Summary

• Broiler welfare and cage-free reforms change the amount of feed needed to produce a given quantity of chicken meat or eggs. So they affect feed production, and therefore result in land use change. The density and welfare conditions of wild animals vary by type of land, so chicken welfare reforms influence wild animal welfare.
• I estimate broiler welfare (cage-free) reforms increase or decrease the welfare of wild arthropods 47.7 (4.66) times as much as they increase the welfare of broilers (hens). Nonetheless, the effects on arthropods can be anything from negligible to much larger. I estimate uncertainty in arthropods’ welfare range alone means broiler welfare reforms increase or decrease their welfare 0 to 1.74 k times as much as they increase the welfare of broilers, and cage-free reforms increase or decrease their welfare 0 to 170 times as much as they increase the welfare of hens (5th to 95th percentiles).
• The effects of chicken welfare reforms on arthropods could be safely neglected if they were less than 10 % of those on chickens. Yet, I have a hard time seeing how one could be confident about this. Even just considering the uncertainty in each and one of the following inputs, for broiler welfare and cage-free reforms:
  • The increase or decrease in feed would have to be smaller than 0.0693 % and 0.108 %.
  • The increase or decrease in the density of arthropods would have to be smaller than 0.0630 % and 0.645 % of the density of arthropods in all of Earth’s land.
  • The increase or decrease in the welfare of arthropods would have to be smaller than 1.05*10^-7 and 1.08*10^-6 QALY/arthropod-year, which are 0.00525 % and 0.0540 % of Rethink Priorities’ (RP’s) median welfare range of silkworms of 0.002.
  • Increasing the welfare of arthropods by 1 QALY would have be less than 0.210 % and 2.15 % as valuable as increasing the welfare of chickens by 1 QALY, which implies strongly rejecting impartiality.
• My results suggest it is unclear whether chicken welfare reforms are beneficial or harmful. The effects on arthropods may well be larger than those on chickens, which would imply chicken welfare reforms being beneficial/harmful if they benefit/harm arthropods. I think these conclusions apply to any intervention targeting vertebrates which change the consumption of feed or food, especially if it mainly aims to increase/decrease positive/negative vertebrate-years.
• I recommend donating and making grants to improve invertebrate welfare. In particular, supporting the Arthropoda Foundation, RP’s work on invertebrate welfare, the Shrimp Welfare Project, or Wild Animal Initiative.
• I encourage organisations helping vertebrates to consider how they can help invertebrates.
• Organisations would need support from funders to change their focus. It would be great if people in Open Philanthropy’s (OP’s) farm animal welfare team or leadership could persuade their funders, Dustin Moskovitz and Cari Tuna, to fund invertebrate or wild animal welfare again.

Effects of cage-free reforms

Overview

Broiler welfare and cage-free reforms change the amount of feed needed to produce a given quantity of chicken meat or eggs. So they affect feed production, and therefore result in land use change. The density and welfare conditions of wild animals vary by type of land, so chicken welfare reforms influence wild animal welfare. I explain below how I estimated the effects of broiler welfare and cage-free reforms on wild arthropods and chickens.

Broiler welfare reforms

From Figure 4 of Gittins et al. (2024), broilers in a conventional scenario need 2.75 feed-kg/meat-kg, and ones in a reformed (slower growth) scenario, corresponding to the European Chicken Commitment (ECC), need 3.70 feed-kg/meat-kg. So I suppose broiler welfare reforms increase feed by 0.950 feed-kg/meat-kg.

According to Gittins et al. (2024), “Based on 5,674 million birds per year moving from standard to ECC production in the EU”, “Feed use would increase by some 7.30 million tonnes (+34.5%)”. “Assuming crop yields remain constant, an additional 1.57 million hectares of land would be needed for crop production”, which implies a cropland requirement of 2.15*10^-4 ha-year/feed-kg. Using this and the above increase in feed, I infer broiler welfare reforms increase cropland by 2.04*10^-4 ha-year/meat-kg, 2.04 m^2 for 1 year per kg of meat.

Rosenberg (2023) “found that there are ≈1 × 10^19 (twofold uncertainty range) soil arthropods on Earth, ≈95% of which are soil mites and springtails”. The Earth has 1.49*10^10 ha of land, so I arrive at a density of arthropods in all of Earth’s land of 671 M arthropod/ha. Based on Brian Tomasik’s results, I estimate the difference between the density of arthropods in rainforest and Cerrado is 90.0 % of the density of arthropods in all of Earth’s land. I speculate additional cropland decreases the number of arthropods 1/3 as much, by 30.0 % of the density of arthropods in all of Earth’s land. So I calculate additional cropland decreases the living time of arthropods by 201 M arthropod-year/ha-year. Combining this with the cropland requirement gives me a decrease in the living time of arthropods caused by broiler welfare reforms of 41.1 k arthropod-year/meat-kg.

The Welfare Footprint Institute (WFI) says the “average [mean] slaughter weight [just before slaughter] of broilers in the EU [European Union]” “in a conventional scenario” is “2.5 Kg”. Based on Table 11 of Gittins et al. (2024), “the eviscerated carcass without the neck, internal organs or abdominal fat” accounts for 72.65 % and 71.05 % of that for broilers in a conventional and reformed scenario, which correspond to 1.82 and 1.78 meat-kg for WFI’s slaughter weight. WFI mentions the slaughter weight for broilers in a conventional scenario in the EU is “reached at 42” “days”, 0.115 broiler-years, and that, in “the reformed scenario”, the “same slaughter weight would be reached in approximately 56 days”, 0.153 broiler-years. So I determine broilers in a conventional and reformed scenario produce 15.8 and 11.6 meat-kg/broiler-year. Multiplying the 1st of these by the result of the previous paragraph, I conclude broiler welfare reforms decrease the living time of arthropods by 650 k arthropod-year/broiler-year.

I guess the absolute value of the (expected) welfare of arthropods is 25 % of the welfare of fully healthy arthropods. A uniform distribution ranging from -75 % to 25 %, whose mean is -25 %, and one ranging from -25 % to 75 %, whose mean is 25 %, would lead to that absolute value of the welfare. I set the welfare of fully healthy arthropods to 2*10^-4 QALY/arthropod-year, which is 10 % of RP’s median welfare range of silkworms of 0.002. So I obtain an increase or decrease in the welfare of arthropods of 5.00*10^-5 QALY/arthropod-year. I do not know whether arthropods would be benefited or harmed. I am uncertain about whether cage-free reforms increase or decrease feed production, as Gemini’s ranges for the FCR of egg production in cages and barns overlap a lot. Furthermore, it is unclear to me whether increased feed production increases or decreases arthropod-years, and whether arthropods have positive or negative lives.

Based on the decrease in the living time of arthropods, and their welfare, each broiler-year improved by broiler welfare reforms increases or decreases their welfare by 32.5 QALYs.

In agreement with my cost-effectiveness analysis (CEA) of corporate campaigns for chicken welfare, I suppose broilers in conventional and reformed scenarios have a welfare of -0.754 and -0.0535 QALY/broiler-year. These mean together with the aforementioned meat production values that broilers in conventional and reformed scenarios have a welfare of -0.0477 and -0.00462 QALY/meat-kg. So I deduce broiler welfare reforms increase welfare by 0.0431 QALY/meat-kg. Multiplying this by the meat production of broilers in a conventional scenario, I arrive at an increase in welfare of 0.681 QALY/broiler-year.

Cage-free reforms

I asked Gemini 2.5 Pro (experimental) on 11 April 2025 about the feed conversion ratio (FCR) of current egg production. Gemini provided a range of 1.9 to 2.1 feed-kg/egg-kg for cages, and 2.0 to 2.2 feed-kg/egg-kg for barns. The means between the lower and upper bounds of the ranges for cages and barns are 2.00 and 2.10 feed-kg/egg-kg, so I assumed cage-free reforms increase feed by 0.100 feed-kg/egg-kg. From Table 3 of Leinonen et al. (2012), which studied egg production in the United Kingdom (UK), hens in cages and barns consume 2.56 and 2.74 feed-kg/egg-kg, which imply cage-free reforms increase feed by 0.178 feed-kg/egg-kg. The lower increase suggested by Gemini’s values might be explained by the faster growth of cage-free production since 2012, which facilitates economies of scale. It makes sense hens in barns need more feed because they can move around, and therefore spend more energy.

Class A eggs from hens in cages and barns in the EU had a mean cost in the 7 days before 9 April 2025 of 2.60 and 2.85 €/egg-kg. From these, and a “commonly assumed” price elasticity of demand for eggs of -0.15, cage-free reforms make consumption 94.6 % (= (2.85/2.60)^-0.15) as high. I did not account for this in my main estimate for the effects on arthropods. The decrease of 5.40 % (= 1 - 0.946) in the consumption of eggs is negligible in light of other uncertainties, and some of it would be replaced by increased consumption of other animal-based products, which also require some feed production. Replacement by animal-based products with higher FCR might even imply higher egg prices increase feed production overall.

From Table 4 of Leinonen et al. (2012), the cropland requirement of the production of non-organic hens’ feed is 1.55*10^-4 ha-year/feed-kg. Organic hens’ feed requires 3.23 times as much cropland, thus implying a larger impact on arthropods. I assume non-organic feed, as I guess it is the most commonly used by far. Combining the cropland requirement with the increase in feed mentioned above, I infer cage-free reforms increase cropland by 1.55*10^-5 ha-year/egg-kg, 0.155 m^2 for 1 year per kg of eggs. Combining this with my estimate for how additional cropland affects arthropods gives me a decrease in their living time caused by cage-free reforms of 3.12 k arthropod-year/egg-kg.

From Table 3 of Leinonen et al. (2012), I use an egg production for hens in cages and barns of 19.5 and 19.0 egg-kg/hen. In addition, I consider a life expectancy of 1.46 hen-years, “20 weeks” for the pre-laying phase from WFI, plus 56 weeks for the laying phase from Table 1 of Leinonen et al. (2012). So I determine hens in cages and barns produce 13.4 and 13.1 egg-kg/hen-year. Multiplying the 1st of these by the result of the previous paragraph, I conclude cage-free reforms decrease the living time of arthropods by 41.8 k arthropod-year/hen-year.

Based on the decrease in the living time of arthropods, and their welfare, each hen-year improved by cage-free reforms increases or decreases their welfare by 2.09 QALYs.

In agreement with my cost-effectiveness analysis (CEA) of corporate campaigns for chicken welfare, I suppose hens in (conventional) cages and barns have a welfare of -0.563 and -0.111 QALY/hen-year. These mean together with the aforementioned egg production values that hens in cages and barns have a welfare of -0.0420 and -0.00850 QALY/egg-kg. So I deduce cage-free reforms increase welfare by 0.0335 QALY/egg-kg. Multiplying this by the egg production in cages, I arrive at an increase in welfare of 0.449 QALY/hen-year.

Comparisons

I estimate broiler welfare (cage-free) reforms increase or decrease the welfare of wild arthropods 47.7 (4.66) times as much as they increase the welfare of broilers (hens). Nonetheless, the effects on arthropods can be anything from negligible to much larger. There is large uncertainty respecting many of the inputs. RP’s 5th and 95th percentile welfare range of silkworms are 0 and 36.5 (= 0.0073/0.002) times their median. I used a welfare range for arthropods equal to 10 % of silkworms’, so I guess the 5th and 95th percentile welfare range of arthropods are also 0 to 36.5 times their median. Consequently, I estimate uncertainty in arthropods’ welfare range alone means broiler welfare reforms increase or decrease their welfare 0 to 1.74 k (= 4.66*36.5) times as much as they increase the welfare of broilers, and cage-free reforms increase or decrease their welfare 0 to 170 (= 47.7*36.5) times as much as they increase the welfare of hens (5th to 95th percentiles).

The increase or decrease in the welfare of arthropods as a fraction of the increase in the welfare of chickens is 10.2 (= 47.7/4.66) times as large for broiler welfare reforms as for cage-free reforms. This is explained by the increase in feed-kg/meat-kg caused by broiler welfare reforms being 9.50 (= 0.950/0.100) times the increase in feed-kg/egg-kg caused by cage-free reforms, the increase in ha-year/meat-kg of the former being 1.39 (= 2.15*10^-4/(1.55*10^-4)) times the increase in ha-year/egg-kg of the latter, and the increase in QALY/meat-kg of the former being 1.29 (= 0.0431/0.0335) times the increase in QALY/egg-kg of the latter (9.50*1.39/1.29 = 10.2).

Discussion

Effects on arthropods

The effects of chicken welfare reforms on arthropods could be safely neglected if they were less than 10 % of those on chickens. Yet, I have a hard time seeing how one could be confident about this. The effects on arthropods of broiler welfare and cage-free reforms would have to be less than 0.210 % (= 0.10/47.7) and 2.15 % (= 0.10/4.66) as large as I estimated. Even just considering the uncertainty in each and one of the following inputs, for broiler welfare and cage-free reforms:

• The increase or decrease in feed would have to be smaller than 0.0693 % (= 0.00210*0.33) and 0.108 % (= 0.0215*0.0500), as I estimated an increase of 34.5 % (= 0.950/2.75) and 5.00 % (= 0.100/2.00).
• The increase or decrease in the density of arthropods would have to be smaller than 0.0630 % (= 0.00210*0.300) and 0.645 % (= 0.0215*0.300) of the density of arthropods in all of Earth’s land.
• The increase or decrease in the welfare of arthropods would have to be smaller than 1.05*10^-7 (= 0.00210*5.00*10^-5) and 1.08*10^-6 QALY/arthropod-year (= 0.0215*5.00*10^-5), which are 0.00525 % (= 1.05*10^-7/0.002) and 0.0540 % (= 1.08*10^-6/0.002) of RP’s median welfare range of silkworms of 0.002.

I also guess I underestimated the effects on arthropods due to factory-farms with improved conditions requiring more land, and the additional land having a lower density of arthropods than the counterfactual land use.

My results suggest it is unclear whether chicken welfare reforms are beneficial or harmful. The effects on arthropods may well be larger than those on chickens, which would imply chicken welfare reforms being beneficial/harmful if they benefit/harm arthropods. I think these conclusions apply to any intervention targeting vertebrates which change the consumption of feed or food, especially if it mainly aims to increase/decrease positive/negative vertebrate-years:

• I estimated GiveWell’s (GW’s) top charities increase or decrease the welfare of wild terrestrial arthropods 1.15 k times as much as they increase the welfare of humans.
• I estimated insecticide-treated nets (ITNs) distributed by the Against Malaria Foundation (AMF) cause 763 times as much harm to mosquitoes as they benefit humans.
• I estimate replacing meat from broilers in conventional scenarios with plant-based food requiring as much cropland as the broilers’ feed increases or decreases the welfare of arthropods 138 (= 47.7*2.89) times as much as it increases the welfare of hens. 2.89 (= 2.75/0.950) times as much as broiler welfare reforms because this is the ratio between the FCR of broilers in conventional scenarios, and the increase in feed-kg/meat-kg caused by broiler welfare reforms.
• I estimate replacing chicken eggs from hens in cages with plant-based food requiring as much cropland as the hens’ feed increases or decreases the welfare of arthropods 93.2 (= 4.66*20.0) times as much as it increases the welfare of hens. 20.0 (= 2.00/0.100) times as much as cage-free reforms because this is the ratio between the FCR of hens in cages, and the increase in feed-kg/egg-kg caused by cage-free reforms.

Here are some updates to past claims I have made based on my very uncertain best guess that increasing cropland harms arthropods due to decreasing positive arthropod-years:

• I have been saying corporate campaigns for chicken welfare are way more cost-effective than GW’s top charities. I now expect their cost-effectiveness to be similarly negative. I estimate broiler welfare and cage-free campaigns increase cropland by 0.00968 and 0.00224 ha-year/$, which are close to my rough estimate for GW’s top charities of 0.0129 ha-year/$.
• I have argued replacing chicken meat with beef or pork is beneficial. I now expect the opposite to be true. Beef or pork require more cropland than chicken meat.
• I estimated Veganuary in 2024, and School Plates in 2023 were 1.20 % and 19.4 % as cost-effective as cage-free campaigns, and I believe decreasing the consumption of animal-based foods is usually less cost-effective than improving the conditions of farmed animals ignoring effects on wild animals. I now expect cage-free campaigns to be harmful, and decreasing the consumption of animal-based products to be beneficial. The former increases cropland, whereas the latter decreases it as long as the animal-based foods are mostly replaced with plant-based ones.

I do not take any of these updates seriously. I am practically agnostic about whether increasing cropland benefits or harms arthropods, and therefore very uncertain about whether interventions with dominant effects on arthropods are beneficial or harmful.

Interventions targeting vertebrates which change the consumption of feed or food can be beneficial due to increasing future support for wild invertebrates, even if it is unclear whether they are beneficial or harmful nearterm, but I am sceptical. I guess such indirect effects are too small to dominate the nearterm effects, and I am not confident they are beneficial. Brian Tomasik thinks “it’s pretty unclear whether promoting vegetarianism reduces or increases total animal suffering, both when considering short-run effects on wild animals on Earth and when considering long-run effects on society’s values”. I agree with Brian on this, and the following.

General concern for animal suffering is crucial if humans are to make wise choices with respect to wild animals once more advanced technologies arrive, and promoting vegetarianism based on reducing suffering seems generally likely to cultivate such sympathies.

However, advancing vegetarianism from, say, the perspective that humans have no right to interfere with animals or that meat causes destruction of intrinsically valuable nature could be counterproductive. Indeed, I find it likely that vegetarianism increases support for wilderness conservation on balance, and the negative impacts of wilderness preservation on wild-animal suffering could be substantial. This concern suggests that the indirect, memetic effects of vegetarianism could very well be net harmful.

Relatedly, I have the impression people working on reducing the consumption of animal-based products are often less sympathetic to wild animal welfare than people working on improving the conditions of farmed animals.

My recommendations

I recommend donating and making grants to improve invertebrate welfare. In particular, supporting:

• The Arthropoda Foundation:
  • They aim to improve the conditions of farmed insects, whose population is expected to grow a lot. RP forecasts there will be 417 billion black soldier flies and mealworms in 2033, 10.9 (= 417*10^9/(38.2*10^9)) times as many as in 2023, and 15.3 (= 417*10^9/(27.2*10^9)) times the number of chickens in 2023.
  • They are not targeting other farmed arthropods, or wild animals for now, but a better understanding of insects seems good longterm to help wild arthropods.
• RP’s work on invertebrate welfare:
  • I feel it has historically been quite cost-effective. It has helped build the invertebrate welfare movement, and informed my cost-effectiveness analysis of the Shrimp Welfare Project.
  • RP’s work on invertebrate and wild animal welfare is only being supported by restricted funds. So one can make restricted donations to those areas without worrying about them being partially offset by a reallocation of unrestricted funds.
• The Shrimp Welfare Project (SWP):
  • I estimate it has been 64.3 k times as cost-effective as GW’s top charities neglecting the effects of these on animals, and 173 times as cost-effective as cage-free corporate campaigns neglecting the effects of these on wild animals.
  • It has plans I like for what to do with over 1 M$ of additional funding.
  • It mainly advocates for electrically stunning shrimp before slaughter via the Humane Slaughter Initiative.
    • This can make shrimp slightly more expensive, decrease its consumption, decrease its feed, and therefore increase the number of wild animals, which may be beneficial or harmful.
    • On the other hand, lower consumption implies fewer farmed shrimp, which is beneficial if they have negative lives as I estimate.
    • Overall, I expect the effects on wild animals to be much less important for interventions which do not change the feed required to produce a kg of animal-based products, such as ones improving slaughter methods. Moreover, it is harder for effects on wild animals to make SWP harmful since I estimate it is much more cost-effective than cage-free campaigns.
• The Wild Animal Initiative (WAI):
  • “To advance our understanding of wild animal well-being, our team conducts research and supports the growth of the wider research community”, in line with their research priorities.
  • I estimate paying farmers to use more humane pesticides would be 51.4 times as cost-effective as cage-free campaigns neglecting the effect of these on wild animals, and guess that research on and advocacy for more humane pesticides would be way more cost-effective than paying farmers to use them more. WAI has supported research on pesticides.
  • Wild animal welfare is super neglected.

I listed the organisations alphabetically. SWP and WAI are recommended by Animal Charity Evaluators (ACE), although this only plays a very minor role in my recommendations.

Here are some thoughts on other prominent organisations working on invertebrate or wild animal welfare:

• Animal Ethics “provides information and resources about the reasons to respect all animals, promotes discussion and debate about issues in animal ethics, and encourages academics and scientists to do research in related areas”.
  • WAI seems much more well connected to academia than Animal Ethics, so I believe they are better positioned to drive academic interest.
  • I also suspect the impact of Animal Ethics’ broad outreach is limited by the lack of academic research on wild animal welfare. WAI fills this gap, thus legitimating more mainstream advocacy. Broad advocacy for the welfare of farmed animals would hardly lead to change if there was basically no research about their welfare, and how to improve it.
• The Insect Institute “address[es] challenges and uncertainties related to the production and use of insects for food and feed. We aim to assist this novel industry, policymakers, and other interested parties by providing evidence-based information surrounding the rearing of insects and the creation of a food system that promotes public health, animal welfare, and sustainable protein production”.
  • I can see their 3 publications slightly slowing down the growth of the insect industry. Nevertheless, this is only clearly beneficial for farmed insects if their lives are negative now, and will remain so over the period affected by the slow down. It may be harmful if their lives are positive now, or will become so over the aforementioned period. I do not know whether farmed insects have positive or negative lives, so it is unclear to me whether preventing the growth of the insect industry is beneficial, especially because it could replace some farmed animals with negative lives like farmed fish. Knowing how much time farmed insects spend in pain, as determined by WFI for broilers and hens, and RP for shrimp, would be great to inform whether farmed insects have positive or negative lives.
  • The Arthropoda Foundation plans to improve the conditions of farmed insects, which is beneficial for these regardless of whether they have positive or negative lives.
  • I think improving the conditions of animals is usually more cost-effective than decreasing their consumption ignoring effects on wild animals.
• Screwworm Free Future (SFF) is “A coordinated initiative to protect South America from the New World Screwworm” by eradicating it.
  • I assume this would be beneficial for the infected animals, but it is unclear to me whether it would be beneficial or harmful overall due to the possibility of screwworms having positive lives.
  • I think it is fine to pursue interventions which may be harmful to wild animals nearterm, but then it is important to learn from them to minimise harmful effects in the future.
  • I have not seen concern for the welfare of screwworms expressed in any of SFF’s posts. However, they say “Wild Animal Initiative is planning on funding a research investigating the welfare effects of screwworm eradication”. Mal Graham, WAI’s strategy director, told me “Any project we do on screwworms will include the effects on the screwworms themselves as well as the effects on wild animals” (Mal said I could share this).

I listed the organisations alphabetically.

I encourage organisations helping vertebrates to consider how they can help invertebrates. RP has a report on strategies to help farmed shrimp. Organisations working on chicken welfare corporate campaigns could run ones asking companies to commit to electrically stun shrimp, as Mercy for Animals (MFA) did to get a commitment from Tesco, UK’s Largest Supermarket Chain.

Organisations would need support from funders to change their focus. It would be great if people in Open Philanthropy’s (OP’s) farm animal welfare team or leadership could persuade their funders, Dustin Moskovitz and Cari Tuna, to fund invertebrate or wild animal welfare again.

Acknowledgements

Thanks to Keyvan Mostafavi, and Michael St. Jules for feedback on the draft. The views expressed in the post are my own.