Antimicrobial peptide CAP18 as a natural alternative to antibiotics: effects on gut health, immunity, and meat quality in broiler chickens.
CAP18, an antimicrobial peptide, just outperformed antibiotics in a head-to-head test in broiler chickens. Researchers in Iran fed 480 chicks four different diets: plain feed, feed with oxytetracycline, or feed with two different doses of CAP18. The goal: see if CAP18 could match or beat antibiotics on growth, gut health, immunity, and meat quality.
BMC Vet Res
by Jebalbarezi P, Afsharmanesh M, Lohrasbi-Nejad A et al.
“Antimicrobial peptide CAP18 as a natural alternative to antibiotics: effects on gut health, immunity, and meat quality in broiler chickens. Jebalbarezi P(1), Afsharmanesh M(2), Lohrasbi-Nejad A(3), Salarmoini M(1), Bami MK(1)(3). Author information: (1)Department of Animal Science, Faculty of Agriculture, Shahid Bahonar University of Kerman, Kerman, Iran. (2)Department of Animal Science, Faculty of Agriculture, Shahid Bahonar University of Kerman, Kerman, Iran. mafshar@uk.ac.ir. (3)Research and Technology Institute of Plant Production (RTIPP), Afzalipour Research Institute, Shahid Bahonar University of Kerman, Kerman, Iran. 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. © 2026. The Author(s). Conflict of interest statement: Declarations. Ethics approval and consent to participate: All animal experiments were performed in accordance with guide-lines for the care and use of laboratory animals and approved by Veterinary Faculty of Shahid Bahonar University of Kerman (approval number: IR.UK.VETMED.REC 2019-03-05). The chicks used in this study were obtained from Mahan Chicken Meat Production Complex Co., Mahan, Iran. Informed consent for the use of these animals was obtained from the company. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests.”
The results? CAP18 kept growth on par with antibiotics. But it did more than just maintain weight. Birds given CAP18 showed a better balance of gut bacteria, with a higher ratio of lactic acid bacteria to coliforms. Gut structure improved too—those fed 20 mg/kg CAP18 had shorter crypts and taller villi, both signs of a healthier intestine.
Meat quality also got a boost. CAP18-fed chickens had less cooking loss and better water-holding capacity than those on antibiotics. Oxidative markers in the meat dropped as well, hinting at longer shelf life and better texture.
Key takeaway: CAP18 didn’t just keep chickens growing. It made them healthier on the inside and improved the final product.
Other notable findings:
Serum IgG, a key immune marker, was higher in birds getting the higher CAP18 dose by day 42.
The growth and feed intake numbers held steady between CAP18 and antibiotic groups, so there’s no trade-off for ditching the antibiotic.
For anyone looking to replace antibiotics in animal research, peptides like CAP18 are shaping up as a serious option. Want to dive deeper into the science? Check out the peptide research index for more studies and background. For sourcing CAP18 or comparing options, the vendor directory is a good starting place.
Bottom line: Antimicrobial peptides aren’t just promising—they’re performing.
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