Nitsan, Z., Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24061-0306, USA.
Turro-Vincent, I., Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24061-0306, USA.
Liu, G., Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24061-0306, USA.
Dunnington, E.A., Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24061-0306, USA.
Siegel, P.B., Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24061-0306, USA.

Experiments were conducted to study the role of residual yolk on growth and development of chicks during the 1st wk after hatch. Surgical removal of the yolk sac at hatch reduced early body weight gains. Intubating chicks with a mixture of soybean meal and soybean oil or with residual yolk obtained from chicks at hatch increased body weights and enhanced development of the liver and pancreas. Whereas intubation with residual yolk reduced absorption of yolk sac contents, absorption was similar for chicks that consumed mash ad libitum or were intubated with the soybean meal-soybean oil diet. After cessation of yolk intubation, absorption of residual yolk resumed. Removal of the yolk sac decreased amylase and lipase activity in the pancreas. In the intestinal chyme, activity of amylase, trypsin, and chymotrypsin was reduced by yolk sac removal. Intubation with yolk increased enzyme activity (amylase excepted) in the pancreas or intestinal chyme only in chicks that had their yolk sacs removed. There was evidence that contents of the yolk sac did not enter the intestine via the yolk stalk, but were absorbed directly via the blood.