Comparative effects of enzymolytic soybean meal and antibiotics in diets on growth performance, antioxidant capacity, immunity, and intestinal barrier function in weaned pigs

The aim of this study was to evaluate and compare the effects of enzymolytic soybean meal (ESBM) and antibiotics on growth performance, diarrhea, antioxidant capacity, immunity and intestinal barrier function in weaned pigs. In Exp. 1, 6 barrows fitted with ileal T-cannulas were allotted to the two 3 x 3 Latin Square design and fed three diets to evaluate the standardized (SID) ileal digestibility of amino acids in soybean meal and ESBM. In Exp. 2, 126 weaned pigs (initial body weight: 7.33 +/- 1.14 kg) were randomly assigned to 3 dietary treatments with 7 replicate pens per treatment and 6 pigs per pen for 28 d. The 3 diets included a basal diet (negative control; NC), NC with 75 mg/kg chlortetracycline (positive control; PC) or NC with 9% enzymolytic soybean meal replacing SBM during d 0-14 and 7.5% ESBM replacing SBM during d 14-28 (ESBM). Pigs fed PC and ESBM had greater (P < 0.05) average daily gain (ADG) and gain to feed ratio (G:F), and lower (P < 0.05) diarrhea rate than pigs fed NC during d 0-14 and d 0-28. On d 14, compared with NC, serum immunoglobulin A (IgA) concentration was greater (P < 0.05) in ESBM. Both PC and ESBM decreased (P < 0.01) malondialdehyde (MDA) concentration, and increased (P < 0.01) glutathione peroxidase (GSH-Px) activity. On d 28, serum IgA concentration was greater (P < 0.05) in PC than in NC. In the liver, the mRNA expression of Gpx1 was higher (P < 0.05) in PC than in NC. Compared with NC, both PC and ESBM up-regulated (P < 0.05) the mRNA expression of Gpx4. Pigs fed PC and ESBM had lower (P < 0.05) concentrations of TNF-alpha in duodenum and jejunum than pigs fed NC. The abundance of zonulin-1 (ZO-1) and occludin proteins were increased (P < 0.05) in the jejunum of pigs fed PC and ESBM compared with pigs fed NC. Compared with NC, ESBM increased (P < 0.05) villus height in duodenum and villus height to crypt depth ratio in duodenum and ileum. In conclusion, ESBM could be a functional feed additives as effective as antibiotics for reducing diarrhea and improving performance in weaned pigs based on the beneficial effects on antioxidant capacity, immunity and intestinal barrier function.