It is proved that the live weight of replacement heifers, the intensity of their formation and milk productivity in primiparous cows depends on father origin, in particular, the value of the index of live weight formation between groups of half-siblings ranges from 68,9 to 82.3 (for comparing ages 6–0 and 12–6 months), from 15,1 to 18,4 (6–3 and 9–6 months), from 23,8 to 28,6 (6–3 and 12–9 months); average daily growth rate in the age of 0–12 months – from 659 to 717 g, 12–18 months – from 500 to 585 g; live weight at the age of 12 months – from 367 to 399 kg; 305-day milk yield – from 5295 to 7595 kg, fat content in milk – from 3,70 to 3,78 %, protein content – from 3,23 to 3,34 %, milk fat – from 197 to 286 kg, milk protein – from 175 to 253 kg.
Regardless of the method of determining the index of live weight formation, the higher values of them had daughters of sires M. Nirvana 101709244 (82,3; 18,3; 26,9, respectively), B. Buick 10789585 (80,0; 18,1; 28,6) and M. W. Tahoe 8189401 (80,1; 18,4; 27,7). There were determined differences (P < 0,001) between half-siblings by the average daily growth at the age 0-12 and 12-18 months. At the age of 0-12 months, the higher average daily growths showed daughters of sires M. W. Tahoe 8189401, Flame 112302008 and B. Buick 10789585 (on average 711 g), aged 12–18 months – daughters of sires M. Nirvana 101709244, N. Alfons 353588796, H. R. Artist 6284191 and H. Hadley 123055802 (on average 566 g).
The higher intensity of growth of replacement heifers up to 12 months was not related to higher milk productivity in primiparous cows. The advantage of milk yield (+606…+1373 kg, P < 0,001), milk fat (+25…+54 kg, P < 0,001) and milk protein (+22…+48 kg, P < 0,001) was observed in daughters of sires M. Estimate 5925716 and N. Alfons 353588796, whose live weight at the age of 18 months did not exceed the average in the group. The low milk productivity (–525…–927 kg of milk compared to the average, –18…–44 kg of milk fat and –8…–30 kg of milk protein) were characterized for daughters of bulls Flame 112302008 and M. W. Tahoe 8189401, which had significantly higher intensity of growth and live weight formation.
Based on the variance analysis it was established that the effect of parentage on the live weight of cows from birth to 18 months was 24,4–43,6 % of the total phenotypic variation, the average daily growth rate – 27,5–47,7 %, traits of milk productivity – 18,0–30,1 % with a high probability (P < 0,001)
Key words: dairy cattle, parentage, half-siblings, the index of live weight formation, milk productivity, power of influence.
