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In a balance trial with 10 pigs (mean body mass 50 kg) the influence of a bacterial protein supplement (Alcaligenes eutrophus) on N-metabolism was investigated. The bacteria were included into the diet at levels of 7 and 14% at the expense of extracted soyabean meal. Thus bacterial "pure protein" (bacterial non-nucleic acid N X X 6.25) amounted to 30 and 60% of the protein of the ration. Consuming 2 kg of feed dry matter per day the animals of the control group (I) and the experimental groups (II and III) ingested 48 g, 52 g and 55 g of total N respectively. The difference in N-intake is explained by the additional nucleic acid-N, amounting to 19,8% of total bacterial N. Daily weight gain (on average 1054 g) and feed conversion efficiency (feed ingested/weight gain; on average 1,9) were relatively improved at the highest dietary level of bacterial cell mass. Faecal N-excretion was increased significantly, whereas renal N-excretion remained unchanged. Mean apparent N-digestibility was 87,4% showing no significant difference between the experimental groups. N-balance values were noticibly increased following the intake of the bacterial protein supplement. The excretion of urinary urea-N was slightly reduced whereas 4-6 times as much allantoin-N was excreted when bacteria were fed. It is calculated that about 80% of the bacterial purines are renally excreted as allantoin and uric acid.

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.

In a feeding trial with growing rats the influence of dietary ribonucleic acid on the composition of body gain was investigated. To a control ration with casein + 50% DL-methionine as the sole protein source (1,64 N% in DM) ribonucleic acid (RNA) from yeast was supplemented at four levels ranging from 7,8% to 31,2% of diets nitrogen. The portion of daily feed and nitrogen intake derived from the basal diet was designed to be equal for all the animals. RNA was ingested in addition. Gain of body fresh and dry matter slightly increased with the dietary RNA-level, due to an increased deposition of body fat. Protein efficiency ratio as well as productive protein value decreased linearly with increasing N-intake. It may be concluded that RNA-N has slightly contributed to body mass gain but was not utilised for protein deposition.