The dependence of live weight of Ukrainian Black-and-White dairy heifers on the method of selection of parental pairs

The article presents the results of research on the dependence of live weight of heifers on the method of selection of parental pairs. The research was conducted in the Vinnytsia region's State Enterprise “Oleksandrivske” on heifers of the Ukrainian Black and-White dairy breed by the method of retrospective analysis of zootechnical records. The effectiveness of combining parental pairs in intra- and inter-linear (crossbreeding) breeding was investigated. It was established that the live weight of heifers depended on the method of selection of parental pairs. In intra-line breeding, the highest live weight at birth, at six and twelve months, was characterised by heifers of the Haneve 1629391 line, and at eighteen months - of the Eleveishna 1491007 line. In the interline breeding, the highest live weight of newborn heifers was in the cross of the Cavalier 1620273 - Eleveishna 1491007 lines, at six and eighteen months - in the cross of the Starbuck 352790 - Eleveishna 1491007 lines, and at twelve months - in the cross of the Eleveishna 1491007 - Starbuck 352790 lines. The coefficient of variability of live weight in intra-line breeding was in the range of 3.9-12.2%, and in inter-line breeding - in the range of 3.8-13.9%. In all the studied variants of selection of parental pairs, the average daily gain and the relative rate of growth of live weight in heifers were the highest from birth to six months of age. The method of selection of parental pairs had the lowest effect on the live weight of newborn animals (7.11%). Later, in the process of growing heifers, this effect increased and, depending on the age period, ranged from 14.2 to 15.8 % (P<0.05). In order to obtain heifers with the desired growth intensity, it is necessary to identify the best lines and establish the possibility of using the effect of their combination. The successful combinations of parental pairs must be identified in each specific herd. To increase the growth rate of live weight of heifers in the herd, animals of the Haneve 1629391 and Eleveishna 1491007 lines should be used for intra-line breeding, and animals of the Cavalier 1620273 - Eleveishna 1491007, Starbuck 352790 - Eleveishna 1491007 and Eleveishna 1491007 - Starbuck 352790 crosses should be used for inter-line breeding. The method of selection of parental pairs had a statistically significant effect on the live weight of heifers during their growing period. In order to obtain heifers with the desired growth intensity, it is necessary to identify the best lines and establish the possibility of using the effect of their combination. The successful combinations of parental pairs must be identified in each specific herd. To increase the growth rate of live weight of heifers in the herd, animals of the Haneve 1629391 and Eleveishna 1491007 lines should be used for intra-line breeding, and animals of the Cavalier 1620273 - Eleveishna 1491007, Starbuck 352790 - Eleveishna 1491007 and Eleveishna 1491007 - Starbuck 352790 crosses should be used for inter-line breeding. The method of selection of parental pairs had a statistically significant effect on the live weight of heifers during their growing period. Key words: breed, methods of selecting parental pairs, live weight, heifer, power of influence.