Genetic Polymorphism Study in Prolactin Receptor (PRLR) Gene and their Association with Milk Production Traits in Indian Cattle Breeds

The aim of the current study was to investigate the status of Prolactin receptor (PRLR) gene polymorphism using PCR-RFLP assay and their association with milk production traits in Sahiwal (n=53) and Hariana (n=50) cattle. Two region of PRLR gene consisting of exon 10 and exon 9 revealed 168 and 582 bp products, respectively. PRLR/SmlI assay resulted in three types of genotypes, namely, GG (168 bp), TT (123 and 45 bp) and heterozygous GT (168, 123 and 45 bp) genotypes with frequencies 27.18, 6.60 and 67.90%, respectively. The allelic frequency of G and T alleles were 0.607 and 0.393, respectively. The DraIII/PCR-RFLP assay revealed three types of genotypes, namely, AA (582 bp), GG (399 and 183 bp) and heterozygous AG (582, 399 and 183 bp) genotypes with frequencies 17.0, 16.0 and 67.0%, respectively. The allelic frequency of A and G alleles were 0.505 and 0.495, respectively. Chi square analysis revealed that screened cattle population was found in Hardy-Weinberg equilibrium for both the SNP. Association studies of PRLR/SmlI genotypes had significant difference for total milk yield (TMY) and milk yield in 300 days (MY300) among three genotypes. The GG genotype showed higher milk yield value than TT and GT animals in first lactation. PRLR/DraIII genotypes had no association with any production traits in first and second lactation. Therefore, the present study demonstrating that G allele of PRLR/SmlI gene could be used as a strong marker for improvement in milk production performance in milch cattle.