Abstract
1. The effect of different levels of protein on the digestibility of the carbohydrate fraction of two compounded diets which differed widely in their contents of indigestible organic matter has been determined. 2. Digestibility of the available carbohydrate (the sugars, dextrins and starches expressed as starch) apparently increased with increase in the protein content of the diet. 3. Alteration in the cereal portion of the diet involves an adjustment in the amount of protein supplement if the nutritive ratio is to remain unaltered.