Population-genetic parameters of the traits of the body structure of cows of Ukrainian Black-and-White dairy breed
Researches of the linear traits of the body structure of cows of Ukrainian Black-and-White dairy breed were conducted in the herd of the breeding plant of the Pidlisnivskoyi branch of PJSC «Rise-Maksymko» in Sumy region. The results of the correlated variability between conformation measurements and the value of animal milk yield in the age-related lactation dynamics were presented. Positive correlation coefficients were determined within the statistical significance between measurements and milk yield of first-born cows: height at withers (r=0,422) and sacrum (0,353), chest depth (r=0,362), width in pin (r=0,311), hip bone (0,271 ) and ischial humps (r=0.366); oblique body length (r=0,286) and rear (r=0,244); chest girth (r=0.391). With age ties are weakening. The degree of heritability measurements varies within the traits and age of cows. In the herd of the breeding farm revealed sufficient, reliable by Fisher's criterion, the level of inheritance coefficients, which will provide adequate efficiency of mass selection by height measurements at the withers (h<sup>2</sup>=0,347) and sacrum (h<sup>2</sup>=0,288), depth (h<sup>2</sup>=0,244) and chest girth (h<sup>2</sup>=0,348), rear width (h<sup>2</sup>=0,251-0,264), oblique body length (h<sup>2</sup>=0,318) and rear part (h<sup>2</sup>=0,216), for which animals differed at the age of the first lactation. It was determined that the share of variability of measurements of the main traits of the body structure is caused by the heritability of improving breed (22.1-36.4 %), parent breeding value of cows (16.1-37.7 %), blood of father (10.9-26, 6 %) and father line (8.6-19.6 %). The positive correlation coefficients have been determined between the majority of body parts measurements and the value of milk yield, and the sufficient level of heritability in age-related lactation dynamics were the motivating factors for efficiency of selective breeding of dairy cattle breed by conformation. Рower of influence of the breeding value of parent and his origin on the indicators of the conformation measurements of their offspring indicated the need to consider when selection of indicators of comprehensive assessment the breeding value of sires.