Porcine intestinal antimicrobial peptide as an in-feed antibiotic alternative improves intestinal digestion and immunity by shaping the gut microbiota in weaned piglets

Antibiotic resistance of pathogens, which is caused by the abuse of in-feed antibiotics, threatens the sustainable development of livestock production. The present study aimed to investigate the efficiency of porcine intestinal antimicrobial peptide (PIAP) as an alternative to in-feed antibiotics in terms of growth performance, intestinal morphology, digestive enzymes and immunity, and microbiota community of the post-weaning piglets. A total of 204 piglets (Duroc × Landrace × Yorkshire, weaned at 28 d age) with a similar body weight of 7.97 ± 1.04 kg were randomly allocated to 4 groups (51 piglets per group): (1) control group: basal diet; (2) AB group: antibiotic, basal diet + chlortetracycline (1000 mg/kg from d 1 to 24; 500 mg/kg from d 25 to 37); (3) P1 group: basal diet + a relatively low dose of PIAP (400 mg/kg from d 1 to 24; 300 mg/kg from d 25 to 37); (4) P2 group, basal diet + a relatively high dose of PIAP (600 mg/kg from d 1 to 24; 500 mg/kg from d 25 to 37). The results showed that serum indicators of hepatocyte damage and relative organ weight were not affected by these treatments (P > 0.05). Compared with the AB treatment, the P1 treatment remarkably decreased jejunal crypt depth and increased jejunal and ileal villus height:crypt depth ratio (P < 0.05). The values of jejunal maltase, lactase, sucrase, intestinal alkaline phosphatase, and secretory immunoglobulin A (SIgA) in the P1 group were sharply increased compared with those in the control and P2 groups (P < 0.05). Compared with the control group, the P1 group decreased serum concentrations of D-lactate, diamine oxidase, and endotoxin (P < 0.05), and increased the abundance of Lactobacillus reuteri (P < 0.05) in the colonic feces. Furthermore, there was a positive correlation between the abundance of L. reuteri and the concentrations of maltase, lactase, sucrase, and SIgA (P < 0.05). Collectively, dietary supplementation with a relatively low dose of PIAP (400 mg/kg from d 1 to 24; 300 mg/kg from d 25 to 37) demonstrates beneficial effects on intestinal morphology, digestive enzymes, immunity, and permeability by shaping the gut microbiota composition in weaned piglets. This study will provide a valuable reference for using PIAP as an in-feed antibiotic alternative in swine production.