Methionine and 2-Hydroxy-4-Methylthiobutanoic Acid Are Partially Converted to Nonabsorbed Compounds during Passage through the Small Intestine and Heat Exposure Does Not Affect Small Intestinal Absorption of Methionine Sources in Broiler Chicks

Abstract

Broiler chicks were fed diets supplemented with DL-methionine or DL-2-hydroxy-4-methyl-thiobutanoic acid. At 4 wk of age the chicks were subdivided into thermoneutral (22 degrees C) and heat-exposed (32 degrees C) groups and maintained under these conditions for 48 h. Highly purified 3H-L-methionine (3H-L-Met) and 3H-L-2-hydroxy-4-methyl-thiobutanoic acid (3H-L-HMB) were used to evaluate treatment effects on the small intestinal passage of sources of supplemental methionine and on the transport of methionine sources across purified small intestinal brush border vesicles. 3H-L-Met was efficiently absorbed in the upper regions of the small intestine; however, 2.5-3.5% of dietary 3H from birds fed 3H-L-Met remained unabsorbed in the distal small intestine. Dietary 3H (15%) initially associated with 3H-L-HMB was not absorbed during passage down the length of the gut. The HPLC analysis indicated that only 10% of the radiolabeled material remaining in the terminal ileum eluted at the time expected for HMB. Partial breakdown of HMB to nonabsorbed, nonmethionine products during passage down the small intestine may contribute to the difference in biopotency of the two sources of supplemental dietary methionine. Heat exposure did not affect in vivo small intestinal passage or in vitro transport of 3H-L-Met and 3H-L-HMB across small intestinal brush border membrane vesicles.

Methionine-hydroxy analogue was found to be significantly less bioavailable compared to dl-methionine for protein deposition in growing pigs

“…The oligomers of liquid MHA-FA are poorly absorbed (Saunderson, 1991) and of a lower bioavailability in poultry compared to the commercial product mix of mono-, di-and oligomers (Van Weerden et al, 1992). Maenz and Engele-Schaan (1996b) also reported that in broilers there was conversion of L-MHA into non-absorbable by-products during its passage through the gastro-intestinal tract. Additionally, Malik et al (2006) showed that liquid MHA was, in fact, more slowly absorbed throughout the digestive tract of pigs than L-Met, which agrees with Drew et al (2003) who observed similar results in broiler chickens.…”

Bioavailability of different methionine sources for broilers from 1 to 21 days old

“…Maenz and Engele-Schaan (1996a) reported a significant conversion of DL-HMBA in non-absorbable subproducts during their passage through the gastrointestinal tract. Furthermore, Lingens and Molnar (1996) have indicated that methionine absorption in broilers was significantly higher when given as DLM compared to HMBA.…”

Apparent absorption of methionine and 2-hydroxy-4-methylthiobutanoic acid from gastrointestinal tract of conventional and gnotobiotic pigs

“…All three studies reported that 10% to 20% of the original radiolabelled MHA-FA activity in the feed was present in the distal sections of the SI compared to 3.5% to 5% for methionine, thus in agreement with our results. Moreover, HPLC analysis of gut contents from the distal ileum showed that only 10% of the residual radioactivity was associated with MHA-FA, suggesting that the compound had been metabolized during intestinal transit (Maenz and Engele Schaan, 1996a) and further supporting metabolism by gut microbiota.…”

“…Many studies in chicken (Esteve Garcia and Austic, 1993;Lingens and Molnar, 1996;Maenz and Engele Schaan, 1996a) used radiolabelled methionine and MHA-FA and estimated intestinal absorption based on residual radioactivity in intestinal contents. This method is not affected by bacterial metabolism of methionine and MHA-FA since the radiotracer would remain within the intestinal contents even following metabolism.…”