In my grammar book, the following is stated:
1. Use ’s when referring to the parts of the body of a living animal.
2. Use ’s when referring to the products of living animals.
3. Do not use ’s for dead animal body parts or products.
But today I read an article, with the following sentence:
a protester eats a raw pig's head outside a vegan ...
So I am thinking how does it fit in the rules above? Clearly, he was eating a part of a dead animal, so why not "pig head" then?