Further Comparisons of the Utilization of Nitrogen of Urea with that of Some Feed Proteins by Sheep

Further experiments on the comparative utilization of the nitrogen of urea and that of some feed proteins are reported. Growing lambs were used as experimental animals and the paired-feeding procedure, with single reversal of rations, was used throughout. Nitrogen balance was the criterion.Eight different comparisons were studied with the following results: The nitrogen in a ration containing 16.2 percent protein equivalent (63 percent from urea) was less efficiently utilized than that in a ration containing 11.4 percent (46 percent from urea). In confirmation of our previously reported data, the nitrogen of urea was as well utilized by growing lambs as were the same amounts of nitrogen from dried skimmilk, dried skimmilk plus cystine, glutenfeed, casein or casein plus cystine, provided the protein equivalent in the rations does not exceed about 12 percent and provided at least 16 percent of the total nitrogen is in the form of preformed protein. The nitrogen of linseed oil meal was more efficiently utilized than that of urea when the rations contained about 12 percent protein equivalent of which one-fourth was supplied by a basal ration containing preformed proteins.