Thrush is so commonly overlooked as a major cause of lameness in horses. In fact thrush is so common it is often just considered “normal”. Many horse owners do not recognise thrush - when I point out that a horse has thrush owners will exclaim “Oh! He’s never had that before!” I can guarantee you that your horse has had thrush before, and most likely has thrush right now.
Why is thrush such a big deal?
Thrush infections weaken the hoof, and alter the way the horse moves and uses his hooves. Horses are designed to land heel first with each stride; the horse fully extends the limb so that the joints are aligned, the fascia of the hoof and limb opens out, proprioceptors can sense where the limb is in space and ready the hoof for impact.The heels and frog impact the ground first, a large, healthy frog transfers the impact through to the digital cushion, and the weight rolls over the hoof as the horse propels itself forwards. Read more about the importance of heel first landings, article coming soon.
Weak, thrush ridden hooves can’t perform in this way, and so the horse starts to alter their movement to accommodate. This doesn’t usually show up as lameness, horses are programmed not to show weakness or they may be the one to get pick off by a predator, so they compensate. They start to land on their toes, causing jarring right up the limb, proprioception cannot work optimally so the horse may start to stumble, the biomechanics of the limb are altered so the horse starts to recruit other muscle groups for locomotion. This altered movement and weight bearing starts to distort your horses hooves (think long toes, contracted heels). Then a few years down the line the horse can no longer compensate, they have over stressed and broken down structures that have been doing more than their share of the work and the horse “suddenly” goes lame.
You can start to see the whole horse effect of that “little bit of funk” in your horses feet!
Why do our horses have thrush?
Thush is something that is always going to need to be managed in our domestic environment. It can’t be cured with a few squirts of some special product, it needs to be managed through environment, diet and hygiene.
Horses are evolved to live in a predominantly dry environment, traveling many kilometers over varied terrain and eating fairly low quality forage. They are constantly cleaning their own hooves through abrasion and exfoliating dead materials so that thrush doesn’t get a chance to take a hold. Do they get foot funk? Yes, probably at sometimes of the year, but the body can handle sometimes, just not all the time.
In contrast, our domestic environment is usually a soft grassy paddock, minimal movement, lots of standing about, often in their own urine and manure, fed on a rich sugary diet that thrush infections love. They are trimmed every 4-8 weeks, rather than the “everyday trimming” that hooves were designed for, so dead hoof creates pockets and layers where thrush thrives.
What is Thrush?
Thrush is a symbiotic relationship between fungus and bacteria, the exact make up is dependent on what is in your soil. Most commonly it is recognised by its pungent smell, and black goo. But thrush can take on different appearances which means it often gets missed.
Hoof 1: Deep central sulcus thrush, fungal pitting of the heel bulbs, weak, atrophied frog. This horse usually has healthy frogs and a great heel first landing, he was still landing on his heels, and due to the heels now taking all the impact, rather than the load being shared out over the heels and frog, you can see the resulting heel bruising. Its only a matter of time before the horse changes his gait and the hoof starts to distort.
Hoof 2: Weak, thrush ridden frog. Deep central sulcus, tissue eaten away in typical thrush patterns. Despite the lack of black funk, thrush is very much thriving in this foot. This horse was landing on her toes to avoid the back of her foot, her heels are contracted and toe was stretched and running forwards. Note how narrow the heel bulbs are compared to hoof 1.
Hoof 2, heel view: Showing how much frog tissue is missing. The frog should have passive ground contact, so on concrete the frog should be touching the ground, but not weightbearing. This frog cannot share the impact and transfer the forces into the digital cushion, not surprising that this horse is avoiding her heels.
Hoof 3: “Typical thrush”, black, sludgy and stinky, but again, the real issue is not just the funk on the surface, its the amount of frog tissue that has been eaten away.
Hoof 4: Severe deep central sulcus thrush, very contracted heels with heel bulbs squeezed together, badly deformed and atrophied. Note the dry conditions, thrush still thrives in drought, it just loves a crevice to hide in.
Hoof 5: A healthy frog that can do it’s job! Wide, heels, plump, rounded heel bulbs, smooth frog tissue, a layer that has shed, but no thrush underneath. This horse can comfortably load the heels, with the frog taking it’s share of the load and transferring impact into a healthy digital cushion.
Hoof 5 again, just to prove that wet conditions don’t mean thrush if managed properly! In the depths of a wet winter, the frog and heel bulbs are still healthy.
How to manage and prevent thrush
Thrush needs to consistently managed to keep hooves healthy. Management and treatment is predominately up to the horse owner, the trimmer or farrier cannot “trim it better”, we can tidy up flaps where thrush might take hold, keep hooves in the best balance that we can so that the horse can load his feet properly, but ultimately, its up to you!
The main factors in healthy hooves are; environment, diet, movement and hygiene. Lets take a look at each.
Environment
Horses are designed to live in predominately dry conditions, and move over a variety of terrain. If your horse lives on dirt and grass then their feet are conditioned to dirt and grass. moving over sand, gravel, rocks, through streams or rivers conditions the horses hooves to a variety of terrain, and helps to clean and exfoliate the hooves.
Movement
Movement over that varied terrain makes a huge difference! Movement stimulates blood flow, flexes and “works” the structures of the hoof (the hoof gains strength or loses it just like any other part of the body), flicks out dirt clods that get packed into the foot, as well as wearing and exfoliating dead hoof.
Diet
Making sure your horse has a balanced diet so that they are getting all the vitamins and minerals they need to build healthy hooves. A diet that is as close to natural as possible, low sugar, high fiber. Thrush loves high sugar.
Hygiene
Daily maintenance to make up for some of the short falls of our domestic environment. Picking out and wire brushing to hooves to expose them to the air and exfoliate some foot, getting right down into the grooves next to the frog. Providing a clean, hygienic surface for your horse to live on, so regular picking up of manure, “hangout” areas in particular need to be waste and mud free.
Topical Treatments
I have put this one last, because it should come last, after putting all the above steps in place! If your horse is just standing around in a cesspit of doom, it is a waste of time applying topical treatments. You need to remove the cause of the thrush, and then use topical treatments to resolve severe cases.
There are many thrush treatments on the market, and few that should actually be used. Always check out the ingredients. Many contain formalin, gentian violet or other harsh ingredients. Sure, they do kill thrush, but they also kill live tissue. This gets us into a cycle of doom, where you kill the thrush, but do nothing to grow in healthy tissue, so you still have a weak, vulnerable structure that is prone to infection…
Hooflex
Asorbine Hooflex Thrush Remedy is currently my preferred topical treatment. I see regularly that when this is used alongside good thrush prevention, it really helps to grow in healthy tissue. I like to put it in a spray bottle for easier use. Available in most saddleries, except in areas where my clients reside because they bought it all!
Nappy rash cream
Cheap, and readily available zinc oxide cream is excellent for treating many cases of thrush. Pick out the feet making sure to get to the bottom of all crevices and grooves. Apply the cream thickly into all grooves and over all surfaces. Dirt will pack in and usually hold the treatment in for longer.
Apple cider vinegar
This can be effective as maintenance, but will not usually sort out more severe cases of thrush. Put it in a spray bottle and keep it with your hoof pick and brush.
Hoof clays and mud
There are some excellent hoof clays and putty’s on the market. If it contains, zinc, french green clay, tea tree, honey etc, its usually good! You can even make your own clay, or add some of these ingredients to nappy rash cream.