The Chick's Response to Choline and its Application to an Assay for Choline in Feedstuffs

DURING our studies on choline assay methods a chick bioassay was needed to determine which of several analytical methods gave results which more nearly paralleled the biological activity. The young chick requires about 1300 mg. choline per kilogram of diet when the ration contains 2750 Calories metabolizable energy per kilogram (Bird et al., 1966). Combs (1963) has related choline requirements to the fat content of the diet. High energy broiler diets usually contain more than the above NRC requirement figure, and practical experience indicates that somewhat more choline is needed (Fritz, 1965a). Classen et al. (1965) concluded that typical broiler diets needed at least 1650 mg. choline chloride per kg. for best performance. As the energy content of the feed is increased, several factors increase the need for dietary choline: the higher energy ingredients contain less choline, the chick consumes less feed per unit gain in weight, and the increased . . .