Th e meta-analysis method is used to combine results from many independent studies conducted in a diff erent region or area on a specific subject qualitatively and quantitatively and achieve a consensus. Th e current meta-analysis was conducted to investigate the association between prolactin gene polymorphism and milk production traits in dairy cattle. Th e data were collected between 2002 and 2021, and a total of 26 published studies were included in this study. Th e standardized mean diff erence (SMD) between genotypes was obtained for statistical evaluation, and to this end, the genetic models (dominant; AA + AB and BB, recessive; AB + BB with AA, co-dominant; AA, BB and AB genotypes) were compared with each other. In the analysis results, cattle with the AB versus BB genotype (SMD=0.289, 95% CI 0.005, 0.573) were found to have a statistically significant higher protein yield in comparison with the AA versus AB and AA versus BB genotypes. Th e relationships between prolactin gene polymorphism and milk yield, fat yield, fat content, and protein content traits were not found to be statistically significant.
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