[Protein quality of dietary yeast ribonucleic acid studied in growing rats. 2. Effect of ribonucleic acid on N balance and urinary N fractions]

In a balance trial with growing rats the influence of dietary ribonucleic acid (RNA) on N-metabolism was tested. Yeast-RNA was supplied at four levels ranging from 7.8% to 31.2% of diets nitrogen (1.64% in DM from casein + DL-methionine). The mean apparent digestibility of the RNA-N ingested was determined as 95%. Of the RNA-N consumed 16.6% were retained as measured by N-balance technique, whereas no retention of the RNA-N was observed by body-N analysis. This discrepancy in RNA-N retention was attributed to the relatively increased N-losses with higher N-intake when using the N-balance method. By regression analysis it was found that 80.2% of the RNA-N consumed were excreted via kidneys. Of the RNA-N intake 45.5% appeared in urea, 30.9% in allantion, only 1.1% and 0.3% in uric acid and creatinine respectively.