<b>Genotype-environment interaction in Brown Swiss dairy cattle</b> - DOI: 10.4025/actascianimsci.v31i2.5197

Abstract

Data from 2,981 first lactation records of Brown Swiss cows, daughters of 151 sires, from 62 herds, calving from 1980 to 2002 were used to evaluate the effects of heterogeneity of variance on genetic evaluation of bulls. The milk yields were used to classify the herds among high and low production level. An animal model used to estimate variance component, included the fixed effect of herds-year, calving season, linear effect of length lactation, linear and quadratic effect of cow age, random effects of animal and temporary environment. Variance components were estimated to milk yield in both levels, considering the milk yield in each production level as a different trait. Estimates of heritability were 0.21 in both levels for milk production and 0.25 and 0.26 for the levels of high and low production, respectively. The genetic correlation between high and low production levels was equal to 0.48. These results showed the presence of heterogeneity of variance. Spearman correlations in breeding values of sires predicted in joint analysis with values in high and low production level were higher; otherwise, the spearman correlations were lower to 10, 20 and 30% of the best sires of the rank. Sires with daughters in more changeable herds would be better ranked in the genetic evaluation, when the heterogeneity of variance is not considered