Evaluation of Prolactin Gene Polymorphism in Holstein and Crossbred Cattle and its Correlation with Milk Traits in Holstein Cattle

The aim of this study was to survey the association between the Prolactin gene and milk performance traits. In the study 145 Holstein cattle and 60 crossbred cattle were used. The frequencies of allele and genotype in Prolactin gene has been recognized through PCR-RFLP using RsaI restriction endonuclease in 294-bp fragment located in exon 4. The GG genotype had the highest frequency in Holstein and crossbred cattle (0.738 and 0.588 respectively). Also frequencies of allele A and G were 0.152 and 0.848 in Holstein and 0.233 and 0.767 in crossbred cattle. Holstein cattle with AG genotype showed the highest milk yield. Dairy cattle with genotype AA showed the highest protein percentage (P<0.05) while there were no significant differences between various genotype in this gene and other milk traits (P>0.05). This polymorphism effect was significant for milk yield and protein percentage. The results of this study showed that this polymorphism could be a marker for selection for milk yield and protein percentage used in the population.