Aim: This study aimed to analyze the efficiency of carbohydrate-enriched rations fed to pasture and stall-housed cows.

Materials and Methods: Forty Holstein cows were divided into four groups of 10 animals each. The experiment lasted 305 days. All animals were kept under the same conditions, except for the amount of energy-carbohydrate rations fed. The control cows were on a standard diet. Experimental groups 1, 2, and 3 received a ration enriched with energy-carbohydrate components at 250, 500, and 700 g/head/day, respectively. Feed intake was measured on 2 consecutive days each month. During the balance trial, when young animals reached 13 months, feed intake was examined daily. Fodder, its residues, feces, and urine collected during the balance trial were used to determine nutrient digestibility and nitrogen exchange.

Results: Nitrogen balance was positive in all experimental animals. Cows in Group 3 made better use of the digested nitrogen. A biochemical blood test showed higher total protein content in the serum of the experimental cows than in the control by 1.47-3.49% (p≤0.05-0.001) in winter and 0.24-0.98% (p≤0.01) in summer. In winter, the serum protein level increased due to changed feeding routines and shorter exercise times, but did not exceed physiological requirements. The alpha- and gamma-globulins levels increased to 0.2-0.5 g/L in winter and 0.3-0.6 g/L in summer, and 0.5-1.4 g/L in winter and 0.1-0.2 g/L in summer, respectively. Beta-globulins decreased. The supplement had a positive effect on milk output, which increased by 67.1-137.3 kg (1.93-3.95%; p≤0.05-0.001) in the first 100 lactation days, then by 198.2-458.8 kg (2.39- 5.53%; p≤0.05-0.001) for the remaining days. All animals had a high milk yield coefficient, with the experimental groups having 0.64-2.64% more milk yield than the control. The lactation curves showed that the average daily milk yield of all experimental cows increased, then gradually decreased along the physiological trajectory from the 3rd month until the end of lactation. Milk quality analysis in the experimental groups indicated an increase in the dry matter content by 0.17- 0.27% (p≤0.001) in summer and 0.16-0.27% (p≤0.001) in winter; higher protein levels by 0.04-0.06% in summer and 0.03- 0.07% (p≤0.05) in winter; increased fat by 0.09-0.14% (p≤0.05-0.001) in summer and 0.09-0.13% (p≤0.05-0.001) in winter; increased density by 0.47-0.61°A (p≤0.05) in summer and 0.17-0.27°A in winter; and increased energy by 1.70-2.63% (p≤0.001) in summer and 1.57-2.54% (p≤0.01-0.001) in winter.

Conclusion: The energy-carbohydrate feed "Tanrem" can provide the required energy intake of Holstein cows. The maximum biological and economic effect wads attained at 500 g per animal.

Keywords: animal breeding, cows, diet, ration cuts.