Insect-derived bioactives offer intriguing possibilities for combatting pathogens, promoting growth, and more

Over the last decade or so, the idea of insects as a source of protein for animal feed has taken off. There are many advantages, particularly in terms of sustainability; bugs can be fed on agri-food residues that would in many cases have gone to waste otherwise, and they can help supplement plant proteins or fishmeal which might not be considered environmentally friendly or nutritionally appropriate for all applications.

However, it is increasingly becoming clear that insectderived ingredients can be seen as more than simply a protein-rich biomass. Instead, as explained by Professor Laura Gasco of the Department of Agricultural, Forest, and Food Sciences at the University of Torino in a webinar organized by the FAO, researchers are beginning to look at different substances found within insects as tools which could reduce antimicrobial use on farms.

It is likely that we have barely scratched the surface of what could potentially be a vast reservoir of alternatives to antibiotics. After all, she points out, there are an estimated 1.5 to 3 million insect species — many of which have yet to even be named, let alone seriously studied.

Still, according to her, we already know of at least three categories of very interesting bioactive compounds within insects which might have antimicrobial, antioxidant, immune system stimulation, or microbiota modulation effects, or other types of positive impacts on an animal consuming them.

The first are antimicrobial peptides (AMPs): small cationic proteins that exhibit activity against bacteria, fungi, parasites, and even viruses. Beyond directly killing microbes, AMPs can also boost host-specific innate immune responses and exert selective immunomodulatory effects. Given the harsh environments in which many insects survive, Prof. Gasco recounted, they have very robust innate immune systems, in which AMPs play a role. Research going back several years has identified that AMPs can potentially be useful against a broad range of pathogens, including both gram-positive and gram-negative bacteria. Indeed, she pointed out, work has even begun on stimulating insects with a pathogen to make them express more of the desired AMP, in order to achieve effects comparable to that of an antibiotic when fed to the target production animal. However, despite the intriguing findings in trials, there is apparently no insect-based AMP which has been introduced to the animal nutrition market.

The second category of interesting bioactives which can be found in insects is chitin. Chitin is a structural polysaccharide with nitrogen which forms a major element in the exoskeleton of insects.

Some knowledge of the effects of feeding chitin already exists, as it is also found in fungi, algae, and certain sea animals like crustaceans. However, she points out, we must move with caution before assuming that insect chitin will have the same medicinal properties; after all, these effects might depend on the size, structure, and composition of the chitin, which can differ between organisms.

Still, chitosan extracted from the mealworm beetle (Tenebrio molitor) has demonstrated antibacterial activity against E. coli, Bacillus cereus, Listeria monocytogenes, and Streptococcus aureus Moreover, Prof. Gasco added in response to a question, there is evidence suggesting that specifically insect-based chitin may have advantages for animal production, based on a trial with diets including ingredients with their origins in crustacean processing, and ones which included discarded exoskeletons (exuviae) from insects. Beyond that, there is evidence from broilers of a probiotic effect from black soldier fly larvae, modulating the microbiome to promote microorganisms which are positive for the animal’s health and productivity.

The final category is one which the animal nutrition industry is broadly familiar with: fatty acids. Some of these, like lauric acid (which has strong antibiotic properties) might be found naturally in insect species like black soldier fly larvae. But beyond the fatty acids which are already present, it is apparently also possible to impact the fatty acid profile of the insects by feeding them on different substrates.

Of course, given that insect-based ingredients are in their infancy, there is much work to be done before their potential can be properly exploited. Indeed, in some of the literature investigating the benefits of feeding insects to animals, it is not necessarily clear whether the positive effects are due to AMPs, chitin, or fatty acids — and may © Vector Tradition / Shutterstock.com well be some combination of all of them. Still, for Dr. Gasco at least, it is clear that this will be a fruitful avenue to explore. She shared an experience of her first visit to an insect factory in China, where the broilers being fed on the larvae the site produced had reportedly seen a marked decrease in mortality. Now, with further investigation, it is becoming evident that insects are more than just an eco-friendly protein source; they can be a powerful tool to keep animals healthy and productive.

Dr. Laura Gasco presented on 9 March 2023 as part of the FAO’s knowledge dissemination dialogues on AMR.

By Shannon Behary, senior editor