Growth and utilization of nutrients in newly-hatched chick with or without removal of residual yolk.

Two experiments were conducted to characterize the growth and utilization of nutrients in newly-hatched chicks, and to determine nutritional roles of residual yolk by comparing chicks with or without deutectomy (removal of residual yolk sac). Rapid growth during 14 days after hatch was shown in the fed chicks. Daily feed intake increased linearly for 15 days posthatch, resulting in a high efficiency (80%) of feed utilization. Residual yolk in the abdomen averaged 6.4 g at hatch and rapidly disappeared during the first 3 days. Posthatch starvation resulted in a decrease in carcass lipid content but did not modify the disappearance rate of yolk in the abdomen. Weight of the digestive tract per unit body weight increased markedly up to 3-7 days of age followed by a gradual decrease in the fed chicks. Metabolizability of dietary energy and absorption of dietary lipid were the highest at hatch, then declined to the lowest at day 5 or 6, and thereafter gradually increased. The deutectomy did not influence the metabolizability of dietary energy and lipid, and the carcass composition, but delayed the growth by 2 days behind the control chicks. These results indicate that the metabolism and nutrition of newly-hatched chicks markedly fluctuate and that the residual yolk has crucial roles in complementing the nutrients absorbed to assure their rapid growth posthatch.