Effects of age on development of digestive organs and performance of chicks fed a corn-soybean meal versus a crystalline amino acid diet

Changes in growth performance and physical and morphological development of the digestive organs were examined in chicks fed a crystalline amino acid (AA) diet compared to chicks fed a corn-soybean meal (SBM) diet. Six pens of eight New Hampshire x Columbian male chicks were assigned to one of three dietary regimens: (1) corn-SBM diet from 0 to 21 d of age; (2) cornstarch-crystalline AA diet from 0 to 21 d of age; and (3) corn-SBM diet from 0 to 7 d of age followed by the crystalline AA diet from 8 to 21 d of age. Weight gain was significantly reduced by feeding a crystalline AA diet from 0 to 21 or 8 to 21 d of age. Feeding a crystalline AA diet for the first 7 d of age depressed absolute weight of the small intestine, pancreas, liver, gizzard, and proventriculus, and continual feeding through 21 d of age further depressed growth of these organs compared with birds fed a corn-SBM diet for 21 d. When expressing organ weight on a relative basis (g/100 g of BW), reductions were observed at 7 d of age due to feeding a crystalline AA diet but not at 21 d of age. Feeding a crystalline AA diet for the first 7 or 21 d of age depressed intestinal villi height and crypt depth. However, chicks fed the crystalline AA diet only from 8 to 21 d of age had further depressed villi height and crypt depth but greater villi width compared with chicks fed the crystalline AA or corn-SBM diet continually from 0 to 21 d of age. These results indicate that the reduced growth of chicks fed a crystalline AA diet is due in part to slower growth and development of the gastrointestinal tract.