Association of prolactin gene variants with milk production traits in Malvi and Nimari cattle

The objective of the present study was to investigate the polymorphism of prolactin gene at exon 3 regions, and its association with milk production traits in Malvi and Nimari cattle. These traits consisted of lactation length (days) and lactation yield (kg) and service period (days). Genomic DNA was extracted from the venous blood collected from 50 Malvi and 32 Nimari lactating cows. Primers were synthesized and polymerase chain reaction (PCR) was carried out to amplify exon 3 region of Prolactin gene in Malvi and Nimari cattle. Amplified PCR products were digested with Rsa I, restriction enzyme for restriction fragment length polymorphism (RFLP) analysis, which revealed three genotypes. A silent (ALG) transition mutation at codon for amino acid at 103 position in exon-3 was identified. Genotypic frequencies in Malvi and Nimari cattle were 0.000 and 0.157 for AA genotype 0.900 and 0.843, for AB genotype and 0.100 and 0.000 for BB genotype, respectively. Estimated allelic frequencies of A and B alleles were 0.450 and 0.550 for Malvi and 0.578; and 0.422 for Nimari cattle, respectively. The effect of the identified genotypes on production traits was analyzed using simple linear model, which revealed significant (P<0.05) association of AA genotype with service period in Nimari cattle. The highly significant (P<0.01) Chi-square value in Malvi and Nimari cattle showed that the population was not in Hardy-Weinberg equilibrium. Present study indicated that the prolactin polymorphism can be used for selection of the cow to decrease the service period in Nimari cattle for future breeding.