Necrotic enteritis is one of the most common, and most financially devastating diseases affecting the global poultry industry. Impacting approximately 40% of commercial broiler flocks worldwide, this intestinal disease can cause mortality rates up to 50% during clinical outbreaks. It is estimated to cost the broiler industry between US$5 to 6 billion annually. Necrotic enteritis primarily affects broiler chickens aged 2 to 5 weeks raised on litter, as well as turkeys between 7 to 12 weeks old. While most noted in broilers, layers and turkeys are also susceptible. The disease typically persists for 5 to 10 days within affected flocks, leading to mortality rates ranging from 2% to 50%.
Although the clinical form is severe, the sub-clinical form often goes unnoticed, silently affecting bird performance and profitability. Sub-clinical infections reduce performance, often resulting in an estimated economic loss of $0.05 to $0.063 per bird, making it a silent but costly burden for producers. Beyond mortality, necrotic enteritis significantly impairs nutrient absorption, growth rates, feed conversion, and overall animal welfare.
Necrotic enteritis is caused by the overgrowth of Clostridium perfringens, a spore-forming Gram-positive bacterium, commonly found as part of the normal gut microbiota. These spores are highly resistant to environmental stressors like heat, disinfectants, and UV light, allowing the bacteria to persist in typical poultry environments.
While C. perfringens normally inhabits the intestines without causing harm, certain predisposing factors disrupt the gut environment, triggering bacterial overload and resulting toxin production. Triggers include intestinal parasites, immune suppression, dietary changes, and shifts in gut microflora due to antibiotics or vaccination.
The disease is primarily associated with toxins produced by C. perfringens type A, especially the alpha-toxin and a more recently discovered pore-forming NetB toxin, which damages intestinal cells - leading to the characteristic necrosis aka tissue death.
Necrotic enteritis physically affects birds by damaging their intestines, especially the middle and lower sections. The disease begins when harmful bacteria destroy the cells lining the gut, causing the tissue to die and the intestines to become swollen with gas, fragile, and filled with foul-smelling fluid. In some cases, a yellowish layer forms inside the gut that looks like a ‘Turkish towel’. Birds may show signs like diarrhea, dehydration, ruffled feathers, and reduced appetite, or they may die suddenly without clear warning. Microscopically, the disease begins with destruction of the intestinal lining cells and can progress to deeper tissue layers.
Several factors contribute to the onset and severity of necrotic enteritis:
Effective prevention and control strategies for necrotic enteritis focus on limiting the overgrowth of Clostridium perfringens by addressing the many factors that contribute to its proliferation. Targeted nutrition plays a critical role, as diets high in indigestible protein, fiber, or poorly balanced amino acids can create an ideal environment for harmful bacteria by increasing protein availability in the lower gut. Managing feed composition to improve digestibility and reduce gut irritation helps maintain intestinal health. Coccidiosis management is crucial, since intestinal damage caused by Eimeria parasites can leak plasma proteins into the gut, providing nutrients for C. perfringens. Designed for seamless integration into rotation or shuttle programs, AccuGut™ C.1 offers a cost-effective approach to Coccidiosis Management, allowing for uninterrupted productivity and increased profitability.
Figure 1. AccuGut™ C.1 reduced oocysts viability in vitro as measured by counting viable (fluorescent) and non-viable (non-flourescent) oocysts of Eimeria maxima.
Probiotic supplementation is also key, especially when applied early in a chick's life. By encouraging the growth of beneficial gut bacteria, probiotics support healthy digestive tract development and reduce the risk of colonization by pathogens. Better still, producers can power up their probiotic approach with Symphiome™ - a complex glycan mixture technically defined as a Precision Biotic. This microbiome metabolic modulator is designed to harness the power of the microbiome by modulating specific and highly conserved functional pathways - enhancing nutritional health and performance.
Additionally, dsm-firmenich’s PoultryStar® is a specially formulated probiotic blend designed to promote gut health and enhance the immune system in poultry. When introduced in the bird’s life, PoultryStar® helps establish a balanced intestinal microbiota, which is critical for preventing the overgrowth of harmful pathogens like C. perfringens. This probiotic not only supports digestion and nutrient absorption, but also strengthens the bird’s natural defenses, making it an effective, antibiotic-free solution to improve flock health and performance.
A recent US study on caged broilers vaccinated against coccidiosis and fed corn and soybean meal demonstrated a reduced mortality rate with Symphiome™. A second study showed increased resilience to enteric challenges, such as reduced frequency of lesions.
Table 1: Effect of Symphiome™ on Broilers under NE Challenge
Table 2: Symphiome™ reduce Necrotic Enteritis Lesion Score and FCR Points for Broilers Under Eimeria and C. perfringens Challenge
A study looked at the combination of PoultryStar® and Symphiome™ on broiler performance and health under necrotic enteritis challenge. 1,296 Cobb broiler chicks were individually inoculated with Eimeria maxima and Clostridium perfringens to induce disease. Results showed that the combination of Symphiome™ with PoultryStar® significantly reduced mortality rates, and improved feed conversion ratio from day 1 to 42 compared to Symphiome™ alone.
While Symphiome™ demonstrated benefits in mortality and feed efficiency, no significant improvements were observed in foot pad dermatitis scores across treatment groups.
Table 3: Dual study of effect of PoultryStar® and Symphiome™ on broiler performance under necrotic enteritis challenge
Strategies such as vaccination, a selected phytogenic additive as AccuGut™ C.1 and probiotic application like PoultryStar® and Symphiome™ to support microbiota and gastrointestinal development, or coccidiostats can help limit risk. Mycotoxin risk reduction involves controlling feed contamination from molds that damage gut integrity[KN1] , reduce immunity, and increase protein leakage, all of which fuel bacterial growth. Additionally, flock management practices such as controlling early growth rates, optimizing brooding temperatures, managing litter quality, and maintaining clean-ish (microbially balanced) environments can significantly reduce pathogen exposure.
Additional management tools such as Verax™ - our microbiome diagnostic platform - offers a powerful tool for poultry producers seeking to strengthen their necrotic enteritis prevention strategies. By providing deep, science-based insights into the gut health status of a flock, Verax™ helps producers monitor microbial balance, identify early signs of dysbiosis, and evaluate the impact of feed additives or management practices. This data-driven approach enables more precise decision-making.
15 July 2025
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