RESULTS OF GENOTYPING OF HOLSTEIN COWS BY THE TLR4/ALUI GENE LOCUS AND STUDYING THE INFLUENCE OF TLR4 GENE ALLELES ON REPRODUCTIVE FUNCTION
The relevance of this study is determined by the need to improve the efficiency of dairy cattle reproduction using molecular genetic markers that can predict animal fertility. The aim of the study was to genotype Holstein cows for the TLR4/AluI gene locus and establish the relationship between its alleles and reproductive function indicators. The objectives included isolating genomic DNA, amplifying a 382-bp TLR4 gene region, and performing restriction analysis with the AluI enzyme. The study included 190 clinically healthy Holstein cows maintained under identical feeding and microclimate conditions at Baiserke-Agro LLP. TLR4/AluI genotyping was performed using PCR-RFLP; the genotype distribution was tested for compliance with Hardy-Weinberg equilibrium. Association analysis was performed taking into account the period of fruitful insemination of cows after calving (45–60; 61–90; 91–120; ≥121 days) and the non-return rate on day 58 (NRI-58). Three genotypes were identified: TT - 39.5%, TC - 43.7%, CC - 16.8%; allele frequencies: T = 0.61, C = 0.39; the distribution corresponds to HWE (χ² = 1.97; p > 0.05). In the 45–60-day group, the TT/TC/CC shares were 42/48/10%, with an increase in the open period (61–90; 91–120 days) an increase in the CC share to 16–22% was noted. According to NRI, 58 animals were registered: TT - 19 heads, TC - 24 heads, CC - 0 (a total of 43 out of 190). The data indicate a favorable role for the T allele and an unfavorable role for the C allele in determining fertility. The TLR4/AluI locus is informative for assessing reproductive function in Holsteins; the T allele is associated with earlier fruitful insemination and better fertility indicators, supporting its use as a selection DNA marker.