Antimicrobial peptide CAP18 as a natural alternative to antibiotics: effects on gut health, immunity, and meat quality in broiler chickens

BACKGROUND: This study evaluated the effects of dietary supplementation with an antibiotic or the antimicrobial peptide CAP18 on growth performance, immune response, intestinal microbiota, gut morphology, and meat quality in broiler chickens. A total of 480 one-day-old Ross 308 broilers were randomly assigned to four dietary treatments in a completely randomized design with five replicates of 24 birds each: (1) basal diet (control), (2) basal diet + 500 mg/kg antibiotic (5% oxytetracycline), (3) basal diet + 10 mg/kg CAP18, and (4) basal diet + 20 mg/kg CAP18. RESULTS: Supplementation with CAP18 at either 10 or 20 mg/kg maintained body weight gain, feed intake, or feed conversion ratio compared with the control or antibiotic treatments. However, CAP18 improved intestinal health by increasing the ileal lactic acid bacteria-to-coliform ratio (P < 0.05) and enhancing ileal morphology, with birds receiving 20 mg/kg CAP18 showing reduced crypt depth and a higher villus height-to-crypt depth ratio (P < 0.05). Meat quality was also enhanced in CAP18-fed birds, as indicated by lower thiobarbituric acid reactive substances, reduced cooking loss, and higher water-holding capacity compared with the antibiotic group (P < 0.05). Moreover, at 42 days, serum IgG levels were elevated in birds receiving 20 mg/kg CAP18, demonstrating enhanced humoral immunity (P < 0.05). CONCLUSIONS: In conclusion, dietary CAP18 at 10 mg/kg maintained growth performance while promoting a healthier intestinal microbiota, enhanced meat quality, and strengthened immune responses compared with the antibiotic treatment.