Safety considerations before using black soldier fly larvae as animal feed

Black soldier fly (Hermetia illucens). Photo by Beatriz Moisset from Wikimedia Commons.

Insects are seen as an alternative feed source for livestock and poultry because of their high protein content. Among the thousands of insect species, the black soldier fly (Hermetia illucens) is the most widely used, with its larvae used as feed for chickens, pigs, and fish.

The black soldier fly larvae (BSFL) is used as a protein supplement due to its nutrient profile — 42% protein and 35% fat, with its protein quality being identical to soybean protein.

Black soldier flies live most of their life as a larva for 18 days, before turning into a pupa for 14 days, and then into their adult form for only nine days. They reproduce in their last stage, producing eggs that need four days before hatching into larvae, thus repeating the cycle.

The Department of Agriculture has launched initiatives regarding the use of BSFL. The Agricultural Training Institute partnered with Kahariam Farms of Lipa, Batangas in 2020 to establish the use of BSFL as feed for pigs in the country. The Region 2 office of ATI also developed a brochure to guide farmers on the use of BSFL.

Continuing on this, the Bureau of Agriculture and Fisheries Standards (BAFS) published a technical report on July 14, 2022, to discuss the safety issues and recommend best practices surrounding the cultivation of BSFL.

Hazards in cultivating BSFL

Black soldier flies are known for their ability to convert various organic materials into nutrients. Their gut enzymes allow them to feed on kitchen waste, manure, and fecal sludge. The hazards relating to the cultivation of BSFL are therefore not the fly, but rather the rearing substrate in which they are fed and grown.  

Different compounds like pesticides, toxic metals, and mycotoxins may aggregate on the substrate. Studies have shown that BSFL accumulates heavy metals such as cadmium, copper, lead, and mercury from their feed. These elements are all known to affect human health when consumed excessively. Though the accumulated metals did not exceed regulatory limits set out by national authorities like the European Commission, consistent monitoring should be conducted to prevent possible issues.

It is worth noting, however, that the BSFL do not accumulate pesticides and toxins due to the natural detoxification process of their guts. 

Possible adverse health effects to humans due to the accumulation of these substances can be inferred as minimal, based on the literature reviewed by BAFS. The agency did not, however, find a specific study concluding this, thus they recommended further research on this aspect.

Another hazard to consider is the cross-reactive allergens found in BSFL, such as tropomyosin, arginine kinase, and myosin. Though these allergens don’t trigger allergic reactions, they increase the likelihood of such reactions among consumers allergic to other animal species containing the same allergens. A documented example of this is tropomyosin being cross-reactive in mites and shrimp, and arginine kinase being cross-reactive in prawns and silkworms.

BFAS recommendations for the cultivation of BSFL

In terms of recommendations, BFAS acknowledged that there are no international standards for the utilization of insects as feed. The only recommendations they could give were those that have been issued by the Food and Agriculture Organization (FAO). 

The recommendations cover a wide range of activities involved in insect cultivation. In collecting the BSF strain to cultivate, farmers should use local species so that the insects would not need to acclimate to their new surroundings. A criterion should also be developed to determine the ease of rearing, taste, and color of a BSF strain.

In feeding BSFL, farmers should use organic wastes that have passed safety checks for chemical and microbiological hazards. Farmers should also ensure that the accumulation of different organic and inorganic compounds in rearing substrates of BSFL is kept at a minimum.

FAO also recommends pre-processing the BSFL through blanching to reduce microbial load, drying them to increase their shelf life, and storing them in temperatures between 0-4°C.

Other recommendations include developing a code of practices, formal training for workers, defining workplace terminologies, and planning a marketing strategy.

The information provided here was taken from a technical bulletin issued by BAFS on July 14, 2022.

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