Effects of the antimicrobial peptide WK3 on diarrhea, growth performance and intestinal health of weaned piglets challenged with enterotoxigenic Escherichia coli K88

Background: Antibiotics are very effective for treating diarrhea in weaned pigs, but the global prohibition of antibiotics makes it urgent to find an alternative to antibiotics. Objective: An experiment was conducted to determine the antimicrobial activity of a linear trpzip-like β-hairpin antimicrobial peptide WK3 in vivo and to assess its effects on growth performance and intestinal health. Design: Thirty-two piglets were weaned at 21 days and housed in individual metabolic cages, which were randomly divided into four groups and were maintained on a corn-soybean meal-based basal diet. Group 1 included a blank group. Groups 2, 3, and 4 were orally infected by feeding with Enterotoxigenic Escherichia coli (ETEC) K88, which was followed by saline treatment (group 2), enrofloxacin injection at a dose of 2.5 mg/ kg (group 3), and WK3 injection at a dose of 2 mg/kg (group 4). The experiment lasted for 6 days, and feed and water were provided ad libitum. Results: Both WK3 and enrofloxacin effectively attenuated diarrhea and improved growth performance of piglets. Compared with the control group, WK3 significantly improved the villus height in the ileum (P < 0.05) but did not affect the villus height in the duodenum or jejunum. Additionally, we did not observe any obvious difference in crypt depth or villus height/crypt depth among the duodenum, jejunum and ileum (P > 0.05). WK3 also reduced the numbers of Enterococcus spp (P < 0.01) in the cecal contents, and the number of Enterobacterium spp tended to decrease (0.05 < P < 0.1). Moreover, the jejunal mucosa of the WK3 group exhibited lower interleukin-1α (IL-1a; P < 0.01), toll-like receptors-4 (TLR-4; P < 0.05), and myeloid differentiation primary response 88 (MyD88; P < 0.01) messenger ribonucleic acid (mRNA) expression levels. The jejunum of the WK3 group also exhibited an increased antioxidant capacity, reduced concentration of malondialdehyde (MDA; P < 0.05), and enhanced superoxide dismutase (SOD) activity (P < 0.05). Conclusions: WK3 has the potential to replace antibiotics as a new generation feed additive.