If you smell a foul odor while picking your horse's feet, chances are he has contracted thrush, a frog-eating, anaerobic bacterium. Thrush is a primary concern, whether your horse lives mainly at pasture or in a stable, especially in wet weather. Since this bacterial disease is anaerobic, it survives without the presence of oxygen. In fact, oxygen will actually kill it. In many minor cases, just a hoof picking a day will be enough to keep thrush away.
Conditions that accelerate thrush are conceptually (but not literally) relative to those that accelerate tooth decay within our teeth. It sounds absurd to hear that someone died of tooth decay. Unfortunately, I have heard of horses being put down due to advanced cases of thrush and I think how absurd, because thrush (frog decay) and cavities (tooth decay) are both hygiene-related and both easily prevented.
Generally speaking, thrush is not deadly. Most studies suggest that minor cases have a three-day window to arrive and a three-day window to disappear, provided that appropriate measures are taken.
Thrush problems for horses are essentially fostered by poor hygiene. It's difficult to comprehend the seriousness of something that appears so subtle, but due to the horse's hoof construction, it can be deadly if not dealt with properly.
The frog has two distinct layers--the external skin is called horn tissue and the corresponding vascular layer of tissue is called the sensitive corium. Beneath the inner sensitive layer lies a pad-like shock absorber that reduces concussion for the horse's hoof and his entire limb, called the deep digital cushion.
The signs of thrush will be noticeable at the deep crevices of the frog (sulci) when a black, puss-like discharge accompanied by a foul odor is present.
Thrush is likely to take over a hoof that is left in unsanitary conditions. A wet environment that primarily consists of urine and acidity from manure is a breeding ground for the anaerobic bacterium that are attracted to any necrotic (decayed) tissue that exists on the horse's frog. Not stopping at that, the bacteria will form deep-seated pockets and literally drill into the frog, eating away at the remaining healthy tissue.
One way to prevent thrush is by a thorough, daily hoof picking. It's not necessarily true that horses at pasture won't get thrush. They can, in certain seasonal situations. Horses left in muddy areas, particularly in the northeastern part of the U.S., may have to cope with wetter climates most months of the year, increasing the odds of contracting thrush. Horses that spend time in unsanitary conditions are also more susceptible to the bacteria.
In serious cases, the thrush bacteria invades the sensitive layers of the frog. It is common in these cases to see bleeding of the frog as well. If this happens, you should move your horse into a clean, dry area and use an antiseptic foot wash with Betadine solution or a foot soak with warm Epsom salt water. If bleeding still persists, apply a temporary bandage.
Remember, it's always a good idea to confer with your vet, who will probably suggest your horse receive a tetanus shot. Once the healing of the frog begins, it would be wise to maintain a "cleanliness-first" policy for your horse's feet.
Bryan Farcus is a Certified Farrier and instructor in West Virginia.
Thrush needs tough treatment to eliminate it. Farrier Bryan Farcus has found several commercial products that successfully combat the frog-eating disease: Thrush Buster by Mustad, Kopertox by Fort Dodge and Thrush Remedy by Absorbine. Remember that regardless of the type of thrush medication you choose, it will be most effective when administered directly after a thorough hoof cleaning.
Prevention is the best cure.
"It's always a good idea to do a routine hoof picking so that you can keep a watchful eye on your horse's hoof health," concludes Farcus.