They do throw cattle--they "throw" them on their sides to brand them--so it would make sense. They way I learned it, the verse after it was something about "they feed in the coolies, they water in the draw, their tails are all matted, their backs are all raw." I was never sure if it meant the cattle (which would make sense with "houlihan") or the horses in the remuda (possibly they were saddle-sore?).