Choline Utilization in the Chick as Influenced By Levels of Dietary Protein and Methionine

Abstract

Four assays with crystalline amino acid diets were conducted to investigate the effect of an excess of either dietary methionine or a balanced amino acid mixture on the young chick's requirement for dietary choline. The effects of choline level, excess methionine, or excess amino acids on whole body composition were also measured. Excess methionine at levels of two or three times the chick's requirement for maximal growth had no effect on the dietary requirement for choline or on the activity of liver choline oxidase. The addition of a balanced amino acid mixture to provide all amino acids at levels twice the chick's requirement, however, increased the choline requirement markedly. Liver choline oxidase activity was again unaffected. The addition of 0.35% excess methionine was without effect on body composition, but the excess mixture of amino acids increased percent body protein and decreased percent body fat and energy retention. Dietary choline concentration had essentially no effect on body composition, and neither dietary choline nor the mixture of excess amino acids influenced the concentration of total body choline. The results of these studies indicate that excess dietary protein, but not methionine, increases the young chick's choline requirement and that dietary alterations do not alter the concentration of body choline.