Feeding carboxylin to bulls of the black-piebald breed for six months with the beet-cutting fattening essentially increases assimilation of nitrogen, in particular of diammonium phosphate nitrogen, from the ration. In the experiments with liver sections and homogenates of animals of the control and experimental groups it is established that carboxylin activates incorporation of acetate-2-14 C into proteins and lipids as well as from NaH14CO3 into the acid-soluble organic substances. In the liver tissue of the animals under experiment the oxygen uptake is intensified. The content of alkaline reserves increased, concentration of area and citrate rises. No difference is established in the content of calcium, phosphorus, allantoin and ketonic bodies in blood between the animals group.