Insect-based protein – living up to expectations?

As the world is facing pressing issues including climate change, global human population growth, and the limited availability of agricultural land, the search for more sustainable proteins continues unabated. Insects are such a source that could partly replace conventional ones.

Insects were recognized as a source of alternative protein – for humans, farm animals and for pets – almost a decade ago. Insects are a natural part of a carnivorous diet for both wolves and feral cats. However, the inclusion rate of insect biomass in the diet of such animals is reported to be negligible: contributing to merely 0.5-1% of the diet.

A question of taste?

For dogs and cats, palatability of insect meal seems to be a limiting factor for using this alternative source of protein. Although many companies offer pet food products with relatively high inclusion rates of insect meal, there is a lack of scientific data providing possible insights into whether different types of insects are tastier, healthier or easier to digest for pets in the final product.

The data that is available – for instance, that based on research conducted by Professor Anton Beynen in 2018 – suggests that dogs tend to prefer dry food containing black soldier fly larvae (BSFL) meal, over those containing yellow mealworm meal.

Different preferences

A study from the University of Berlin research group (Passlack & Zentek, 2018) illustrates that cats and dogs can have different preferences when it comes to various insect species. It also mentions that higher inclusion rates may cause lower feed intake or food refusal. It is, therefore, essential to bear this in mind when formulating feed products.

According to this research also, for dogs, accepted inclusion rates are 10% for BSFL meal and 24% for banded crickets. For cats, the inclusion rate is up to 5% BSFL. Additionally, dogs show good acceptance of dry foods containing 20% BSFL meal while, interestingly, at a similar inclusion rate (22%), cats reduced their food intake.

The sustainable and nutrient-efficient alternative?

Insect farming is more sustainable as it requires less space and resources in terms of water or feed. Insects are known to have lower conversion rates than any other species, which makes them efficient at a level that is not comparable to any other higher species.

It has been found that the amino acid profile from insect meal is readily available when fed to farm animal species. But at the same time, this profile can be variable and depends on insect species and their life stage.

For instance, BSFL meal has lower amino acid digestibility for sulfur-containing amino acids, methionine and cystine. These amino acids are limiting for cats and dogs. Since BSFL is one of the most used insect meals in pet food, pet food manufacturers should be careful to balance out the amino acid profile in the final product.

Also, threonine and leucine which are found in certain insect species are reported as being limiting amino acids for cats and dogs.

What about digestibility?

Results from available scientific literature report variable protein digestibility rates: depending on the species consuming the insect-based food product, as well as the life stage and species of insects used.

Dogs appear to have high in vitro digestibility rates, ranging from 76.4 to 93.3% for house crickets, yellow mealworms, BSFL and BSFL pupae. This is based on research conducted by the Dutch Wageningen University research group (Bosch et al., 2016). Reported values are higher than in vivo, where apparent fecal-N digestibility of foods containing BSFL in dogs ranged from 73.2 to 87.2%. Values were affected by inclusion rate and processing, where higher inclusion rates decreased digestibility.

Digestibility was highest at a 30% crude protein level coming from dried BSFL meal, as reported by Dr. Ryan Yamka in 2019. This implies that in vivo digestibility trials should be the golden standard, seeing as processing, drying methods and mineral content in the exoskeleton can have a negative impact on digestibility.

Fat and functional

The fat content of insects varies between 10 and 70% on a dry matter basis and, similarly to other nutrients in insects, seems to be dependent on the insect species, its life stage, diet, and microclimate conditions of rearing.

It has been noted that commercially reared insects have a higher fat content. In case of a diet fed to insects that is rich in omega-6 fatty acids, their fatty acid profile can be such, that these high levels in turn lead to decreased levels of linolenic acid.

Interestingly, BSFL has an unusual fatty acid profile rich in lauric acid, irrespective of the diet. Lauric acid has antibacterial, antiviral and anti-fungal properties that could potentially act as a nutraceutical. Additionally, if insects’ diets are enriched with omega-3 fatty acids, insects would serve as the enriched product themselves. This poses an interesting approach to the development of functional foods for pets.

Variable content

Similarly, the mineral and vitamin content of insects seems to be quite variable and widely influenced by their diet. Diet poses a great resource for final product enrichment. At the same time, it is a risk factor: diets need to be reformulated if the insect mineral composition is different in another batch, coming from another supplier where rearing conditions are different.

Generally, insects contain low levels of calcium. However, thanks to their mineralized exoskeleton which contains high levels of calcium and other minerals, BSFL stand out from other insect species, providing a well-balanced Ca to P ratio. A proportional relation exists in BSFL between calcium and phosphorus, in the form of phosphate in-body fluids and bone.

Fiber

One more important nutrient in insects is fiber. Such fiber is markedly different from that originating from plants. The components in insect fiber fractions include sclerotized proteins and proteins, minerals, and other nutrients that are bound to chitin to make a firm exoskeleton for insect protection.

The cuticle properties vary between insect species, depending on the required functionalities for the insect. Current research suggests that the undigested fraction of insects does not significantly affect the intestinal microbiome and acts more like insoluble fiber, such as cellulose. But additional research should provide more information on insect fiber and its properties.

Allergy trigger or hypoallergenic?

Another interesting fact about insect-based food for dogs and cats is that it is often marketed as being ‘hypoallergenic’. However, so far, no studies have been published evaluating the effectiveness of insect-based hypoallergenic food in dogs or cats, where food allergy has been confirmed.

In fact, research has shown that insects can also be a trigger for food allergies. 

Such an allergy related to the consumption of insects may be caused by a primary sensitization or a cross- reaction with another allergen.

In a study by the University of Ljubljana (Bajuk et al., 2021), results imply that dogs allergic to mites may also show cross-reactivity with mealworm proteins. For this reason, in some cases, it could be inadvisable to use yellow mealworm larvae as an alternative protein source.

Other hazards associated with the contamination of insects can be the result of flawed processing procedures related to anthropogenic factors during breeding, packaging, cooking or feeding. Contaminants include the presence of bacteria, mold fungi, mycotoxins and heavy metals, among others. Importantly also, as an undesirable consequence of insects’ readily incorporating nutrients from their diet into their body composition, we must be aware of heavy metal accumulation such as copper, cadmium and lead.

Quality control is key

All-in-all, well-established quality control is paramount where insect meal and insect byproducts are concerned. They should undergo sufficient safety and efficacy testing.

It’s why, although numerous pet food companies are including insects as an exciting new addition to their pet food product portfolio, some are still waiting for a stronger body of scientific evidence before making the decision in the insect’s direction.

As with everything in pet nutrition, things are not all good or all bad. The middle road covers most uses. And that is certainly the case with insects: they offer many benefits, with many variables and come with some serious limitations.

To include insects successfully in a pet diet, we must identify all limitations and enhance the positive aspects of this exciting protein source. The good news is that the Animal Nutrition Group at Wageningen University has markedly improved our knowledge of insects in pet nutrition – and new research groups are joining in to address insect and insect-based pet food topics.