Influence of Dietary Heat-labile Factors in Soybean Meal upon Bile Acid Pools and Turnover in the Chick

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Abstract
Heat-labile components of soybeans depress absorption of dietary triglycerides when fed to young chicks (up to 2 weeks of age). Feeding dietary sodium taurocholate along with soybeans improves fat absorption. These observations suggested that factors present in soybeans cause a bile acid insufficiency when they are included in diets for young chicks. Experiments were conducted to estimate the half-life, pool size and excretion rate of bile acids in two ages of chicks fed diets with and without unheated soybean meal. We have obtained half-life estimates of 6 to 9 days and bile acid pools of 18 to 23 mg/100 g body weight in chicks fed a control diet. Using 14C-labeled bile acids and gas-liquid chromatographic analysis of bile acids in bile and excreta in studies with both control chicks and those fed a diet containing unheated soybean meal we have demonstrated that a) factors present in unheated soybean meal markedly increased fecal excretion and lowered the half-life of bile acids; b) differences in pool sizes occurred from feeding unheated soybean meal, suggesting that young chicks are unable to replenish excreted bile acids as readily as older chicks; and c) bile acids are associated with insoluble contents from the gastrointestinal tract of chicks fed unheated soybean meal.