The energy requirements for growth and maintenance were studied in male and female chicks and turkeys, kept in environmental chambers for 4 to 5 weeks following the brooding period. In both species and sexes, the maintenance requirement decreased with constant temperatures from 12 to 24 C, reaching a low between 24 and 28 C, followed by an increase as the temperature was raised further. At 12 C, the maintenance ranged between 2.45 and 2.70 kcal/g 2 / 3 , for chicks and turkeys, respectively. Requirements for weight gain averaged 1.87 kcal/g and .7 kcal/g in chicks and turkeys, respectively. This species difference was explained on the basis of carcass composition. Turkeys fed a high-protein diet had an apparently greater maintenance requirement than those fed a diet appropriate for their age. Weight gain decreased between 19 and 34 C in chicks and between 18 C and 32 C in turkeys. Feeding of a high protein diet tended to reduce but did not overcome the growth depression by temperature. In turkeys, weight gain at 12 C was inferior to that at 18 C for both sexes. The calculated amino acid per kilocalorie dietary requirements for 6-week-old chicks increased with temperature to a peak at 27 C, followed by a decrease as the temperature was raised further. (

Starch digestion and glucose absorption were determined in vivo along the chick's (Gallus domesticus) intestine, using 91Y and 51Cr-EDTA as unabsorbed reference substances. About 65% of the ingested starch was digested up to the end of the duodenum, 85% up to the end of the jejunum and about 97% at the terminal ileum. A fraction of about 97% of the glucose, ingested or released from ingested starch, was absorbed. The duodenum was the major site of glucose absorption which continued at a decreased rate down the small intestine. Glucose absorption increased linearily with luminal concentration with no indication of saturation. The apparent permeability for glucose was similar for the jejunum and ileum.

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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.

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