Abstract
Nitrogen balance studies with a total number of 64 Friesian bull calves were carried out to compare the effectiveness of a number of agents with a possible anabolic effect on nitrogen-retention. The animals, housed individually in balance units, were fed a liquid milk replacer diet. When treated at 11 or 12 weeks of age, the maximum of the cumulative response for N-retention was found as for live weight gain, at 4 to 5 weeks after treatment in most cases. The relative effectiveness of the agents in improving N-retention correlates well with their effectiveness in promoting growth. The mean effects per calf were as follows: In normal veal calves the percentage of digested feed protein converted into body protein gradually decreases from 70% to less than 40% during the growing period. By administration of the most effective anabolic agent tested (20 mg estradiol/140 mg trenbolone) the percentage of digested protein converted into body protein was over an experimental period of 38 days increased from 39% in the control to 58% in the treated group. Copyright © 1975. American Society of Animal Science. Copyright 1975 by American Society of Animal Science.