Polymorphism of the Prolactin (PRL) Gene and Its Effect on Milk Production Traits in Romanian Cattle Breeds

In the present study, we investigated one polymorphism of the PRL gene (rs211032652 SNP) and assessed its influence on milk production and chemical composition in two Romanian cattle breeds. A total of 119 cattle from two breeds reared in Western Romania (64 Romanian Spotted and 55 Romanian Brown) were included in the research herd. A PCR-RFLP genotyping assay was used for the identification of the rs211032652 SNP variants. Shapiro's test and Levene's test were used to verify ANOVA assumptions and ANOVA and Tukey's test were employed to test the associations between PRL genotypes and five milk traits. Among the studied breeds, our results showed that PRL genotypes were significantly associated (p < 0.05) with fat and protein percentage in the milk of Romanian Brown cattle. The AA genotype was associated with a higher fat percentage in milk (4.76 ± 0.28) compared to the GG genotype (4.04 ± 0.22, p = 0.048), as well as a higher protein percentage (3.96 ± 0.32% vs. 3.43 ± 0.15%, p = 0.027) in Romanian Brown cattle. Moreover, the PRL locus favored a significantly higher fat (p = 0.021) and protein (p = 0.028) percentage in the milk of Romanian Brown cattle compared to the Romanian Spotted breed, with a difference of 0.263% and 0.170%, respectively.