Leah Sattler wrote:
tell me more!
Not to doubt you, and I have no basis for saying this, but don't intestinal parasites attach to the intestinal wall and suck blood? Now there's a source of oxygen!
I can't imagine how, except for the ruminant's gathering of material, eating contents of the bowels is a net energy gain over simply eating the green material before it gets in the bowels. But perhaps I simply lack imagination...