Effect of Osteopontin gene variants on milk production traits in Holstein Friesian crossbred cattle of Kerala

Osteopontin gene (OPN) is located in the quantitative trait loci (QTL) for milk production traits in bovine chromosome 6. In the present study the impact of cytosine to thymine transition in the intron-4 of OPN gene (g.8514C > T) on milk production traits was analysed in the Holstein Friesian crossbred cattle of Kerala. Genomic DNA was isolated and a fragment of 290 bp enclosing the polymorphic site was amplified and genotyped by restriction fragment length polymorphism (RFLP) using endonuclease, BSeN1. The genetic variants were distributed according to Hardy-Weinberg equilibrium. The T allele was found to be the major one (T/0.76, C/0.24) and the genotype frequencies were TT/0.60, CT/0.32, and CC/0.08. The amplicons of genotypes were sequenced by sangers dideoxy termination technique and confirmed the mutation. Association study using the General Linear Model-Analysis of Variance (GLM-ANOVA) considering marker, season of calving, parity and herd as fixed factors and dairy trait as dependent variable revealed that none of the yield traits (305 day milk yield, peak yield, fat yield, protein yield, solids not fat yield, lactose yield, daily milk yield) or composition traits (fat percent, protein percent, solids not fat percent and lactose percent) of milk production analysed were significantly differed between CT and TT genotyped animals. The OPN gene polymorphism (g.8514C > T) can be suggested for marker assisted selection (MAS) for future breeding programmes for dairy cattle only after extensive association studies.