Characteristics of Holstein cows in terms of productive qualities, depending on age

Relevance. The breeding of highly productive Holstein cattle is accompanied by problems related to reproduction and reduced productive longevity, often explained by the high milk load on the body. Studying the influence of age and duration of economic use on the productive qualities of cows is crucial for optimizing the housing system and increasing the economic efficiency of dairy farming. The aim of the work was to assess the dynamics and variability of productive and reproductive qualities of Holstein cows depending on lactation number. Methods . The object of the study was Holstein cows that had completed lactation. Data from the IAC “SELEX-Dairy Cattle” database and the results of own observations were used. The dynamics of milk yield, mass fraction of fat (MF) and protein (MP), yield of milk fat and protein, as well as the duration of the service period and the reproductive capacity coefficient (RCC) by lactation were studied. Statistical processing was carried out with calculation of mean values (M), standard deviation (σ), standard error of the mean (m) and coefficient of variation (Cv). Results. It was found that milk yield significantly increased until the 4th lactation (maximum 10,166 kg), after which it gradually decreased. MF showed an inverse relationship with milk yield. The most stable indicators of productivity and nutrient yield were observed in cows of 3–4 lactations. The duration of the service period decreased with age, reaching a minimum (85 days) by the 6th lactation, while the RCC increased. High variability of traits was revealed in first-calf heifers (Cv of milk yield >15%), decreasing in mature animals. The scientific significance of the work lies in establishing clear patterns of age-related dynamics of productive and reproductive traits in Holstein cows in the conditions of the Ural region. The practical value consists in substantiating the feasibility of using cows up to the 5th–6th lactation, provided their reproductive function is controlled, and in the need to strengthen the selection of replacement heifers to reduce herd heterogeneity.