Publication Alert: When is grinding an instantaneous slaughter method for farmed black soldier fly larvae?
Grinding as a slaughter method for farmed black soldier fly (Hermetia illucens) larvae: Empirically-supported recommendations for more instantaneous and humane practice (Barrett et al. 2024; Animal Welfare)
Acknowledgement of Funding and Conflicts of Interest: MB and BF report a relationship with the Insect Welfare Research Society that includes: board of advisors (unpaid). CP reports a relationship with the Insect Welfare Research Society that includes: employment. JKT reports a relationship with EVO Conversion Systems, LLC. Regarding funding, MB was an NSF postdoctoral research fellow (2109399) at the time this work was conducted. CP was supported by the Insect Welfare Research Society. JKT and CF appreciate financial support from the Texas A & M AgriLife Research State Air Quality Initiative (SAQI). JKT and CM used resources from the Texas A&M AgriLife Institute for Advancing Health Through Agriculture.
Barrett collaborated with the Tomberlin lab (at Texas A & M) to produce empirically-supported recommendations for improving the welfare of black soldier fly larvae (BSFL) at time of slaughter when using grinding as a methodology. The insects as food and feed industry already rears at least 290 billion BSFL each year; rearing of this species in particular is predicted to grow substantially in the coming decades, necessitating urgent research into humane or instantaneous slaughter standard operating procedures. Developing humane slaughter methods for this species is important for the welfare of the animals and the industry’s social license to operate.
“Humane slaughter may be defined as “when an animal is either killed instantly or rendered insensible until death ensues, without pain, suffering or distress”...standard operating procedures (SOPs) are needed to define what practices achieve humane death using each method while remaining practical and economical.
We set out to test if grinding can result in instantaneous (< 1 s), and thus humane, death for BSFL...From these data, we develop a set of practical recommendations for producers on how to generate grinding SOPs with the greatest likelihood of instantaneous death ...[and] we provide a protocol for producers interested in testing their own machinery and SOPs for BSFL at four different body sizes.”
We find that larval body size did not affect the likelihood of instantaneous death for larvae that are 106–175 mg in mass (typical slaughter weights for BSFL). However, particle size plate hole diameter in the meat grinder design we used had a significant effect on the likelihood of instantaneous death. Only 54% of larvae experiencing an instant death when using the largest particle size plate (12-mm hole diameter) compared to 84% using the smallest particle size plate (2.55 mm).
Further, we found that a higher percentage of instantaneous death (up to 99%) could be achieved by reducing the proportion of larvae that become stuck in the machine at the blade at the end of a ‘run’ (as a result of a lack of force from larvae loaded after them, to push them through the particle size plate). By running a filler through at the end of each batch, producers can make sure all larvae are pushed through the particle size plate, increasing the likelihood of instant death for all larvae in a run.
We conclude by outlining specific recommendations to support producers in achieving a 99% instantaneous death rate through specific SOPs to be used with similarly designed machines. And, we link to supplemental materials designed to help producers assess and modify their own SOPs to maximize the proportion of larvae humanely slaughtered using this method.
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