HERITABILITY AND CORRELATIVE VARIABILITY OF LINEAR TYPE TRAITS OF THE FIRST-BORN COWS OF UKRAINIAN BROWN DAIRY BREED WITH MILK PRODUCTIVITY TRAITS

Abstract

This study has been conducted in the aspect of determining the heritability degree of linear type traits of the first-born cows of Ukrainian Brown dairy breed in the breeding herd of Sumy region. An assessment of the combined variability between linear traits and milk productivity was carried out, and the relationship of final grade per type with traits of cow longevity was determined. The revealed level of heritability coefficients of group traits indicated about the possibility of effective selection based on the results of cow selection by the assessment of dairy type (h2 = 0.395), body (h2 = 0.355), udder (h2 = 0.433) and, especially, on the final grade (h2 = 0.477). The heritability of descriptive traits was significantly variable and varied from h2 = 0.087 (rump angle) to h2 = 0.486 (angularity). The degree of heritability of descriptive traits, which have a significant functional load, was sufficient for effective selection for them, and at the same time, most of them are positively correlated with milk productivity. These include body depth (h2 = 0.412), angularity (h2 = 0.486), rear width (h2 = 0.313), front (h2 = 0.393) and rear (h2 = 0.355) udder attachment, central ligament (h2 = 0.404) and locomotion (h2 = 0.307). Close relationships (r = 0.323–0.487) with a high level of reliability were found between group traits and milk yield and milk fat yield, except for the group of traits that characterize the condition of limbs (r = 0.108 and 0.097). Descriptive traits of cows, which characterize condition of the body development, closely and positively influenced on amount of milk yield and yield of milk fat. These include the following: height (r = 0.268 and 0.255), body depth (r = 0.451 and 0.464), angularity (r = 0.444 and 0.422) and rear width (r = 0.455 and 0.467). Descriptive traits that characterize the limbs condition are more weakly correlated with milk yield and milk fat indicators: hock joint angle (r = 0.083 and 0.062), pelvic limbs posture (r = 0.288 and 0.294) and foot angle (r = 0.258 and 0.266). From the morphological characteristics of the udder, only three are positively correlated with milk yield and milk fat – front udder lobes attachment (r = 0.474 and 0.461), height of the rear udder attachment (r = 0.392 and 0.383) and central ligament (r = 0.427 and 0.411). Within the estimated population of first-born cows, the highest percentage of animals received the rating "Good plus" (60%). According to the duration of life, productive use and lactation, cows with a score of "Very good" prevailed over cows with a lower score with a significant difference, respectively, by 302–1327, 314–1352 and 316–1318 days (Р < 0.01–0.001). In terms of lifetime milk yield, this group of cows with an estimate of 85–89 scores exceeded other groups with lower estimates by 3843–24589 kg of milk (Р < 0.001). With slight variability in fat content, 142.4–860.8 kg more milk fat was obtained from the same group of cows compared to animals from the other groups (Р < 0.001). The selection of cows according to the final assessment can serve as an effective predictor of early selection, which will allow to increase the indicators of longevity of cows in herds from the breeding of Ukrainian Brown dairy breed.