The estimation of the dynamics of genetic variability for the indicators of the body type of 1-st calf cows of Holstein black-and-motley breed of Moscow region

The objective of the study was to research the dynamics of selection and genetic parameters of first calf cows of Holsteinized black-and-motley breed. The objects of the research were first calf cows of Holsteinized black-and-motley breed, the population of which was leading number of livestock in the complexes of Moscow Region. The researches conducted on the evaluation of the exterior of first calving cows in samples, divided by years 2000-2018 with an interval of three years (generation) of 34.357 animals using the RISC ‘Mospleminform’ database. Moderate heritability of the height at the withers (0.20-0.46) and the length of the nipples (0.21-0.29) throughout the years of observation indicated that these values should be taken into account when breeding bulls based on the growth of daughters and adaptation to machine milking technology. The intercept behind the shoulder blades (0.39±0.08) and the roof-like backside (0.37±0.07), noted in 2018, had high heritability values among the exterior. Genetic diversity of the exterior indicators for the studied population was at the level of 0.3-2.7 %, which was 14.3-28.3 times lower than the phenotype variability. Quite high positive genetic correlations were established between growth and other indices: dairy type 0.6082±0.00001-0.6526±0.00002), the height of the heel (0.5386±0.00001), udder depth (0.4877±0.00004…0.554±0.00001), the attachment of the front lobes (0.4587…0.5774±0.00001). According to the distribution by categories of relative breeding value (RBV) among studied population, the smallest percentage of animals falls into the categories "+ +" (0.7 ... 4.1%) and "- -" (1.1-8.8 %). The main proportion of animals (about 40-79 %) were neutral in groups of characteristics. Established correlation between the studied characteristics of the exterior indicated the need for exterior’s linear assessment of the cows, as well as the need for regular monitoring of the selection and genetic parameters for assessing the exterior of the population of black-and-motley cows in Moscow Region.