Low transfer of cadmium, lead and aflatoxin B1 to eggs and meat of laying hens receiving diets with black soldier fly larvae reared on contaminated substrates

Summary

Replacing soybeans with insects in egg and poultry meat production could improve environmental sustainability. Black soldier fly larvae (BSFL) have a favorable nutrient composition and can be reared on low-grade waste, but this is associated with the risk of feed and food contamination. The aim of this study was to assess the transfer of selected contaminants from larval substrates to poultry-derived food. Two different control substrates were used. Substrate CCH (produced in Switzerland) was based on side streams approved for insect rearing in the European Union (EU), while substrate CIND (produced in Indonesia) included non-EU approved waste. In addition, substrate CIND was spiked with either heavy metals (HM; 1.9 mg cadmium and 18.8 mg lead/kg dry matter (DM)) or 1.5 mg aflatoxin B1/kg DM (AF)). The larvae fed HM contained 7 mg cadmium and 16 mg lead/kg DM. These values were about 30 times the concentrations of cadmium and 30–60 times the concentrations of lead found on average in the BSFL reared with the two non-spiked substrates. Although substrate AF contained 842 μg aflatoxin B1/kg DM as analysed, the AF larvae contained only 4 μg aflatoxin B1/kg DM. Larval meals were integrated at 200 g/kg in two control diets (diets CCH and CIND) and two diets based on contaminated BSFL (diets HM and AF) designed for late-laying hens (n = 9/treatment). After feeding these diets for 4 weeks, the hens were slaughtered. Diet HM and AF did not affect laying performance or egg quality compared with the control diets. In the body tissue, the cadmium concentrations (per kg DM) were nearly doubled by diet HM in the breast meat (13.3 μg), kidneys (12.3 mg) and liver (1.86 mg) compared to diet CIND. The same diet increased lead in kidneys from below 0.1 to 0.5 mg/kg DM. No lead was detected in the meat and eggs, and no cadmium was found in the eggs. In conclusion, despite cadmium and lead also occurring in BSFL meals of CCH and CIND, the levels in all corresponding hen-based feed and food materials were below the maximum content, except for the kidneys. The aflatoxin B1 level of diet AF (1 μg/kg DM) suggests that the risk might also be small when BSFL are reared on moldy substrate containing aflatoxin-producing fungi. In conclusion, postconsumer waste apparently poses a lower risk than expected in poultry food chains for these contaminants when used as larval substrate.