Having spent some time with animals, it seems obvious that they have wants and needs and preferences, just as humans do. And they feel better (worse) when those preferences are satisfied (frustrated), just as humans do. Therefore, I find it implausible that if an action of mine causes harm to an unconsenting human, policy should be constructed such that I internalize that cost; but if the harm is instead to an unconsenting animal, policy should do nothing. The magnitude of these externalities will differ — if my actions cause an innocent human to be locked in a cage for her entire life, that is worse than if my actions cause an innocent hen to be locked in a cage for her entire life — but I don't see how the latter could be worth nothing.
At present, approximately the entire field of economics (implicitly) disagrees. We analyze policies as if animal welfare counts for precisely nothing. This should change. Or, at the very least, we should better understand the conceptual bullets we are biting by taking this stance.
I have written some on this topic myself, and I am on the advisory board of the Animal Welfare Economics Working Group. Please be in touch if you want to learn more or be involved in this research agenda!
Some Further Reading:
Regulators should value non-human animals (Cass Sunstein)
Is it time for development economists to start considering the welfare of non-human animals? (Berk Özler)
The Animal Welfare Levy (Romain Espinosa and Nicholas Treich)
Animal Welfare and Social Decisions: Is it time to take Bentham Seriously? (Olof Johansson-Stenman)
Experiment on whether pigs have preferences: The rolling over, exposing belly, and moaning supports the hypothesis.
Further Speculation: The (cardinal) utility loss to a pig from being confined indoors for her entire life exceeds the utility I gain from purchasing and consuming a pig's worth of sausage.
Policy Implications: While I do love a good sausage and pepper sub, the optimal tax should raise the price enough to discourage my purchase of sausage (or incentivize me to purchase high-welfare meat instead).