BACKGROUND Improvements in immunosuppression, operative procedure, and posttransplant management have made clinical small bowel transplantation (SBT) feasible. Ischemia and reperfusion injury, total parenteral nutrition (TPN), and devoidment of enteral feeding lead to graft atrophy, gut barrier dysfunction, and bacterial translocation. Glutamine (Gln) is the principal fuel for the enterocyte. The influence of Gln dipeptide-supplemented TPN, especially long-term TPN, on intestinal graft permeability and bacterial translocation is not clear following SBT in the large animal model. Therefore, we studied the effect of glutamine dipeptide, glycyl-glutamine (Gly-Gln), on bacterial translocation following SBT in the pig, which has a physiology similar to humans. METHODS The outbred pigs underwent segmental small bowel autotransplantation and were divided into two groups. In the STPN group (n = 5), the animal received standard TPN devoid of Gly-Gln for 28 days. In the GTPN group (n = 5), the animal received isonitrogenous (0.3 g/kg.day) and isocaloric (33 kcal/kg.day) TPN solution with 2% Gly-Gln for 28 days. RESULTS At the end of the experiment, Gly-Gln-enriched TPN could maintain the plasma Gln level, graft mucosal Gln and protein concentrations, and skeletal muscle Gln and protein concentrations. Gly-Gln-enriched TPN significantly decreased the bacterial number of mesenteric lymph nodes in the liver and spleen and intestinal permeability to 99mTc-DTPA. There were no significant differences in body weight gain. CONCLUSIONS The Gly-Gln-enriched long-term TPN may maintain the plasma Gln level, mucosal and muscle Gln, and protein concentrations and attenuate the intestinal permeability to 99mTc-DTPA and bacterial translocation following small bowel transplantation in the pig.