Sulfur Amino Acid Requirement for Lactation in the Rat.

A short-term lactation test has been used to study the effects of cystine supplementation for purified diets containing casein as sole protein source. Supplementation of 12, 18, and 24% casein diets with 0.5% L-cystine markedly improved lactation performance as judged by weaning weights of young and mother. Cystine supplementation of 30% casein diet improved weaning weights of young significantly with less beneficial effects on maternal weight. The data indicate that total sulfur amino acid requirement for optimal lactation in the Long-Evans rat may be placed at slightly more than 1% of the diet and that cystine may furnish at least half of this requirement.