Proportion of Pit-1 Gene Hinfi Polymorphism in Different Cattle Breeds: A Meta-Analysis

The Pit-1 gene is reported to be one of the strong candidate genes associated with body weight, average daily gain, milk production, and reproductive traits in cattle. This study aimed to determine the pooled frequencies of genotypes and alleles of Pit-1/HinfI gene polymorphism in different cattle breeds by meta-analysis and to compare these frequencies between breeds by subgroup analysis. According to the meta-analysis results, the pooled proportion of the A allele was 0.268 (95 % CI: 0.237-0.299), while the pooled proportion of the B allele was 0.733 (95 % CI: 0.702-0.764). High heterogeneity was found between studies for all genotypes and alleles. According to the subgroup analyses, the lowest frequency of the AA genotype was found in the local group (0.051 (95 % CI: 0.023-0.080)), while the highest frequency was observed in the hybrid group (0.011(95 % CI: 0.021-0.189)). The highest frequency of the AB genotype was found in the local breed group (0.444 (95 % CI: 0.377 – 0.510)). The BB genotype frequency was highest in the Simmental breed (0.592 (95 % CI: 0.558-0.627)). The A and B allele frequencies were highest in local breeds (0.279 (95 % CI: 0.225-0.330)) and Simmental breed (0.768 (95 % CI: 0.680-0.856)) respectively. According to the subgroup analyses, it was thought that the distribution of allelic frequencies of Holstein, Simmental, and Brown Swiss breeds, which were bred in the yield direction, was shaped according to their yield traits, while the highest variation was found in local breeds, suggesting that it may be an important indicator of the sustainability of the desired allele in the gene pool in the future.