Exploring the chemical safety of fly larvae as a source of protein for animal feed

There is an urgent need to increase the supply of sustainable protein for use in animal feed and the use of insect protein provides a potential alternative to protein crops and fishmeal. For example, fly larvae are highly compatible with use in animal feed containing much digestible protein with levels of key amino acids that are comparable with those found in high value alternatives such as soybean. However, the safety of protein from insects and subsequently the meat and fish from animals fed on such a diet requires further assessment. Here we present safety data from the larvae of the four fly species that have perhaps the greatest economic relevance in relation to their use as animal feed being: house fly (Musca domestica), blue bottle (Calliphora vomitoria), blow fly (Chrysomya spp.) and black soldier fly (Hermetia illucens). Diverse rearing methods were used to produce larvae fed on a range of waste substrates and in four geographically dispersed locations being; UK, China, Mali and Ghana. Chemical safety data were collected by a fully accredited laboratory in the UK. The levels of the main subclasses of chemical contaminants considered for animal feed were determined, being; veterinary medicines, pesticides, heavy metals, dioxins and polychlorinated biphenyls, polyaromatic hydrocarbons and mycotoxins. The larvae analysed generally possessed levels of chemical contaminants which were below recommended maximum concentrations suggested by bodies such as the European Commission, the World Health Organisation and Codex. However, the toxic heavy metal cadmium was found to be of concern in three of the M. domestica samples analysed.