Autoclaved Egg White as a Protein Source for Chick Diets Low in Zinc

Abstract

Spray-dried egg white was evaluated either as the sole source or the primary source of protein in purified, low-zinc diets for chicks. The effects of unheated and autoclaved egg white were compared for chicks fed diets supplemented with graded amounts of biotin. Growth rate and pancreas weight were used as the criteria of nutritional adequacy. The data indicated that extra biotin did not completely overcome the adverse effects of unheated egg white. Chicks fed unheated egg white and excess biotin had decreased body weights and showed signs of pancreatic hypertrophy, probably due to proteinase inhibitors in the egg white. Autoclaving rehydrated and spray-dried egg white for 30 rain at 121C, but not at 80 C, markedly reduced the biotin-binding and proteinase-inhibitor activities of unheated egg white. Extracting autoclaved egg white with water did not improve the growth rate or reduce the amount of zinc in the egg white. Chicks fed diets of autoclaved egg white and gelatin with low concentrations of zinc showed symptoms of severe zinc deficiency. Chicks fed diets with adequate concentrations of zinc had body weights similar to those fed casein-gelatin control diets. When graded amounts of zinc were added to the diet, the growth rate of the chicks and the tissue concentration of zinc reflected zinc intake. These data demonstrated that rehydrated, spray-dried egg white autoclaved for 30 min at 121 C is an excellent source of protein for use in low-zinc diets for chicks.