GENETIC DETERMINATION OF GROWTH INTENSITY IN REPLACEMENT HEIFERS

The influence of genetic factors on the growth intensity of replacement heifers was studied in 1,262 animals of the Ukrainian Red Dairy (771 head), Ukrainian Black-and-White Dairy (169), and Holstein (322) breeds in the breeding herd of Agrofirm LLC “Svitanok” in the Maryinskyi district of Donetsk region. The dynamics of body weight and average daily gains of the animals were assessed from birth to 18 months of age. It was established that paternal origin significantly affects offspring growth, especially in the period up to one year of age. The highest body weight and growth rates were observed in daughters of Holstein bulls V. L. Snow and Candy Red, showing an advantage of up to 18% over their peers (P < 0.001). One-way analysis of variance revealed that paternal origin accounted for 7.6–25.6% of the total phenotypic variability in body weight and 2.7–18.2% in average daily gains. Comparable influence was found for linear affiliation and conditional Holstein blood percentage, which correlated most closely with the studied traits during the 6–12-month period. A low and statistically insignificant correlation was found between the breeding value of sires and the growth intensity of heifers. The obtained results confirm the advisability of considering genetic factors in the rearing of replacement dairy young stock.