difference between each factors category was done. Within first observed factor which was breeding method was found, that the best results are reached by embryotransfered calves with birth weight 46.81 kg, weight at 120 days 201.11 kg and weight at 210 days 318 kg. The weight at 210 days within artificial insemination group was only 304.33 kg and within natural breeding group 297.68 kg. Furthermore it was found that bulls reach better results in all observed indicators in comparison with heifers. In the light of birth difficultness is important birth weight which was 46.66 kg within group of bulls and 43.45 kg within group of heifers. Weight at 210 days was 321.59 kg, respectively 294.21 kg in case of heifers. It was also found that in 2015 the studied group of calves reached better results than in year 2014 in all observed indicators. Live weight in 210 days was 326 kg and 295.63 kg respectively. The evaluation of observed indicators according to sires showed that a sire significantly affects birth weight; however the effect was not significant on weight at 210 days. The best of compared sires was ZSI 478, birth weight of calves was 48.8 kg.

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 ± 1.2 d later than 75% Simmental cattle and 5.1 ± 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 ± 1.4% less likely to calve as 3-yr-olds and had 4.9 ± 1.0 d longer calving intervals. Cows with hard pulls were 9.0 ± 2.1% less likely to return and had 6.5 ± 1.6 d longer calving intervals. Cows requiring Cesarean section were 23.1± 2.5% less likely to return and had 19.6 ± 2.4 d longer calving intervals. Heritability estimates were .17 ± .04 for first calving date, .07 ± .06 for second calving date, .04:105 for calving interval and .11 ± .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 ± .37, respectively. The genetic correlation between first and second calving dates was .66 ± .41. Given current data recording procedures, calving date appears to be the most useful potential selection criterion to improve reproductive fitness. / Master of Science