RESUMEN
Records on growth traits were obtained from five Midwestern agricultural experiment stations as part of a beef cattle crossbreeding project (NC-196). Records on birth weight (BWT, n =3,490), weaning weight (WWT, n = 3,237), and yearling weight (YWT, n = 1,372) were analyzed within locations and pooled across locations to obtain estimates of breed of sire differences. Solutions for breed of sire differences were adjusted to the common base year of 1993. Then, factors to use with within-breed expected progeny differences (EPD) to obtain across-breed EPD were calculated. These factors were compared with factors obtained from similar analyses of records from the U. S. Meat Animal Research Center (MARC). Progeny of Brahman sires mated to Bos taurus cows were heaviest at birth and among the lightest at weaning. Simmental and Gelbvieh sires produced the heaviest progeny at weaning. Estimates of heritability pooled across locations were .34, .19, and .07 for BWT, WWT, and YWT, respectively. Regression coefficients of progeny performance on EPD of sire were 1.25+/-.09, .98+/-.13, and .62+/-.18 for BWT, WWT, and YWT, respectively. Rankings of breeds of sire generally did not change when adjusted for sire sampling. Rankings were generally similar to those previously reported for MARC data, except for Limousin and Charolais sires, which ranked lower for BWT and WWT at NC-196 locations than at MARC. Adjustment factors used to obtain across-breed EPD were largest for Brahman for BWT and for Gelbvieh for WWT. The data for YWT allow only comparison of Angus with Simmental and of Gelbvieh with Limousin.
Asunto(s)
Peso Corporal/genética , Cruzamiento , Bovinos/genética , Animales , Peso al Nacer/genética , Bovinos/crecimiento & desarrollo , Femenino , Variación Genética , Masculino , Análisis de Regresión , DesteteRESUMEN
Data were weights of F1 calves and weaning weights of top-cross progeny from sires and maternal grandsires of 13 breeds. Three analyses were performed on each trait to obtain estimates and standard errors of breed effects needed to calculate across-breed EPD and accuracies. Model (R) for records of F1 progeny contained fixed effects for birth year and date of birth, sex, age and breed of dam, and breed of sire, and a random residual effect. The second analysis included random effects for sires (RS), and the third analysis included random effects for sires and dams (RSD). In maternal analysis of top-cross progeny, model (Rm) contained fixed effects for cycle of experiment, age of dam, year of birth, sex, breeds of maternal grandam and grandsire, and breed of sire, and a random residual effect. In addition, the second and third analyses fit random effects for maternal grandsires (RSm) and for maternal grandsires and daughters of maternal grandsires (RSDm). Estimates of breed of sire effects changed only slightly for different models. Total variance increased in RSD and RS relative to R. Standard errors of breed of sire comparisons were underestimated with Model R, compared to Models RS and RSD. Standard errors of other contrasts were generally not affected. Variance components, breed effects, and standard errors followed patterns for Rm, RSm, and RSDm similar to those for R, RS, and RSD. Ignoring random variation due to sires and dams underestimated standard errors of breed of sire comparisons.
Asunto(s)
Cruzamiento , Bovinos/genética , Modelos Genéticos , Animales , Peso Corporal/genética , Femenino , Vigor Híbrido , Masculino , FenotipoRESUMEN
Data were tenderness measures on steaks from 237 bulls (Group II) slaughtered after producing freezable semen and on 1,431 related steers and heifers (market animals, Group I) from Angus, Hereford, Pinzgauer, Brahman, and Sahiwal crosses from the Germ Plasm Evaluation project at the U.S. Meat Animal Research Center. Tenderness was assessed through Warner-Bratzler Shear Force (SF), taste panel tenderness (TPT), marbling score (MS), and myofibrillar fragmentation index (MFI). For all traits, as fraction Bos indicus inheritance increased, implied tenderness decreased. Heritability estimates were generally not significantly different from zero. Genetic correlations generally indicated favorable associations among the traits. The range in predicted breeding values of bulls for market animal tenderness was small and from -.34 to .32 kg for market animal shear force. Because of low estimates of heritability for SF or TPT, results from this experiment indicate that selection based on tenderness of steaks sampled from intact or late castrate males slaughtered following collection of freezable quality semen would not be very effective in improving average tenderness of steaks from steers of heifer progeny. If a mean of heritability estimates reported in the literature of .27 for shear value was assumed for market steer and heifer progeny instead of .02 as found in the present study, then selection based on estimates of shear force in young bulls would be relatively more effective in improving shear force of market progeny.