The aim of this study was to analyze the possible protective effects of a glutamine and arginine precursor (ornithine-α-ketoglutarate [OKG]) on the mucosa of a transplanted intestine when administered with either a defined formula oral diet (DFD) or a standard chow. Isogenic male Lewis rats (250 g) were submitted to a laparotomy (groups 1 and 2) or to an orthotopic small bowel transplantation (SBT; groups 3-6). Groups 1, 3, and 5 received a DFD 14 days after surgery. Groups 2, 4, and 6 received standard chow. In addition, groups 5 and 6 received a daily oral supplementation of 1.4 g/kg of OKG. Weight changes and food intake were recorded daily. At the end of the study, bacterial translocation (BT) was measured in mesenteric lymph nodes, liver, and spleen. The protein/DNA index was also determined in intestinal mucosa. SBT induced BT in all transplanted groups, especially in those fed DFD. Addition of OKG (groups 5 and 6) significantly reduced BT in comparison with groups 3 and 4 and improved the protein/DNA index as well as weight gain. It is concluded that OKG supplementation protects the intestinal barrier after SBT, and that this effect is more marked when it is added to a standard chow.