Laminitis is something every horse owner has probably heard, if not actually had experience, of. But what exactly is it? Why does it happen? And what can we do about it?
What is laminitis?
As the name suggests, laminitis is damage to the sensitive tissues (laminae) of the foot, leading to characteristic signs. It is a disease of the whole horse, although the most obvious symptoms relate to the feet.
It is also an extremely common disease, and has major welfare implications as affected horses are in a lot of pain.
To understand the changes that take place within the foot of a laminitic horse, it is important to understand the basic anatomy of a normal horse’s foot.
The majority of the horse’s weight is taken through the pedal bone, which is suspended inside the hoof capsule by interlocking ‘fingers’ of tissue called laminae, which attach the pedal bone to the inside of the hoof.
In the normal horse these laminae act as a shock absorbing system, reducing stress on the limbs during movement and ensuring even energy transfer.
What causes laminitis?
Anything that causes a metabolic imbalance can result in laminitis, but some of the more common causes are:
· Carbohydrate overload
· Ingestion of certain toxic plants
· Endotoxaemia (eg following colic, or retained placenta in a mare)
· Steroids (though recent research suggests this may not be as common as previously thought)
· Excessive weight bearing (eg non-weightbearing lameness on opposite leg)
· Repeated concussion
· Under-exercised overweight ponies.
Laminitis can also occur secondary to other conditions such as septicaemia, Cushing’s disease and Equine Metabolic Syndrome.
Risk factors that may predispose a horse to developing laminitis can include:
· Being overweight
· Lush grass (primarily in spring and autumn)
· Trauma to the hoof
· Prolonged stabling on hard ground
· Standing for long periods (eg when transported long distances)
· Previous laminitis attacks
· Liver disease.
But sometimes the underlying cause of the laminitis is not immediately obvious.
Some laminitis myths...
Allowing a horse to drink cold water immediately after exercise causes laminitis. Not true, this may cause colic but not laminitis!
Laminitis can be the result of allergies. Not true, there is no scientific evidence to suggest an allergic basis to laminitis.
Pregnant mares can’t get laminitis. Not true, they can and they do!
My horse can’t have laminitis because his feet aren’t hot. Not true, this actually a very unreliable indicator as the temperature of the feet fluctuates throughout the day even in normal healthy horses.
Standing my horse in cold water will help with laminitis. Not true, and it may even be counterproductive as cold will make the blood vessels in the laminae constrict even more.
Laminitis is genetic. Not true. Some causes of laminitis may have a genetic basis, but the disease itself does not.
Horses never get laminitis in their back feet. Not true, any combination of feet can be affected.
Only ponies get laminitis. Not true, horses can and do get it too!
What happens to the foot in laminitis?
Laminitis leads to a disruption to the blood supply to the foot, resulting in death of the tissues that make up the laminae.
Regardless of the underlying cause, the resulting signs are very similar and easily recognisable.
Why does it happen?
This is still the subject of much research. There are several theories, though neither seems to provide all the answers for every case.
In the normal horse, the forces exerted down a limb should equal the supporting forces provided by the laminae, the frog and sole, and the pull of the tendons.
When it all goes wrong...
Three phases to laminitis are recognised.
Separation of the laminae is triggered. This happens before any signs of foot pain.
IMPORTANT! By the time the horse shows any signs of pain, damage to the laminae and destruction of the all-important attachments has already started!!
This lasts from the onset of pain and lameness to the time when the pedal bone begins to move within the hoof, and we can see evidence of this on xrays.
Any combination of feet can be affected, but signs are usually more obvious in the forelimbs because of the extra weight carried through the forehand. When the front feet are worse affected than the hind feet, the horse usually leans back on its hind legs with the forelegs stretched out in front.
If all four feet are affected the horse may stand with all four feet tucked under its abdomen.
Affected horses may lie down for abnormally long periods, and be extremely reluctant to move. When standing they often shift their weight from foot to foot or rest alternate feet. If they can walk, the feet are placed on the ground heel-first. The affected feet are very painful, and may be warm to the touch (but not always, so do not rely on this), and there may be bounding digital pulses (but again not in every case). The heart and respiratory rates may be increased as a result of pain.
Progressive death of the laminae results in the hoof separating from the pedal bone. This separation can lead to rotation of the pedal bone, which is made worse as the horse tries to move, due to the lever action of the dorsal hoof wall and the horse’s weight through the pedal bone. This is why strict box rest is such an important part of treatment.
In the worst case scenario, if this rotation continues untreated, it can drive the pedal bone through the sole of the foot. Any convexity of the sole should therefore ring warning bells. These horses are also very sensitive to hoof testers over the tip of the frog.
‘Sinkers’: These are usually (but not exclusively) very acute cases in which the pedal bone sinks straight down within the hoof capsule, without rotating. There may be a distinctive depression around the coronary band, and in severe cases the hoof capsule may separate completely, or the coronet may slough over limited areas.
The changes within the feet of these horses are a result of many frequent, usually milder, episodes of laminitis. There is usually rotation of the pedal bone, which leads to thickening of the dorsal hoof wall over time. The sole may also thicken, and the white line is wider at the toe, having a stretched appearance. There will also be rings visible on the hoof wall, wider at the heel than the toe.
These horses also walk with their weight on their heels, and this, combined with a faster than normal rate of hoof growth, can lead to a ‘Turkish slipper’ effect if remedial farriery is not undertaken regularly.
The Obel Grading System
This is a useful way of grading the severity of laminitis, in particular when assessing the progress of a horse.
Grade 0: The horse is sound in walk and trot in a straight line on a hard surface.
Grade 1: The horse shifts weight from foot to foot when at rest, but is sound at walk. There is a stilted gait at trot in a straight line on a hard surface and when asked to turn at walk does so carefully.
Grade 2: The horse walks stiffly and has a stilted gait at trot on a hard surface, and also finds it very difficult to turn. It is still possible to lift a foot up without great difficulty.
Grade 3: The horse is reluctant to move at walk on any surface, and it is difficult to pick up a foot.
Grade 4: The horse will not move voluntarily, and if forced to walk is especially reluctant to move from a soft to a hard surface. It is almost impossible to pick up a foot.
Taking X-rays of the horse’s feet is an important part of assessing and forming a treatment plan for a laminitic horse. So what are we looking for on xrays?
We will place a metal marker on the dorsal wall of the hoof, this makes it easier to see on the xrays, so we can assess if the dorsal wall of the hoof is parallel to the dorsal wall of the pedal bone, ie if the pedal bone has rotated.
There may be dark lines visible where the laminae have separated (‘gas shadows’).
The sole may be reduced in thickness.
There may be changes in shape of the pedal bone, particularly at the tip, in chronic cases.
Sinking – if the pedal bone has dropped within the hoof capsule, but the dorsal wall of the hoof and the pedal bone are still parallel.
Ideally the key to treating an attack of laminitis is to treat the underlying cause, if known.
We will usually prescribe ACP – this dilates the blood vessels in the feet, improving the circulation to the laminae. It may also sedate the horse a little and make him more inclined to lie down and take the weight off his feet.
Pain relief is of course very important, so ‘bute will usually be given as well, and the horse should be kept on a soft, deep bed (ideally shavings) so help support the feet.
Remedial farriery is also very important, and some cases may need extra support for the feet in the form of frog pads or heart bar shoes.
Absolute rest is essential! Walking will only cause more damage to the laminae.
Chronic lamintics also require regular attention from the farrier in order to keep the feet trimmed correctly. Shortening the toes reduces the lever effect of the dorsal hoof wall and reduces the pull on the laminae.
In some cases we may decide to remove part of the dorsal hoof wall. Although this sounds dramatic, it can help release any fluid that has built up where the laminae have separated, therefore reducing pressure and relieving pain, as well has helping to restore the blood supply and counteract rotation. It also helps realign the hoof growth with the pedal bone.
This can be a common cause of laminitis in older horses, and is caused by a benign tumour in the pituitary gland at the base of the brain. Other signs can include excessive drinking and urination, an abnormally long, dense, curly coat which does not shed in summer, sweating and weight loss, and fat pads above the eyes.
As mentioned earlier, the best way to treat laminitis is to treat the underlying cause if we know what that is, and in Cushing’s horses we often struggle to control the laminitis unless we also treat the Cushing’s Disease.
Equine Metabolic Syndrome (EMS)
This is another common cause of laminitis and is a complex subject in itself, being similar to Type II Diabetes in humans. We have produced a separate information sheet on EMS, which gives further detailed information.
Feeding the laminitic
If the horse is overweight, we will discuss feeding reduced rations for weight loss. The main component of the diet should be forage, and sugars and starches should be avoided. If concentrate feeds are needed, these should be brands approved by the Laminitis Trust and bearing their logo.
If more energy is needed (eg to keep weight on an older horse, or one with Cushing’s Disease), use oil rather than starch.
Sugar (fructan) concentrations in grass have been much discussed in recent years as a cause of laminitis, and although it is unclear whether this would be entirely responsible for a laminitis attack it could certainly be a contributing factor, so in a laminitis-prone horse it is probably best to avoid turning out on stressed grass (eg frosted or overgrazed ground), so some sources suggest use of a grazing muzzle rather than a conventional starvation paddock.
Recent research has suggested that most laminitics are insulin resistant, and that it is this excess insulin that causes the laminitis. Although at present we can’t treat the insulin resistance itself, monitoring a horse’s insulin levels has been shown to give a good indication of the long-term outlook, as horses whose insulin levels remain high following an acute episode of laminitis are much more likely to suffer further attacks than those whose insulin levels return to normal. It has also been shown to be a good way of monitoring a horse’s response to medication for Cushing’s Disease, as Cushing’s horses are also resistant to insulin.
Ok, I think my horse has laminitis. What should I do?
- If he is in the field and if he is able to walk, bring him into a stable on a deep (4 – 6 ins) bed, preferably shavings.
- Call your vet as soon as possible.
- Feed him concentrate or haylage until you have discussed his diet with your vet. Plain hay is best, preferably soaked.
- Try and fit pads to his feet. If they are fitted wrong and put pressure on the sole this will cause him more pain.
- Make him, or even allow him to, walk. Exercise will tear the remaining laminae and make the situation worse.
- Ask your farrier to take his shoes off until your vet has assessed the condition of his soles. If they are convex then removing the shoes will make him stand on his soles which will be painful.
- Starve him. He may need his diet restricting, but your vet will advise on this.
- Ask your farrier to fit heart bar shoes unless your vet has seen the horse and taken x-rays. They can do more harm than good if fitted incorrectly.
- Delay calling the vet and medicate the horse yourself. Antibiotics are of no use in laminitis, and painkillers will mask the severity of the condition.
- Panic! Cases that are treated promptly have a much better chance of recovery than those that are left to ‘see if it sorts itself out’ before calling the vet.
Management of the laminitic horse
Successful treatment and management of any laminitic must be a team effort. This requires time and dedication from 3 key people...
· Your vet
· Your farrier
· And you!
Foot care for the laminitic
In the long term, your vet will not always be there when the horse’s feet are trimmed, and it may well be up to you and your farrier to ensure the feet are managed appropriately.
This may sound obvious, but laminitic feet are not normal!! Therefore it is no good trimming a laminitic foot as though it were a normal foot.
So what’s different?
The heels tend to grow faster than normal;
The soles tend to be thickened and therefore flatter than normal;
The white line is abnormally wide at the toe;
The dorsal wall grows slower than normal.
Because of all this, laminitic feet need attention from your farrier much more regularly than normal feet, most will need trimming on a 4 – 6 weekly basis in order to stay in control of the situation. Long or unbalanced feet can bring on another attack of laminitis due to abnormal strain placed on the laminae, so it’s very important to keep on top of this aspect of foot care.
If the toe is left too long it will act as a lever and tear the laminae apart each time the horse takes a step.
If the front wall becomes too thick it will cause inward pressure on the laminae.
And there should be no pressure on the soles, from either the ground, or shoes.
Therefore it is especially important to keep the feet short and balanced, even if the horse does not have active laminitis at the moment, because if there has been previous damage to the laminae he will be prone to further attacks. If in any doubt X-rays will help your farrier establish how much there is to trim, probably more than you will think from just looking at the foot!
The end result should be a balanced hoof with the dorsal wall a straight line from the coronary band to the ground.
Trimming the feet may reveal a crescent shape of exposed separated laminae at the toe, there may also be some bruising/bloodstaining exposed if there has been recent laminitis. Don’t panic, this is ok! But do be careful if conditions are muddy, as infection can track up these areas and lead to foot abscesses, which are a not uncommon complication of laminitis.
If thickened soles are causing pressure, shoes may be needed. Your farrier will seat these out so they do not press on the sole, and the horse’s weight is taken through the walls of the hoof. Shoes can be glued on rather than nailed if necessary. Open toed shoes, or reversed shoes, are not recommended.
If your farrier isn’t happy about any aspect of the foot, eg how thick the sole may or may not be, get advice from your vet, who will X-ray the feet if appropriate.
If your horse is normally good to shoe and suddenly starts to object to having shoes nailed on he may be trying to tell you something so ask your vet to check him over.