Population Genetic Analysis Of Prolactin (PRL) Gene Polymorphisms In  Bushuev Breed Cattle In Uzbekistan

This study investigated genetic variability in the prolactin (PRL) gene (g.8398A>G) and its association with milk production traits in the Bushuev cattle population of Uzbekistan. A total of 96 lactating cows from Tashkent and Syrdarya regions were genotyped using allele-specific real-time PCR. Genotype frequencies were 0.250 (AA), 0.542 (AG), and 0.208 (GG), with corresponding allele frequencies of 0.521 (A) and 0.479 (G). The population showed moderate genetic diversity, with observed heterozygosity (Ho = 0.542) slightly exceeding expected heterozygosity (He = 0.500), Nei’s genetic diversity index (H = 0.500), and a negative fixation index (FIS = −0.084), indicating an excess of heterozygotes and absence of inbreeding. The population conformed to Hardy–Weinberg equilibrium (χ² = 0.669, p > 0.05), suggesting its genetic stability. Association analysis revealed a significant effect of PRL genotypes on milk production traits (p < 0.001). The heterozygous AG genotype exhibited the highest milk yield (5489.3 ± 30.5 kg), while the AA genotype showed significantly higher milk fat (4.72 ± 0.05%) and protein (3.97 ± 0.06%) contents. The GG genotype displayed intermediate performance for milk yield and lower compositional traits. These results indicate a clear genotype-dependent trade-off between milk yield and quality traits, suggesting possible heterozygote advantage at the PRL locus. Overall, the findings demonstrate that the g.8398A>G polymorphism of the PRL gene is an informative genetic marker influencing economically important dairy traits. The study highlights the potential application of this marker in breeding programs aimed at improving milk productivity while maintaining desirable milk composition in Bushuev cattle. Funding: Support was provided by the Academy of Sciences of the Republic of Uzbekistan in the program of “Genotyping of genes responsible for milk productivity and quality in cattle breeds”.

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