Well, the argument agains killing animals seems to be "you wouldn't kill humans" (I don't consider "animals suffer" a valid argument, because there are viable killing methods that don't cause suffering), so then you can use the same argument "you wouldn't enslave humans" with any kind of farm-raising. Like, the only possibly moral alternative would be foraging - picking unfertilized eggs of wild birds - but I don't think that would scale...
> Well, the argument agains killing animals seems to be "you wouldn't kill humans"
That's not my argument, so I'll try to explain my personal reasoning. To me, the main real reason we have for not killing or hurting other creatures is that we believe they have some level of emotional life, and are capable of things like happiness, love (at least in some form), sadness, fear, and suffering beyond just physical pain. We love our dogs, cats, etc. because we believe at some level they are capable of loving us back (perhaps a stretch for cats I know).
Thus, for me personally I draw the line at mammals because I believe they possess all of these qualities. I will eat poultry, fish and shellfish because I don't believe they have the same capacity of "emotional sentience" as humans, though I'm fully open to the idea that my ideas about poultry are wrong.
Thus, while I "wouldn't enslave humans" I also believe it's possible to keep hens and cows for eggs and dairy in a manner where the animal does not suffer, and I don't see this as any kind of "enslavement".
