Hi Andrew, welcome to the forum! I am keenly interested in this subject -- I am one of the commentators you mentioned and have written on the subject previously (Towards non-meat diets for domesticated dogs).

Without getting to much into the specifics here, I wish to gently counsel you on EA forum norms in a way that might help the message go down better for readers.

1. We generally assume good intent. It is true that I am not persuaded by some elements of your analysis, which is why I stated a preference for the Alexander et al. estimation methods, but I would not describe that disagreement as "seeking to undermine [your] studies." My disagreement is not coming from a place of malice.
2. We generally do not use maximalist language to describe each other's perceived mistakes, e.g. "profoundly misrepresents," "dramatically incorrect," etc. Instead it is more in line with how we talk to say "This is mistaken" or "this is not what I intended."
3. We tend to address each other by name/username and use tags-- by all means please call me Seth rather than "a commentator" 😃 

Anyway, looking forward to more engagement, 

Thanks for this response, Andrew. It's made me realise I was misrepresenting your methodology, although I still have reservations. I hope it wasn't disheartening to see criticism of your work on the Forum, and that you stick around and continue to engage in good faith. I'm appreciative of your efforts to help the animals, and want to reassure you that the commentators here share your goal. Far from being speciesists or "seeking to undermine the science," we're a very pro-animal, and very truth-seeking, community.

I think we have three disagreements here:

• Whether or not vegan pet food is a leading effective altruist cause area

I don't think that it is because I don't think it clears the bar on cost-effectiveness, or looks competitive with other EA animal welfare interventions.

But I think we should have a fairly broad church, and a spirit of investigation, not outright dismissal, so I'm glad that you've looked into this. I'm open to considering other interventions in this space, like trying to move cats and dogs towards smaller-bodied animals.

• Scale

You're right here: I'm wrong to describe this as double-counting as your methodology doesn't literally count a cow, pig or chicken body twice over. I'll edit my original comment accordingly.

That said, I continue to disagree with your methodology; let me take another stab at explaining why I disagree, and I'll be curious to hear your response.

Your methodology is attributive, not consequential. It tells us what proportion of the world's livestock are physically consumed by companion animals (based on some assumptions).^[1] But, as you acknowledge, much of this is the consumption of by-products. Your papers don't look into the economics of by-products, so your methodology doesn't tell us how many animals would be counterfactually spared farming and slaughter with vegan pet food.

To be honest, I found your writing a bit misleading about this before (e.g., your paper has a section titled, "Number of 'food animals' spared from slaughter"). I find this comment really helpful and clarifying:

The commentator also assumes the drivers of farmed animal production and slaughter are relevant to the calculations, and that the calculations are wrong because ABPs do not primarily drive farmed animal production. This position is also incorrect. The calculations make no assumptions about which factors or components drive farmed animal production. These factors are, in fact, not relevant to the calculations. The calculations rely solely on knowledge of the actual farmed animal species used within pet food, and the actual proportions of those carcasses that supply the meat and ABPs used, and the total average carcasses that are actually required. These are actualities, determined by physical realities relating to pet food ingredients, carcass proportions, and (simple) mathematics. They’re unaffected by drivers of production.

I think our disagreements about your methodology are really less about nitpicking the details - but, again, I concede that I did misrepresent your methodology by calling it 'double counting' - and more about what the methodology should be trying to figure out. To me, the proportion of farmed animals eaten by companion animals is an interesting proxy for scale, but the really relevant question is: how many animals would be saved if the demand fell away? Farm animal advocacy should be about actually getting animals out of the food system (or improving conditions in factory farms).

My current sense is that scale isn't as high as you suggest not because I disagree with your allocation model, but because:

1. I think farm animal by-products will be realloacted to other uses. If it's true that, as your paper claims, "if not consumed within pet food, all meat ingredients, ABPs [animal by-products] and their derivatives, would normally be consumed either directly by people, or within other sectors of society" then the marginal use case of the by-product will change but production will not be seriously disrupted. (@Seth Ariel Green 🔸 points out that there could still be a demand signal encouraging a decrease in production; it still wouldn't be a perfectly elastic signal).
2. Even if farm animal by-products become waste products, that will reduce the efficiency of animal farming and so probably decrease production, but it wouldn't be perfectly elastic. The production would drop only a little.

The economic allocation model seems a step closer to considering actual economic demand than a model based on physical consumption. I think the reason I like the Alexander paper and you don't is that I'm more interested in thinking about how production would change given demand shifts. (Economic allocation still seems to struggle thinking at the margin, and I would still like to see a system expansion model).

• Tractability

The surveys you cite were a slight update for me, but they're not a knock-down argument. For one, I could present different data from the same surveys to colour the argument quite differently. Dodd, et al. tells us, for example, that 75% of omnivores say they'll never feed their pet a plant-based diet, and majorities of omniores, pescetarians and vegetarians are concerned that plant-based diets for companion animals are unnatural, unhealthy or incomplete.

But also, more importantly, surveys aren't a perfect way to measure consumer intention (given, e.g., social desirability bias), consumer intention isn't a perfect proxy for consumer behaviour (given, e.g., the intention-behaviour gap), and consumer behaviour isn't the only thing that matters here (consider also, e.g., scaling up production; achieving cost competitiveness; securing support from vets; making vegan food that's healthy for cats).

I'm open to hearing out the tractability case, but I don't think enough evidence has been presented so far.

1. ^{^}

   I'll also concede that some of these assumptions are conservative. But some of them are also broad / arbitrary / hard to assess, like the conversion factor, which makes me take the whole exercise as one model, but not authoritative.

Hi Andrew,

I appreciate how Seth is playing nice because you are new to the EA Forum.

However, I'm strongly downvoting for the following reasons:

1. "leading cause area" are very strong words to then not follow with any comparison to any other cause areas.
2. Strong claims such as ‘The case is overstated’ and ‘The calculations double-count a lot of livestock carcasses’ appear to have resulted from those commentators not having read the relevant studies with sufficient care, or from failing to understand the mathematics of the calculations, or their implications. Reasonable people can disagree on how to count byproduct allocation. Calling that a failure to read carefully or understand mathematics misrepresents the disagreement.
3. These incorrect claims undermine the case for sustainable pet diets. Similar attempts to defend the status quo were made, and are being made, by those seeking to undermine the science demonstrating the adverse effects of smoking, and the consumption of animal products, and of fossil fuels. However, these claims are incorrect, and sometimes profoundly so. This is not an argument, and does not belong here. This is just rethoric.
4. Your paper is published in MDPI, a known pay-to-publish venue.

I have absolutely no idea if making pets eat plant-based is a good intervention, and how it competes with other possible uses of our resources, and refuse to make any object-level claims about it here.

Executive summary: The author argues that transitioning dogs and cats to nutritionally sound vegan diets would spare billions of farmed animals and yield major environmental benefits, making sustainable pet diets one of the most neglected yet high-impact EA cause areas.

Key points:

1. Prior studies (e.g., Okin 2017) estimated that 25–30% of the environmental impacts of US animal farming were attributable to pet diets, and subsequent studies have similarly found large environmental and animal welfare impacts.
2. The author’s 2023 study incorporated the role of animal byproducts (ABPs) and newly available industry data on pet food ingredients to calculate carcass use and estimate savings from replacing conventional pet diets with nutritionally sound vegan diets.
3. The 2026 study estimates that globally, average annual consumption of farmed land animals is 13 for dogs, 9 for people, and 3 for cats (based on 2018 data), implying that transitioning an average dog spares more animals per year than transitioning an average person.
4. The author calculates that if all global pet dogs transitioned to nutritionally sound vegan diets, “at least six billion” land animals would be spared annually, alongside greenhouse gas savings equivalent to “1.5 times” the UK’s annual emissions and food energy sufficient to feed “450 million people.”
5. Surveys of thousands of pet carers suggest that more than 150 million dogs and cats could realistically be transitioned, using conservative assumptions such as one pet per household.
6. The author argues that criticisms about double-counting carcasses, neglecting literature, or low tractability misunderstand the mathematical allocation of carcass proportions, the engagement with prior studies (75 sources cited in 2026), and survey-based estimates of willingness to switch.

This comment was auto-generated by the EA Forum Team. Feel free to point out issues with this summary by replying to the comment, and contact us if you have feedback.

I'm really appreciating this conversation! 

Thank you Dr. Knight for raising awareness about a prospective cause area that is certainly neglected. I appreciate you working through the counterarguments you received and offering rebuttals. 

Really appreciate the folks offering guidelines to help craft conversation that gets at the best possible outcome. Comparing efficacy of cause areas can be a heavy research lift for one who wants to get a convo started, but I can see how commenters would want the burden of proof to fall on the person who made the claim. 

I like the synergy around teasing out viable interventions. It sounds like there are some initial leads, and more research would add confidence. 

It seems to me that people look to their vets for determining a nutritious diet. Dr. Knight has already made tremendous headway to get the veterinary community to relax restrictions or even support plant-based diets for companion animals. Expanding upon this could be a key step toward social validation. It begs the question: if vets supported plant-based diets the way the medical community does, would people see it as superior product for their beloved furry friends?

Overall I'm excited about the potential of this being a backdoor approach to getting animals out of our food system without requiring (human) diet change.

Thanks everyone for the ongoing interest in my studies. Due to workload I'm very short on time so will provide collated responses to various points. I may not have time to comment further in which case my apologies.

• Commentators on the initial post made a series of claims about my recent study. Several were strong claims, negative claims, and false claims. This certainly did not demonstrate “good faith”, but quite the contrary. In light of this my rebuttals were indeed appropriate. A number of the criticisms they responded to, were not. 

• I acknowledge that my calculations determined the number of average farmed animals (being weighted averages of the various species used) that are actually consumed by the different dietary groups (dogs, cats, humans). These calculations of actual consumption were as correct as the data allowed and can be verified by examination of the relevant studies. E.g. within the US in 2020 (as likely also true of other high pet owning nations), 20% of all farmed land animals were consumed by dogs and cats, rather than people. These numbers were then used as proxies for the numbers of farmed land animals that would be spared from slaughter, were nutritionally sound vegan (or cultivated meat-based) diets used instead. This is reasonable, on the face of it. e.g. if dogs consume 2 million farmed land animals annually, then switching those dogs to nutritionally sound vegan diets would prima facie (i.e. on the face of it), spare 2 million farmed land animals from slaughter annually. However, I accept that the actual effects of such a change could differ from the prima facie outcome, depending on effects on the demand and supply of animal-based ingredients in other (non dog food) sectors. Those who wish to argue that something other than the prima facie outcome would occur, face the burden of providing the reasoning and data to demonstrate and quantify this. This could be extremely complex to determine, if sufficient data could be sourced at all, and was well beyond the scope of my studies. I acknowledge that this could be possible however. My study built on others previously as described above, to provide the most accurate figures so far, but these are certainly not a perfect representation of reality. Maybe a future study will extend this work further, by managing to demonstrate how the real world might deviate from the prima facie outcome. Even if such deviations occur, however, I think the results would still show that billions of farmed land animals are killed annually to feed pet dogs and cats. Hence my point about the enormous scale of this problem, and the potential benefits offered by a large-scale transition to nutritionally sound vegan pet diets, would almost certainly remain valid. Additionally, as noted, my calculations were also quite conservative. There were several major and minor estimations made within my studies, that in general probably underestimated the true consumption levels of pets compared to people. Perhaps some of these might also be made more precise in future studies.

• My claims about tractability come from the most comprehensive studies to date (Dodd et al., Mace et al.), which collectively surveyed thousands of dog and cat guardians. These were not perfect (surveys can usually be critiqued) but provide the best data currently available on this issue. As noted above, my study claims re tractability are also quite conservative. My study calculated that at least 150 million dogs and cats worldwide could be transitioned onto nutritionally sound vegan diets. However, this assumed only a single dog or cat per household. In fact, many households have more than one, and so the true numbers of dogs and cats who could be transitioned are substantially higher. Furthermore, conservative percentages of pet carers open to vegan diets were used, which were far lower than those reported in another large-scale survey discussed within this section. Additionally, awareness of vegan pet diets is likely to be much higher today than when these surveys were conducted (before 2019, and in 2020).

As noted, I have a very heavy animal advocacy workload. Unfortunately this means I don't normally have time to follow or contribute to discussion fora, which is a shame as like many of you I expect, I find EA discussions extremely interesting. However, if any reader is genuinely struggling to understand any point within the relevant studies or calculations, rather than simply seeking to undermine these studies (e.g. by making negative and false claims as occurred in the initial post https://forum.effectivealtruism.org/posts/aQzD87AErAvhEdQqi/is-ea-sleeping-on-making-dogs-and-cats-vegan?utm_campaign=post_share&utm_source=link), then I’ll do my best to explain the relevant points. Such readers are welcome to contact me.