Global health and factory farming are two main cause areas in EA. However, as a person who supports animal rights, is the scale of factory farming problem MUCH more serious than global health? I'm very unsure on whether the scale is 10,100 or 1000 times bigger. This is one crucial problem to prioritize ending factory farming over global health.
The number of land farmed animals is around 30 billions, and there are about 0.4-0.8 billions of humans who are in severe diseases. Given the moral weight of animals is quite uncertain,so the life quality of farmed animals may not be as important as humans. But one argument is that the suffering of farmed animals is much more torturing.
(By intuition, I think comparing with the suffering of farmed animals, human diseases may only be a piece of cake. But I'm really unsure, I want some persuasive arguments. Also,I don't have expertise on the seriousity of farmed animals and severe human diseases.)
The main suffering of farmed animals:
1.Starving
Some humans diseases would make you starve also if seriously ill, but we are often treated with liquid nutrition, so we won't starve to death.
2.Small living space, lack of exercise(But for humans who are sickbed, isn't this similar suffering?)
3.Overweight and crippling(It seems serious, but I'm unsure how it is, how about the disabled humans?)
4.Chronic diseases(Also happening in humans)
5.Not getting anaesthetization
6.Not enough sleep(Human also gets insomnia)
7.Dirty and lots of infectious disease(Also happens in global diseases)
8.Fearing
9.Cruel slaughtering (This might be the most painful, but the time is relative short than the above)
Farmed animals live quite a bad life. BUT, how can we compare this suffering to a seriously ill person, such as the dying advanced cancer patients, or a person who is suffering from malaria, or depression? I think both are serious suffering, I don't know how to compare the seriousity of factory farming vs human diseases.
I think your argument is strong
To answer your question how to compare, I think Rethink Priorities research on moral weights is excellent - in depth, and well communicated even though I don't agree with all of it.
https://rethinkpriorities.org/publications/category/Moral+Weight
I'm primarily a neartrmist global health person who wholeheartedly supports animal advocacy. At my life stage with my competitive advantage I don't think it would make sense to change causes even if working on it was potentially 1000x more impactful.
I think that animal suffering from factory farming could easily be 1000x or even 10,000x more important than human suffering as you say, but it could also be 100x less. Although we are closer to answering the classic "how many suffering chickens equals a suffering human" question, I think EAs sometimes underrate the enormous uncertainty in "how bad" animal suffering is compared with humans and that EA research can lean towards overweighting animal suffering (although I would say that).
I think your suffering questions are important, but I doubt many would disagree that factory farmed chickens suffer badly in all the ways you stated. The moral weight is where the greater uncertainty lies.
To compare with humans, I think the equation is crudely
suffering x moral weight -and judging the moral weight is a far greater difficulty.