There is no such thing now. Horses were made to cover vast amounts of open
range and rarely had to eat grass in the same place for long periods of time. In
a closed enviroment there is almost no way any horse does not have worms. A
horse that has a large pasture with a few buddies is therefor going to have
fewer worms as well as have a healthier gut, because that is closer to the
way God intended them to be.
