Abstract. The aim of the research is to study the selection and genetic parameters of the characteristics of productivity and the exterior of Holstein first-calf cows, depending on their body type. Research methods. Based on the data from the SELEX database, we researched the performance indicators and measurements of the trunk of first calving cows in the amount of 4049 heads. Based on the RENUMF90 software shell of the BLUPF90 program, we obtained digital values of the genetic variability of productivity indicators and the external structure of animals in accordance with the equation of the mixed model. Results. The most broad-bodied animals classified as airysomal type had the highest milk yield in the first lactation, and exceeded animals of the leptosomal type by 563.3 kg (p ≤ 0.001). According to the "B" system, broad-bodied cows are superior to narrow-bodied animals: stature – by 1 point (p ≤ 0.001); body depth – by 0.8 points (p ≤ 0.01); rump width – by 1.9 points (p ≤ 0.001); rump angle – by 0.9 points (p ≤ 0.01); fore udder attachment – by 1 point (p ≤ 0.01). Animals of the narrow-bodied type reliably (p ≤ 0.001) had a high genetic relationship between milk yield in 305 days of first lactation and the mass fraction of protein in milk (0.59 ± 0.005). At the same time, the leptosomal type of cows also had the greatest correlation between milk yield and mass fraction of fat (0.51 ± 0.005) (p ≤ 0.001). According to body measurements, the highest correlation coefficients were found in animals of the airysomal type – 0.24 ... 0.50. All Holstein heifers of different body types have high heritability coefficients in terms of fat mass fraction (h2 = 0.37 ... 0.49) and protein mass fraction (h2 = 0.42 ... 0.51). Scientific novelty. For the first time, studies of the genetic variability of productivity indicators and the exterior of Holstein cows, depending on their body type, were conducted.

The experiment is carried out on 3 groups of cows (1 - with productivity up to 7500 kg, 2 – from 7500 to 9000 kg and the 3rd group-9000 and above kg of milk for the previous lactation). Milk yield for 305 days of lactation of cows of group 3 averaged 9068 kg (P≤ 0,01), group 2-8682 (P≤ 0,05) and group 1 – 7940 kg of milk. Milk fat production in cows of group 3 - 369 kg (P≤ 0,05), group 2-351 and group 1 – 326 kg. The yield of milk protein from cows of group 3 is 285 kg (P≤ 0,01), group 2-270 (P≤ 0,05) and group 1-248 kg. A comparative analysis of the growth and development of heifers with mothers with different levels of productivity was carried out. At the 2nd month of growing, the weight of heifers of the 3rd group is 76 kg (P≤0,10), the 2nd - 72 kg (P≤0,10). The average daily growth of group 3 heifers at 6 months was 1244 g (P≤0,10), group 2 - 1127 and group 1-617 g.Group 3 Heifers at 9 months weighed 301,2 kg (P≤0,05), group 2 – 299,3 kg (P≤0,05). Heifers of group 3 at 12 months reached 380,6 kg (P≤0,05), group 2–378,5 (P≤0,05) and group 1 – 353,7 kg. The growth of experimental heifers of group 2 was 887,6 g (P≤0,05), group 3–829,6 and group 1 – 710 g per day. Monitoring of growth and development of heifers continues.

The article deals with a comparative analysis of biochemical and morphological parameters of blood of Holstein cows during the transit period of lactation and obtained from them heifers of the dairy period. The content of globulin in the blood serum of group 1 cows at 1 month of lactation is 56,0 g/l, at 3 months 53,9 g / l, which is significantly higher than the level in other groups (P≤0,05). In group 3 cows at the 3rd month of lactation, creatinine significantly increased to 74,8 mmol/l (P≤0,05). The blood content of alkaline phosphatase in 1 month of lactation in all examined animals is normal. The blood glucose level in cows is kept in the range of 3,6-4,0 at 1 month and 2,7 – 4,3 at 3 months of lactation (at the norm of 2,0 – 4,8 mmol/l). The concentration of total blood protein in calves at 3 months is within the normal range, but the variation was from 70,3 in group 1 to 84,4 g / l in group 3 (P≤0,05). Significant changes in the serum creatinine content at the 3rd month of life of experimental calves of group 3 up to 73,6 mmol/l (P≤0,10) within the normal range determine the intensity of adaptive mechanisms. Glucose in the blood serum of heifers is at the upper limit of the norm in groups 1 and 2 – 4,9 mmol/l (the norm is 4,8 mmol/l), which indicates a fairly high energy security of the calves ' diet. Total bilirubin in the blood serum of heifers of groups 1 and 2 is slightly higher than normal (the upper limit of the norm is 8,15) – 9,3 and 8,7 mmol/l. By the third month, the total bilirubin content in the blood of group 2 heifers increased to 10,7 mmol/l (P≤0,05), in the rest – within the normal range.

Abstract. The purpose of the research is the possibility of applying the equation of multiple two-factor regression to reveal the reliable conjugacy of signs affecting the level of milk productivity of Holstein cows. Research methods. The research was carried out in CJSC BP “Aksin’ino” of Stupinskiy district of the Moscow region. Based on the IAS “SELEX”, a database was created, including a sample of 11 017 heads. Data on milk productivity were taken for 305 days of 1st, 2nd, 3rd and maximum lactation. Results. For 305 days of the 1st lactation, milk yield averaged 7909.5 kg of milk, for the 2nd – 8289.1 kg (p ≤ 0,001) and the 3rd lactation – 8446.2 kg (p ≤ 0,001). Milk yield for maximum lactation was 8964.3 kg of milk (p ≤ 0.001). The fat and protein content in cow milk between the 1st and 3rd lactation is 4.03–4.08 and 3.22–3.23 %. The multiple two-factor regression coefficient represents the response bias from 7787.81–8239.00 (1st, 2nd, 3rd lactation) to 8841.63 (maximum lactation). The scattering diagrams of the multiple regression model show that the value of the variable "milk yield" is statistically dependent on the indicators of the mass fraction of fat and the mass fraction of protein in milk. The coefficient of determination at the level of 0.997–0.998 indicates that the regression equation explains 99.7–99.8 % of the variance of the effective feature. The significance of Fischer’s F-test indicates the high reliability of the results and the absence of randomness and the presence of a pattern justified in our study. The fat and protein content had a negative relationship with milk yield (p ≤ 0,001) by lactation. High values of the relationship between milk yield and protein content (–0.518…–0.766), fat and protein content (0.626–0,784) were obtained. Scientific novelty. For the first time, studies were conducted on the correspondence of the equation model to the experimental data obtained, and the presence of the number of independent variables (mass fraction of fat and protein) included in the equation to describe the dependent variable (milk yield).

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