A Study on the Effect of Prolactin Gene Variants on Milk Production Traits of Holstein Cattle

Abstract

Recent studies aiming to improve the daily milk production of cattle using both genetic and environmental factors are extremely important. The aim of this study is to determine the possible relationships between daily milk production and polymorphic distribution of exon 3 region of the prolactin (PRL) gene, which is an important marker for selection. With this purpose, 155 Holstein cows were included in the study, and the demographic data of the cattle were recorded. Venous blood was collected from the jugular vein of cows in 2 tubes of 2 mL each containing EDTA for DNA isolation. Genomic DNA were isolated from these whole blood samples. The prolactin gene region of the cattle were identified using PCR/RFLP and Sanger DNA sequencing method. The genotype, allele frequencies and Hardy–Weinberg equilibrium were calculated using Arlequin version 3.5.1.3 package software. Accordingly, it was found that cows with genotype AA had statistically higher milk yield as compared to those with genotype AB and BB. Missense mutation, frameshift and silent mutations were detected in the prolactin gene exon 3. It was also found that cows with missense mutation had statistically lower milk fat percentage as compared to the others. Consequently, the effects of genotypic distribution and mutation in the prolactin gene on the milk production of Holstein cows, which is a special breed in terms of milk productivity, have been revealed.