Growth of crossbred progeny of polled Hereford sires divergently selected for yearling weight and maternal ability.

Abstract

Polled Hereford sires (n = 47) were divergently selected on published yearling weight (YW) and maternal (MAT) expected progeny differences (EPD) and mated to grade Angus cows to produce 457 calves in five spring calf crops. Sires selected for high and low YW differed by an average of 6.3 kg in YW EPD and those selected for high and low MAT differed by an average of 4.0 kg in MAT EPD based on 1989 EPD values. Calves by high-YW sires were heavier at birth (2.2 kg; P less than .10) and weaning (7.5 kg; P less than .01) and as yearlings (16.4 kg; P less than .01) than calves by low-YW sires and were taller at weaning (1.90 cm; P less than .01). Regressions of calf performance on corresponding 1989 EPD were 1.18 +/- .20 kg/kg for birth weight, .75 +/- .24 kg/kg for weaning weight and 1.79 +/- .42 kg/kg for YW. Expected progeny differences for individual sires were calculated from the data collected in this study and had correlations with published EPD of .53 for birth weight, .37 for weaning weight and .54 for YW. These corresponded to expected correlations based on accuracies of evaluation of .68, .61 and .58, respectively, and yielded estimates of the genetic correlation between performance in the environment of the study and the environment of the purebred herds where the published EPD were derived of .78 for birth weight, .61 for weaning weight and .93 for YW. The very large regression of YW on YW EPD (1.79 +/- .42 kg/kg) may have resulted from bias in published EPD due to culling of calves at weaning in purebred herds. Use of multiple traits analyses to account for such culling is recommended.

Relationship between milk expected progeny differences of polled Hereford sires and actual milk production of their crossbred daughters1,2

“…Given this assumption, if milk has a genetic correlation of 1 with 12-h milk production, heritability of 12-h production is a. For sires in this study, a , , , was obtained transforming Beef Improvement Federation (BIF) accuracy (Benyshek et al, 19881, reported in the Polled Hereford Sire Summary, into the correla tion between the predicted (EPD,", and the true breeding value of the individual (G,") (Mahrt et al, 1990) and averaged .98. The observed correlation of .26 would thus equate to an estimate of l-& of .28, which is reasonably consistent with previous reports of heritabilities of milk production in dairy cows Maijala and Hanna, 1974;Wade and Van Vleck, 1989).…”

“…The pooled within-group SD in YW EPD, MAT EPD, and MILK EPD were 4.1, 3.4, and 2.9, respectively, indicating that significant differences among sires groups in EPD were achieved. Details of sire sampling and general cow-calf management were given by Mahrt et al (1990). At milking, cows were 2 to 6 yr old and had calved between February 13 and April 24.…”

Effects of selection for ultrasound intramuscular fat percentage in Angus bulls on carcass traits of progeny

“…Direct selection using EPD has been demonstrated to improve growth traits (Hough et al, 1985;Mahrt et al, 1990), birth weight (Arnold et al, 1990;Lykins et al, 2000), and carcass traits (Gwartney et al, 1996;Vieselmeyer et al, 1996;Bertrand et al, 1997) in beef cattle. Traditional carcass evaluation programs have utilized carcass data produced from a structured sire progeny testing program.…”

Influência da interação touro x rebanho na estimação da correlação entre efeitos genéticos direto e materno em bovinos da raça Nelore

“…BERTRAND et al (1985), analisando dados da raça Hereford, nos quais o número de touros era relativamente grande (de 87 a 373), obtiveram componentes de variância da interação touro x rebanho igual ou mesmo maior que o componente entre touros. De qualquer forma, a importância da interação touro x rebanho tem sido vista com reserva à luz da sua menor importância quando observada em experimentos delineados (MAHRT et al, 1990; NOTTER e CUNDIFF, 1991) e em análises de dados de campo usando diferente metodologia (GARRICK et al, 1989). Entretanto, NOTTER et al (1992), na raça Angus, na Austrália, usando o método de máxima verossimilhança restrita (REML), obtiveram estimativas significativas para o componente de variância da interação touro x rebanho no peso à desmama.…”