Influence of Various Carbohydrates on the Utilization of Low Protein Rations by the White Rat

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Abstract
Growth, nitrogen balance, carcass analysis and liver fat studies were made on rats fed low protein, low fat diets with sucrose or dextrin as the dietary carbohydrate. Substitution of dextrin for sucrose in isonitrogenous diets stimulated growth by stimulating food, and hence protein, intake. Growth was proportional to protein intake irrespective of the type of dietary carbohydrate; therefore, although protein or amino acid requirements expressed as percentage of the diet differed with the type of dietary carbohydrate, expressed as protein required per unit of weight gained they did not. Nitrogen balance experiments indicated that the type of dietary carbohydrate affected neither protein digestibility nor nitrogen retention; however, metabolic fecal nitrogen increased and endogenous urinary nitrogen decreased when dextrin was substituted for sucrose in a low protein diet containing fibrin. Calorie intake per unit of body weight increased when dextrin was substituted for sucrose, particularly in diets containing low levels of high quality proteins, and this was accompanied by elevation of carcass fat content. Liver fat content was elevated when sucrose was substituted for dextrin in low protein diets containing methionine-supplemented casein; however, when liver fat content was expressed per unit of protein consumed, the difference due to the change in carbohydrate was small.