STUDY OF SNP POLYMORPHISMS ASSOCIATED WITH MASTITIS RESISTANCE IN COWS

In dairy cattle breeding, assessment of animals’ natural disease resistance using molecular genetic methods is an important area of modern selection aimed at reducing economic losses associated with mastitis and improving overall herd health. The aim of this study was to comprehensively evaluate polymorphism, allelic frequencies, and genotypes at the MASP2 (g.14248T>C) and CATHL2 (807G>A) gene loci, which are involved in immune response and may be associated with resistance to mastitis, in a population of Holstein cows from the breeding farm of “AkSut LLC” LLP in the Almaty Region. During the study, DNA samples isolated from the selected animals were assessed for concentration and purity using a NanoDrop™ 2000 microspectrophotometer. Polymorphic variants of the target gene loci were identified using PCR-RFLP (polymerase chain reaction–restriction fragment length polymorphism) analysis. The FokI restriction endonuclease was used for analysis of the MASP2 gene fragment, while MseI was used to digest the amplification products of the CATHL2 gene. In addition, quarterly rapid screening for subclinical mastitis was performed in the herd using the DeLaval test kit to monitor the clinical status of the animals. Based on the population genetic data obtained, the chi-square (χ²) test was used to assess conformity with the Hardy–Weinberg equilibrium and to evaluate the genetic structure of the studied herd. The results of this comprehensive screening may serve as an analytical tool for breeding programs aimed at identifying favorable genetic variants associated with mastitis resistance, supporting the development of selection strategies to improve udder health and maintain the productive potential of the herd.