When a horse founders, there is an increase of blood flow to its hooves. The extra blood puts pressure on the bones in the horse's feet. If the pressure is strong enough or goes on long enough, the bones will shift, leading to permanent lameness.
When a horse founders, it will rock back on its heels in an attempt to take the pressure off its sore feet.
Instructions
How to Minimize the Damage
Call your veterinarian and tell her what is happening.
Remove all of your horse's food. Horses don't have any innate sense about their health and digestive system
Run cold water over your horse's hoof. This water serves two different purposes: The most obvious is to reduce the amount of swelling in the hoof. The more controlled the swelling, the less likely the damage will be permanent. The second benefit of the cold water is that it will help numb your horse's hoof, and your horse will feel better and start to relax.
Give your horse a bute (equine anti-inflammatory) tablet. This will help reduce the swelling and alleviate your horse's discomfort. The best way to administer a bute tablet is to dissolve it in a small amount of water. When the pill is completely dissolved, pour all of the moisture into a syringe. Insert the syringe in your horse's mouth and depress the plunger. Make sure the medication lands on the back of your horse's tongue; otherwise, she will spit it out. DO NOT attach a needle to the syringe.
Put your horse in a stall that has deep bedding. The hope here is that the horse will lay down and take the pressure off his feet.
Keep an eye on your horse. She should start feeling better in a day or so. Keep giving her bute for several days. Do not feed your horse any grain, and only give her first-cutting hay.
Restrict the amount of exercise your horse gets. If possible, keep him on stall rest for 15 to 30 days after he has foundered. Hand-walk him several times a day, which will keep his muscles stretched and supple.
Aftercare
Take preventive measures to make sure your horse's founder doesn't lead to permanent lameness. Remember that once your horse founders, there is an increased risk she will founder again.
Have your farrier put shoes and pads on your horse's feet. The pads will help protect his soles. Some horses require a wedge shoe, which will lift their heels and help restore the structure of their hooves.
Monitor your horse's food. You probably won't be able to turn her out to grass anymore, and you will have to limit the amount of grain she eats. Horses that have foundered do best on first-cutting grass hay.