The eater "feeds on" something. Polar bears feed on seals.

The person who gives someone (or an animal) food, "feeds" the person (or the animal). She fed the child porridge. He feeds the pigeons breadcrumbs.

In your examples, you're conflating these verbs.

The eater "feeds on" something. Polar bears feed on seals.

The person who gives someone (or an animal) food, "feeds" the person (or the animal). She fed the child porridge. He feeds the pigeons (with) breadcrumbs.

In your "fed him on lamb" example, you're conflating these verbs.