[Studies with 15N-labeled lysine in colostomized hens. 1. 15N excretion in urine]

0.2% L-lysine with an atom-% 15N-excess (15N') of 48% were given per day through a throat probe in an experiment to three colostomised laying hybrids in addition to a pelleted ration of 120 g per animal and day. In the following 4 days unlabelled L-lysine was given. As the labelled lysine was given three times a day, the development of 15N'-excretion could be pursued. 80 minutes after the 15N'-lysine dose a distinct atom-% 15N' could be detected in urine. 6 hours after the 15N'-application we rediscovered 2.9% (hen 1), 4.2% (hen 2) and 2.7% (hen 3) of the applied 15N'-amount in urine. 8 days after the beginning of the experiment the excretion of 15N' in urine averaged 17.5% of the consumed 15N'-amount. 44% of the nitrogen in the ration, however, was excreted in urine. The results showed that the lysine-N is excreted to a considerably lower extent in urine than the nitrogen in the remaining ration.