INFLUENCE OF PARENT SELECTION METHODS BY B ANTIGEN SIMILARITY INDEX IN THE BLOOD GROUPS ON WEIGHT AND LINEAR GROWTH OF BULLS

In solving the problem of qualitative improvement of beef breeds, it is important to improve the methods of practical use of existing parent couples selection methods, using histocompatibility antigens, polymorphic proteins and blood group systems. The purpose of the thesis is to determine the influence of homogeneous and heterogeneous selection of parent couples by blood group factors on the weight and linear growth of bulls of Ukrainian beef breed. The Ukrainian beef breed was bred using four breeds and is characterized by high variability in polymorphic features. The type of parent selection was determined by the index of B antigen similarity (ras) of cattle blood groups. The formula of D.A. Zhyvotovskyi and A.M. Mashurov was used to calculate the index of antigenic similarity of parents. Selection by ras of parents ≥ 0,268 was considered homogeneous, and by ras ≤ 0,267 heterogeneous. It has been proven that bulls that are descended from their parents with more ras pravail in the test on average daily gains and have a higher live weight. If ras of the parents is over 0.268, animals tend to improve their growth rate up to 8 months of age. After weaning this trend persists. The average daily gain of bulls obtained from parents with ras up to 0.267 is better in the period from 15 to 18 months, which indicates their lower precocity. If the antigenic similarity index of parents is more than 0.268, the animals are better in terms of the severity of meat forms at the age of 15 and 18 months. At the age of 15 months, bulls obtained from homogeneous selection by ras have smaller height measurements, better developed front of the torso in width and depth of the chest, longer torso and buttocks. Homogeneous selection of parental couples according to the B antigen similarity index of blood groups leads to improvement of weight growth and severity of meat forms of bulls of Ukrainian beef breed.