Introduction: Due to global restrictions on antibiotic use in poultry and concerns about antimicrobial resistance, bacteriophages have increasingly emerged as biological control agents to reduce the microbial load of pathogens like Escherichia coli. Objective: This study evaluated and compared the effects of dietary supplementation with a probiotic and graded levels of bacteriophages (0.05%, 0.10%, and 0.15%) on growth performance, blood biochemistry, gut microbiota, intestinal histomorphology, immune response, and carcass traits in broilers. Methods: A total of 250 male Ross 308 chicks were randomly allocated into 5 treatments with 5 replicates (10 birds per replicate). Treatments included a basal diet (control), basal diet plus 0.025% probiotic, and three phage levels (0.05%, 0.10%, 0.15%). Blood and intestinal sampling occurred on day 42. Results: Supplementation during the starter phase decreased feed intake and significantly improved the feed conversion ratio. The highest overall average daily gain was recorded in the 0.05% phage group. Phages significantly reduced serum triglycerides and ALT enzyme activity, while increasing HDL and LDL. The lowest Escherichia coli and coliform populations were observed in the 0.15% group, whereas Lactobacillus populations remained statistically unchanged. Villus height and the villus-to-crypt ratio improved in all supplemented groups. The highest Newcastle and Gumboro antibody titers were found in the 0.05% and 0.15% groups, respectively. The 0.15% group exhibited the highest relative breast yield and the lowest percentages of liver and abdominal fat. Conclusion: Bacteriophage supplementation acts as an efficient, dose-dependent antibiotic alternative. Specifically, the 0.05% level optimizes growth performance and Newcastle immunity, whereas the 0.15% level is superior for managing liver metabolism, improving carcass quality, and enhancing Gumboro immunity. These findings indicate that phages are highly adjustable tools in modern poultry nutrition.
Sepahvand, B. , Masouri, B. , Parizadian Kavan, B. and Khosravinia, H. (2026). Comparative effects of probiotic and graded levels of bacteriophage on growth performance, gut Health, immune response, and carcass quality in broiler chickens. Veterinary Research & Biological Products, 39(3), 32-45. doi: 10.22092/vj.2026.371775.2274
MLA
Sepahvand, B. , , Masouri, B. , , Parizadian Kavan, B. , and Khosravinia, H. . "Comparative effects of probiotic and graded levels of bacteriophage on growth performance, gut Health, immune response, and carcass quality in broiler chickens", Veterinary Research & Biological Products, 39, 3, 2026, 32-45. doi: 10.22092/vj.2026.371775.2274
HARVARD
Sepahvand, B., Masouri, B., Parizadian Kavan, B., Khosravinia, H. (2026). 'Comparative effects of probiotic and graded levels of bacteriophage on growth performance, gut Health, immune response, and carcass quality in broiler chickens', Veterinary Research & Biological Products, 39(3), pp. 32-45. doi: 10.22092/vj.2026.371775.2274
CHICAGO
B. Sepahvand , B. Masouri , B. Parizadian Kavan and H. Khosravinia, "Comparative effects of probiotic and graded levels of bacteriophage on growth performance, gut Health, immune response, and carcass quality in broiler chickens," Veterinary Research & Biological Products, 39 3 (2026): 32-45, doi: 10.22092/vj.2026.371775.2274
VANCOUVER
Sepahvand, B., Masouri, B., Parizadian Kavan, B., Khosravinia, H. Comparative effects of probiotic and graded levels of bacteriophage on growth performance, gut Health, immune response, and carcass quality in broiler chickens. Veterinary Research & Biological Products, 2026; 39(3): 32-45. doi: 10.22092/vj.2026.371775.2274
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