Protein and Amino Acid Requirements of the Guinea Pig I. Effect of Carbohydrate, Protein Level and Amino Acid Supplementation

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Abstract
The need for high levels of casein in purified diets for guinea pigs has been shown to be due to the need for a few specific amino acids rather than for protein per se. The most limiting amino acid in casein for the young guinea pig is arginine, apparently owing to a relatively high requirement of the guinea pig for arginine and to the relatively low level and limited availability of the arginine in casein. With arginine supplementation, methionine becomes limiting in 25% casein-sucrose diets and both tryptophan and methionine become limiting in 20% casein-sucrose diets. The guinea pig was shown to be extremely sensitive to dietary changes, such as the omission of an essential item or the addition of a component in excess. No definite protein sparing action was found with dextrin, and the differences between sucrose and dextrin diets that were observed were usually not marked. In general, the responses to combined amino acid supplements were slightly greater with sucrose diets but in a few specific instances dextrin appeared more effective.