The Effect of Level of Dietary Protein on the Growth of Chicks Fed Purified Diets Containing Sucrose or Dextrin

Abstract

A previous report that chicks fed purified diets containing dextrin as the carbohydrate grow at a faster rate than those fed similar diets containing sucrose has been extended. The effects of different levels of dietary casein, of certain protein-containing supplements and of an antibiotic mixture included in such diets have been studied. With the exception of groups that received antibiotics the best rate of growth occurred consistently in groups fed a diet containing 18% casein and dextrin. Chicks receiving dextrin grew more rapidly than those receiving sucrose when the level of casein was 18% or less. However, when the casein content of the sucrose diets was increased above 18% or when amino acids or supplements of other proteins were provided with 18% casein in sucrose diets, growth approached that of chicks receiving 18% casein with dextrin. The rate of growth of chicks receiving either sucrose or dextrin with 18% to 25% casein was increased when a mixture of penicillin and bacitracin was included in the diets, the effect of the antibiotics being much less in the presence of dextrin and higher levels of casein. The effect of dextrin in improving growth was most evident in female chicks and it is suggested that dextrin exerts this effect largely by permitting better utilization of dietary protein.