An Assessment of the Safety of BSF Larvae Reared on Different Substrates for Use in Animal Feeds – Chemical Contaminants

The use of black soldier fly (BSF) larvae as a protein source for animal feed is gaining popularity. However, the safety of the larvae and the substrates used for rearing them has not been fully investigated, which is important for economic feasibility. This study aimed to evaluate the safety of BSF larvae and rearing substrates in Kenya by analysing chemical contaminants. To achieve this, the BSF larvae were reared on common production substrates, namely kitchen waste, fruit waste, and brewer's waste, in a Completely Randomised Design (CRD). Chemical contaminants such as cadmium, chromium, thallium, and lead were analysed using atomic absorption spectrometry (AAS). The data obtained were statistically analysed using the R statistical package version 4.0.5 and compared with recommended levels by KEBS, Codex Alimentarius, and the European Union (EU) standards. The study found that the larvae had lower levels of chemical contaminants (0.005±0.001 mg.kg-1 to 0.028±0.006 mg.kg-1) compared to the substrates used (0.008±0.0006 mg.kg-1 to 0.102±0.002 mg.kg-1). The average concentration of lead in BSFL was 0.0192±0.014 mg.kg-1 and 0.0391±0.037 for chromium. Cadmium was the only metal that showed an increase in concentration in the larvae reared on brewery waste (0.028±0.006) compared to larvae on other substrates. Based on the results, the study recommended the use of safe substrates such as kitchen and fruit waste for BSFL rearing.