You usually won't see worms in a horses stool before worming unless: The horse is really full of the larger variaties, and the sample is right out of the "oven". Most dry out and die rather quickly once they hit the air and are really hard to see. Some worms have a cycle where some will slough off and come out in the stool also. You can see segments of tapeworm, which look like wiggly pieces of rice, if you look at a very fresh stool. They are very hard to see once dried as they turn opaque. You can recognize roundworms as they look like spaghetti. Smaller roundworms look like inch long spaghetti. Bots look like wax worms, or kinda like maggots. There are a few others you can actually see but these are the main ones. It is a relief to see these things after you worm-sometimes up to 3 days later, as it means you got 'em. If you don't see any it could mean your horse doesn't have any worms, or that you didn't dose correctly, or you didn't rotate wormers correctly, but more than likely the horse passed them and they were too small to see. A fecal exam by your vet is easy and fairly inexpensive and it can tell you about eggs etc. Good luck, sometimes they can be hard to get. Linda