Just like humans, a healthy gut is critical for chickens, supporting digestion, nutrient absorption, and immunity. Disruptions in gut bacteria (dysbiosis) can lead to diseases affecting productivity and overall health. Thus, fostering a balanced gut microbiome is essential for poultry. Diet is a key factor shaping this microbiome. While antibiotic growth promoters (AGPs) were historically used for gut health, concerns about antibiotic resistance have prompted a search for alternatives. Consequently, research into nutritional strategies and new feed ingredients has increased. Insect-based diets, particularly those containing black soldier fly larvae (BSFL), show promise as feed additives for enhancing gastrointestinal function and gut health in poultry. The black soldier fly (Hermetia illucens L.) is notable for its ability to convert organic waste into valuable biomass, offering benefits in waste management, animal feed, and improved chicken gut health.
The Gut Microbiome: A Chicken's Inner World
Inside a chicken's gut lives a vast community of tiny organisms, mostly bacteria, collectively known as the gut microbiome. Think of the chicken's gut as a bustling city, with a diverse population of microbes (the citizens), a strong wall (the gut barrier), efficient transportation systems (nutrient absorption), and a dedicated defence force (the immune system). When this city functions harmoniously, the chicken thrives.
What is Gut Health?
Gut health in chickens refers to the optimal state of the gastrointestinal tract (GIT), characterized by a balanced and diverse microbial community, effective digestion and absorption of nutrients, a strong intestinal barrier function, and a well-regulated immune response. A healthy gut microbiome plays crucial roles in the fermentation of undigested feed components, production of essential vitamins, and energy from short-chain fatty acids (SCFAs), and protection against pathogenic bacteria through colonization resistance.
Why Gut Health Matters in Chickens
A healthy gut is essential for:
Optimal nutrient digestion and absorption (e.g., fibres, chitin).
Energy production from short-chain fatty acids (SCFAs, such as butyrate, acetate, propionate).
Better growth rates and feed conversion efficiency.
Strong immune defence (colonization resistance).
Reduced risk of infections (e.g., Salmonella, Escherichia coli (E. coli))
Black Soldier Fly Larvae (BSFL): A Superfood for Chickens
BSFL are increasingly used in poultry diets due to their:
High protein (40–50%) and fat (30–35%) content.
Balanced amino acid profile
Healthy fats (including lauric acid, known for antimicrobial properties)
Prebiotic fibre (chitin) that supports beneficial gut bacteria
How BSFL Improves Chicken Gut Health
So, how do black soldier fly larvae fit into this picture? It turns out that feeding chickens BSFL can actually change the makeup of their gut microbiome in positive ways. BSFL contain antimicrobial and immunomodulatory compounds like chitin, lauric acid, and antimicrobial peptides. These antimicrobial peptides can kill both Gram-positive and Gram-negative bacteria. Antimicrobial peptides in BSFL have shown greater power against Gram-negative bacteria (e.g., Campylobacter spp. such as Escherichia coli, Salmonella enteritidis) if the BSFL are reared on high protein diets and greater power against Gram-positive bacteria (e.g., Clostridium perfringens, which is responsible for necrotic enteritis in chickens) if reared on high chitin or cellulose diets.
BSFL Boosts Beneficial Gut Bacteria
BSFL can directly modify the chicken's gut microbiota via a substance called chitin, a polysaccharide that makes up a large part of the BSFL's outer shell (exoskeleton). Chickens can't easily digest chitin on their own, but certain beneficial bacteria in their gut can. When chickens eat BSFL, the undigested chitin acts as a special food for these beneficial bacteria (e.g., SCFA producers like Faecalibacterium, Roseburia, Butyricicoccus, Bacteroides; immune regulators like Ruminococcus torques, Oscillospiraceae; pathogen inhibitors like Parabacteroides, Lactobacillus, Bifidobacterium), which produce ''chitinase'' – an enzyme that can break down chitin. This process helps the beneficial bacteria to grow and multiply, creating a prebiotic effect by feeding the good bugs already living in the gut.
When these beneficial bacteria munch on chitin, they produce helpful substances called short-chain fatty acids (SCFAs). These SCFAs, such as butyrate, acetate, and propionate, are like superheroes for the gut. Butyrate, in particular, has been shown to have anti-inflammatory. They can help block the growth of harmful bacteria (e.g., Clostridium perfringens, E. coli, Salmonella), provide energy for the cells lining the gut, and even strengthen the gut lining and reduce the risk of leaky gut.
BSFL Fat Enhances Immune Function
Besides chitin, the fat in BSFL also plays a role in gut health. BSFL fat is rich in medium-chain fatty acids (MCFAs), particularly lauric acid. Lauric acid is known for its antimicrobial and anti-inflammatory properties, meaning it can help to kill or inhibit the growth of bad bacteria and reduce gut inflammation. This reduction in inflammation means less energy is wasted on immune responses and more is directed toward growth. Therefore, by reducing the number of harmful microbes, lauric acid can help create a more favourable environment for beneficial bacteria to thrive, thereby improving disease resistance.
Improves Digestive Efficiency
The enzymes in BSFL help break down feed more effectively, leading to better nutrient absorption. The protein component of BSFL may also play a role in modulating the gut microbiota by providing different substrates for microbial fermentation compared to traditional protein sources like soybean meal. The specific amino acid composition and digestibility of BSFL protein could influence the types of metabolites produced by the gut bacteria.
Reduces Dependency on Antibiotics
With growing concerns over antibiotic resistance, BSFL offer a natural alternative to promote gut health without drugs. The antimicrobial properties of BSFL can help control harmful bacteria naturally. The physical form of BSFL (meal vs. live larvae) might also impact the gut microbiota, with live larvae potentially acting as a mechanical vehicle for introducing beneficial bacteria into the poultry gut. Overall, the modulation of gut microbiota by BSFL is a complex process involving the interplay of chitin, fatty acids, proteins, and possibly the introduction of novel bacteria, all contributing to a healthier gut ecosystem in chickens.
Research Evidence
Several studies support the benefits of BSFL for chicken gut health. In broiler chickens, BSFL inclusion (27-30%) generally improved phosphorus digestibility and retention (Matin et al., 2021). A study by Mazlan et al. (2024) found that heat-stressed broilers fed BSFL meal at 0%, 5%, and 10% of the diet for 35 days exhibited reduced pathogenic bacteria (E. coli, Clostridium spp.) and increased beneficial Lactobacillus spp., indicating BSFL's potential as a functional feed during stress conditions.
For laying hens, partially defatted BSFL meal at 9% and 18% inclusion levels (8 weeks) enhanced intestinal morphology by increasing villus height and crypt depth (Khan et al., 2024), which may improve nutrient absorption and overall productivity. Additionally, BSFL altered gut microbiota composition, increasing beneficial bacteria such as Ruminococcus and Bacteroidales while reducing Prevotellaceae (Khan et al., 2024). These bacteria are often linked to better immune regulation and the production of SCFAs. Similarly, hydrolyzed BSFL meal partially replacing soybean meal at 1%, 3%, or 5% for 56 days improved duodenal and jejunal structure in Xuefeng black-bone chickens (Liu et al., 2022), reinforcing its role in gut health optimization. However, excessive inclusion (e.g., 18% BSFL meal) sometimes led to reduced benefits (Khan et al., 2024), suggesting a need for balanced dietary formulations.
Potential Challenges
Cost & Availability: While sustainable, BSFL production must scale up to meet demand.
Regulations: Some regions have strict guidelines on insect-based feeds.
Conclusion
Black soldier fly larvae are more than just a protein source, they're a gut health powerhouse for chickens. By enhancing microbiome balance, boosting immunity, and improving digestion. Supplementation of chicken diets with BSFL can lead to healthier, more productive flocks while reducing reliance on antibiotics. As we continue to learn more about these fascinating insects and their interactions with the chicken gut, they could become a key player in creating healthier chickens, more sustainable farming practices, and safer food for everyone.
References
Khan, S., et al. (2024). Black soldier fly larvae meal and oil in laying hen diets: Effects on performance, egg quality, serum profile, intestinal structure, and gut microbiota. Poultry Science, 103(10), 104460. https://doi.org/10.1016/j.psj.2024.104460
Liu, S., Luo, H., Wang, M., Wang, Q., Duan, L., Han, Q., Sun, S., Wei, C., & Jin, J. (2022). Microbiome analysis reveals the effects of black soldier fly oil on gut microbiota in pigeon. Frontiers in microbiology, 13, 998524. https://doi.org/10.3389/fmicb.2022.998524
Matin, N., Utterback, P. L., & Parsons, C. M. (2021). Phosphorus digestibility and relative phosphorus bioavailability in two dried black soldier fly larvae meals and a defatted black soldier fly larvae meal in broiler chickens. Poultry science, 100(8), 101221. https://doi.org/10.1016/j.psj.2021.101221
Mazlan, N. A. F., Miswan, N. A., Ahmad, S., Hassim, H. A., Jamien, E. S., Wei Ee, H., ... & Idrus, Z. (2024). Black soldier fly (Hermetia illucens) larvae meal for heat-stressed broiler chicken: its effects on gut health, stress biomarkers, and growth performance. Italian Journal of Animal Science, 23(1), 1391-1402. https://doi.org/10.1080/1828051X.2024.2401444