I based my vote on the fact that I have close to 0 doubt about the fact that antispecism is true (the fact that you can't discriminate someone on the base of his specie). 
If you consider antispecism true, you have to take in consideration that humanity is a really small part of all animals living. Moreover, we have pretty good reasons to think that animals are living in worse conditions than humans (pretty obvious for farm animals that live in industrial farms, more challenging intuitively for wild animals but many studies make us things that suffering in wild animal is even a more important subect than farm animals). 
Therefore, if you accept these three premices: 
1- Antispecism is true. (consensus in moral philosophy)
2- Other animals are in greater number than humans. (fact)
3- Other animals live in worse conditions than humans. (fact)

You arrive to the conclusion that it is more valuable to give to animal welfare funding than global health. 
The only argument I can see that can make change the balance is the fact that it is not possible/really hard to improve animal welfare but it looks like it is not the case.

Hello ! 

Thanks a lot from sharing all this knowledge. It is pretty insightfull, even for people who don't follow EA news for years.

There are several claims that surprised me a little bit. I would be pleased to have more infos about these particular claims: 

1-Low probability: People generally have a deep ethical obligation to change their diet to help animals: If it is pretty clear that it is not the most efficient way to help animals, it is not that clear that we do not have a moral duty to at least not eat animal products.To my mind, I think that we have to differenciate moral duties to efficacities issues. 
Moreover, it is also close to impossible to convince people that animal welfare is a problem while eating animal products

2-Low probability: We can make meaningful progress on abolishing factory farming or improving farmed animal welfare by 2050: I would be pleased to know more about the facts that leed you into thinking that.

3-Low probability: I have a strong moral obligation to prevent future negative lives from occurring: Same than two.

4- High probability: It was good for animal welfare that the EAs “won” the abolitionist/welfarist debates: I would be interested about details of the historical fact (how EA "won" that debate") and also why it is a good news. 

I know it's a lot of questions. Feel free to answer from all to none :) .

Like others I also feel like you had more impact that you aknowledge to yourself :). 

Thanks again for the quality of the reasoning.