Polymorphism of prolactin (PRL) and beta-lactoglobulin (Β-LG) genes in the Lacaune sheep and their relationship with milk productivity
Introduction . Dairy sheep breeding in Russia is a new and understudied area. Prolactin and beta-lactoglobulin genes are known to be the genes controlling milk production in many mammalian species, including sheep. The aim of the study was to examine the effect of DNA marker genotypes of prolactin and beta-lactoglobulin genes on the sheep milk productivity. Materials and methods. The study focused on the formed groups of the Lacaune sheep (n=248) bred at Nikolaev farm enterprise, Krymsky district, Krasnodar Krai. The gene polymorphism was determined through PCR-RFLP analysis. The amount of milk for 180 days of lactation was measured individually by carrying out control milking every 14 days. Qualitative parameters of milk - the content of fat and protein - were determined using Laktoscan M analyzer according to the study protocol. Results, discussion. This study reveals that the polymorphism of the PRL and β-LG genes is represented by the following alleles: PRL<sup>А</sup>, PRL<sup>B</sup>; β-LG<sup>А</sup>, β-LG<sup>В</sup> and PRL<sup>AA</sup>, PRL<sup>AB</sup>, PRL<sup>BB</sup>, β-LG<sup>AA</sup>, β-LG<sup>AB</sup>, β-LG<sup>BB</sup> genotypes, respectively. The PRL<sup>A</sup> allele was found to have a high frequency of 0.81 and the PRL<sup>B</sup> allele has a low frequency of 0.19. The β-LG<sup>B</sup> allele frequency amounted to 0.66, while the β-LG<sup>A</sup> frequency was 0.34. The animals with homozygous genotypes PRL<sup>АА</sup> and β-LG<sup>АА</sup> had better milk yield per lactation. The ewes with homozygous genotypes PRL<sup>ВВ</sup> and β-LG<sup>ВB</sup> had more fat and protein in their milk than their counterparts. Conclusion. The results obtained indicate the expediency of using as an additional criterion the selection of Lacaune sheep with the PRL<sup>BB</sup> , β-LG<sup>BB</sup> genotype for milk production with the aim of its further processing into cheeses.