Reproduction of Rats Fed Protein-Free Amino Acid Rations

Abstract

Protein-free rations containing mixtures of 10, 11 or 16 amino acids were fed to rats during growth, two pregnancies, and lactation, in one instance for as long as 4 successive filial generations without evidence of gradual deterioration of the reproductive or lactation performance. A ration containing 12.2% of mixture of 16 amino acids supported better lactation than a ration containing 15.9% of a mixture of the 10 “essential amino acids.” Lactation was better when the level of the mixture of 16 amino acids was increased from 12.2 to 18.3% but a further increase to 24.4% failed to improve reproduction or lactation. A dietary supply of glycine, alanine, aspartic acid, tyrosine and cystine was not essential for reproduction or lactation but when they were fed the loss of weight of lactating mothers was greatly decreased. The nutritive value of a protein-free ration is affected by the relative proportions in which the individual amino acids are present as well as by the absolute amounts. None of the rations used was completely adequate for optimum preweaning or postweaning weight gains of the young or for the prevention of fatty livers during lactation.