Research summary: farmed cricket welfare

By abrahamrowe @ 2024-03-06T22:10 (+112)

This post is a short summary of Farmed Cricket (Acheta domesticus, Gryllus assimilis, and Gryllodes sigillatus; Orthoptera) Welfare Considerations: Recommendations for Improving Global Practice, a peer-reviewed, open access publication on cricket welfare in the Journal of Insects as Food and Feed under a CC BY 4.0 license. The paper and supplemental information can be accessed here. The original paper was written by Elizabeth Rowe, Karen Robles López, Kristin Robinson, Kaitlin Baudier, and Meghan Barrett; the research conducted in the paper was funded by Rethink Priorities as part of our research agenda on understanding the welfare of insects on farms. 

This post was written by Abraham Rowe (no relation to Elizabeth Rowe) and reviewed for accuracy by Meghan Barrett. All information is derived from the Elizabeth Rowe et al. (2024) publication, and some text from the original publication is directly adapted for this summary.

Summary

• As of 2020, around 370 to 420 billion crickets and grasshoppers were farmed annually for food and feed, though today the number may be much higher.
• Rowe et al. (2024) is the first publication to consider species-specific welfare concerns for several species of crickets on industrialized insect farms.
• The authors identify 15 current and 5 future welfare concerns, and make recommendations for reducing the harms from these concerns. These concerns include:
  • Stocking density
    • High stocking densities can increase the rates of aggression, cannibalism, and behavioral repression among individuals on cricket farms.
  • Disease
    • Diseases are relatively common on cricket farms. Common diseases, such as Acheta domesticus densovirus, can cause up to 100% cricket mortality.
  • Slaughter
    • Common slaughter methods for crickets on farms include freezing in air, blanching/boiling, and convection baking. Little is known about the relative welfare costs of these methods, and the best ways for a producer to implement a given method.
• Future concerns that haven’t yet been realized on farms include:
  • Novel feed substrates
    • Farmers have explored potentially giving crickets novel feeds, including food waste. This might be nutritionally inadequate or introduce diseases or other issues onto farms.
  • 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 crickets.

Background information

Cricket farming

Insect farming, including of crickets, has been presented as a more sustainable approach to meet the protein demand of a growing human population. While wild-caught orthopterans (crickets and grasshoppers) are a traditional protein source around the world, modern cricket farming aims to industrialize the rearing and slaughter of crickets as a food source. As of 2020, 370–420 billion orthopterans were slaughtered or sold live, with crickets being the most common.

Welfare framework

The Five Domains model of welfare, which has been promoted for invertebrates, evaluates animal welfare by looking at the nutrition, environment, physical health, behavior, and mental states of the animals being evaluated. The authors use this model for evaluating cricket farming and potential improvements that could be made on farms for animal welfare.

Cricket biology

Three of the most common species of crickets farmed belong to the Gryllinae subfamily: Acheta domesticus, Gryllus assimilis, and Gryllodes sigillatus. All three species live between 80 and 120 days from hatching to natural death, with a 10-21 day incubation period. Crickets are hemimetabolous insects: they hatch from an egg, molting through a series of nymph stages called instars, before going through a terminal molt (where they gain wings and functional genitalia) and entering the adult stage. Thus they do not go through a ‘complete metamorphosis’ (e.g., pupation) or have a larval stage, like the other insects commonly farmed for food (such as black soldier flies or yellow mealworm beetles, which are holometabolous insects).

Crickets have multiple broods of offspring per year. In captivity, a population might cycle through 6-7 generations per year.

A female cricket will lay 500-3100 eggs in her lifespan, depending on her species. She may have multiple mating partners throughout her life.

Wild cricket diets are not well understood, but crickets are believed to be omnivores who primarily eat plants, fungi, and scavenge on dead insects.

Current practices

While cricket farming has been widespread since the mid-20th century in the West, industrial-size cricket farms have only appeared in the last decade. Individual farms can rear billions of crickets per year.

Industrialized cricket farming is typically done in completely closed environments (though in Thailand, where semi-rural, small-scale farming is common, semi-open facilities may be used).

On industrialized cricket farms, female crickets lay eggs into a moist substrate to incubate. Often, farms are designed so that newly hatched nymphs crawl out of this substrate to a container, where they can be transferred to a separate space for rearing.

Nymphs are typically reared in stackable closed containers. These are closed to allow for precise climate control and to prevent escape. Often, this approach is more labor intensive (compared to having a large open rearing space), but reduces pathogen spread, since groups of crickets are separated from each other. A single rearing unit might have thousands to millions of crickets, depending on the design.

Within the containers, crickets are generally given material to climb (increasing the surface area and thus storage capacity for the space), often made out of cardboard. Water and feed are provided within the container.

The light within farms is typically artificial. No reports exist of a standardized light cycle that is widely used, though alternating light and dark periods of 12 hours each are often recommended by industry guidelines.

When around 85% of the population has reached adulthood, crickets are removed from their containers for slaughter. In smaller-scale factories, this might mean shaking the cardboard matrices from containers by hand into a collection container, or using light to herd live crickets into a collection container. In larger-scale farms, the cardboard might be fed into a machine, where crickets are removed via suction or brushes, then collected.

A population is generally reared separately to adulthood from those slaughtered for food and feed for reproduction, though on some farms, eggs are supplied by a separate farm or company. Adult females tend to be slaughtered after two weeks of egg production, as female crickets lay fewer eggs over time, despite living 1-3 months as adults (dependent on species, sex, and conditions).

Many crickets are sold or transported to markets live, either for human consumption or exotic pet feed (such as for lizards). If sold live, they are typically packaged in cardboard boxes or plastic bags filled with sawdust or a cardboard packing material. Live transport may be experienced by the minority of all crickets reared globally, but often results in high mortality.

Most crickets processed for food and feed are slaughtered prior to transport. They may be fasted for 24-48 hours to clear their digestive systems and decrease microbial load (though it is unclear if or when this practice is effective).

Crickets are typically slaughtered via boiling, immersion in pressurized steam, immersion in hot, non-boiling water, drowning, freezing in air, heating in dry air, shredding, or asphyxiation. Freezing in air is likely the primary slaughter method for mass-produced crickets, and anesthetics are typically not used though some producers may apply carbon dioxide prior to freezing.

Welfare concerns and recommendations

Note that this report is broadly covering three species of crickets (A. domesticus, G. sigillatus, and G. assimilis). Not all concerns will apply equally to all species, and recommendations shouldn’t be taken as applying to all species. Check the original report to determine when recommendations are species-specific.

Further, the authors list several caveats they recommend readers bear in mind when reviewing these recommendations:

1. Studies referenced in their paper looked at issues at laboratory scales, not industrial scales, so not all findings may replicate on farms.
2. Specific populations on farms might have evolved different welfare-relevant characteristics, just due to their specific genetic makeup.
3. The authors often assume that higher production outcomes are an indicator of better welfare, as they can indicate that crickets are surviving at higher rates, growing faster, or mating more frequently. However, production outcomes and welfare should not necessarily be considered one and the same in all cases — for example faster growing chicken breeds might have worse welfare than slower growing chickens, despite high productive outcomes. More data are needed to better understand the relationships between production outcomes and welfare in crickets, and insects broadly.
4. Many welfare concerns interact, so addressing a single issue might not address the underlying concern fully.
5. Species identification for some of these crickets can be difficult; therefore, it is possible the literature may not accurately reflect which species of crickets were actually studied.

Concern 1: Accidental or intentional dietary restriction

Some farms may not provide adequate nutrition, either via the amount/accessibility of feed or the composition of the feed. Economic incentives might push farms to try to minimize the amount of feed provided, given that feed cost is a large portion of farm expenses. Feed might accidentally be provided in forms inedible to juveniles (due to particle sizes being too large). These nutritional restrictions decrease the fitness of adults, slow growth, increase juvenile mortality, and may increase cannibalistic behavior.

Recommendations

1. Provide adequate quantities of feed during juvenile rearing. Avoid fasting, and limit fasting necessary for human safety to 24 hours.
2. Feed should be ground to a 20 mesh particle size (0.0331 inches) for juveniles, especially at early instars.

Concern 2: Inappropriate macronutrient or micronutrient provisioning

Minimal information is available on the natural diet of crickets and, due to economic factors, diets may be highly variable across farms. Grains such as wheat, corn meal, soybean meal, oats, and others are often used. Even less information is available on micronutrients. Homogenous diets might be unable to meet the nutritional requirements of crickets, and are unlikely to mimic their natural diets as scavenging omnivores.

Recommendations

1. Provide minimally 20%, and preferably 30-35% protein, in cricket diets
2. Supplement cricket diets with more varied materials to increase nutrient self-selection opportunities.
3. Supplement vitamin B-12 in crickets that are not fed animal products. Consider supplementing phosphorus, vitamin C, sterol, and manganese for all crickets.

Concern 3: High stocking densities

Crickets tend to aggregate even when they could spread out. But, in many species, high-density natural populations are self-limiting and not persistent across generations, as density causes an increase in the number of individuals who develop larger wings in order to leave the population. When dispersal is not possible, such as in captivity, high densities may lead to higher mortality via restricting access to water or other resources, and via behavioral changes such as increased cannibalism.

Recommendations

1. Rear A. domesticus at densities near 0.09 crickets/cm², and never above 0.4 crickets/cm². Rear G. assimilis at  0.37 ml crickets/L space.

Concern 4: Long-winged individuals in closed facilities

Density and temperature can impact cricket morphology. For instance, it is possible that cricket species with long-winged morphs may retain these wings to be able to escape from crowded environments (which has been observed in natural settings). On farms, long-winged individuals in crowded conditions are unable to disperse (since they are trapped in a closed environment), limiting this natural behavior.

Recommendations

1. Monitor density and temperature to avoid the production of long-winged individuals when rearing A. domesticus and G. sigillatus.
2. Provide opportunities for flight in G. assimilis.

Concern 5: Aggression, injury, and cannibalism

Fighting is common but may cause negative welfare states in crickets. In the wild, crickets fight over mating partners, food, and shelter. Fighting can lead to physical injuries and is energetically costly. In farming conditions, there is some evidence that fighting and aggression rates may sometimes be higher. Additionally, cannibalism seems to be an issue on some farms, though with current evidence it is unclear if this is occurring before or after the death of the crickets.

Recommendations

1. Reduce fasting periods to a maximum length of 24 hours and provide adequate food and water.
2. Maintain stocking densities recommended under concern 3 to avoid self-thinning behavior such as aggression.
3. Remove live individuals being cannibalized or who are severely injured from farms and humanely euthanize them.

Concern 6: Mortality and welfare issues caused by disease and parasites

Both lethal and non-lethal disease, viral, and parasitism issues are present on cricket farms. The most widely studied is A. domesticus densovirus (AdDNV), which has caused millions of dollars of losses on farms in Europe and North America. The virus spreads via fecal-oral transmission or cannibalism, and can cause up to 100% mortality in some cricket species. As it can survive on external surfaces for months, eliminating it from a farm is very difficult. The virus typically paralyzes crickets, making them unable to move or eat for several days before dying from sepsis. AdDNV also causes lower welfare in surviving crickets via worse nutritional status and poorer health. Not all cricket species are equally affected by AdDNV: A. domesticus is much more susceptible than G. assimilis or sigillatus. Other viruses have also been found on industrialized farms with lethal and sublethal effects.

Some other bacterial, fungal, pathogenic, or parasitic organisms have been found to infect crickets, often leading to a broad range of negative health outcomes or higher mortality.

Recommendations

1. Follow best practice guidelines for hygiene, including disease monitoring and management protocols.
2. Keep humidity low (depending on the species) and refresh damp substrates every 24 hours to minimize the development and spread of pathogens.
3. Keep stocking densities low to prevent and reduce the spread of diseases, especially those that spread via cannibalism.
4. When disease cannot be treated, isolate and humanely euthanize sick crickets, disposing of them using biosafety protocols.

Concern 7: Slaughter and depopulation

Insects are not protected by legislation requiring humane slaughter, as is present in some countries for vertebrate livestock. Little research or guidance on humaneness exists for producers when choosing to implement different slaughter methods. Anesthesia is not commonly used during slaughter, and while some producers consider cold or carbon dioxide to serve this purpose, there is no guidance on the appropriate utilization or efficacy of these procedures. No pre-slaughter electrical stunning procedures currently exist for insects.

Recommendations

1. Develop standard operating procedures (SOPs) for slaughter and depopulation that are instantaneous.
2. Avoid freezing in air for slaughter or anesthesia, and especially prior to heating.
3. For methods that are not instantaneous, implement stunning or anesthesia protocols prior to slaughter, such as electrical stunning.

Concern 8: Lack of climate control in semi-open facilities, or inappropriate climate control in closed facilities

Cricket body temperatures are directly influenced by environmental temperatures, which in turn impact everything from the insects’ metabolism to water loss. Too high temperatures increase mortality and limit maximum adult size, suggesting a negative welfare impact. 

Additionally, too high humidity, or significant and regular variance in temperature/humidity, may negatively impact welfare. Wild population sizes are negatively correlated with relative humidity, which may mean that high-humidity environments might be worse for cricket welfare. Limiting fluctuation in temperature may also be less stressful than a high variance environment.

Recommendations

1. Rear crickets in closed, climate controlled facilities wherever natural temperatures exceed recommended rearing temperatures, and keep temperatures close to the recommended temperatures (see Table 3 in the original publication).
2. Limit temperature fluctuations over time, but provide temperature gradients within a rearing space between 27 and 33 °C for adult male G. assimilis.
3. Relative humidity should be kept high enough that crickets do not cluster around water sources, but not higher than the limits suggested under recommendation 6b.

Concern 9: Inappropriate climate control during live transport

Both extreme high and low temperatures can cause acute and long-term harms to crickets, including risking coma or death. During live transport, there is a heightened risk of extreme high or low temperatures, since shipping vehicles might not have climate control.

Recommendations

1. Producers should use cooling or heating packs to manage temperature during live transit, though these packs should not come into contact with insects.
2. Ship crickets at temperatures slightly below the recommended rearing temperatures.

Concern 10: Poor ventilation leading to hypoxia or CO₂ accumulation

Farmed crickets produce carbon dioxide, ammonia, methane, and nitrous oxide via excretion or their metabolic processes. If rearing containers are not properly ventilated, these gasses can accumulate and cause hypoxia in crickets, reducing growth rates and increasing mortality, especially in juveniles. Additionally, higher levels of carbon dioxide specifically can cause desiccation in crickets — directly increasing mortality.

Recommendations

1. Continuously monitor gas flow and oxygen and carbon dioxide levels in rearing containers.
2. Use breathable covers instead of closed lids to improve ventilation in small containers, and active ventilation in large containers.

Concern 11: Stress associated with the use of light and handling during rearing

Crickets have stress/fear responses to certain types of stimuli. Handling can be perceived by crickets as a predation threat, and directly increases octopamine levels  (octopamine is a stress hormone found in many insects). Insects are often handled during rearing, especially when being moved between rearing containers, and prior to slaughter. Additionally, overhead shadows (e.g., of a human moving) might be perceived as a predation threat.

 On farms, light is sometimes used to induce a fear response to control cricket motion during maintenance or harvest.

Recommendations

1. Avoid the use of a fear response (caused by targeted direct light) for controlling cricket motion, or provide shelters nearby for crickets when using light for control.
2. Reduce the frequency and duration of handling events.

Concern 12: Inappropriate light cycling or light types in closed facilities

Crickets have varied circadian rhythms (more research is needed), depending on the species. Closed production facilities set their own light/dark cycles through artificial light, which may disrupt these circadian rhythms. Disrupting the circadian rhythm can impact welfare by leading to abnormal behavior and higher rates of disease. 

Crickets, like many insects, are red-blind. This means red lights may be used to provide a safe working environment for humans that must enter cricket rearing areas during dark parts of the cycle.

Recommendations

1. Avoid permanent light. Use light cycles that promote the specific cricket species’ natural circadian rhythm.
2. If lights must be turned on during dark parts of the cycle, use red lights (assuming it doesn’t interfere with worker safety).
3. Provide at least 4 hours of UVB light exposure when using artificial lights for rearing.

Concern 13: Stress associated with vibrations during transport

Vibrations cause crickets to engage in anti-predator behaviors, and octopamine levels increase in crickets subjected to vibrations. While providing hiding places mitigates these effects, repeated vibrations increased baseline stress responses, similar to the effects of chronic stress on vertebrates. Within the industry, producers report that live shipping frequently leads to death, even when care is taken to pack crickets well, sometimes called “shipping sickness”. Some producers go as far as to pack extra crickets to account for this effect.

Recommendations

1. Minimize frequency and duration of vibrations through changes in transport method or packing materials.

Concern 14: Exposure to dead crickets

Some cricket species demonstrate a strong reaction to the bodies or chemical cues of death in their environment, avoiding areas treated with chemicals produced by dead cricket bodies. Similarly to vertebrates, this avoidance may be a fear response, resulting in worse welfare.

Recommendations

1. Frequently monitor for and remove dead crickets.

Concern 15: Lack of appropriate enrichment

Enrichment on farms may improve insect welfare (based on behavioral and neurobiological changes that result from some enrichments), through better enabling the crickets to meet basic biological needs and reducing behavioral restrictions. Crickets in particular may benefit from the ability to climb vertical spaces, having resting and hiding spaces hidden from light, and diet variety and choice (though more research on the welfare impacts of enrichment for insects of any species is needed).

Recommendations

1. Provide vertical space within rearing containers for climbing.
2. Provide resting places that protect crickets from light.
3. Consider providing novel sensory enrichments, especially dietary choice.

Future welfare concerns and recommendations

Industrialized cricket farming is novel. Similar to changes seen in vertebrate farming, the nature of farms may change over the coming decades. The authors also reflected on potential welfare concerns that haven’t been realized yet, but might arise on farms in the future.

Future Concern 1: Novel waste feeds containing pathogens or contaminants, or those that are nutritionally inadequate.

Given that feed costs are a major portion of the costs of rearing crickets, new feeds are always being explored for farms. New feeds might introduce new types of contaminants or pathogens, leading directly to higher mortality. In particular, diets of food waste pose many contamination risks for cricket farms, but are pursued by farmers due to their potential sustainability benefits. Further, new feeds should always be assessed for adequate nutrient profiles.

Recommendations

1. Avoiding feeding crickets waste streams that contain compounds known to be detrimental to their health or welfare, and test new feed types for safety.
2. Pre-process new feeds to reduce disease and pollutants, such as through freezing or heating.
3. When using new feed types, test nutritional composition and digestibility; especially consider using animal preference data.

Future Concern 2: Selection events or genetic modification that result in behavioral restriction or poor physical health

No reports indicate that selective breeding specifically targeting desirable characteristics is widespread in insect farming, however this practice will likely become more common in the future. Gene editing and selective breeding are beginning to be explored for farmed insects, so we may see an increase in novel lines of farmed crickets, specifically crickets with faster growth, larger body sizes, or who are able to lay more eggs.

Recommendations

1. Avoid artificial selection efforts with small breeding populations, to avoid genetic drift and impacts from inbreeding.
2. Test novel strains and modifications for negative welfare impacts across the entire cricket lifecycle.
3. Monitor novel strains for accidental selection of traits that might negatively impact welfare, such as increased aggression.

Future Concern 3: Novel diseases on farms

As cricket farming becomes more common, new diseases might arise on farms (particularly for the more novel farmed species, such as G. assimilis and G. sigillatus).

Recommendations

1. Proactively manage and monitor all species for disease.
2. Avoid moving crickets between facilities to prevent the spread of new diseases.

Future Concern 4: New species of orthopterans potentially being farmed

There are already many species of orthopterans farmed beyond the three species covered in the paper. Other species becoming farmed at a large scale might lead to unique welfare challenges, requiring different standards on farms to protect those insects.

Recommendations

1. When considering farming a new species of orthopteran, collaborate early with researchers to understand the best conditions for their welfare.

Future Concern 5: Highly automated facilities introducing aversive electrical fields or shocks

Most insects tend to avoid electrical fields, and proximity to electrical fields can increase stress hormones in insects that find electricity aversive. While this is not studied in crickets, automated facilities might accidentally introduce electrical fields and shocks into rearing containers.

Recommendations

1. Reduce electrical equipment’s proximity to live crickets, and reduce the use of equipment that could produce shocks unintentionally.

Directions for future research

Ultimately, the research that can be cited in the paper is relatively limited. Many of the welfare concerns raised are understudied at the time of publication, and there are major research gaps in several areas, including the following:

• The impact of dietary restriction on welfare
• Climate conditions throughout cricket lifecycles
• Stocking density on farms
• Preventing disease spread on farms
• Best practices for minimizing the harms of slaughter methods
• The viability of anesthesia and stunning protocols prior to slaughter
• Preventing or better understanding causes of cannibalism on farms
• The welfare impacts of gas levels, ammonia, and ventilation on farms
• Welfare impacts of restricting the natural behavior of long-winged crickets
• The cause and prevention of shipping sickness
• Cricket dietary preferences and composition
• The effect of non-lethal insecticide concentrations in cricket feed
• The impact of fasting periods prior to slaughter on welfare
• The viability of acoustic monitoring for farmed cricket welfare
• The impact of reduced water access on welfare, and methods for increasing water access while avoiding drownings
• The impact of feed contaminants from novel feeds on welfare
• The viability of antibiotic use on crickets, and their welfare impacts
• How future accidental or artificial selection might impact welfare
• How dominance hierarchies in some cricket species play out in farm conditions
• The frequency and causes of physical injury on farms
• The viability of vitamin and micronutrient supplementation for farmed crickets
• Determining the critical thermal maxima and minima for farmed species of crickets across developmental species to inform slaughter practices
• Determining stress associated with egg-laying substrates used on farms
• Positive behavior indicators in farmed crickets (existing documentation of indicators focus on negative behaviors)
• Possible enrichments for cricket farms, and their impact on welfare
• Exploring how diet impacts behaviors associated with positive welfare during mating
• How disturbance-associated stress could be reduced on farms
• How natural light, artificial light, and UVB impacts farmed crickets.

Acknowledgements

This research is a project of Rethink Priorities. This post was written by Abraham Rowe, summarizing work by Elizabeth Rowe (no relation), Karen Robles López, Kristin Robinson, Kaitlin Baudier, and Meghan Barrett. Thanks to Meghan Barrett for helpful feedback and Adam Papineau for copy editing. If you like our work, please consider subscribing to our newsletter. You can explore our completed public work here.

References

Rowe, E., K.Y. Robles López, K.M. Robinson, K.M. Baudier, and M. Barrett. "Farmed cricket (Acheta domesticus, Gryllus assimilis, and Gryllodes sigillatus; Orthoptera) welfare considerations: recommendations for improving global practice". Journal of Insects as Food and Feed (published online ahead of print 2024). https://doi.org/10.1163/23524588-00001087 Web.