Systematic Review Open Access

Countering Antimicrobial Resistance: Impacts of Natural Growth Promoters on Growth Performance, Immunity, Gut Microbiota and Morphology in Broiler Chicken: A Systematic Review

Authors

CORRESPONDING AUTHOR
Ednah Masila
Veterinary Science Research Institute, Kenya Agricultural and Livestock Research Organization (KALRO), P.O. Box 32-00902, Kikuyu, Kenya
|
Edwin Murungi
Veterinary Science Research Institute, Kenya Agricultural and Livestock Research Organization (KALRO), P.O. Box 32-00902, Kikuyu, Kenya
|
Nathan Langat
Veterinary Science Research Institute, Kenya Agricultural and Livestock Research Organization (KALRO), P.O. Box 32-00902, Kikuyu, Kenya
|
Christine Inguyesi
Veterinary Science Research Institute, Kenya Agricultural and Livestock Research Organization (KALRO), P.O. Box 32-00902, Kikuyu, Kenya
|
Irene Ogali
Veterinary Science Research Institute, Kenya Agricultural and Livestock Research Organization (KALRO), P.O. Box 32-00902, Kikuyu, Kenya
|
Johnstone Neondo
Institute for Biotechnology Research, Jomo Kenyatta University of Agriculture and Technology (JKUAT), P.O. Box 62000-00200, Nairobi, Kenya
|
Jeremiah Gathirwa
Centre for Traditional Medicine and Drug Research, Kenya Medical Research Institute (KEMRI), P.O. Box 54840-00200, Nairobi, Kenya
|
Eric Too
Veterinary Science Research Institute, Kenya Agricultural and Livestock Research Organization (KALRO), P.O. Box 32-00902, Kikuyu, Kenya
|
Peter Ndirangu
Veterinary Science Research Institute, Kenya Agricultural and Livestock Research Organization (KALRO), P.O. Box 32-00902, Kikuyu, Kenya
|
Monicah Maichomo
Veterinary Science Research Institute, Kenya Agricultural and Livestock Research Organization (KALRO), P.O. Box 32-00902, Kikuyu, Kenya
|
Moses Olum
Veterinary Science Research Institute, Kenya Agricultural and Livestock Research Organization (KALRO), P.O. Box 32-00902, Kikuyu, Kenya
DOI 10.66920/ijps.2026.141.153
PDF

Abstract

Background and Objective: Antibiotic Growth Promoters (AGPs) have been widely used to improve broiler performance. However, their use is declining due to concerns about antimicrobial resistance (AMR) and increasing consumer demand for antibiotic-free products. This systematic review aimed to evaluate the effects of alternative growth promoters on growth performance, immune response, gut microbiota, and intestinal morphology in broiler chickens.

Materials and Methods: Relevant studies published between 2015 and 2025 were collected from PubMed, ScienceDirect, Scopus, and Google Scholar. A total of 183 articles were identified, and 99 were included after a rigorous screening process. Data on growth performance, gut morphology, microbial modulation, and immune responses were synthesized qualitatively.

Results: The findings showed improved growth performance, indicated by better Feed Conversion Ratio (FCR) and increased Body Weight Gain (BWG). Enhanced immune function was observed through higher serum antibody levels and increased weights of immune organs. Natural alternatives also promoted beneficial microbes while reducing pathogenic populations. Positive changes in gut morphology were noted, including increased villus height and a higher villus height to crypt depth ratio. Dietary inclusion was the primary method of administering these growth promoters.

Conclusion: Alternative growth promoters have positive and often synergistic effects on growth performance, gut health, immune function, and intestinal microbiota in broiler chickens. However, existing challenges and knowledge gaps highlight the need for optimized formulations and standardized application protocols.

Keywords:

Antibiotics, growth promotion, natural alternatives, poultry nutrition

Geographical Article Usage

Article Metrics

346 Abstract Views
127 File Views
0 Downloads

Article Citation Metrics

How to Cite

Masila, E., Murungi, E., Langat, N. ., Inguyesi, C. ., Ogali, I., Neondo, J. ., Gathirwa, J., Too, E., Ndirangu, P., Maichomo, M., & Olum, M. (2026). Countering Antimicrobial Resistance: Impacts of Natural Growth Promoters on Growth Performance, Immunity, Gut Microbiota and Morphology in Broiler Chicken: A Systematic Review. International Journal of Poultry Science, 25, 141–153. https://doi.org/10.66920/ijps.2026.141.153

References

1.
Rahman, M., I. Fliss and E. Biron, 2022. Insights in the development and uses of alternatives to antibiotic growth promoters in poultry and swine production. Antibiotics, Vol. 11. 10.3390/antibiotics11060766 DOI: https://doi.org/10.3390/antibiotics11060766
2.
Ikusika, O.O., C. Haruzivi and T.C. Mpendulo, 2023. Alternatives to the use of antibiotics in animal production. In: Antibiotics and Probiotics in Animal Food, Ali, K.A, (Ed.). IntechOpen, London, United Kingdom, pp: 1-12.
3.
Hou, L., S. Cao, Y. Qiu, Y. Xiong, H. Xiao and Z. Jiang et al., 2022. Effects of early sub‐therapeutic antibiotic administration on body tissue deposition, gut microbiota and metabolite profiles of weaned piglets. J. Sci. Food Agric., 102: 5913-5924. DOI: https://doi.org/10.1002/jsfa.11942
4.
Rathnayaka, S.D., S. Selvanathan and E.A. Selvanathan, 2021. Demand for animal‐derived food in selected Asian countries: A system‐wide analysis. Agric. Econ., 52: 97-122. DOI: https://doi.org/10.1111/agec.12609
5.
Rehman, A., M. Arif, N. Sajjad, M.Q. Al-Ghadi, M. Alagawany and A.A. Swelum et al., 2020. Dietary effect of probiotics and prebiotics on broiler performance, carcass, and immunity. Poult. Sci., 99: 6946-6953. DOI: https://doi.org/10.1016/j.psj.2020.09.043
6.
Van, T.T.H., Z. Yidana, P.M. Smooker and P.J. Coloe, 2020. Antibiotic use in food animals worldwide, with a focus on Africa: Pluses and minuses. J. Global Antimicrob. Resist., 20: 170-177. DOI: https://doi.org/10.1016/j.jgar.2019.07.031
7.
Lam, Y., J.P. Fry and K.E. Nachman, 2019. Applying an environmental public health lens to the industrialization of food animal production in ten low- and middle-income countries. Globalization Health, Vol. 15. 10.1186/s12992-019-0479-5 DOI: https://doi.org/10.1186/s12992-019-0479-5
8.
Djordjevic, S.P. and B.S. Morgan, 2019. A one health genomic approach to antimicrobial resistance is essential for generating relevant data for a holistic assessment of the biggest threat to public health. Microbiol. Australia, 40: 73-76. DOI: https://doi.org/10.1071/MA19021
9.
Naeem, M. and D. Bourassa, 2025. Probiotics in poultry: Unlocking productivity through microbiome modulation and gut health. Microorganisms, Vol. 13. 10.3390/microorganisms13020257 DOI: https://doi.org/10.3390/microorganisms13020257
10.
Dai, D., K. Qiu, H.-j. Zhang, S.-g. Wu, Y.-m. Han and J. Wang et al., 2021. Organic acids as alternatives for antibiotic growth promoters alter the intestinal structure and microbiota and improve the growth performance in broilers. Front. Microbiol., Vol. 11. 10.3389/fmicb.2020.618144 DOI: https://doi.org/10.3389/fmicb.2020.618144
11.
Aminullah, N., A. Mostamand, A. Zahir, O. Mahaq and M.N. Azizi, 2025. Phytogenic feed additives as alternatives to antibiotics in poultry production: A review. Vet. World, 18: 141-154. DOI: https://doi.org/10.14202/vetworld.2025.141-154
12.
Lucio, B.S.V.-D., E.M. Hernández-Domínguez, M. Villa-García, G. Díaz-Godínez, V. Mandujano-Gonzalez and J. Álvarez-Cervantes et al., 2021. Exogenous enzymes as zootechnical additives in animal feed: A review. Catalysts, Vol. 11. 10.3390/catal11070851
13.
Alagawany, M., S.S. Elnesr and M.R. Farag, 2018. The role of exogenous enzymes in promoting growth and improving nutrient digestibility in poultry. Iran. J. Vet. Res., 19: 157-164.
14.
Ayalew, H., H. Zhang, J. Wang, S. Wu, K. Qiu and D. Chanie et al., 2022. Potential feed additives as antibiotic alternatives in broiler production. Front. Vet. Sci., Vol. 9. 10.3389/fvets.2022.916473 DOI: https://doi.org/10.3389/fvets.2022.916473
15.
Froebel, L.K., S. Jalukar, T.A. Lavergne, J.T. Lee and T. Duong, 2019. Administration of dietary prebiotics improves growth performance and reduces pathogen colonization in broiler chickens. Poult. Sci., 98: 6668-6676. DOI: https://doi.org/10.3382/ps/pez537
16.
Wang, S., X. Zeng, Q. Yang and S. Qiao, 2016. Antimicrobial peptides as potential alternatives to antibiotics in food animal industry. Int. J. Mol. Sci., Vol. 17. 10.3390/ijms17050603 DOI: https://doi.org/10.3390/ijms17050603
17.
Xiao, H., F. Shao, M. Wu, W. Ren, X. Xiong and Y. Yin et al., 2015. The application of antimicrobial peptides as growth and health promoters for swine. J. Anim. Sci. Biotechnol., Vol. 6. 10.1186/s40104-015-0018-z DOI: https://doi.org/10.1186/s40104-015-0018-z
18.
Sarrami, Z., M. Sedghi, I. Mohammadi, W.K. Kim and A.H. Mahdavi, 2022. Effects of bacteriophage supplement on the growth performance, microbial population, and PGC-1α and TRL4 gene expressions of broiler chickens. Sci. Rep., Vol. 12. 10.1038/s41598-022-18663-1 DOI: https://doi.org/10.1038/s41598-022-18663-1
19.
Żbikowska, K., M. Michalczuk and B. Dolka, 2020. The use of bacteriophages in the poultry industry. Animals, Vol. 10. 10.3390/ani10050872 DOI: https://doi.org/10.3390/ani10050872
20.
Page, M.J., J.E. McKenzie, P.M. Bossuyt, I. Boutron, T.C. Hoffmann and D. Moher et al., 2021. The prisma 2020 statement: An updated guideline for reporting systematic reviews. Int. J. Surgery, Vol. 88. 10.1016/j.ijsu.2021.105906
21.
Hooijmans, C.R., M.M. Rovers, R.B.D. Vries, M. Leenaars, M. Ritskes-Hoitinga and M.W. Langendam, 2014. SYRCLE’s risk of bias tool for animal studies. BMC Med. Res. Methodol., Vol. 14. 10.1186/1471-2288-14-43 DOI: https://doi.org/10.1186/1471-2288-14-43
22.
Saleh, H., M.T. Mirakzehi, H.M. Bidokhti and M. Kazemi, 2025. Evaluation of the effect of bacteriophages and organic acids as a feed additive to reduce Salmonella enteritidis in challenged chickens. J. Anim. Physiol. Anim. Nutr., 109: 881-890. DOI: https://doi.org/10.1111/jpn.14103
23.
Shokri, A.N., H.A. Ghasemi and K. Taherpour, 2016. Evaluation of Aloe vera and synbiotic as antibiotic growth promoter substitutions on performance, gut morphology, immune responses and blood constitutes of broiler chickens. Anim. Sci. J., 88: 306-313. DOI: https://doi.org/10.1111/asj.12629
24.
Latif, A., A. Shehzad, S. Niazi, A. Zahid, W. Ashraf and S.A. Korma et al., 2023. Probiotics: Mechanism of action, health benefits and their application in food industries. Front. Microbiol., Vol. 14. 10.3389/fmicb.2023.1216674 DOI: https://doi.org/10.3389/fmicb.2023.1216674
25.
Pourabedin, M. and X. Zhao, 2015. Prebiotics and gut microbiota in chickens. FEMS Microbiol. Lett., Vol. 362. 10.1093/femsle/fnv122 DOI: https://doi.org/10.1093/femsle/fnv122
26.
Saleh, A.A., A.H. El-Far, M.A. Abdel-Latif, M.A. Emam, R. Ghanem and H.S.A. El-Hamid, 2018. Exogenous dietary enzyme formulations improve growth performance of broiler chickens fed a low-energy diet targeting the intestinal nutrient transporter genes. PLoS ONE., Vol. 13. 10.1371/journal.pone.0198085 DOI: https://doi.org/10.1371/journal.pone.0198085
27.
Biswas, S. and I.H. Kim, 2025. A thorough review of phytogenic feed additives in non-ruminant nutrition: Production, gut health, and environmental concerns. J. Anim. Sci. Technol., 67: 497-519. DOI: https://doi.org/10.5187/jast.2025.e26
28.
Abbas, R.Z., A.F. Alsayeqh and A.I. Aqib, 2022. Role of bacteriophages for optimized health and production of poultry. Animals, Vol. 12. 10.3390/ani12233378 DOI: https://doi.org/10.3390/ani12233378
29.
Luo, X., Y. Chen, Y. Xiao, Y. Hu and Y. Feng, 2025. Overall assessment of antimicrobial peptides in broiler chickens: A meta-analysis. Poult. Sci., Vol. 104. 10.1016/j.psj.2025.105623 DOI: https://doi.org/10.1016/j.psj.2025.105623
30.
Chukwudi, P., P.I. Umeugokwe, N.E. Ikeh and B.C. Amaefule, 2024. The effects of organic acids on broiler chicken nutrition: A review. Anim. Res. One Health, 3: 43-53. DOI: https://doi.org/10.1002/aro2.85
31.
Jankowski, J., B. Tykałowski, A. Stępniowska, P. Konieczka, A. Koncicki and K. Ognik et al., 2022. Immune parameters in chickens treated with antibiotics and probiotics during early life. Animals, Vol. 12. 10.3390/ani12091133 DOI: https://doi.org/10.3390/ani12091133
32.
Ifrah, M.E., B. Perelman, A. Finger and Z. Uni, 2017. The role of the bursa of Fabricius in the immune response to vaccinal antigens and the development of immune tolerance in chicks (Gallus domesticus) vaccinated at a very young age. Poult. Sci., 96: 51-57. DOI: https://doi.org/10.3382/ps/pew232
33.
Hristakieva, P., S. Laleva, T. Koynarski, M. Oblakova, I. Slavov and N. Ivanov, 2025. Enhancing growth performance and innate immunity in broiler chickens through combined probiotic and herbal supplementation. Open Vet. J., 15: 4885-4893. DOI: https://doi.org/10.5455/OVJ.2025.v15.i10.8
34.
Younas, S., D.A. Bukhari, Z. Bibi, A. Ullah and A. Rehman, 2025. Impact of multistrain probiotics on growth performance, immune response, and gut morphometry in broiler chicken Gallus gallus domesticus. Poult. Sci., Vol. 104. 10.1016/j.psj.2025.105026 DOI: https://doi.org/10.1016/j.psj.2025.105026
35.
Ricke, S.C., 2018. Impact of prebiotics on poultry production and food safety. Yale J. Biol. Med., 91: 151-159.
36.
Vera-Álava, J.O., J.G. Arteaga-Solórzano and S.L. Reyna-Gallegos, 2023. Organic acids, microbiota, gut health and productive response in broilers chickens. Rev. Colomb. Ciencia Anim. - RECIA, Vol. 15. 10.24188/recia.v15.n2.2023.1019 DOI: https://doi.org/10.24188/recia.v15.n2.2023.1019
37.
Oni, A.I. and O.E. Oke, 2025. Gut health modulation through phytogenics in poultry: Mechanisms, benefits, and applications. Front. Vet. Sci., Vol. 12. 10.3389/fvets.2025.1616734 DOI: https://doi.org/10.3389/fvets.2025.1616734
38.
Huang, C.M. and T.T. Lee, 2018. Immunomodulatory effects of phytogenics in chickens and pigs — A review. Asian-Australas. J. Anim. Sci., 31: 617-627. DOI: https://doi.org/10.5713/ajas.17.0657
39.
Liu, X., X. Wang, X. Shi, S. Wang and K. Shao, 2024. The immune enhancing effect of antimicrobial peptide LLv on broilers chickens. Poult. Sci., Vol. 103. 10.1016/j.psj.2023.103235 DOI: https://doi.org/10.1016/j.psj.2023.103235
40.
Dittoe, D.K., S.C. Ricke and A.S. Kiess, 2018. Organic acids and potential for modifying the avian gastrointestinal tract and reducing pathogens and disease. Front. Vet. Sci., Vol. 5. 10.3389/fvets.2018.00216 DOI: https://doi.org/10.3389/fvets.2018.00216
41.
Olawade, D.B., O. Fapohunda, E. Egbon, O.A. Ebiesuwa, S.O. Usman and S.C. Fidelis et al., 2024. Phage therapy: A targeted approach to overcoming antibiotic resistance. Microbial Pathogenesis, Vol. 197. 10.1016/j.micpath.2024.107088 DOI: https://doi.org/10.1016/j.micpath.2024.107088
42.
Cai, Y., Y. Zhang, O. Hamada, P. Sun and Z. Song, 2025. Effects of antimicrobial peptides (AMPs) on egg quality, immunity, antioxidant capacity, and intestinal microbiota in late-laying hens. Ital. J. Anim. Sci., 24: 1404-1414. DOI: https://doi.org/10.1080/1828051X.2025.2519828
43.
R, G.K., R.B. Narasingappa and G.V. Vyas, 2024. Unveiling mechanisms of antimicrobial peptide: Actions beyond the membranes disruption. Heliyon, Vol. 10. 10.1016/j.heliyon.2024.e38079 DOI: https://doi.org/10.1016/j.heliyon.2024.e38079
44.
Sureshkumar, S., J. Song, V. Sampath and I. Kim, 2023. Exogenous enzymes as zootechnical additives in monogastric animal feed: A review. Agriculture, Vol. 13. 10.3390/agriculture13122195 DOI: https://doi.org/10.3390/agriculture13122195
45.
Moita, V.H.C. and S.W. Kim, 2022. Nutritional and functional roles of phytase and xylanase enhancing the intestinal health and growth of nursery pigs and broiler chickens. Animals, Vol. 12. 10.3390/ani12233322 DOI: https://doi.org/10.3390/ani12233322
46.
Al-Baadani, H.H., A.A. Aboragah, A.S. Alharthi and R.A. Alhotan, 2025. Interaction effect of prebiotic products as feed additives and rearing systems on performance, slaughter yield and intestinal health of broiler chickens. J. Appl. Poult. Res., Vol. 34. 10.1016/j.japr.2025.100535 DOI: https://doi.org/10.1016/j.japr.2025.100535
47.
Singh, P., V.K. Singh and D. Tewari, 2025. Assessment of efficacy of phytobiotic mixture as an alternative of antibiotic growth promoters in broiler production. Int. J. Adv. Biochem. Res., 9: 277-280. DOI: https://doi.org/10.33545/26174693.2025.v9.i4Sd.4127
48.
Ceylan, N., E. Yenice, İ. Yavaş, A.A. Çenesiz, N.N. Toprak and İ. Çiftçi, 2023. Comparative effects of medium‐chain fatty acids or phytobiotics‐based feed additives on performance, caecum microbiota, volatile fatty acid production and intestinal morphology of broilers. Vet. Med. Sci., 9: 2719-2730. DOI: https://doi.org/10.1002/vms3.1249
49.
Waghmare, S., M. Gupta, K.B. Bahiram, J.P. Korde, R. Bhat and N.V. Kurkure et al., 2025. Effects of organic acid blends on the growth performance, intestinal morphology, microbiota, and serum lipid parameters of broiler chickens. Poult. Sci., Vol. 104. 10.1016/j.psj.2024.104546 DOI: https://doi.org/10.1016/j.psj.2024.104546
50.
Muneeb, M., E.U. Khan, S. Ahmad, I. Hussain, S. Batool and A.E. Abudabos et al., 2025. A comprehensive review of the application of bacteriophages against enteric bacterial infection in poultry: Current status, challenges, and future prospects. Antibiotics, Vol. 14. 10.3390/antibiotics14121207 DOI: https://doi.org/10.3390/antibiotics14121207
51.
Oso, A.O., R.U. Suganthi, G.B.M. Reddy, P.K. Malik, G. Thirumalaisamy and R. Bhatta et al., 2019. Effect of dietary supplementation with phytogenic blend on growth performance, apparent ileal digestibility of nutrients, intestinal morphology, and cecal microflora of broiler chickens. Poult. Sci., 98: 4755-4766. DOI: https://doi.org/10.3382/ps/pez191
52.
Grishina, L.S., A.Y. Zhigalov, I.P. Bolodurina, A.E. Shukhman, P.L. Niryan and E.V. Sheida et al., 2025. Machine learning-driven analysis of feed additives and intestinal microbiota diversity in broiler chickens: Clustering of mineral profiles and predictive diet modeling. Vet. World, 18: 3390-3408. DOI: https://doi.org/10.14202/vetworld.2025.3390-3408
53.
Himu, H.A., I.Z. Moni and A. Raihan, 2025. An exploration of the effects of selected growth promoters on broiler chickens. J. Vet. Med. Sci., Vol. 3. 10.61148/JVMS/010
54.
Vlaicu, P.A., A.E. Untea and A.G. Oancea, 2024. Sustainable poultry feeding strategies for achieving zero hunger and enhancing food quality. Agric., Vol. 14. 10.3390/agriculture14101811 DOI: https://doi.org/10.3390/agriculture14101811
55.
Acharya, A. and S.R. Barsila, 2025. Exploring alternatives to antibiotics in poultry production: A comprehensive review of emerging strategies and their implications for avian health. World's Poult. Sci. J., 81: 1427-1460. DOI: https://doi.org/10.1080/00439339.2025.2522139
56.
Abdelsattar, M.M., W. Zhao, M. Diaby, E. Vargas-Bello-Pérez and N. Zhang, 2025. Recent nutritional strategies and feed additives to stimulate proper rumen development in young goats. Transl. Anim. Sci., Vol. 9. 10.1093/tas/txae164 DOI: https://doi.org/10.1093/tas/txae164
57.
Xu, Q.-L., C. Liu, X.-J. Mo, M. Chen, X.-L. Zhao and C.-X. Zhao et al., 2022. Drinking water supplemented with acidifiers improves the growth performance of weaned pigs and potentially regulates antioxidant capacity, immunity, and gastrointestinal microbiota diversity. Antioxi ts, Vol. 11. 10.3390/antiox11050809 DOI: https://doi.org/10.3390/antiox11050809
58.
Oladokun, S. and D.I. Adewole, 2020. In ovo delivery of bioactive substances: An alternative to the use of antibiotic growth promoters in poultry production—A review. J. Appl. Poult. Res., 29: 744-763. DOI: https://doi.org/10.1016/j.japr.2020.06.002
59.
Tavaniello, S., G. Maiorano, K. Stadnicka, R. Mucci, J. Bogucka and M. Bednarczyk, 2018. Prebiotics offered to broiler chicken exert positive effect on meat quality traits irrespective of delivery route. Poult. Sci., 97: 2979-2987. DOI: https://doi.org/10.3382/ps/pey149
60.
Cai, F., M. Huang, W. Liu, X. Wan, K. Qiu and X. Xu, 2025. Dietary addition of compound organic acids improves the growth performance, carcass trait, and body health of broilers. Front. Nutr., Vol. 12. 10.3389/fnut.2025.1536606 DOI: https://doi.org/10.3389/fnut.2025.1536606
61.
Ogunola, K.M., A.V. Jegede, A.O. Fafiolu and O.E. Oke, 2025. Responses of broiler chickens to diets of different nutritional planes supplemented with or without organic acids. Vet. Med. Sci., Vol. 11. 10.1002/vms3.70332 DOI: https://doi.org/10.1002/vms3.70332
62.
Hamid, H., H.Q. Shi, G.Y. Ma, Y. Fan, W.X. Li and Q.G. Ma et al., 2018. Influence of acidified drinking water on growth performance and gastrointestinal function of broilers. Poult. Sci., 97: 3601-3609. DOI: https://doi.org/10.3382/ps/pey212
63.
Mahmoud, E.-k., M.S. Refaie and A.M.S. Ibtesam, 2025. Impact of organic acids supplementation on growth performance, nutrient digestibility, and some blood parameters in broiler chicks. Egypt. Poult. Sci. J., 45: 171-185. DOI: https://doi.org/10.21608/epsj.2025.440400
64.
Bagal, V.L., V.K. Khatta, B.S. Tewatia, S.K. Sangwan and S.S. Raut, 2016. Relative efficacy of organic acids and antibiotics as growth promoters in broiler chicken. Vet. World, 9: 377-382. DOI: https://doi.org/10.14202/vetworld.2016.377-382
65.
Grozina, A.A., L.A. Ilina, G.Y. Laptev, E.A. Yildirim, E.S. Ponomareva and M.N. Romanov et al., 2023. Probiotics as an alternative to antibiotics in modulating the intestinal microbiota and performance of broiler chickens. J. Appl. MicroBiol., Vol. 134. 10.1093/jambio/lxad213 DOI: https://doi.org/10.1093/jambio/lxad213
66.
Roy, B.C. and B.C. Ray, 2023. Potentiality of Saccharomyces cerevisiae in replacing antibiotic growth promoters on growth, gut microbiology, histology, and serum antibody titers of commercial broilers. J. Appl. Poult. Res., Vol. 32. 10.1016/j.japr.2023.100352 DOI: https://doi.org/10.1016/j.japr.2023.100352
67.
Roy, B.C., S.D. Chowdhury and S.M.L. Kabir, 2015. Effects of feeding bacillus subtilis to heat stressed broiler chickens with or without an antibiotic growth promoter. Asian J. Med. Biol. Res., 1: 80-88. DOI: https://doi.org/10.3329/ajmbr.v1i1.25502
68.
Ma, T., W. Wang, A. Ali, C. Yin, B. Syed and H. Zhang et al., 2025. Evaluating the efficacy of compound probiotics as an antibiotic alternative: A comprehensive analysis of growth performance and intestinal health via feed and water routes. Anim. Nutr., 23: 535-545. DOI: https://doi.org/10.1016/j.aninu.2025.04.011
69.
Dong, Z., Z. Liu, Y. Xu, B. Tan, W. Sun and J. Zeng et al., 2024. Potential for the development of Taraxacum mongolicum aqueous extract as a phytogenic feed additive for poultry. Front. Immunol., Vol. 15. 10.3389/fimmu.2024.1354040 DOI: https://doi.org/10.3389/fimmu.2024.1354040
70.
Talayi-Anbaran, A., J.R. Jáber, B. Rasouli, A. Seidavi, E. Sanjuán and M.R. Ventura et al., 2025. Compatible alternative to antibiotics in broilers: Evaluating Nigella sativa as a natural growth promoter. Org. Agric., 15: 651-668. DOI: https://doi.org/10.1007/s13165-025-00521-9
71.
Parobali, T., H. Lin, J.A. Hounkpevi, B. Adjei‐Mensah, O. N'nanle and K. Eklu‐Gadegbeku et al, 2025. Influence of Citrus sinensis seeds on the growth performance, Ceca bacterial population and the immune system response of broiler chickens. Vet. Med. Sci., Vol. 11. 10.1002/vms3.70553 DOI: https://doi.org/10.1002/vms3.70553
72.
Haq, Z., A. Rastogi, R.K. Sharma, P. Raghuwanshi, M. Singh and S.M. Ahmad et al, 2024. Exploring the efficacy of a novel prebiotic-like growth promoter on broiler chicken production performance. Vet. Anim. Sci., Vol. 23. 10.1016/j.vas.2023.100331 DOI: https://doi.org/10.1016/j.vas.2023.100331
73.
Biswas, A., R. Messam, M. Kumawat, M. Namit, A.B. Mandal and N.A. Mir, 2018. Effects of prebiotics on intestinal histo-morphometry and gut microflora status of broiler chickens. Indian J. Anim. Res., 53: 785-789. DOI: https://doi.org/10.18805/ijar.B-3579
74.
Landy, N., F. Kheiri and M. Faghani, 2020. Evaluation of cottonseed bioactive peptides on growth performance, carcase traits, immunity, total antioxidant activity of serum and intestinal morphology in broiler chickens. Ital. J. Anim. Sci., 19: 1375-1386. DOI: https://doi.org/10.1080/1828051X.2020.1844085
75.
Gao, M., Z. Wang, H. Zhao, Z. Li and H. Shen, 2025. Safety and effects of scorpion-derived antimicrobial peptides as an alternative to antibiotic growth promoters in broilers: Growth performance, immune function, and intestinal development. Front. Vet. Sci., Vol. 12. 10.3389/fvets.2025.1677663 DOI: https://doi.org/10.3389/fvets.2025.1677663
76.
Zhu, C., Y. Bai, X. Xia, M. Zhang, X. Wu and X. Zhao et al, 2022. Effects of the antimicrobial peptide mastoparan X on the performance, permeability and microbiota populations of broiler chickens. Animals, Vol. 12. 10.3390/ani12243462 DOI: https://doi.org/10.3390/ani12243462
77.
Horng, Y.B., Y.H. Cheng, Y.H. Yu and W.J. Chen, 2025. Effect of antimicrobial peptide Q4-15-2A7P on growth performance, gut morphology, intestinal gene expression, and ileal microbiota in broilers challenged with Clostridium perfringens toxin. Braz. J. Poult. Sci., Vol. 27. 10.1590/1806-9061-2025-2134 DOI: https://doi.org/10.1590/1806-9061-2025-2134
78.
Dai, Z., L. Shang, F. Wang, X. Zeng, H. Yu and S. Qiao et al, 2022. Effects of antimicrobial peptide microcin C7 on growth performance, immune and intestinal barrier functions, and cecal microbiota of broilers. Front. Vet. Sci., Vol. 8. 10.3389/fvets.2021.813629 DOI: https://doi.org/10.3389/fvets.2021.813629
79.
Upadhaya, S.D., J.M. Ahn, J.H. Cho, J.Y. Kim, D.K. Kang and I.H. Kim et al, 2021. Bacteriophage cocktail supplementation improves growth performance, gut microbiome and production traits in broiler chickens. J. Anim. Sci. Biotechnol., Vol. 12. 10.1186/s40104-021-00570-6 DOI: https://doi.org/10.1186/s40104-021-00570-6
80.
Aljuhaishi, D.A. and F.H.K. Albawi, 2024. Using bacteriophage in poultry diet as therapeutics against Escherichia coli in broiler chickens. J. Anim. Health Prod., 12: 23-31. DOI: https://doi.org/10.17582/journal.jahp/2024/12.s1.23.31
81.
Giacobbo, F.C.N., C. Eyng, R.V. Nunes, C.D. Souza, L.V. Teixeira and C. Bortoluzzi et al, 2021. Influence of enzyme supplementation in the diets of broiler chickens formulated with different corn hybrids dried at various temperatures. Animals, Vol. 11. 10.3390/ani11030643 DOI: https://doi.org/10.3390/ani11030643
82.
Broch, J., R.V. Nunes, C. Eyng, G.M. Pesti, C.D. Souza and L. Teixeira et al, 2018. High levels of dietary phytase improves broiler performance. Anim. Feed Sci. Technol., 244: 56-65. DOI: https://doi.org/10.1016/j.anifeedsci.2018.06.001
83.
Maynard, C.J., C.W. Maynard, G.J. Mullenix, A. Ramser, E.S. Greene and S. Dridi et al, 2023. Impact of phytase supplementation on meat quality of heat-stressed broilers. Animals, Vol. 13. 10.3390/ani13122043 DOI: https://doi.org/10.3390/ani13122043
84.
Moita, V.H.C., M.E. Duarte and S.W. Kim, 2021. Supplemental effects of phytase on modulation of mucosa-associated microbiota in the jejunum and the impacts on nutrient digestibility, intestinal morphology, and bone parameters in broiler chickens. Animals, Vol. 11. 10.3390/ani11123351 DOI: https://doi.org/10.3390/ani11123351
85.
Stefanello, C., D.P. Rosa, Y.K. Dalmoro, A.L. Segatto, M.S. Vieira and E. Santin et al, 2020. Protected blend of organic acids and essential oils improves growth performance, nutrient digestibility, and intestinal health of broiler chickens undergoing an intestinal challenge. Front. Vet. Sci., Vol. 6. 10.3389/fvets.2019.00491 DOI: https://doi.org/10.3389/fvets.2019.00491
86.
Negm, M.H., S.S.A. Ela and M.E.A. El-Hack, 2021. Does the use of lactic acid as an antibiotic substitute in broiler diets affect growth, carcass traits, blood indices and intestinal microbiota? Anim. Biotechnol., 34: 1163-1169. DOI: https://doi.org/10.1080/10495398.2021.2015360
87.
Islam, Z., A. Sultan, S.Z. Khan and S.B. Khan, 2022. Effect of organic acids blend, micro-encapsulated phyto-essential oils individually or in combination on growth performance, gut health and nutrients utilization of broilers. Pak. J. Zool., 54: 2391-2399. DOI: https://doi.org/10.17582/journal.pjz/20210714190714
88.
Rauf, U., A. Khan, A. Khan, M. Imran, M. Ahmad and H.M.S. Rahman et al, 2024. Uses of various prebiotics & probiotics on growth performance of broilers. Biol. Clin. Sci. Res. J., Vol. 2024. 10.54112/bcsrj.v2024i1.1035
89.
Wang, X., Y.Z. Farnell, E.D. Peebles, A.S. Kiess, K.G.S. Wamsley and W. Zhai, 2016. Effects of prebiotics, probiotics, and their combination on growth performance, small intestine morphology, and resident Lactobacillus of male broilers. Poult. Sci., 95: 1332-1340. DOI: https://doi.org/10.3382/ps/pew030
90.
Tomczyk, G., J.S. Niczyporuk, W. Kozdruń, A. Sawicka-Durkalec, Ł. Bocian and M. Michalski et al, 2024. Probiotic supplementation as an alternative to antibiotics in broiler chickens. J. Vet. Res., 68: 147-154. DOI: https://doi.org/10.2478/jvetres-2024-0009
91.
Abudabos, A.M., H.A. Al-Batshan and M.A. Murshed, 2015. Effects of prebiotics and probiotics on the performance and bacterial colonization of broiler chickens. South Afr. J. Anim. Sci., 45: 419-428. DOI: https://doi.org/10.4314/sajas.v45i4.8
92.
Hassa, H.M.A., A.W. Youssef, H.M. Ali and M.A. Mohamed, 2015. Adding phytogenic material and/or organic acids to broiler diets: Effect on performance, nutrient digestibility and net profit. Asian J. Poult. Sci., 9: 97-105. DOI: https://doi.org/10.3923/ajpsaj.2015.97.105
93.
Ferdous, M., M. Arefin, M. Rahman, M. Ripon, M. Rashid and K. Rafiq et al, 2019. Beneficial effects of probiotic and phytobiotic as growth promoter alternative to antibiotic for safe broiler production. J. Adv. Vet. Anim. Res., 6: 409-415. DOI: https://doi.org/10.5455/javar.2019.f361
94.
Sonawane, H.S., M.M. Yadav, G.S. Hingonekar, D. Kankhare and V.M. Vasave, 2020. Effect of dietary supplementation of multienzymes with prebiotics and probiotics on growth performance and feed conversion efficiency of broilers. Int. J. Curr. Microbiol. Appl. Sci., 9: 2455-2462. DOI: https://doi.org/10.20546/ijcmas.2020.912.290
95.
Zhao, Z., S. Liswaniso, N. Qin, S. Cao, X. Wu and X. Sun et al, 2024. Effects of a novel synbiotics-enzyme complex as a replacement for antibiotics on growth performance, slaughter and meat characteristics, immune organ index, and intestinal morphology of broilers. Front. Vet. Sci., Vol. 11. 10.3389/fvets.2024.1468847 DOI: https://doi.org/10.3389/fvets.2024.1468847
96.
Ma, J., J. Wang, S. Mahfuz, S. Long, D. Wu and X. Piao et al, 2021. Supplementation of mixed organic acids improves growth performance, meat quality, gut morphology and volatile fatty acids of broiler chicken. Animals, Vol. 11. 10.3390/ani11113020 DOI: https://doi.org/10.3390/ani11113020
97.
Mustafa, A., S. Bai, Q. Zeng, X. Ding, J. Wang and K. Zhang et al, 2021. Effect of organic acids on growth performance, intestinal morphology, and immunity of broiler chickens with and without coccidial challenge. AMB Express, Vol. 11. 10.1186/s13568-021-01299-1 DOI: https://doi.org/10.1186/s13568-021-01299-1
98.
Zhen, W., Y. Shao, X. Gong, Y. Wu, Y. Geng and Y. Guo et al, 2018. Effect of dietary Bacillus coagulans supplementation on growth performance and immune responses of broiler chickens challenged by Salmonella enteritidis. Poult. Sci., 97: 2654-2666. DOI: https://doi.org/10.3382/ps/pey119
99.
Murugesan, G.R., B. Syed, S. Haldar and C. Pender, 2015. Phytogenic feed additives as an alternative to antibiotic growth promoters in broiler chickens. Front. Vet. Sci., Vol. 2. 10.3389/fvets.2015.00021 DOI: https://doi.org/10.3389/fvets.2015.00021
100.
Liu, S.J., J. Wang, T.F. He, H.S. Liu and X.S. Piao, 2021. Effects of natural capsicum extract on growth performance, nutrient utilization, antioxidant status, immune function, and meat quality in broilers. Poult. Sci., Vol. 100. 10.1016/j.psj.2021.101301 DOI: https://doi.org/10.1016/j.psj.2021.101301
101.
Wang, G., Q. Song, S. Huang, Y. Wang, S. Cai and J. Zhang et al, 2020. Effect of antimicrobial peptide microcin J25 on growth performance, immune regulation, and intestinal microbiota in broiler chickens challenged with Escherichia coli and Salmonella. Animals, Vol. 10. 10.3390/ani10020345 DOI: https://doi.org/10.3390/ani10020345
102.
Attia, Y.A., S. Basiouni, N.M. Abdulsalam, F. Bovera, A.A. Aboshok and H.M. Hafez et al, 2023. Alternative to antibiotic growth promoters: Beneficial effects of Saccharomyces cerevisiae and/or Lactobacillus acidophilus supplementation on the growth performance and sustainability of broilers’ production. Front. Vet. Sci., Vol. 10. 10.3389/fvets.2023.1259426 DOI: https://doi.org/10.3389/fvets.2023.1259426
103.
Khan, R.U., S. Naz, F. Raziq, Q. Qudratullah, N.A. Khan and M. Ragni et al, 2022. Prospects of organic acids as safe alternative to antibiotics in broiler chickens diet. Environ. Sci. Pollut. Res., 29: 32594-32604. DOI: https://doi.org/10.1007/s11356-022-19241-8