Mixed model methodology under bivariate animal models was used to predict (co)variance components and genetic parameters of 11,070 field data records of calf weight at birth (BW), 120 (W120), 240 (W240), 365 (W365), 550 (W550) and 730 (W730) and scrotal circumference at 365 (SC365) and 550 (SC550) days of age. Herd-year-season, calving age of cow and sex were considered as fixed effects and genetic direct animal effect and error were considered as random. Heritabilities, genetic and environmental correlations were estimated from the appropriate (co)variances and phenotypic correlations were computed. All data came from 9 herds of purebred Nellore seedstock raised in tropical southeastern and northern Brazil and bom from 1980 to 1993. Heritability estimates for direct effects were 0.29 (BW), 0.20 (W120), 0.25 (W240), 0.24 (W365), 0.26 (W550) and 0.21 (W730), 0.25 (SC365), and 0.43 (SC550). Genetic correlations between yearling scrotal circumference and other growth traits were positive, suggesting that selection for yearling scrotal circumference should not adversely affect other growth traits in Nellore Cattle. Environmental correlation estimates among those traits were hight and positives.

Raysildo B Lôbo, de los A. Reyes, Jose Bento Ster Ferraz, Luiz Antonio F Bezerra, M. EZ Mercadante, F. AM Duarte

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 17. Genetics and breeding of dairy and beef cattle, swine and horses, , 199–201, 1994
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