UDC 636. 32/38. 082. 12
A correct assessment and selection of the most valuable rams is of primary importance in the system of breeding sheep with different productivity directions, because breeders provide almost 80% of the genetic improvement of the herd. Currently, the most studied method, which is successfully used in animal production practices, is the use of polymorphic systems for genetic examination of origin. It is proved that the errors in the pedigrees are very common.Errors in the pedigree documentation entails significant losses in production, especially in the breeding work. The breeding entries accuracy determines the effectiveness of selection work, including the purity of lines, the objectivity of the inheritance calculation, variability and correlation of economic-useful signs, the detection of genetic parameters. Without regard to these conditions, it is impossible to evaluate the quality of sheep breeding objectively and to make an effective selection and breeding of animals. For a more accurate assessment of studs breeding qualities an objective assessment of the stud rams genotypes was carried out based on the data obtained by genetic expertise of their descendants’ origin. The difference between our research and previous studies is that the genetic expertise of the young animals’ origin was carried out taking into account the results of animals typing not only based on polymorphic proteins but also according to blood groups. The assessment was conducted by the method of “Daughters of the same age.” For comparison of productive traits were used indicators such as: live weight at birth and weaning, the average number of lambs produced per ewe using verifiable ram (multiple pregnancy).It was found that the immunogenetic control when checking the studs on the quality of the descendants of origin, confirmed by genetic expertise, enables to establish objectively the rank of the stud, to identify the improvers that have a positive effect on the herd gene pool and to exclude from the selection the impairs timely, and also it becomes possible to trace the studs potential to breed true.