Growth and development of the digestive organs and some enzymes in broiler chicks after hatching∗

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Abstract
1. Body weight and the weight of the digestive organs and activities of some digestive enzymes were determined from hatching to 23 d of age. 2. Relative daily growth rate peaked at 11 d of age (22% gain/d) and then decreased gradually. 3. The vitelline residue was decreased rapidly from 4.6 g at hatching to negligible values from 4 d of age. 4. Maximal allometric growth of the pancreas and small intestine was 4‐fold and that of liver 2‐fold greater than that of the body. 5. Activities (units/kg body weight) of the digestive enzymes measured in the pancreas and intestinal contents increased with age. In the pancreas maximal values were attained on day 8 for amylase and lipase and 11 for trypsin and chymotrypsin. In the small intestine maxima were attained on day 4 for lipase, 11 for trypsin and chymotrypsin and 17 for amylase. 6. The development of secretion of digestive enzymes in the post‐hatched chick could be a limiting factor in digestion and subsequently in food intake and growth.