51Cr-EDTA, 91Y and 141Ce as nonabsorbed reference substances in the gastrointestinal tract of the chicken.

The use of 91Y, 51Cr-EDTA, and 141Cr as nonabosrbed reference substances in the gastrointestinal tract of the chick was examined. In single oral dose experiments, more than 95% of the isotopes administered was recovered from the gastrointestinal tract 3 hours after dosing. 51Cr was higher in blood than the other isotopes tested. When the isotopes were fed continuously, the ratio of 91Y to 141Cr changed little throughout the gastrointestinal tract. However, the ratio of 91Y to 51Cr was higher in the crop and gizzard and lower in the duodenum than in the feed. Thus, passage time was shorter for 51Cr in the crop and gizzard and longer in the duodenum than that of 91Y. On the basis of distribution between solid and liquid phases in the intestinal contents, 91Y or 141Ce appears to be a suitable reference substance for studying the absorption of nitrogen and fatty acids, wheras 51Cr-EDTA would be preferable for bile acid absorption studies.