You know that song, right decen2000?
We had a storybook with the tape, it showed a picture of a horse eating oats, a deer eating oats, and a lamb eating ivy. My mom knew it, though I had never heard of it before this lovely book/tape combo.
I think the song is a run together version of
Mares eat oats, and does eat oats,
and little lambs eat ivy,
a kid will eat ivy, too,
wouldn't you?