Insects in cat nutrition raise questions about digestibility

Research from the University of Illinois Urbana- Champaign has been published in the Journal of Animal Science, the official publication of the American Society of Animal Science. Its conclusion: healthy adult cats showed a slight preference for wet diets containing black soldier fly meal, ground whole black soldier fly larvae, or black soldier fly oil – compared to a control diet of poultry by-products.

The black soldier fly ingredients did, however, inhibit the cat food’s digestibility. This was “still what we would call adequate,” according to professor of animal nutrition Kelly Swanson. “No one had loose stools or anything like that, but it was lower digestibility.”

Black soldier fly
While cat owners may not notice the difference, the findings do have potential implications for the inclusion of insect-based ingredients in cat food products, highlights Swanson. The study made use of black soldier fly at relatively high inclusion rates – 10% for the defatted black soldier fly meal and 5% for the ground whole black soldier fly, which still included the fat component. A third experimental diet used 1.5% black soldier fly oil. The team chose to limit the oil’s inclusion, based on previous research implying the oil could trigger issues with palatability.

Unexpected outcome
That was ultimately the surprise of the study. The team anticipated that cats might reject the insect-based diets, but had assumed that so long as they ate the food, the insects would have a favorable – perhaps even superior – nutritional profile. “We thought they would be well digested, that was the main thing, and nothing would be a negative.” 

Chitin, Swanson suspects, is likely to blame for the unexpected result. Despite this, the professor believes black soldier fly is a safe and potentially useful ingredient for cat foods, and may yet come with some potential nutritional benefits. The ingredient still contains an interesting lipid profile, and it could have anti-inflammatory, antioxidant and antibacterial properties. But future cat diets might have to limit the inclusion of black soldier fly ingredients in order to maintain digestibility.

From wet to dry?
Other solutions, such as considering the form and technical properties of the food product, may also be worthwhile, according to researchers. Although the Illinois study added black soldier fly to wet diets, professor Swanson believes the nature of insect meal could be best suited to a dry kibble instead.