Association of polymorphic variants of the KCNB1 gene with productive traits and physicochemical properties of milk under the inclusion of the probiotic supplement «KLUVER PRO» in the diet

With the increase in milk productivity of high-yielding dairy cows, a reduction in their productive lifespan and a higher culling rate have been observed, primarily due to metabolic disorders associated with feeding practices. In modern dairy production, high productivity is maintained through the inclusion of readily digestible carbohydrate- rich feeds in the diet, which has been associated with adverse effects on ruminal metabolic processes in ruminants, increasing the risk of nutrition-related diseases. These metabolic disruptions manifest as decreased fertility, impaired pregnancy dynamics, and reduced lactational performance, directly affecting milk yield and the economic profitability of the dairy industry.In current dairy farming practices, the focus should be placed not only on supplying adequate nutrients to the cow's body but also on creating optimal conditions for the development of the foregut microbiota, which is a key determinant of maintaining health and improving productivity. One of the promising approaches for the prevention of alimentary diseases and correction of metabolic disorders is the use of probiotic supplements, including preparations based on live yeast cultures. Genetic factors also play a significant role in the stable expression of productive traits in livestock. The KCNB1 gene has been recommended as a marker gene associated with high milk productivity in cows, as it is involved in tissue regeneration processes of the mammary gland and apoptosis. This study presents the results of analyzing the effect of the probiotic yeast supplement “KLUVER PRO” and polymorphic variants of the KCNB1 gene on milk productivity, milk quality indicators, and physicochemical properties in Holstein cows. The experimental results demonstrated that, compared to the control, cows with the KCNB1AA genotype showed a statistically significant increase in milk fat yield by 11.86% (p ≤ 0.05), while cows with the KCNB1GG genotype exhibited an increase in milk protein yield by 8.64% (p ≤ 0.05). Statistically significant differences were also observed in the group of cows with the KCNB1GG genotype regarding certain physicochemical milk parameters: the lactose content increased by 2.91% (p ≤ 0.05), whereas the somatic cell count decreased by 41.29% (p ≤ 0.05).