DYNAMICS OF THE EXTERIOR CHARACTERISTICS OF FIRST-CALF HEIFERS DAIRY BREEDS

Introduction. One of the main goals of the dairy industry is to achieve high productivity of cows with minimal costs for maintaining the herd. In recent years, when selecting cows, preference has been given to animals that combine the best productivity and reproduction with longevity and body type.In countries with developed animal husbandry, considerable attention is paid to the evaluation of the exterior of animals. Quantitative evaluation of the exterior by the method of linear classification according to the type of body structure is a necessary element of the comprehensive analysis of dairy cattle. With the intensive use of dairy cows, the introduction of modern technological solutions dependent on the biological characteristics of animals, the highest quality products can be obtained only under the conditions of successful selection of cows for breeding in the conditions of industrial technology. At the same time, the integral characteristic of a whole organism, reflected through a complex of exterior indicators, is presented in a modern linear assessment of the type of body structure of animals, which combines the analysis of cows by productivity and appearance (exterior).Research materials and methods. The research was carried out in the herd of the breeding farm LLC "Agrofirma "Svitanok" of the Maryinsky district of the Donetsk region. The analysis included information on 945 cows, the exterior of which was evaluated in the second – fourth month of the first lactation during the years 2007‒2020. By breed, 581 of the cows under control were classified as Ukrainian Red Dairy, 239 – Ukrainian Black-and-White Dairy, and 125 – Holstein breeds.In the studied animals, conditional blood of the improving Holstein breed was taken into account, considering its possible significant influence on the exterior and productivity of cows. We also took into account the age (months) of the assessment of the exterior of the first-calf heifers.Research results. Over 14 years of research, a noticeable improvement of the exterior in the direction of an increase in overall dimensions, better development of the breast, pelvis and udder was noted, which was accompanied by a significant increase in milk productivity. According to the proportions of the body structure, the indices of long-leggedness, shortness, massiveness, thoracic and eirisomia increase curvilinearly, while the index of stretch decreases. The chronological year factor reliably determines 9.0‒40.6% of the total phenotypic variability of measurements, 5.9‒39.8% of the variability of descriptive features of linear classification by body structure type, 5.9–37.3% of the variability of exterior indices and 59.2% of the variability of the milk yield of first-calf heifers.Improvement of the exterior and milk productivity of controlled animals was caused not only by the paratypical influence of a complex of economic and natural conditions of different years of animal use, improvement of technological conditions of keeping, feeding, raising the level of breeding of repair heifers, but also by the simultaneous influence of the genetic progress of the herd through the use of improver bulls, breed improvement and growth of conditional blood for the improving Holstein breed.A reliable (P < 0.001) direct relationship (r = 34.8 ± 3.12%) of the proportion of non-pigmented skin areas with conditional blood was established by the Holstein breed. The share of "white" color, as well as conditional blood by the improving breed, reveals a reliable level of relative variability with certain features of the exterior of first-calf heifers and productivity of cows. An increase in conditional blood for the improved Holstein breed leads to an improvement in the exterior, an increase in the proportion of non-pigmented skin areas and milk productivity of cows.The season of birth practically does not affect the general development and proportions of the body structure of animals. It accounts for only 0.1‒1.3% of the total phenotypic variability in the measurements of first-calf heifers, 0.06‒1.5% of the variability of individual descriptive features of linear assessment by type, and 0.03‒1.3% of the variability of body structure indices at a mostly unreliable level statistical significance (P = 0.004‒0.972). The influence of the season of birth on the milk yield of first-calf heifers was also low (1.6 ± 0.33%) at a statistically significant level of confidence (P = 0.002).Holstein cows, despite being younger by 3.0‒3.6 months at the age of assessment (as a result of higher precociousness), prevailed over the first-calf heifers Ukrainian Black-and-White and Red Dairy breeds in terms of most measurements and other external characteristics. The weight gain of Holstein cows in 305 days of the first lactation exceeded that of the Ukrainian Black-and-Dairy cows by 1840 ± 146.3 kg and Ukrainian Red Dairy cows by 2093 ± 130.2 kg (P < 0.001). Belonging to the breed determined 1.3‒20.5% of the total phenotypic variability of the measurements of first-calf heifers, 0.06‒7.6% of the variability of the descriptive features of linear classification by type, and 0.3‒7.3% of the variability of body structure indices. The influence of breed affiliation on the share of non-pigmented skin areas was more significant (12.2%), and the largest (19.8%) on the number of days after 305 days of the first lactation.The genetic factor of paternal origin has the most significant influence on the variability of external features of cows. Paternal descent accounted for 8.8‒45.9% of the variability in the measurements of first-calf heifers, 10.5‒40.5% of the variability in descriptive features of linear classification by type, and 8.2‒42.0% of the variability in body structure indices. The influence of the father on the share of non-pigmented areas of the skin was 22.6 ± 3.39% (P < 0.001), on the hope of the first-calf heifers – 57.6 ± 1.85% (P < 0.001). The best development in terms of most exterior traits and higher milk productivity were noted in the daughters of Holstein bulls С. E. Altadecree US64633889, Sarucco DE350995813 and Shirly NL447860719, from breeders of the Ukrainian Red Dairy breed – daughters of Tsvitok UA435 and Surguch UA6500134711. The worst in terms of appearance and performance were the first-calf heifers from the Holstein bulls Motabo DE578507835 and Campino Red DE112825601 and the breeders of the Ukrainian Red Dairy breed Misyats UA6333 and Ducat UA125.Conclusions. Improvement of the exterior and milk productivity of controlled animals was caused not only by the paratypical influence of a complex of economic and natural conditions of different years of animal use, improvement of technological conditions of keeping, feeding, raising the level of breeding of repair heifers, but also by the simultaneous influence of the genetic progress of the herd through the use of improver bulls, breed improvement and growth of conditional blood for the improving Holstein breed.A reliable (P < 0.001) direct relationship (r = 34.8 ± 3.12%) of the proportion of non-pigmented skin areas with conditional blood was established by the Holstein breed. The share of "white" color, as well as conditional blood by the improving breed, reveals a reliable level of relative variability with certain features of the exterior of first-calf heifers and productivity of cows. The season of birth practically does not affect the general development and proportions of the body structure of animals.Holstein cows, despite being younger by 3.0‒3.6 months at the age of assessment (as a result of higher precociousness), prevailed over the first-calf heifers Ukrainian Black-and-White and Red Dairy breeds in terms of most measurements and other external characteristics. The genetic factor of paternal origin has the most significant influence on the variability of external features of cows. The influence of the father on the share of non-pigmented areas of the skin was 22.6 ± 3.39% (P < 0.001), on the hope of the first-calf heifers – 57.6 ± 1.85% (P < 0.001).