Effect of heterogeneity of variance components on genetic evaluation of protein yield in Holstein top sires and dams

The objective of this research was to study the heterogeneity of variance components for protein yield from the first three lactations of Iranian Holstein cows which collected from 1983 to 2014 by the Animal Breeding Center and Promotion of Animal Products of Iran. Data set were 141670, 115395 and 82529 records in the first, second and third lactations. Data were classified into three categories of Mediteranean, Dry desert and Humid using Domarten method. The heterogeneity of variances was studied using the Bartlett’s test. The results of Bartlett’s test before data transformation in the first three lactations were significant (P