i have pigs liver to try but its currently in the freezer needs to be defrosted and cooked!

i want to do some training with him today and remembered i had cans of tuna. not caring if its mesy - just so long as it works and most importantly is safe for him to eat!! just the way things like onions and chocolate etc are poisonous, just wanted to check that tuna was ok as havent heard of anyone using it for thier dogs