"That pig's head is very big."
Translation:La cabeza de ese cerdo es muy grande.
I got this wrong at first. But clearly 'esa carbeza del cerdo' means 'that head of the pig' which implies more than one head on one pig. I need to be more careful.
I did the same. To me "the head of that pig" and "that pig's head" mean the same thing. "That head of the pig" does not necessarily imply that the pig has more than one head.