Rethinking Poultry Health: Non-Antibiotic Strategies to Combat Necrotic Enteritis

Necrotic enteritis (NE), predominantly caused by Clostridium perfringens, is one of the most economically damaging bacterial diseases in the poultry industry. Traditionally, this disease has been managed through the prophylactic use of antibiotic growth promoters (AGPs) in feed. 

However, rising concerns over antimicrobial resistance and drug residues in meat have prompted a global shift towards antibiotic-free poultry production. With Europe banning AGPs and other countries considering similar measures, finding effective, non-antibiotic alternatives has become urgent and essential.

Understanding Necrotic Enteritis

NE manifests in two forms:

• Clinical NE: Characterized by wet litter, chicken diarrhea, and undigested feed, it can result in mortality rates of up to 30%.
• Subclinical NE: Often goes undetected but leads to decreased weight gain and feed efficiency, causing significant economic losses.

The major culprit, C. perfringens type A, is a naturally occurring gut bacterium that turns pathogenic under certain conditions. Risk factors include:

• Coccidial infections (especially Eimeria spp.)
• High-protein, non-starch polysaccharide-rich diets (e.g., wheat, rye, barley)
• Immunosuppressive diseases
• Stress and environmental challenges

Table 2 Key Virulence Factors of Clostridium perfringens and Their Roles

The Limitations of Antibiotic Approaches

The routine use of antibiotics has led to:

• Development of resistant microbial strains
• Residual drug traces in meat products
• Regulatory pushbacks and consumer resistance

As AGPs are phased out, NE has re-emerged strongly, underlining the need for sustainable, non-antibiotic alternatives.

Non-Antibiotic Strategies for NE Control

1. Vaccination

While vaccines are a logical alternative, NE pathogenesis remains partially understood, limiting vaccine effectiveness. Key takeaways:

• Alpha-toxin was once considered a prime target, but alpha-toxin-deficient strains still induce NE.
• NetB toxin shows potential, but not all NetB-positive strains cause disease, nor do NetB-negative strains guarantee safety.
• Crude supernatants and recombinant vaccines show partial success but require further refinement and field validation.

2. Coccidiosis Control

Since coccidiosis predisposes birds to NE, controlling Eimeria spp. is essential. Alternatives include:

• Live and attenuated vaccines
• Probiotics like Pediococcus and Saccharomyces
• Botanicals such as Artemisia, Aloe, and Curcuma longa

However, cost, regional strain variability, and vaccine-associated reactions can limit effectiveness.

3. Probiotics

Probiotics help maintain the poultry gut health by:

• Competing with pathogens
• Enhancing immune function
• Lowering gut pH via organic acids

Species such as Bacillus subtilis, Lactobacillus spp., and Bifidobacterium spp. show promising results in reducing C. perfringens counts and improving bird performance.

4. Competitive Exclusion Products (CEPs)

CEPs involve administering gut flora from healthy birds to neonates, establishing protective microbial communities early. Though undefined, these mixtures are effective against a broad spectrum of enteric pathogens, including C. perfringens.

5. Prebiotics

Prebiotics are non-digestible feed ingredients that support beneficial microbes. Examples:

• Fructo-oligosaccharides (FOS)
• Mannan-oligosaccharides (MOS)
• Inulin

They enhance butyrate production, lower gut pH, and reduce pathogen binding. Prebiotics perform best when combined with probiotics for a synbiotic effect.

6. Egg Yolk Immunoglobulins (IgYs)

IgYs are antibodies extracted from egg yolks of hyperimmunised hens. Though results are mixed, recent studies show IgYs can protect against C. perfringens, E. coli, and Salmonella spp. They offer passive immunity but require further optimization for field application.

7. Bacteriophages

Phage therapy uses viruses that infect and lyse bacteria. Phages specific to C. perfringens (e.g., CP25L, ɸ3626) show targeted activity. Delivery through genetically engineered Lactobacillus strains or phage cocktails like INT-401 is being explored. However, specificity, stability, and regulatory issues remain challenges.

8. Organic Acids

Acids such as butyric, propionic, and formic acids reduce gut pH and bacterial load. While they can suppress C. perfringens, their broad-spectrum activity may also reduce beneficial flora and have limited effect on lesion reduction or mortality.

9. Feed Enzymes

Enzymes like NSP’ases and phytase break down non-starch polysaccharides and phytates, improving nutrient absorption and reducing substrate for bacterial fermentation. This leads to improved performance and less risk of NE.

10. Botanicals and Essential Oils

Botanicals like thyme, cinnamon, Artemisia annua, and essential oils (e.g., thymol, carvacrol) offer antimicrobial, antioxidant, and immunomodulatory benefits. However, efficacy varies due to:

• Source plant species
• Extraction methods
• Environmental conditions

11. Nutritional Modifications

Diet composition directly impacts NE incidence:

• Animal proteins like fish meal increase NE risk
• Soy-based proteins and vegetable oils are safer
• Whole grains (e.g., whole wheat) reduce gut pH and pathogen load
• Pelleting and grinding methods enhance digestibility and feed hygiene

Conclusion

The phasing out of AGPs in poultry production necessitates an integrated approach to disease control. While vaccines hold promise, they are not yet fully effective. Among all alternatives, probiotics, egg yolk-derived IgYs, and nutritional management (e.g., feed form and composition) offer reliable, cost-effective, and sustainable solutions against necrotic enteritis.

Effective control of NE will ultimately rely on:

• Improved understanding of disease pathogenesis
• Judicious integration of multiple non-antibiotic strategies
• Enhanced biosecurity and husbandry practices

By fostering these innovations, the poultry industry can ensure productivity, animal welfare, and food safety in a post-antibiotic era.

References
Mahmood, K., Rahman, S.U., Hussain, I., Abbas, R.Z., Khaliq, T., Arif, J., & Mahmood, F. (2014). Non-antibiotic strategies for the control of necrotic enteritis in poultry. World’s Poultry Science Journal, 70(4), 865–880. doi:10.1017/S0043933914000919