What is thrush in horses?

Look at the underside of the foot. The frog is the triangular, rubbery structure pointing forward from the heel. Either side of it runs a groove, and between the heel bulbs at the back sits a narrower cleft called the central sulcus. Healthy grooves are shallow and open enough to get a pick into.

Thrush-affected grooves are the opposite: deep, packed, and wet. When you run a pick through one you get black, greasy material rather than dry dirt, and the smell is unmistakable. A deep central sulcus that splits up between the heel bulbs is the version to take most seriously, because it can run further up than it looks.

Footing and bedding. A muddy gateway, a wet run-in, or a stall that does not get stripped often enough all do the same thing: they pack the grooves and keep them wet. Manure is worse than plain mud, because it adds bacteria to the moisture.

Not being picked out. Daily picking is the single biggest difference between a horse that gets thrush and one that does not. A foot that goes a week between picks holds whatever it collected in it the whole time.

Hoof shape. Contracted heels and a deep central sulcus trap material and hold moisture, so some horses simply get it more easily than their field mates on identical ground. Long toes and underrun heels tend to come with the same problem. If one horse in the barn keeps getting it and the others do not, that is worth raising with your farrier.

It is worth saying plainly: thrush is not a sign of a neglected horse. Plenty of well-kept horses get it in a bad autumn, because the weather did most of the work.

Thrush. In the frog grooves. Black, greasy discharge, strong rotten smell. The horse is usually sound in a mild case, and sensitive to the pick in a bad one.

White line disease. At the white line where the hoof wall meets the sole, not in the frog. A crumbly, chalky separation that works upward. It does not smell the way thrush does, and it is a farrier conversation rather than a bottle.

Abscess. Comes on fast. A horse that was fine yesterday is suddenly very lame, often with heat in the foot and a stronger digital pulse. There is no black discharge in the frog. This one needs a vet or farrier, not a topical.

Canker. Rare, but worth knowing about. Looks like an overgrowth of ragged, cauliflower-like tissue rather than a hole packed with black material, and it bleeds easily. It needs a vet.

1. Clean. Pick out both grooves and the central sulcus properly, not just the middle of the sole. A stiff brush on the pick helps get the last of it out so the treatment reaches the tissue rather than sitting on top of packed dirt.

2. Treat. Apply the product to the affected areas of the frog, not over the whole sole. The two long-standing choices are copper naphthenate, sold as Kopertox, and gentian violet, sold as Thrush Buster. Follow the label rather than a habit -- some are meant to go on weekly and some daily, and more is not better.

3. Dry. This is the step people skip. Clean, dry standing does more than any bottle. If the horse goes straight back into the mud, you are starting over.

For a deeper or more painful case, packing the foot and wrapping it keeps the treatment against the tissue and keeps fresh dirt out between applications.

One caution worth repeating: bleach, turpentine, and undiluted disinfectants get recommended in barn conversation and they are hard on healthy frog tissue. Products made for the job are milder on the parts you want to keep.

Mustad Thrush Buster 2oz.View ›

KopertoxView ›

Farrier's Fix Hoof Oil 16ozView ›

Rebound Hoof PackView ›

A mild case in a horse standing on dry ground usually does not need wrapping at all. Pick, treat, keep it dry.

Wrapping earns its place when the groove is deep enough that a topical runs straight back out of it, or when turnout is a swamp and there is nowhere dry to put the horse. Change it daily rather than leaving it on -- a wrap left too long traps its own moisture and you have swapped one problem for another.

Hoof wraps are not turnout or riding gear. They are for standing in while the treatment works.

UltraFlex Flex Foam Hoof Wrap - Set Of 4View ›

Dura-Tech® Vet Flex 4" Bandage WrapView ›

EquiFit Pack-N-Stick Hoof TapeView ›

Pick daily, and pick properly. Both grooves and the central sulcus, every day, not the middle of the sole on the way to the mounting block. This one habit prevents more thrush than anything you can buy.

Fix the wet spot. Gateways, the area round the water trough, and the mouth of a run-in are where horses stand longest and where the ground goes first. Improving drainage or footing in those few square metres does more than improving the whole field.

Keep stalls genuinely dry. Strip properly rather than topping up. Wet bedding under a clean-looking surface layer is a thrush factory.

Use a drying powder on horses living in wet conditions, and on the ones you already know are prone.

Talk to your farrier about a horse that gets it every year. Trimming that opens up a contracted heel and keeps the toe back changes how much material the foot traps in the first place.

Schneiders Hoof PickView ›

Schneiders Hoof Pick with BrushView ›

Coat Defense® Daily Preventive Powder Refill Bag - 64 OzView ›

What you should see first is the smell going and the discharge drying up. The grooves shallowing out and the frog firming up takes longer, because that is the foot growing rather than the infection clearing.

Deep central sulcus cases take considerably longer and are the ones most likely to need a farrier involved, because the crack often needs opening up before anything applied to it can reach the bottom.

Call sooner rather than later if the horse is lame. Thrush bad enough to cause lameness has usually gone deeper than it looks from underneath, and a foot that is painful to pick out is telling you something.

Your farrier is often the better first call for a recurring case in a sound horse, because the fix is usually trimming and hoof balance rather than a different bottle.