author(s)
Ruksana M Shah, NA Ganai, FD Sheikh, S Shanaz, HM Khan, Safeer Alam, Nusrat N Khan, Tavsief Sheikh, Saba Bukhari, Ambreen Hamadani and Mubashir A Rather

abstract
Prolactin plays an important regulatory function in mammary gland development, milk secretion, and expression of milk protein genes. Hence the PRL gene is a potential quantitative trait locus and genetic marker of production traits in dairy cattle. We analysed the best genotypes of Exon IV of PRL gene influencing the yield and quality of milk. 120 Jersey and Crossbred HF cows (60 each) were phenotyped for milk yield and quality traits. Genomic DNA was extracted using Phenol-chloroform method. 50ml morning milk samples were collected on weekly basis and analysed for quality using Speedy Lab Milk Auto-analyser. SAS 9.3 Statistical software was used for association analysis. The PRL gene (294 bp) was screened for polymorphisms by PCR-RFLP using Rsa I enzyme yielded three genotypes (RR, Rr and rr) for Crossbred cows and two genotypes (RR and Rr) in Jersey cows. The frequency of allele “R” was 0.50 in Crossbred HF cows and high in Jersey cows (0.70). In Crossbred HF cows genotype RR showed significant (p<0.05) differences on all the yield traits under study whereas it was genotype Rr found to be responsible for higher milk yield traits in Jersey cows. Genotypic effect was found to be significant (p<0.05) on protein%, fat% and density in Crossbred HF cows whereas in Jersey cows effect was non-significant (p>0.05) on all quality traits.