PROCEDURE
If the horse is cast, roll it over using ropes or pull it away from the wall by their tail and mane.
If the horse is not cast, then try the following. To get the horse to stand up start by slapping them on their rear. Any response? If that doesn’t work, clap your hands together right near the horse’s ear? Any response? If this doesn't work, try standing 3 feet behind the horse’s head, rush towards them stomping your feet hard on the ground in a menacing, threatening way. Any response? At this point, the horse should have at least rolled onto their chest (sternal).
Assuming the horse is now on its chest, try pulling the lead rope back around toward the tail, over the legs, release and repeat. If this does not work, then try slapping the horse on the soft part of the sides of the muzzle and continue slapping until the front limbs come forward. This is highly effective but dangerous because you are in front of the horse when you do it, so be prepared to move out of the way quickly.
If the strategies above do not work, you may need to roll the horse. Rolling a horse over will sometimes enable a horse to get up. To roll a horse, you need 2 cotton lead ropes and three people. Consider the space and where the horse will end up when you roll it.
Position the horse first by pulling the tail and mane. Working from the back of the horse and staying out of the path of the legs, place a long length of thick cotton rope under the front feet and another on the hind feet, crossed over itself (not tied or knotted) over the pastern or fetlock.
One person holds the rope looped around the front limbs and another person holds the rope looped around the hind limbs. On the count of three, these two team members steadily pull the rope back and over the horse, folding the limbs and then slowly rotating the legs over the body.
The person on the head simply pivots the head as the horse rolls keeping it aligned with the body, to keep it from twisting its neck. The team must get out of the way quickly as the horse rolls to the opposite side. A horse's legs may spring out and can injure people in the way.
You can learn a great deal as you watch your horse attempt to rise. Your horse may not respond at all, they may try unsuccessfully to rise, they may stand momentarily and then lie down again, or they may stay standing. Regardless, share your findings with your vet.
TIPS FOR SAFETY AND SUCCESS
Consider whether the horse simply cannot rise because of positioning, i.e. is it cast?
A disease process that causes a horse to lie down for any considerable period of time is usually serious, so call your vet right away.
A down horse is dangerous. You must stay out of the way of the limbs at all times. Do this by staying behind the horse's back, neck and head. Stay away from their legs A down horse can roll very fast as well, trapping you underneath them or inadvertently kicking you when they roll over. Stay on your toes, ready to move out of the way quickly.
In my opinion, it is not cruel to use some force in your attempt to get your horse to stand up. The alternative is worse. If you ever feel uncomfortable performing this skill, always call your vet for assistance. Always remember that your safety is the most important consideration.