The worming is super important and it's my understanding that a HUGE percentage of colic's are related to internal parasites. One things it's very important to understand is that even though your horse may have been wormed by the previous owner many folks don't understand that wormers must be switched in order to stay effective. The parasites become immune to the same wormer given over and over. Also if the former owner did not make sure that the horse got the complete dose and we all know how easy it is for them to pull their head up and spit part of the meds out, then again you have a heavy parasite load of worms that are immune to the wormer. Panacure is really good and i'm told it gets EVERYTHING if you dose for 5 days straight. Breaking the parasite circle is part of why you are supposed to rotate grazing areas for your horses which is not always possible depending on where you keep your horse but if you can it's a worthwhile strategy to help with the parasite load. Final thoughts is keep him/her parasite free and you'll probably be ahead of the problem. We feed out horses Datamatious (sp) earth in every feeding and we worm them too every two months, we rotate wormers and I have never had a horse that colic'd on me....I had a freind who raised race horses and he had one that would colic all the time once he started worming with the diatamaceous earth the horse never colic'd again and he has almost no horse flies or flies of any kind due to the fact that they can't lay eggs on the horse dung or they can lay eggs but the diat earth kills the fly larva.