Circular feed needs pathway-specific BSE risk control

Circular protein systems need risk assessments that distinguish individual exposure pathways. A new Wageningen University & Research study examines whether insects reared on residual streams containing animal proteins could reintroduce a BSE risk into livestock production. Such substrates are currently not permitted for insect rearing in the EU precisely because of that concern.

The model assessed yellow mealworms and black soldier fly larvae reared on former supermarket food, household kitchen scraps or category 2 meat meal. It considered cross-contamination of ruminant feed, fertilisation of pasture with pig or poultry manure or frass, and calf milk replacer. Because data on prion carry-over are limited, the researchers deliberately applied conservative assumptions, including no prion inactivation during insect rearing.

Even under these assumptions, calculated exposures were very low. The highest overall median exposure occurred for mealworms reared on kitchen scraps; the linked probability of at least one new BSE infection remained far below one case per 100,000 BSE-infected cattle escaping detection at slaughter. That result is not an automatic clearance for use: the study does not replace process validation or animal-by-product rules.

Its practical value lies elsewhere. The debate on insects and by-product valorisation should not be reduced to a blanket verdict of “safe” or “unsafe”. It must distinguish input material, insect species, destination of the biomass and conceivable pathways back to ruminants. For the meat sector, the study underlines that circularity becomes credible only where stream segregation, traceability and exposure scenarios are specified and verifiable.