Environmental effects and heritibility for growth traits in Sardo Negro cattle from Mexico

Abstract

Information on Sardo Negro cattle obtained from 1997 to 2005, from breeding herds, from the Mexican Association of Zebu Breeders, localized in herds of Mexico was used. The objectives of the study were to evaluate the effect of several environmental factors on birth weight (BW), weight adjusted to 205 (W205), 365 (W365), and 550 days of age (W550), and pre-weaning daily weight gain (DWG) and to estimate heritability (h2) for those traits. The statistical models included the fixed effects of herd, year and season of birth (dry and rainy) and sex of the calf (male or female). The model to estimate the h2 included the fixed effect of contemporary group (herd-year-season-sex) and the direct additive random effect. Analyses were carried out using general linear models and multiple traits derivative-free restricted maximum likelihood procedures. Means for BW, W205, W365, W550, and DWG were 32.9 ± 1.5, 185.1 ± 34.8, 281.4 ± 50.1, 384.9 ± 58.5 y 0.742 ± 0.170 kg, respectively. Heritability estimates for BW, W205, W365, W550, and DWG were 0.00 ± 0.08, 0.27 ± 0.14, 0.26 ± 0.13, 0.12 ± 0.19 y 0.27 ± 0.14, respectively. The results of this study show that environmental factors are important sources of variation for W205, W365, and DWG. The high h2 estimates indicates that it is possible to improve the growth of Sardo Negro cattle by selection.