Abstract
The nutritional efficiency for young rats was studied of the diets containing excessive L-metionine and L-cystine.
(1) When fed on the test diets with excessive L-methionine, rats showed severe growth depressions and reduced nitrogen efficiencies.The test diets had about 1.0% dietary nitrogen level and had methionine/tryptophan ratios (M/T) ranging 30-40.
(2) When fed on the diet with excessive L-cystine, having 1.0% of dietary nitrogen level and cystine/tryptophan ratio of about 30, rats showed no depression in the growth and in nitrogen efficiency.
(3) when fed on the diets with an excesses of both L-methionine and L-cystine having various proportion between the two amino acids, the growth depression of rat was effected exclusively by the amount of excessive methionine.
(4) The excretion of methionine in the urine of rats fed on excessive methionine diets showed the highest value of 4.6% to ingested methionine, while very slight excretion of cystine was observed in the urine of rats fed on excessive cystine.
