Results of use of bulls breeds of black-and-pestlay breed

The aim of the research was to determine the effectiveness of the selection of the same type of sires for black-and-white cows and to evaluate the results of their use. The results of the analysis showed that the use of bulls Lira 967 and Loma 826 in a herd of black-and-white cows had a positive selection effect on milk yield, while the best results are characteristic of a bull with a lower genetic potential for this indicator. Despite the stable inheritance of the increased fat-milk content of the bull Loma 826, it was not possible to obtain a selection effect with respect to the fat-milk content. The results obtained clearly prove the need for a systematic analysis of the results of the selection of sires for the timely adjustment of the breeding process.