Effects of dietary methionine supplementation on growth performance, intestinal morphology, antioxidant capacity and immune function in intra-uterine growth-retarded suckling piglets

This study investigated the effects of dietary supplementation with (L)-methionine ((L)-Met), (DL)-methionine ((DL)-Met) and calcium salt of the methionine hydroxyl analog (MHA-Ca) on growth performance, intestinal morphology, antioxidant capacity and immune function in intra-uterine growth-retarded (IUGR) suckling piglets. Six normal birthweight (NBW) female piglets and 24 same-sex IUGR piglets were selected at birth. Piglets were fed nutrient adequate basal diet supplemented with 0.08% (L)-alanine (NBW-CON), 0.08% (L)-alanine (IUGR-CON), 0.12% (L)-Met (IUGR-LM), 0.12% (DL)-Met (IUGR-DLM) and 0.16% MHA-Ca (IUGR-MHA-Ca) from 7 to 21 days of age respectively (n = 6). The results indicated that IUGR decreased average daily milk (dry matter) intake and average daily gain and increased feed conversion ratio of suckling piglets (p < 0.05). Compared with the NBW-CON piglets, IUGR also impaired villus morphology and reduced antioxidant capacity and immune homeostasis in the intestine of IUGR-CON piglets (p < 0.05). Supplementation with (L)-Met enhanced jejunal villus height (VH) and villus area and ileal VH of IUGR piglets compared with IUGR-CON piglets (p < 0.05). Similarly, (DL)-Met supplementation increased VH and the ratio of VH to crypt depth in the jejunum compared with IUGR-CON pigs (p < 0.05). Supplementation with (L)-Met and (DL)-Met (0.12%) tended to increase reduced glutathione content and reduced glutathione: oxidized glutathione ratio and decrease protein carbonyl concentration in the jejunum of piglets when compared with the IUGR-CON group (p < 0.10). However, supplementation with MHA-Ca had no effect on the intestinal redox status of IUGR piglets (p > 0.10). In conclusion, supplementation with either (L)-Met or (DL)-Met has a beneficial effect on the intestinal morphology and antioxidant capacity of IUGR suckling piglets.