Genotypic and technological factors in selection of black-and-white cattle when using the bull-sires of Holstein breed

In our country crossbreeding of Black-and-White breed with Holstein sires is actively used. Many arrays reached an average of more than 75% of Holstein genes (HF), but even now the process of crossbreeding raises questions among breeders. The scientific work presents the results of crossing Black-and-White cattle with Holstein breed. The share of genes for Holstein in the herd was 76.8%. It was established that during the study period, the normal distributions of traits of milk productivity were traced in the herd. The number of cows in the herd decreased, but their breeding qualities increased. The main reason for culling from the herd was gynecological diseases (in some years culling reached 175-188 heads). Variation in protein content in milk ranged from 2.90 to 3.39%. Most cows had protein in milk at a level of 3.00-3.19%. In the herd positive correlations were observed between yields for mothers and daughters for 305 days: 0.234 for the whole herd, 0.517 for the group of cows with 50% of the genes for Holstein (HF), 0.098 for the group with 51-75% HF, group with 76% HF and higher - 0.189. The heritability coefficient for milk yield for 305 days in the herd (h2) was 0.468. % Of protein in milk had a high heritability at 50% for Holstein - 0.668. The correlations between the fat content of milk in mothers and daughters were positive only in cows of the M. Chieftain line, and in the protein content in milk - in the lines of W. B. Ideal and M. Chieftain. With an increase in% of Holstein breed genes (HF) from 25 to 75% and above, there were no significant differences in milk yield among first-born cows (they amounted to 5424 ± 83--5520 ± 116 kg of milk). In the herd the percentage of fat and protein in milk was positively correlated (r = + 0.460). On average daughters exceeded their mothers by 23.3% for milk yield and 2.0% for the percentage of fat in milk (of the value of the trait). The amount of milk fat and protein increased by 25.8 and 22.5%, respectively. Based on the research results, it was concluded that the Holstein breed has a positive effect on the productive characteristics of dairy cattle, but optimization of technological processes is necessary for further selection.