The aim of this study is to determine the efficiency of Forsythia suspense extract (FSE) as an antibiotics substitute on performance, nutrient digestibility, serum antioxidant capacity, fecal Escherichia coli concentration and intestinal morphology of weaned piglets. A total of 108 Duroc × (Landrace × Yorkshire) weaned piglets (28 days (d) weaned, average body weight of 8.68 ± 1.36 kg) were randomly assigned into three dietary treatments, six pens per treatment, three barrows and three gilts per pen. The treatments contained a corn-soybean meal basal diet (CTR), an antibiotic diet (basal diet + 75 mg/kg chlortetracycline; CTC), and an FSE diet (basal diet + 200 mg/kg FSE; FSE). The experiment included phase 1 (d 1 to 14), phase 2 (d 15 to 28) and phase 3 (d 29 to 35). Compared with CTR, piglets fed FSE show improved (p < 0.05) average daily gain (ADG) and average daily feed intake in phase 2, as well as enhanced (p < 0.05) ADG from day 15 to 35 and day 1 to 28. Piglets supplemented with CTC and FSE showed a reduced (p < 0.05) diarrhea rate in phase 1, while piglets fed FSE showed enhanced (p < 0.05) apparent total tract digestibility (ATTD) of dry matter, organic matter, crude protein and gross energy, as well as lower (p < 0.05) nitrogen output in phase 2 compared with CTR and CTC. The content in the form of Colony-Forming Units (CFUs) of fecal E. coli on day 14 and 28 was lower (p < 0.05) in piglets fed FSE in comparison with CTR. The contents of total antioxidant capacity, superoxide dismutase and catalase in serum are enhanced (p < 0.05) compared with CTR and CTC, whereas the concentration of malondialdehyde in serum was decreased (p < 0.05) for piglets fed FSE on day 28 compared with CTC. The villus height to crypt depth ratio in ileum was numerically higher (p < 0.05) in piglets fed FSE in comparison with CTR. In conclusion, dietary FSE supplementation could substitute CTC in improving antioxidant capacity, nutrients digestibility and reducing fecal E. coli content, so as to reduce nitrogen output and diarrhea rate, and eventually improve performance in weaned piglets.
Keywords: Escherichia coli; Forsythia suspense extract; performance; serum antioxidant status.