DEPENDENCE OF THE MILK YIELD OF DAIRY COWS ON LINEAR ESTIMATION BY TYPE
Authors: Khmelnychyi L. M. , Vechorka V. V. , Khmelnychyi S. L. 
Published: October 2022

Sires breeding value determination was based on classification daughters at the age of first lactation, studies related to the breeding and genetic aspects of line scoring were limited to animals array scoring at the same age. Considering indisputable importance of linear estimation, existing correlative variability between individual descriptive and complex traits growth with dairy productivity and age-related variability in body parts of conformation development, a study was carried out of evaluation influence level of traits linear classification at the age of first lactation on cow milk productivity of subsequent second and third lactations.

While maintaining a positive correlation in further use of cows, reliability of linear estimation by type was confirmed. Studies conducted on the livestock of Ukrainian Black-and- Red-and-White dairy breeds showed positive correlations between evaluation conformation traits and cow milk yield with variability in their direction, degree and reliability, depending on the recorded lactations. First of all, at the age of first lactation, positive correlation coefficients were determined between conformation traits and milk yield amount of cows, which were a significant confirmation of this breeding event use as one of components in the comprehensive determination of dairy cattle breeding value in the world. Next important element in the aspect of correlative variability conformation traits of linear estimation with productivity was the establishment of sufficiently high correlation coefficients between evaluation four complexes of linear traits by 100-score system with milk yield for first lactation within experimental dairy breeds.

Positive relationship was, within group traits framework, by estimation of first lactation and milk yield of Ukrainian Black-and- Red-and-White dairy breeds for: dairy type (r=0.502 and 0.447), body (r=0.385 and 0.309), limbs (r=0.129 and 0.154), udder (r=0.404 and 0.383), respectively. Examining the question of whether existing relationship between assessment of group traits of conformation and milk yield amount of cows obtained at the age of first lactation, and between these traits and milk yield for subsequent lactations is preserved, it was found that within compared animals groups of both breeds, separate correlation coefficients received at the age of first lactation, repeated in the second with less force, but at sufficient reliability level. Correlation between indicators of linear estimation group traits of first-calf cows and milk yield for third lactation didn’t repeat level of similar relationships obtained at the age of first and second calving, although a certain pattern of their direction was followed with confirmation reliability of different level. Significant part of descriptive traits of the conformation was associated with milk yield amount for first lactation, as evidenced by reliable correlation coefficients.

But they decrease with age, and by data of third lactation such relationship was almost absent. Descriptive traits of conformation, correlated with milk yield at the age of first lactation and repeating these relationships with yield at the second and third, belonged to the traits of dairy-type animals were reliable indicators of cow milking. They included: height, chest width, body depth, angularity, rear width, pelvic limb posture, fore udder attachment, rear udder attachment height and central ligament. Thus, reliable level of positive correlation established between estimation of group traits of linear classification at the age of first lactation and milk yield for the next second and third lactation testified about effectiveness of dairy cattle selection, evaluated by conformation type. Level of correlative variability a part of descriptive traits of the conformation with milk yield of first-calf cows will not be repeated in combination indicators of the same estimation with yield at the age of second and third lactations, which was explained by natural unevenness of age-related variability in body type parts development under genotypic and paratypic factors influence.