Humoral and cellular components of the natural defense system in limousin cows of different breeding lines

The problem of animal resistance has recently become increasingly important as the genetic potential of newly developed dairy cattle breeds has increased, and the animals are highly susceptible to various diseases, metabolic disorders, and disruptions in general homeostasis. This contributes to a significant culling of cows, prevents their planned selection, and, in turn, slows down the pace of breeding work. The state of natural resistance in animals is determined by nonspecific protective factors of their organism, which depend on several factors: species, breed, physiological state, conditions of care, housing, feeding, individual and constitutional characteristics, etc. The research aimed to study the natural resistance of Limousin cows of different selections. The studies were conducted at Lvivske LLC, Lviv region, on Limousin cows of Hungarian, Polish, and Ukrainian breeding. The natural resistance of the controlled animals was studied by analyzing the complex cellular and humoral blood factors in the third month after calving, according to the methods described in the reference book Laboratory Research Methods in Biology, Animal Husbandry, and Veterinary Medicine. It was found that Limousin cows of domestic and imported breeding differed in terms of natural resistance. In particular, the phagocytic activity of blood neutrophils, the phagocytic index, the phagocytic number, and the lysozyme and bactericidal activity of blood serum were highest in cows of Ukrainian breeding. However, their superiority in these traits over Polish and Hungarian breeding animals was statistically insignificant in almost all cases. A slightly higher level of protective functions in animals of the Ukrainian Limousin breed is also indicated by a higher number of T-lymphocytes, including T-helper cells. On the other hand, the number of T-suppressors was lower in Ukrainian cows by 3.1 % and 1.4 %, respectively, compared to Hungarian and Polish breeding animals. The immunoregulatory index in the controlled cows, depending on their country of breeding, ranged from 1,85 to 2,74, with the highest value observed in domestically bred individuals and the lowest in animals imported from Poland.