Beta-casein (CSN2) polymorphism in Ongole (Indian zebu) and Frieswal (HF × Sahiwal crossbred) cattle

Realizing the significant association of A1 and A2 β-casein (CSN2) polymorphism with health promoting properties and milk performance traits, the present investigation was undertaken to explore A1/A2 polymorphism in Indian zebu breed, Ongole (Bos indicus) and crossbred, Frieswal (HF × Sahiwal) cattle using allele-specific (AS)-PCR. Thirty eight Ongole cow, 124 Frieswal heifers and 48 Frieswal bulls were included in the study. The frequency of A2 allele was observed to be 0.94 in Ongole, 0.68 in Frieswal heifers; and 0.56 in Frieswal bull populations. Although all the three genotypes were observed in Frieswal bulls and heifers; however, no animal of A1A1 genotype was found in Ongole cattle and only four animals were of heterozygous genotype (A1A2). Considering the fact of healthfulness of A2 milk as well as positive relationship of A2 allelic variant with milk performance traits in different cattle breeds, the existing variability in β-casein (A1/A2) locus in Frieswal population may be exploited in near future for genetic selection. However, association of A2 variant with performance traits needs to be addressed before selection of Frieswal bulls at the time of birth.