ABSTRACT
The kappa (CSN3) and beta-casein (CSN2) genes are intensively genotyped in dairy cattle for selection purposes. This information is also generated and disseminated for Zebu breeds adapted to tropical climates. The objective of this work was to gather information on the genotypes for the CSN3 and CSN2 genes in three breeds (Gyr, Guzerat and Sindhi), and to verify the genotypic frequencies in the populations. The genotype AA and allele A frequencies are high for the CSN3 gene, without changes in values over the years, possibly indicating a small gene participation in traits under selection. In addition, the A2A2 frequencies are high for the CSN2 gene (<â¼0.80). It is recommended to verify the association and contribution of CSN3 genotypes in productive traits for these breeds. The potential of A2 milk production by these genetic groups is also confirmed.
