The main objective of the study was to conduct a population-statistical analysis of integrated varying selection characteristics according to such parameters as: coefficients of heritability, repeatability, correlation, mean-square deviation. At the same time, the breeding parameters of dairy cows — milk yield, mass fraction of fat and protein, as well as key reproductive indicators — show variability within acceptable limits and pronounced correlations. Genomic assessment of breeding bulls is currently the main generally accepted and widely used method in world practice for determining breeding value; an innovative and effective method for increasing the efficiency of dairy cattle breeding and implementing the producer's genotype. The basis of the genomic forecast and calculation of the breeding differential is the assessment of the varying characteristics of the breed range; with its correction and refinement of new phenotypic data. The high repeatability of traits between lactation increases the predictive value of the first lactation data and justifies early selection, while a pronounced regression to the mean with low accuracy indicates insufficient breeding value of the producer. Descriptive statistics confirm the expected structure of the phenotype: milk yield for 305 days has a median of 9,820 kg with an interquartile range of 8,54910,944 kg and moderate relative dispersion (CV≈18%); the mass fractions of fat and protein are stable (3.60% 3.46–3.75 and 3.25% 3.13–3.39, respectively; CV≈6.9% and 5.5%), while the yield of components in kilograms varies more widely (fat 351.5 kg 310.1–390.1, CV≈17.8%; protein 321.8 kg 270.8–366.0, CV≈20.7%). The reproductive block is represented by a large range of variability: the median service period is 114 days 75-187 with a CV of 66.9%, and the distribution of somatic cells is expressed as follows (137×103 77-300×103, CV≈138%). There are moderate negative associations at the junction of productivity and reproduction: earlier first insemination is associated with higher milk yield and yield of components (r≈-0.40 with milk yield; -0.47 and -0.35 with protein and fat in kilograms; with a mass fraction of protein p≈-0.48), reflecting the combined effect of biological maturity and management. The relevance of the research problem lies in the need for continuous monitoring of incoming data and correction of the genomic forecast.
Olontsev et al. (Fri,) studied this question.
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