YOLK UTILIZATION IN THE NEWLY-HATCHED POULT

1. Routes of yolk utilisation and some aspects of intestinal digestion and absorption were determined in the hatching poult and compared to the chick. 2. Transfer from yolk to blood was observed pre-hatch and u p to 72 h post-hatch. From hatch the transport pattern was similar to the chick. 3. Transport from the yolk sac into the intestine via the y olk stalk was observed up to 120 h after hatch. Secretion was initiall y to the proximal ileum and reflux occurred, transporting contents to the proximal small intestine and gizzard. Antiperistaltic movements in creased after hatch and secretion continued for longer post-hatch than in the chick. 4. In Situ uptake of glucose per unit of duodenum did n ot change with age, whereas uptake of methionine and oleic acid decrea sed with age. In contrast, in the chick glucose and methionine uptake capacity increased slightly between hatch and 7 d. 5. The lipid class distribution of intestinal contents resembled that of yolk close to ha tch, however, some lipolysis was observed in the duodenum. With age th e proportion of free fatty acids increased rapidly, first in the duode num then in the ileum and finally in the caecum. Yolk in the distal sm all intestine close to hatch did not appear to be utilised.