Methionine replacement value of N-acetylmethionine and homocysteinethiolactone hydrochloride for growing rats.

The ability of young growing rats to absorb DL-homocysteinethiolactone hydrochloride (HCTL-HCl) and N-acetyl-DL-methionine (NAM) and to use them for growth when fed a methionine-deficient diet was studied. In situ intestinal absorption studies demonstrated that both compounds are readily absorbed. Intestinal half-times were 24 minutes for NDTL-HCl and 44 minutes for NAM. Adding molar equivalents of 0.2 or 0.4% methionine to a 0.2% methionine basal diet fed ad libitum resulted in 28-day gains that were 83.2 and 91.1%, respectively, for NCTL-HCl and 94.6 and 99.8% for NAM of the average gain resulting when DL-methionine was added at equivalent levels. Feed efficiencies were also significantly (P smaller than 0.05) improved over rats fed the basal diet. Increasing the HCTL-HCl addition to 0.6% reduced feed intake and gain but not feed efficiency.