Effects of increased dietary supplementation with DL-methionine (Met) or with DL-methionine hydroxyl analogue (MHA-Ca) on the intestinal morphology, and intestinal permeability- and immunity-associated gene expression, in growing pigs

Forty barrows (average body weight 21.5 ± 2.50 kg) used in two feeding trials (20 pigs each) were randomly assigned to four treatment groups. Groups 1 and 2 received a basal diet, Group 3 received a DL-Met-supplemented diet, and Group 4 received an MHA-Ca-supplemented diet. After 3 weeks feeding, pigs were injected with 10 mL saline (Group 1) or 10 mg/kg-BW diquat in 10 mL saline (Groups 2, 3, and 4), and then continually fed for one more week and euthanized at the ends of the trials. Ileal tissue samples were collected for histomorphometric analysis of villus height, villus width (VW), crypt depth, and goblet cell counts. Additionally, the mRNA expression levels of the gut permeability- and immunity-associated marker genes were also respectively determined. Results showed that the VW in Group 4 was shorter ( P = 0.01) than in Group 3. Group 2 showed lower ileal mRNA levels of Muc-4 and ZO-3 ( P < 0.05) compared to Group 1. Group 3 showed higher Muc-2 ( P < 0.05) and lower TNF-α ( P < 0.05) levels compared to Group 2. Group 4 showed higher ( P < 0.05) IL-6 and TNF-α level compared to Group 3. These results suggest that at an equivalent bioefficacy level, DL-Met is more effective than MHA-Ca in enhancing the small intestinal immunity.