Unfortunately, seeds that pass through a horse, cow, sheep, etc. often
remain viable or are even stimulated to germination. If you are using
livestock to control weeds, you have to have them do the eating before
any seed are present.

M. Reed

But I think the greatest value of horses which has not been recognized
is the fact of what
they eat. And to utilize what they eat. The purpose of a horse in
terms of ecology, the science
of ecology is what the animal eats. The purpose is equated to what it
eats.

So, I have 5 acres of grass and weeds which I never cleared. So what
is the world's best solution
for that 5 acres. The answer is a horse, donkey and Llama. Set the
three in those 5 acres and
everyone wins. The soil wins in fertilizer. I win in having a cleaned
out 5 acres. The donkey and
horse and Llama love it.