Poultry plays a significant role in generating income and providing livelihood to millions of farmers in India. As per 20
th Livestock Census, poultry population in India was 851.81 million (
BAHS, 2019). In India, the meat production from poultry was 4.995 million tonnes and egg production were 138.38 billion during year 2022-23 (
BAHS, 2023). Poultry meat and eggs are important sources of nutrients, contributing significantly to human nutrition. The uses of in-feed antibiotics in chickens are aimed at improving production performance, controlling enteric diseases and reducing the production cost
(Eid et al., 2020). However, the use of antibiotics as growth promoters have been associated with antibiotic residues in animal products leading to bacterial resistance to these drugs, posing a global health challenge
(Anee et al., 2021). Now days, there is increasing health awareness, consumers are demanding high-quality, safe and nutritious food products. In light of this, several alternatives have been studied recently to replace antibiotic growth promoters in chickens to improve growth performance, product quality and health
(Gosai et al., 2023; Qiu et al., 2023). Bacteriophage as a newer feed additive in chickens has been investigated as an alternative to replace antibiotic growth promoters
(Shaufi et al., 2024).
Bacteriophages have been studied as a viable alternative to antibiotic growth promoters. This review discusses the biological mechanisms, applications and advantages of bacteriophages in poultry farming.
This review was prepared through a systematic evaluation of published literature retrieved from Google Scholar, Scopus, ScienceDirect and Web of Science. Keywords including bacteriophage, phage therapy, poultry, broiler, layer, feed additive and antibiotic alternative were used. Studies published between 2010 and 2024 focusing on poultry performance, gut health, immunity, pathogen reduction and food safety were included.
Bacteriophages: Biology and mechanism of action
Bacteriophages are bacteria-infecting viruses which multiply in a specific bacterial host. They are ubiquitous and classified into two categories: virulent and temperate. Discovered independently by
Frederick Twort (1915) and
Felix d’Herelle (1917), with an estimated global population of 10
31 particles (
Kazi and Annapure, 2016). They are naturally present in water, soil, plants and even the human gut microbiome.
Phages are categorized into two main types based on their life cycles:
1. Lytic (Virulent) Phages: These infect bacteria, replicate inside and subsequently lyse the bacterial cell to release new phages (
Loc-Carrillo and Abedon,2011).
2. Lysogenic (Temperate) Phages: These integrate their DNA into the host bacterial genome, remaining dormant until triggered to enter the lytic cycle
(Shaufi et al., 2024).
Lytic phages, due to their ability to destroy bacterial cells, are considered for therapeutic use in livestock production.
Application of bacteriophages in poultry production
Bacteriophages are being explored as a novel feed additive in poultry to address various challenges such as bacterial infections and food contamination. Their main applications are categorized into the following:
Phage therapy in poultry disease management
Phage therapy utilizes bacteriophages to target and eliminate bacterial pathogens like
Campylobacter jejuni,
Salmonella enterica and
Escherichia coli, which are of zoonotic concern
(Wernicki et al., 2017). Lytic phages, with their specific host-targeting abilities, offer an advantage over antibiotics, which indiscriminately kill both harmful and beneficial bacteria
(Abedon et al., 2017).
In a european food safety authority (EFSA) report, campylobacteriosis, salmonellosis and shiga toxin-producing
E.
coli infections were the most common zoonotic diseases linked to poultry (
EFSA, 2019). Bacteriophage therapy has shown efficacy in reducing these bacterial pathogens in poultry, mitigating risks to public health
(Dlamini et al., 2023).
Phages have been used experimentally to control diseases such as necrotic enteritis, salmonellosis and colibacillosis. Targeted phage therapy can lower pathogen loads in the gastrointestinal tract, reduce mortality and minimize economic losses due to infectious outbreaks
(Sarrami et al., 2022).
Bacteriophage as a feed additive
Recent studies demonstrate that bacteriophages can be administered as a feed additive to improve growth performance, modulate gut microbiota and reduce pathogen loads in poultry
(Shaufi et al., 2023; Huff et al., 2002). For example,
Upadhaya et al., (2021) found that bacteriophage supplementation enhanced broiler weight gain and positively impacted the gut microbiome, particularly increasing the relative abundance of
Lactobacillus.
Food biocontrol and decontamination
Bacteriophages are used as bio-preservatives to reduce bacterial contamination in meat products. Commercial products like ListShield™ and Listex™ have been developed to target
Listeria monocytogenes in ready-to-eat foods
(Bigot et al., 2018). Phage-based treatments can decontaminate poultry carcasses without affecting the organoleptic properties of the food. Phages also serve as disinfectants in hatcheries and transport systems, reducing surface contamination and biofilm formation
(Atterbury et al., 2003). Commercial phage-based sprays have shown efficacy in reducing surface contamination without altering the product’s quality or appearance
(Garcia et al., 2008).
Advantages of bacteriophages over antibiotics
Phages offer several advantages over traditional antibiotics:
•
High specificity: Phages target specific bacterial strains without disturbing the host’s beneficial microbiota
(Wernicki et al., 2017).
•
Reduced resistance development: Phage cocktails can be designed to minimize the risk of bacterial resistance
(Allen et al., 2013).
•
Safety and tolerability: Bacteriophages do not replicate in animal cells, ensuring minimal toxicity or side effects
(Pirnay et al., 2011).
•
Self-replicating: Amplifies at the site of infection,sustaining its activity naturally
(Upadhaya et al., 2021).
•
Low risk of dysbiosis: Unlike antibiotics, does not disrupt gut microbial balance
(Shaufi et al., 2024; Huff et al., 2010; Waseh et al., 2010).
•
Minimal environmental impact: No chemical residues; does not contribute to environmental pollution (
Kazi and Annapure, 2016).
•
Versatile applications: Used in feed, water, sprays and as surface sanitizers
(Dlamini et al., 2023).
Challenges and Limitations
Despite their potential, several challenges limit the widespread adoption of bacteriophages in poultry production:
•
Bacterial Resistance: Bacteria may develop resistance to specific phages, although this can be mitigated by using phage cocktails.
•
Stability and Storage: Phage viability may be compromised under extreme storage conditions, requiring careful formulation and preservation
(Burrowes et al., 2011).
•
Regulatory Hurdles: The use of bacteriophages in food production is subject to stringent regulatory approval processes, which vary across regions
(Garcia et al., 2008).
•
Immune neutralization: Host immune system may inactivate phages before they act (
Kazi and Annapure, 2016).
•
Risk of horizontal gene transfer: Lysogenic phages can potentially spread antimicrobial resistance genes (ARGs)
(Pirnay et al., 2011).
Further research is needed to determine optimal dosing strategies, administration methods and long-term impacts of bacteriophage use in poultry.
Recent research findings
Several recent studies provide promising insights into the use of bacteriophages in poultry farming:
•
Upadhaya et al., (2021) reported that supplementation of a bacteriophage cocktail (0.05%) significantly improved body weight gain and feed conversion ratio in broiler chickens, with performance comparable to antibiotic growth promoters. The same study also observed increased populations of beneficial Lactobacillus species in the gut.
•
Shaufi et al., (2024) found that broilers fed diets supple- mented with phage cocktails exhibited improved growth performance and enhanced gut microbial diversity. Further research by
Shaufi et al., (2024) demonstrated synergistic effects when bacteriophages were combined with probiotics, resulting in better feed efficiency and intestinal health.
•
Dlamini et al., (2023) evaluated encapsulated Salmonella- specific bacteriophages and observed a significant reduction in intestinal Salmonella counts, along with improved intestinal histomorphology and meat quality traits, although growth responses varied with dosage.
•
Sarrami et al., (2022) reported enhanced immune response markers and modulation of gut health-related gene expression in broilers receiving bacteriophage supple-mentation.
• Phage-based interventions have also shown effectiveness in reducing
Campylobacter jejuni and
Escherichia coli colonization in poultry, thereby lowering zoonotic risk and improving food safety
(Wernicki et al., 2017; Atterbury et al., 2003;
Clavijo et al., 2018).
• These findings suggest that bacteriophage therapy can effectively substitute for antibiotics as a growth promoter in poultry, offering an eco-friendly and safe alternative.
Future prospects
Despite encouraging results, phage therapy in poultry remains an emerging field. Research is ongoing to:
• Optimize phage dose, frequency and administration methods.
• Develop stable, commercial-grade phage formulations.
• Combine phages with other feed additives (
e.
g., probiotics, prebiotics, enzymes) for synergistic benefits (
Asrore et al., 2023).
• Study long-term effects on antibiotic resistance genes and microbiome composition
(Shaufi et al., 2024).
