[Utilization of urea nitrogen in young calves]

The influence of an increasing intake of urea in feed rations for calves on its levels in blood plasma and urine, development of health condition, weight gains and on other biochemical characteristics in the blood of calves was studied. The experimental group (n = 4) received urea in feed ration from the 17th day of age, at the beginning in the preparation Syrur, later on (from the 66th day) in the synthetic form only. The feed ration of the control group (n = 3) differed only in the zero content of urea. Over the period of ten weeks the blood was sampled for biochemical examination twice a week, since the 52nd day of age urine was also taken at the same intervals. Starting the 24th day of age, the levels of urea in the blood plasma of experimental animals were significantly higher (P less than 0.05). The concentrations of urea in the urine of the animals belonging to the experimental group were also higher, however, the differences in the average values were not significant. In both groups of animals under study no significant differences in the content of vitamin A, concentration of total protein, glucose, bilirubin, activities of aspartate aminotransferase (AST), gammaglutamyl transferase (GMT) and lactate dehydrogenase (LD) were observed. The average daily weight gains were higher in the calves of the control group, however, the differences were not significant. Over the whole experimental period the health condition of both groups of calves was good.