Milk composition of Jersey cows with different genotypes of somatotropin cascade gene loci

This article presents the results of a study examining the influence of somatotropin cascade gene polymorphisms (PRL, PIT1, GH) on physico and chemical parameters of Jersey cow milk, with the aim of identifying genotypes associated with improved milk quality characteristics. Allelic variants of PRL, PIT1 and GH genes were identified using polymerase chain reaction followed by restriction fragment length polymorphism (PCR-RFLP). The results demonstrate that prolactin gene polymorphism has the most pronounced effect on milk quality. In particular, cows with the PRL AB and BB genotypes are characterized by a significantly higher content of dry matter (16.16% and 16.22% versus 15.82% for AA), fat (6.27% and 6.24% versus 6.07% for AA), protein and lactose, as well as an increased energy value of milk (95.1 and 95.2 kcal versus 92.7 kcal for AA). With regard to the pituitary transcription factor gene, it was found that cows with PIT1 AB genotype have an advantage in terms of dry matter (16.23%), dry nonfat milk residue (10.55%), protein (3.99%) and lactose (5.20%), while the highest fat content (6.35%) was found in animals with the PIT1 AA genotype. Animals with GH LL genotype demonstrate a higher dry matter content (15.46%) and energy value of milk (95.6 kcal) compared to cows with GH LV and GH VV genotypes. The study confirms the potential of using somatotropin cascade gene polymorphisms as genetic markers for breeding aimed at improving the quality of milk in Jersey cows.