Single nucleotide polymorphisms within exon four of the prolactin gene and their effect on milk traits in cattle populations of Ethiopia

Bovine prolactin (PRL) gene is essential for the initiation and maintenance of lactation and exerts multiple effects on mammary alveoli to promote the synthesis and secretion of major components of milk. The objectives of this study were to identify mutations in PRL gene and to evaluate the mutations as potential markers of milk performance traits in cattle populations of Ethiopia. For this purpose, genomic DNA from whole blood was extracted through salting out procedure from 87 animals of five cattle populations of Ethiopia. Accordingly, three single nucleotide polymorphisms (SNPs) were identified of which one SNP g.8323T > A showed missense mutation while the other two SNPs revealed silent mutations. FST values showed statistically significant genetic differentiation among the studied populations. Intermediate polymorphic information content was noted for most SNPs, which indicates the presence of sufficient genetic variation at this locus. Two SNPs showed heterozygote deficiency as a result of positive FIS values. Only g.8398A > G SNP have statistically significant (p < 0.05) effect on average daily milk yield, fat and solid not fat percentage in all studied cattle populations. Therefore, g.8398A > G SNP identified in this study influences cattle milk production and may be used as possible candidate SNP for marker-assisted selection programs in cattle populations of Ethiopia.

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.