Productive qualities of Holstein cows in dynamics of lactation

Relevance. The transition of dairy farming in the Sverdlovsk region to breeding Holstein cattle is accompanied not only by increased productivity but also by problems of declining reproductive functions and productive longevity of animals. Studying the relationship between milk productivity and reproductive traits across lactation cycles is of significant scientific and practical interest for the sustainable development of the industry. Methods. The study was conducted on cows born in 2018. Analysis of breeding records was performed using the information and analytical system "SELEX — Dairy Cattle". Milk productivity (305-day milk yield, fat and protein content) was monitored using control milking. Reproductive qualities were assessed by the duration of the service period and the calculated reproductive ability coefficient (RAC). Statistical processing included calculation of mean values, standard error, and coefficient of variation. Results. It was found that the maximum average milk yield was achieved in the second lactation (10,484.48 ± 135.86 kg). However, the presence of animals with fat and protein content in milk below the minimum breed requirements was identified. A systemic excess of the optimal service period duration was observed, most pronounced in cows of the second lactation (deviation +50.76 days, or +56.34%). The average reproductive ability coefficient across all lactations was 0.89–0.90, indicating a satisfactory but insufficient level of reproduction. No direct correlation was found between milk yield and the duration of the service period. Despite the high genetic potential for milk productivity, the Holstein herd exhibits problems related to reduced milk quality (fat and protein content) and impaired reproductive function. To improve the efficiency of breeding, comprehensive selection is required, combining the assessment of not only milk yield but also milk quality and reproductive indicators. The research results justify the need to develop and implement management and breeding solutions aimed at reducing the service period and increasing the productive longevity of cows.