Methionine, DL-homocysteine thiolactone and n-acetyl-DL-methionine for ruminants.

Plasma amino acid response of wethers to abomasal infusions of DL-methionine (DLM), DL-homocysteine thiolactone-HCl (HCTL) and N-acetyl-DL-methionine (NAM), in vivo rumen stability of the latter two methionine analogs and preintestinal absorption of HCTL were studied. The daily infusion of 1.06 g of DLM elevated molar percentage of methionine and lysine in plasma'and decreased molar percentage of threonine. Infusion of equal molar quantities of NAM and HCTL resulted in increased plasma methionine 1 hr. post-infusion. The oral administration of HCTL and NAM resulted in abomasal recoveries of only 10.5 and 15.7%, respectively; however, the methionine in abomasal fluid was significantly (P< .05) increased when HCTL was orally administered. Plasma methionine increased significantly following the intraruminal administration of HCTL to wethers with a ligated pyloric sphincter, but the intraruminal addition of methionine had no effect on plasma methionine.