[Studies on the protein and amino acid metabolism of laying hens using 15N labeled casein. 2. 15N incorporation into the N fractions and basic amino acids of the hen stomach and into the contents of the crop and stomach].

4 colostomated laying hens received 15N labelled casein as sole protein source for a period of 6 days. Two birds each were slaughtered on the 8th and 12th day of experiment. 23.5% of the total N in the glandular stomach and the gizzard were TCE soluble. The amino acid composition of the gastric proteins was broader than that of the proteins of flesh, with the exception of lysine and histidine. The atom % 15N' of the N of the stomach was roughly the same as that of the protein N; the level of labelling in the TCE soluble N fraction was only slightly higher. 2 and 6 days after the final administration of tracer N an appreciable proportion of 15N was found in the N fractions and in the basic amino acids contained in the crop and the stomach. From this is may be concluded that a considerable portion of the N-containing substances previously absorbed were secreted into the lumen of the crop and the stomach.