Tamed Otters do not eat regular meat, only fish meat. My otter was refusing to eat even though she had plenty of meat in her inventory and plenty of meat in a nearby trough. To remedy this, I tried multiple things; moving the trough closer, giving her more meat, and even force feeding her. She would not gain hunger with regular meat. The moment I got fish meat, she ate. I'm not sure if they can eat other types of meats like mutton though.