RESUMEN
Organic acids (OA) and phytogenic compounds have been used in pig feeding as alternatives to antibiotic growth promoters. However, few studies have evaluated the systemic effect of the combination of these additives. The aim of this study was to assess the impact of an organic acid-based feed additive (OAFA), containing a blend of OA and cinnamaldehyde, on the tissue integrity of bacterially challenged piglets. Thirty weaned piglets 21 d old were used in a 19-d trial. Pigs received a standard diet during the first 7 d and afterward were allotted to five treatments. Dietary treatments were: Control (basal diet), Escherichia coli (basal diet and challenge with E. coli), colistin (basal diet + 200 mg colistin/kg feed + challenge with E. coli), OAFA1 (basal diet + 1 kg OAFA/ton feed + challenge with E. coli), and OAFA2 (basal diet + 2 kg OAFA/ton feed + challenge with E. coli). Seven days after the beginning of the treatment, the animals were challenged with an enterotoxic strain of E. coli (K88) for pigs. Five days after the challenge, all animals were euthanized for tissue sampling for histological and oxidative stress (intestine and liver) analysis. The reduced glutathione (GSH), ferric-reducing ability potential (FRAP), and free-radical scavenging ability (ABTS) assays were used to evaluate the intestinal antioxidant defense. Lipid peroxidation and superoxide anion production were evaluated through the levels of thiobarbituric acid-reactive substances (TBARS) and nitroblue tetrazolium (NBT) reduction assay, respectively. Animals fed the OAFA (1 and 2) diets had a decrease (P < 0.05) on histological changes in the intestine, liver, mesenteric lymph nodes, and spleen. Greater villus height (VH) and a higher ratio of VH to crypt depth (CD) were observed in animals of the OAFA2 group compared with the control and E. coli groups. The colistin and OAFA groups decreased (P < 0.05) the number of inflammatory cells in intestinal lamina propria. OAFA2 group increased (P < 0.05) intestinal cell proliferation. Colistin and OAFA2 supplementation induced a decrease (P < 0.05) in the levels of TBARS in both the intestine and liver compared with the E. coli group. In addition, an increase (P < 0.05) in GSH and FRAP ileal levels was observed in the OAFA2 group compared with E. coli group. These results show that the supplementation with OAFA in the diet of weaned piglets, especially at a dose of 2 kg/ton (OAFA2) protected tissues against enterotoxigenic Escherichia coli (ETEC) damage.