Research summary - Farmed yellow mealworm welfare (Rethink Priorities)
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As of 2020, around 300 billion yellow mealworms (Tenebrio molitor) are farmed annually (though recent estimates now put this figure at over 3 trillion individuals (Pells, 2023)).
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Barrett et al. 2023 is the first publication to consider species-specific welfare concerns for farmed mealworms.
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The authors identify 15 current and future welfare concerns, including more pressing current concerns such as:
- Disease — Bacterial, fungal, protist, and viral pathogens can cause sluggishness, tissue damage, slowed growth, increased susceptibility to other diseases, and even mass-mortality events.
- High larval rearing densities — Density can cause a range of negative effects, including increased cannibalism and disease, higher chances of heat-related death, competition over food leading to malnutrition, and behavioral restriction near pupation.
- Inadequate larval nutrition — This may result from not providing enough protein in the animals' largely grains-based diet.
- Light use during handling — Photophobic adults and larvae may experience significant stress due to light use during handling.
- Slaughter methods — While we have high empirical uncertainty about the relative harms of slaughter methods, it is clear that some approaches to slaughter and depopulation on farms are more harmful than others.
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Future concerns that haven't yet been realized on farms include:
- Novel, potentially toxic, or inadequate feed substrates — Polymers (like plastics) and mycotoxin-contaminated grains may be more likely to be used in the future.
- Selective breeding and genetic modification — In vertebrate animals, selective breeding has caused a large number of welfare issues. The same might be expected to become true for mealworms.