О. А. Воронина Rationing of dairy cattle is one of the critical challenges faced by every farm. A comprehensive approach to addressing this challenge involves both theoretical substantiation and practical analysis of the actual composition of both feedstuffs and the resulting milk. Crucially, regular milk analyses enable the “response” to be recorded, allowing for an assessment of the actual level of nutrient assimilation and transformation from the diet. Our investigation was conducted as a single-point study on Simmental cows (n = 15) at a training farm located in the Voronezh Region. The feeding ration comprised 3.0 kg of mixed hay, 0.5 kg of straw, 32.0 kg of green mass (mixed grasses), and 4.6 kg of concentrates. Feed sampling was performed in parallel with milk sampling. Milk component composition analysis was performed using the “CombiFoss-7” analytical system; trace element analysis was conducted using an “atomic absorption spectrometer ZEEnit 650 P” (Analytik Jena AG); and feed composition analysis adhered to the relevant GOST standards. The results indicated satisfactory levels of metabolic energy, protein, and trace element supply, which aligned with the physiological requirements of the animals (considering productivity level, live weight, etc.). However, an excessive intake of iron via feedstuffs was identified. Based on the assessment of milk component composition, specifically the milk protein content and urea levels, it appears that the energy and protein provided by the feedstuffs in the diet are not optimally utilized. For instance, in 40 % of the investigated cows, milk protein content (MPC) was below 3.20 %; for 47 %, it ranged from 3.21 % to 3.60 %; and for 13%, MPC exceeded 3.61 %. Furthermore, 69 % of the cows exhibited milk urea levels below 10 mg* 100ml -1 (with levels only slightly higher in individual cows, but no samples exceeding 15 mg* 100ml -1 ). The average milk fat content (MFC) observed in our study was 23.1 % lower than the typical values for the Simmental breed. Positively, 20 % of the animals investigated showed MFC above 3.61 %. This comprehensive evaluation of feed composition and milk biochemical parameters revealed a discernible imbalance. We recommend close attention be paid to balancing the dietary requirements of cows for energy, protein, and micronutrients. This balance can be disrupted by factors such as feeding behavior ethology, as well as specific physiological and biochemical aspects of digestion in dairy cows, thus necessitating continuous monitoring.
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баланс рациона