Akademik Veri Yönetim Sistemi
JOURNAL OF THE HELLENIC VETERINARY MEDICAL SOCIETY, sa.1, 2025 (SCI-Expanded)
This study aims to investigate by meta-analysis using different genetic models the associations between insulin-like growth factor-1 (IGF-1/SnaBI) polymorphism and certain milk production traits, such as total milk yield, fat and protein yield, and content in cattle. The results of this analysis can provide important contributions to breeding programs and animal husbandry practices maximize the genetic potential of cattle and increase efficiency in milk production. The study employed the meta-analysis method and examined four genetic models for each genotype region of the data set: dominant (TT + CT vs. CC), recessive (TT vs. CT + TT), over-dominant (TT + CC vs. CT), and co-dominant (TT vs. CT, TT vs. CC, and CT vs. CC). Standard mean differences (SMD), standard errors, and 95% confidence intervals were calculated to assess the strength of the relationship between the yield trait averages of the gene variants. The fixed model was applied when study results were homogeneous, and the random-effects model was applied when they were heterogeneous. The estimation of heterogeneity was calculated based on the I-2 statistic. For SMD results, Hedges' method was used due to the low number of studies. According to the results of the test applied in the published studies examining the relationship between IGF-1 polymorphism and milk yield traits, it is seen that there is no publication bias. The results of the evaluation according to genetic models indicate that the associations of the IGF-1 gene with the other yield traits should generally be examined using a codominant genetic model. The IGF-1 gene polymorphism appears to have significant effects on fat yield, fat content, protein yield, and protein content in cattle, but not lactation milk yield. Significant differences were observed between TT-CT genotypes for fat yield and fat content, and between TT-CC genotypes for protein yield and between CT-CC genotypes for protein content, while there was no significant overall effect of the IGF-1 gene polymorphism on lactation milk yield. As a result, the impact of IGF-1 gene polymorphism on milk production traits may vary according to genotypes, and it is suggested that the IGF-1 gene can be used as a significant molecular marker in breeding studies, especially for increasing the fat and protein percentage in milk.