Genetic polymorphism of kappa casein gene and its association with milk production and milk composition traits in Gir and Mulki cattle

The present study investigates the genetic polymorphism of the kappa casein (CSN3) gene and its association with milk production and composition traits in Gir and Mulki cattle breeds from Narmadapuram Division of Madhya Pradesh state, India. A total of 256 cows, including 167 Mulki and 89 Gir, were analyzed. Genomic DNA was extracted from blood samples, and PCR-RFLP was employed to identify polymorphisms in the kappa casein gene. The study identified three genotypes-AA, AB, and BB—at the kappa casein locus. Allelic frequencies were found to be 0.83 (A) and 0.17 (B) in Gir cattle, and 0.89 (A) and 0.11 (B) in Mulki cattle. Statistical analysis revealed that Gir cattle exhibited significantly higher milk yield and daily milk yield across all genotypes compared to Mulki cattle. The BB genotype was associated with superior milk yield in both breeds. However, no significant associations were observed between kappa casein polymorphisms and milk composition traits such as fat percentage, protein content, SNF, density, pH, and freezing point. This study underscores the importance of kappa casein genetic variants in improving milk yield in indigenous cattle breeds, providing valuable insights for breed selection and dairy management practices.