Multivariate regression analysis of dairy characteristics of Holstein cows

Abstract

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).