Authors : R.J. Estrada-Leon , J.G. Magana and J.C. Segura-Correa
Abstract: The objectives of this study were to estimate genetic parameters for Age at First Calving (AFC), Interval Calving to First Service (ICFS), Interval Calving to Conception (ICC), Number of Services per Conception (NSC) and Calving Interval (CI) in a Brown Swiss herd and to estimate the relationship between sire’s Predicted Transmitting Ability (PTA) for milk yield and their daughters’ phenotypic means for those reproductive traits. Data used in this study were obtained from 358-623 Brown Swiss cows in Yucatan, Mexico. The herd was founded from 1982-1985 from 120 cows bought in the region, daughters of bulls and cows imported from the United States and heifers and semen brought from the United States and Canada. The animals were kept in a semi-intensive dairy management system. Genetic parameters were estimated by Restricted Maximum Likelihood procedures using the derivative free algorithm. Except for AFC (0.28) and CI (0.11), heritability estimates were close to zero. Repeatability estimates were also low (from 0.07 for ICFS to 0.19 for ICC). Simple regression analysis showed no association (p>0.05) of sire’s PTA for milk yield and phenotypic means of their daughters for ICC and NSC traits but an unfavourable association for ICFS (0.013�0.007) and CI (0.046�0.016).
R.J. Estrada-Leon , J.G. Magana and J.C. Segura-Correa , 2008. Genetic Parameters for Reproductive Traits of Brown Swiss Cows in the Tropics of Mexico. Journal of Animal and Veterinary Advances, 7: 124-129.