Effect of Carbohydrates on Utilization of Protein and Lysine by Rats

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Abstract
The effect of various carbohydrates (raw-potato starch, cornstarch, sucrose, dextrin, glucose, and cooked-potato starch) on utilization of dietary protein as well as the availability of lysine from wheat gluten were determined in rats. Without lysine supplementation, the digestibility of protein by rats fed rawpotato starch was 87% and by those fed cooked-potato starch, 93%. With the other three sources of carbohydrates tested, the digestibility of wheat gluten-protein ranged from 94 to 97%. With the addition of 0.7% of L-lysine to the diets, the digestibility of the protein for the rats fed rawpotato starch was 94%, for the rats fed cooked-potato starch, 95%, and for those fed dextrin, 96%. There was no significant change in the digestibility of the protein with L-lysine supplementation when the rats were fed the other three carbohydrates tested. Raw-potato starch, cooked-potato starch, dextrin, sucrose, cornstarch, and glucose, without the addition of lysine, and different effects on the availability of lysine. The availability of lysine increased in the order indicated. With the addition of 0.7% of L-lysine, the lysine availability in the rats fed cornstarch, sucrose, and glucose was similar and was considerably higher than the lysine availability in the rats fed raw-potato starch, cooked-potato starch, and dextrin. Lysine supplementation increased by lysine availability, weight gain, food intake, and protein efficiency ratio of rats fed all sources of carbohydrates.