Fillers at the end of processing improve instantaneous death via grinding for farmed yellow mealworm larvae (Tenebrio molitor; Coleoptera: Tenebrionidae)

Three hundred billion or more yellow mealworms (Tenebrio molitor; Coleoptera: Tenebrionidae) are reared each year as food and feed. Instantaneous, and thus likely humane, death may be achieved for farmed insect larvae through the use of grinding/shredding. However, due to differences in morphology and neurophysiology, species-specific guidance is needed to create standard operating procedures that ensure a high likelihood of instantaneous death for each insect species; no such data has been collected for yellow mealworms. Further, prior studies recommend – but have not tested – the use of a filler to improve the likelihood of instantaneous death for the last larvae to exit the machine. Data are needed to demonstrate if this recommendation actually improves the likelihood of instantaneous death. In this study, we test how larval body size, particle size plate hole diameter (2.55 v. 5.5 mm), and the use of filler at the end of a run all affected the likelihood of instantaneous death for yellow mealworm larvae that are slaughtered using a standard meat grinder. Our results suggest that very few yellow mealworm larvae will die instantly when receiving a single cut to any particular body segment. The overall likelihood of dying instantly varied based on the interaction between plate size and the use of filler. In the best case, a 96.47 ± 1.19% likelihood of instant death could be produced with a 2.55 mm plate and the use of filler; both the larger plate size and the lack of a filler reduced the overall likelihood of instant death (73.27 ± 3.66% for the 5.5 mm plate without filler). We conclude with a protocol for producers that wish to test their own machinery (as different machine designs may cause variance from our results) and with recommendations to support producers in more humane slaughter practices using this method.