LAUSR

The exclusive pre-selective effect of BLAD carriers reproducing in the exposed Holstein-Friesian cattle population prompted to search for the candidate gene variants of high quality of milk performance traits within the bovine ITBG2 gene or loci linked with bovine ITBG2 gene. Theoretical considerations indicated that the "silent mutation" C →T localized at the position of 775 bp of the gene encoding the CD18 subunit might be a potential QTL marker of high milk productivity. An association study between the polymorphism of SNP 775C>T, and the diversification of milk performance traits was carried out on the progeny of four bulls with genotypes BL/TL and 775C/T and one bull with genotypes TL/TL and 775C/T. The results documented statistically sig - nificant differences in the protein content percentage of milk in two half-sib families of bulls with BL/TL and 775C/T genotype and one half-sib family of bull with TL/TL and 775C/T genotype. It was further concluded that the polymorphism of SNP 775C>T was found to be a more efficient QTL marker than that of D128G, since in all the analysed milk performance traits for half-sib families higher values of the F coefficient were obtained for the SNP 775C>T mutation in comparison with D128G.