l-Methionine supplementation maintains the integrity and barrier function of the small-intestinal mucosa in post-weaning piglets

This study was conducted to test the hypothesis that different dietary Met levels affect small-intestinal mucosal integrity in post-weaning piglets. Two groups of piglets (n = 6/group) were weaned at 28 days of age and randomly allotted to a basal diet (without extra Met supplementation) or a Met-supplemented diet (with 0.12 % l-Met) for 14 days. The standardized ileal digestible (SID) Met levels were 0.24 and 0.35 %, respectively. At days 7 and 14 of the trial, venous blood samples were obtained from piglets, followed by their euthanasia for tissue collection. Piglets fed the diet supplemented with l-Met had a higher average daily gain during days 7–14 and improved feed efficiency during the entire period. Concentrations of sulfur amino acids (SAA), glutamate acid (Glu), glutamine (Gln), and taurine in the plasma and tissues were higher for the piglets in the Met-supplemented group. Met supplementation increased cysteine (Cys) and glutathione (GSH) concentrations in the plasma and tissues, leading to reductions in plasma Cys/CySS redox potential and tissue GSH/GSSH redox potential. The small-intestinal mucosa of Met-supplemented piglets exhibited improved villus architecture, compared with control piglets. Met supplementation increased transepithelial electrical resistance of the jejunal mucosa. Transport of Met, Gln and Cys across the jejunal mucosa did not differ between control and Met-supplemented piglets. The abundance occludin was higher, whereas the abundance of active caspase-3 was lower, in the jejunum of the Met-supplemented piglets. Collectively, adequate dietary Met is required for optimal protein synthesis and mucosal integrity in the small intestine of post-weaning piglets.