Использование обменной энергии у бычков в период выращивания при разном уровне обменного протеина в рационе

Experimental investigations carried out using Kholmogory bulls, kept under vivarium conditions, have been aimed to study the effect of different levels of metabolizable protein in the diet on the use intensity of metabolizable energy. The main diet contained 478 g of metabolizable protein and included cereal hay, mixed grass silage and compound feedstuff. According to experimental scheme the bulls were consequently supplied with increasing levels of metabolizable protein (491, 513 and 526 g.) at the expense of partial replacement of the compound feedstuff by feed additives with different protein degradability (sunflower meal or soybean cake). According to the indicators of energy balance, the efficiency of metabolizable energy use for the increase in body weight was established. On the basis of the balance of energy substrates the correlation was determined between substrate expenditures for heat production and expenditures for deposition in body weight gain of bulls during the growing period. When soybean cake (750 g) was supplied with the diet the expenditure of energy substrates for heat production was the highest, that led to the decrease in output gain. When sunflower meal (250 g) was included in the ration the contribution of enegy substrates to gain was most significant.