Estimation of genetic parameters for fertility traits in Brown Swiss cattle under subtropical conditions of Mexico.

Pedigree and reproductive records of 151 Brown Swiss cows were analyzed with the objective of estimating the heritability (h2) and the repeatability (r) for different measures of fertility. Cows were daughters of 49 sires and 102 dams. The study was carried out at Las Margaritas research station located in Puebla, Mexico. The pedigree was the same for all traits; it consisted of 287 individuals, and included dams without records and sires. Genetic parameters were estimated for conception rate at first service (CR), days to first registered heat after calving (OH), days to first registered service after calving (DS), days open (DO), and calving interval (CI). Estimations were made independently for each trait with a repeatability animal model, which included the direct additive genetic effect, as well as the permanent environmental effect of the cow. Genetic parameters were estimated with restricted maximum likelihood. In general, estimates of permanent environmental variance were greater than estimates of additive genetic variance, so that r was mainly determined by permanent environmental effects. Estimates of h2 and were: 0.02 ±0.06 and 0.16, 0.00 ± 0.05 and 0.15, 0.03 ± 0.03 and 0.03, 0.00 ± 0.03 and 0.14,and 0.03 ± 0.07 and 0.12 for DH, OS, CR, DO and CI. Artificial selection as a tool to induce genetic change in measures of fertility studied would be slightly effective because additive genetic variance is scarce. [ABSTRACT FROM AUTHOR]