Oh, it never even occurred to me that the ratios might be right. I just assumed there was some sort of bug in the system. But if I feed a hamburger to my pet guinea pig, she will gain a lot of weight, but if I feed the same hamburger to my pet hippopotamus, her weight gain will be hardly noticeable.
(I don't recommend hippopotamuses as house pets, by the way, although there is this: Jessica the Hippo )
Thanks for your answer.