The effectiveness of feeding different doses of bypass soy to high-yielding cows during the first 100 days of lactation using zinc proteinate

The article highlights the relevance of balancing the diets of high-yielding dairy cows in terms of the slowly degradable protein fraction that passes through the fore-stomachs without fermentation. It also examines the effectiveness of rumen-protected protein supplements based on bypass soy. A high-energy protein supplement with protected protein was substantiated, developed, and tested, and its impact on the milk yield and quality of lactating cows was studied. The research was conducted at Resilient Matyushi LLC (Matyushi village, Bila Tserkva district, Kyiv region) on Ukrainian Black-and-White dairy cows after their first lactation, which were in the second half of the dry period. Based on an analysis of the nutritional value of feeds, a protein-mineral supplement with an optimal ratio of protected protein and organic zinc was developed. The experiment lasted 85 days and included four groups of cows, each consisting of 10 animals. The animals received balanced diets containing different levels of bypass soy (ranging from 2 to 3 kg per head) and organic zinc (50 % of the norm in the 4th experimental group). Analysis of the chemical composition of feeds and their nutritional value showed that the optimal level of rumen-undegradable protein is 40 % of the total crude protein content. Including bypass soy in the diet at a rate of 2–3 kg per head increased milk yield by 1.2–2.3 kg or 2.3–4.3 % compared to the control group. The highest milk yields were obtained in cows of the 4th experimental group, which received 2 kg of bypass soy, 1 kg of which was additionally enriched with organic zinc at a rate of 50 % of the norm. In this group, the average daily milk yield was higher by 2.8 kg or 5.3 %, and the yield of 4 % fat-corrected milk exceeded that of the control group by 3.3 kg or 6.9 % (P < 0.001). The study also showed that the use of rumen-protected protein supplements affects milk quality indicators. The fat content in the milk of experimental cows (except for the 4th group) was lower by 0.04–0.05 %, which can be explained by changes in energy balance due to increased protein intake. At the same time, the protein content in the milk of the experimental cows was higher compared to the control, indicating an improvement in nitrogen metabolism in the body. Economic analysis showed that the use of bypass products positively affects the cost of milk production. The lowest cost per 1 kg of milk was recorded in the 4th experimental group (5.82 UAH), which was 3.3 % lower than in the control group. The value of milk in this group increased by 1.8 % compared to the control, and the total income per cow was the highest among all groups.