Safety and transfer of veterinary drugs from substrate to black soldier fly larvae.

There is an increasing interest in edible insects in Europe for feed and food purposes. Quantitative information on the transfer of chemical hazards from substrates to larvae is needed to evaluate food and feed safety aspects. This evaluation is especially needed when organic substrates or residual streams such as manure will be applied as substrate, contributing to a circular food system. This study investigated the transfer of veterinary drugs from spiked substrate to black soldier fly larvae (Hermetia illucens). Veterinary drugs that are commonly administered to chicken, fattening pigs, and cattle and regularly detected in manure were included: three different antibiotics (enrofloxacin, oxytetracycline, sulfamethoxazole), three coccidiostats (narasin, salinomycin, toltrazuril) and one antiparasitic drug (eprinomectin). The chemicals were spiked to insect substrate to reach final concentrations of 0.5 and 5 mg/kg for the antibiotics and the antiparasitic drug, and 5 and 50 mg/kg for the coccidiostats. Black soldier fly larvae were reared for 1 week on the spiked substrates, and the transfer of the veterinary drugs to the larvae and frass was quantified using liquid chromatography coupled with tandem mass spectrometry. Only oxytetracycline and eprinomectin reduced the average weight and/or survival of the black soldier fly larvae. The transfer of the veterinary drugs to the larvae was on average 19.2% for oxytetracycline, 12% for enrofloxacin, 9.5% for narasin, 8.1% for eprinomectin, 3.9% for salinomycin, 4.2% for toltrazuril, and 0.2% for sulfamethoxazole, relative to concentrations in the substrate. Mass-balance calculations revealed that the larvae seem to metabolise veterinary drugs, and indeed, metabolites of enrofloxacin, sulfamethoxazole, and toltrazuril were detected in the larvae and frass. In conclusion, insect-rearing substrates should be evaluated for the presence of veterinary drug residues to ensure feed (and food) safety, as well as because of possible effects on insect growth.

A ring shear device to simulate cryosphere processes.

We have developed a new cryogenic ring shear device at the University of Wisconsin-Madison to simulate cryosphere processes, with an emphasis on the physics of glacier slip. The device spins a ring of ice (inner diameter of 20 cm, outer diameter of 60 cm, height of ∼20-30 cm) at the pressure melting point over a rotationally fixed bed. The ice ring is spun at a prescribed velocity (range of ∼0.01-1000 m a-1) while the resistance to slip is measured. A ram at the base of the device applies a vertical load to the sample chamber to simulate the overburden pressure (range ∼5-915 kPa) felt at a glacier's base. The sample chamber is constructed with transparent acrylic walls, allowing subglacial processes to be observed directly by a series of cameras. The entire device is housed in a large walk-in freezer. In the freezer, the sample chamber is submerged in a tub of temperature-controlled fluid that precisely regulates heat flux into the sample chamber, replicating in situ conditions and allowing for prolonged experiments that last weeks to months. This device can be used to study several of the most unconstrained physical processes that regulate glacier movement and, in doing so, greatly improve predictions of glacier contributions to sea-level rise.