Heritability and correlative variability of the conformation linear traits of first-born cows of black-and-white cattle with milk yield

Abstract

An in-depth analysis the publications of domestic and foreign authors was carried out in the aspect of research on the heritability of linear traits of the conformation type and their correlative variability with milk productivity.The research authors established that the level of existing variability in the heredity of linear traits depends on many genotypic and paratypic factors. However, they argue that despite the variability of traits heritability of dairy cows conformation, their level is generally sufficient for effective selection by linear type traits. Studies on the correlation between linear traits of type and milk productivity of cows of various breeds around the world have shown a high level of this relationship. This testifies about the effectiveness of indirect selection of dairy cattle by type, which will allow obtaining not only constitutionally strong and healthy animals, but also with high milk productivity.The population-genetic aspect of determining the heritability and correlative variability of linear traits with milking of first-born Holstein cows of domestic selection and Ukrainian Black-and-White dairy in the private enterprise "Burynske" of the Podlisniv branch of the Stepaniv territorial community in Sumy district was described. The magnitudes and reliability of the heritability coefficients of group linear traits indicate that they are controlled by the genotype of animals by 24.5-42.2 % in first-born cows of the Holstein breed, and by 26.6-40.1 % in female cows of Ukrainian Black-and-White dairy breed. The final score by type of 48.2 and 45.4 %, respectively, ensures the efficiency selection of cows by genotype. Variability of descriptive traits of Holstein cows ranges from insignificant and unreliable (h2=0.084; location of front teats) to high and reliable (h2=0.484; angularity). In females of the same age of Ukrainian Black-and-White dairy breed, the variability varies from 0.077 (location of rear teats) to 0.422 (angularity).In Holstein and Ukrainian Black-and-White dairy cows, the most reliable relationship was found between the characteristics of the dairy type (0.428 and 0.387), body (0.446 and 0.439), udder (0.486 and 0.478) and, especially, the final type score (0.492 and 0.488), which gives reason to assert about the effectiveness of selection based on these traits.The highest level of reliable positive correlation with the amount of milk yield for the first lactation was found according to the scores of descriptive traits of Holstein and Ukrainian Black-and-White dairy breeds, respectively: height (r=0.363 and 0.322), body depth (r=0.468 and 0.484), angularity (r=0.477 and 0.466), back width (r=0.366 and 0.322), posture of pelvic limbs (r=0.369 and 374), attachment of front (r=0.482 and 0.426) and rear (r=0.371 and 0.351) udder parts, central ligament (r=0.364 and 0.375) and locomotion (r=0.363 and 0.322) at Р<0.001. Key words: Holstein, UkrainianBlack-and-Whitedairy, lineartypeevaluation, conformation, milkyield, first-borncows.