Interfamiliar specific fertility in Italian Brown Swiss cattle

The aim of this study is to evaluate the effects of interaction between sire of cow and service sire on the success/unsuccess of inseminations. Data from insemination events of Italian Brown Swiss cows collected from January 1993 through August 2007 were restricted to repeat breeder cows. A cluster analysis was carried out to group herds with very few observations in clusters with at least 15 observations. The edited data set included 102,710 services of 10,708 cows, daughters of 1,716 sires and mated to 3,108 service sires. The success or unsuccess at each insemination was evaluated by a linear mixed model including the fixed effects of herd-year interaction, month of insemination, age, and the random effects of sire service-sire of cow interaction and residual. The distribution of bull combination estimates was bimodal. When the tails of distribution (best and worst 5% of estimates) were considered, 271 service sires were included in both tails. Results suggest that major gene can affect the survival of embryos and that positive or negative interactions between paternal and maternal genotype can affect this reproductive trait.