In the Magical World, there are still non-magical animals. And they are treated badly. There are parts of them used in Potions, and Hagrid, even though he likes magical creatures, uses them, and treats them badly. He has a mole skin jacket, made of the skin of moles. He once walked through Hogwarts swinging a dead pole cat, which looks like a weasel. He did take care of chickens though, if you Remember Chamber of Secrets. Also, what was in Hagrid's beef casserole? Hermione found a talon in hers. But what was it from? Probably an unfortunate bird. As if we didn't already need more dead birds, because of the ways they keep hitting window.