Relationship of STAT5A gene polymorphism with milk composition in Holstein dairy cattle

In this study, we investigated the relationship between STAT5A gene polymorphisms with production yield and milk composition. 340 animals from four herds were randomly selected with the desired information and then genomic DNA was extracted from blood samples using Miller salt method. We have observed three different genotypes GG, GC and CC with a frequency of 0.31, 0.455 and 0.235 for this polymorphism. Statistical analysis showed that genotype had a significant effect on milk fat percentage (P<0.05). The highest milk fat (3.288) was referred to CC genotype compared with the GC and GG genotypes, which have showed 3.117 and 2.970 milk fat, respectively. In addition, we showed that the genotype had a significant effect on the protein percentage .The CC genotype showed the highest value of 3.05 while the GC and GG protein percentage was 2.952 and 2.902, respectively. Finally, results confirmed the use of this locus in order to improve the qualitative characteristics of milk in Holstein dairy cattle .