WHAT IS LAMINITIS?
To understand what laminitis is requires some knowledge of the anatomy of the hoof. In a healthy hoof the pedal bone (also known as the coffin bone, distal phalanx, or P3) is attached to the hoof wall by the laminae. The dermal (or sensitive) laminae have a blood and nerve supply and grow outwards from the pedal bone and lateral cartilages (below).
The epidermal (or insensitive) laminae are made of horn and face inwards from the inside of the hoof wall (below left). The two interlock forming a strong bond.
In the laminitic hoof this bond has weakened or failed. The laminae stretch or tear apart and the weight of the horse causes the hoof wall to move away from the pedal bone. Arteries and veins are torn or crushed, cutting off the blood supply.
WHAT CAUSES LAMINITIS?
Laminitis has a number of causes. By far the most common is a diet that is high in non-structural carbohydrates (NSC’s) – sugar and starch. These NSC’s are present in the horses diet in manufactured feeds that contain molasses and cereals/grains, and in grass. Other causes include high fever, blood poisoning (eg. from retained placenta), stress, cushings disease and non-weighting bearing lameness in the other leg.
WHY ARE THE FEET AFFECTED?
Laminitis is most commonly caused by digestive upset from a diet that is high sugar (NSC's). The following is a brief explanation of how excessive NSC's (non-structural carbohydrates) in the diet affects the feet.
The horse is designed to eat a high fibre/low sugar diet. Its body does not produce enzymes that can break down fibre, so this is done for it by microbes that live in the large intestine. The microbes break down the fibre into a form that the horse can absorb and use.
A small amount of sugar can be digested by enzymes in the small intestine, but if there is too much it passes through and enters the large intestine. As a result the intestines contents become more acidic. This damages the intestinal lining, making it leaky.
Specific microbes that can digest sugar proliferate, fibre digesting microbes die off. Their decaying bodies release toxins that pass through the leaky intestinal wall and into the blood stream. It is believed that bacteria also pass through into the blood stream.
In the laminae of the hooves are enzymes that detach then reattach the dermal laminae from the epidermal laminae in tiny amounts at a time. This allows the hoof wall to grow downwards whilst still staying firmly attached to the pedal bone. When the toxins and bacteria reach the dermal laminae they cause the enzymes to detach the laminae faster than it can reattach. The connection between the hoof wall and pedal bone weakens.
The shearing force of the horses’ weight causes the hoof wall to separate from the pedal bone, rotating away from it, and the pedal bone can sink down within the hoof capsule. This damages the blood vessels that supply the laminae resulting in the blood supply being cut off and starvation and death of the tissues.
Follow this link:http://www.hoofrehab.com/LaminitisUpdate.htmlto Pete Rameys website for an in depth and straight forward explanation of the process.
THE DAMAGED BLOOD SUPPLY.
The picture below shows a venogram of a healthy foot with normal blood supply (inset), and a laminitic foot (main picture). To produce a venogram radio opaque material is injected into the blood vessels so that they can be seen on x-ray. In the laminitic hoof the toe area has no blood supply, no oxygen and nutrients reach the cells of the laminae and they die.
In the next picture a process of acid erosion has been used to illustrate the loss of blood supply. This involves injecting resin into the blood vessels, the rest of the tissue is then dissolved in acid leaving the resin behind. On the left we see the blood supply of a healthy foot, and on the right a laminitic foot.
TERMS USED WHEN DISCUSSING LAMINITIS.
When talking about laminitis the terms we use can cause confusion. The terms laminitis and founder tend to be used interchangeably. Laminitis is Latin and means inflammation of the laminae.
The laminae can be mildly inflamed and the horse does not show lameness, but by definition it is suffering with laminitis. This low grade laminitis would go unnoticed in the shod horse (remember that shoeing decreases blood flow within the hoof, which causes loss of sensation). However, in the barefoot horse, with full sensation in its feet, you would notice sensitivity on stony ground. Many people do not acknowledge low grade laminitis, and would say this is a horse who “just needs shoes”.
We tend to use the term laminitis to mean a far more serious situation where the hoof wall at the toe has disconnected from the pedal bone. This leads to:
1. CAPSULAR ROTATION – the pedal bone stays correctly aligned to the bones of the pastern but the hoof capsule rotates out of position. Below: the yellow line shows the bones all correctly aligned, the toe wall should be parallel to the yellow line, it is not because the hoof capsule has rotated away from the pedal bone.
2. PEDAL BONE ROTATION - the pedal bone rotates so that it is not aligned with the bones of the pastern. Below: note that the yellow line is not straight. The term pedal bone rotation is used a lot when discussing laminitis when what is actually ment is capsular rotation, which is far more common. The pedal bone does not tend to rotate much because there are many strong ligaments holding it and pastern bone in alignment.
3. DISTAL DESCENT (or sinker) – where the bone has descended within the hoof capsule. Below: the lower line marks the top of the extensor process of the pedal bone, the upper line marks the hairline. The 2 should be level or nearly so.
Laminitis is extremely painful for the horse which exhibits lameness and in severe cases the classic leaning back laminitis stance, as he tries to move the weight from the damaged toes back to the heels.
SIGNS THAT A HORSE IS OF INCREASED RISK OF LAMINITIS.
There are easily spotted signs that a horse has an increased risk of developing laminitis. Unfortunately there is no way of knowing how soon. Whilst some cases of laminitis are caused by unavoidable accidents: horse breaks into feed room, retained placenta etc., in most cases of laminitis the writing was on the wall months, even years before, and it could have been prevented, if only people knew how to recognise the warning signs and how to manage the horses diet and lifestyle correctly to prevent the laminitis from ever happening.
1. OBESITY – indicates diet is unsuitable, likely too high in NSC’s. Unfortunately for domestic horses we tend to base our assessment of the horses weight on horses that we see winning in the show ring. They are winning, so we assume they are in the ideal condition. This is not the case, these horses are obese and at increased risk of laminitis. The high incidence of laminitis in show horses is kept from public knowledge. The horse below left is in typical show ring condition. In the same way that a high sugar diet and obesity can cause humans to develop type II diabetes, several years of high sugar diet and obesity causes horses to develop insulin resistance (also known as metabolic syndrome). Insulin resistance increases susceptibility to laminitis. The horse on the right is in ideal condition, but sadly most people would consider it to be underweight. NB: Highlands are not supposed to be fat, nor are shetlands or cobs!
2. FATTY DEPOSITS - Cresty neck, fat pads on shoulders, back and rump, and fatty deposits above the eyes all indicate insulin resistance (also known as equine metabolic syndrome). Insulin resistant horses are high risk for laminitis. For more information on insulin resistance visit www.ecirhorse.com
3. HORIZONTAL RINGS IN HOOF WALLS – these indicate minor episodes of low grade laminitis. They are interruptions in normal horn growth caused by metabolic stress and indicate a diet too high in NSC’s.
4. FLARED HOOF WALLS – low grade laminitis has weakened the laminae connection so the hoof wall is not held tightly against the pedal bone. The problem is exacerbated by shoes and peripheral loading.
5. FLAT OR BULGING SOLE - accompanies flared walls. Indicates a weakened laminae connection which has allowed the pedal bone to drop too low in the hoof capsule (left). The sole should have shallow concavity all the way around (right).
6. RAISED DIGITAL PULSES – If the laminae are inflamed (low grade laminitis) a mild pulse will be felt in the digital artery. In a severe episode of laminitis this pulse will be very strong. In a hoof that has no inflammation no pulse will be found. Imagine you have banged your finger, normally there is no pulse in the ends of our fingers, but if you bang it you will feel a throbbing pulse. To learn how to check the digital pulse visit http://www.ironfreehoof.com/equine-digital-pulses.html
7. HAS SUFFERED FROM LAMINITIS IN THE PAST - It is very likely that the horse is already has insulin resistance/metabolic syndrome, and is at increased risk of developing laminitis again.
EARLY SIGNS THAT A HORSE IS DEVELOPING LAMINITIS.
1. Horse seems a bit lazy, less forward going.
2. Moves with a slightly stiff legged gait in the front legs.
3. Looks ok on straight lines but uncomfortable turning.
4. Raised digital pulses.
5. Looks ok on flat or soft ground but uncomfortable on rough or stony ground.
Catch laminitis at this stage, make management changes (get the horse off grass and onto soaked hay) and you can turn the situation around quickly, minimising damage to the hooves. Ignore these signs (leave the horse at grass) and it can deteriorate fast, resulting in excruciating pain for the horse and months of care to get the feet back to normal. You could even lose your horse.
IF YOU SUSPECT YOUR HORSE HAS LAMINITIS:
1. Take the horse off grass – immediately and completely. Feed him ad lib hay that has been soaked for at least 1 - 2 hours (this leaches out 18-30% of the sugar). Do not starve a laminitic horse, he could develop hyperlipaemia which can be fatal. Feed only a small amount of unmolassed sugar beet as a carrier for a good quality vitamin and mineral supplement. A probiotic will help stabilise the hind gut.
2. Get your vet out to confirm that the problem is laminitis and give pain relief as needed. Your vet may suggest blood tests for insulin sensitivity and cushings disease. If the results are positive medication will be given.
FOLLOW UP CARE:
1. Support the hoof with boots and pads. A 12mm easycare comfort pad is needed inside the boot.
2. Keep the horse on a grass free area that is big enough for him to move around as much as he feels comfortable to, but small enough to discourage running around. A quiet companion is ideal to prevent the recovering horse becoming stressed, but it must be one that will not bully the laminitic horse, or encourage it to run around. Gentle exercise increases blood flow in the foot, whereas box rest reduces blood flow and delays healing. Walking on damaged laminae can worsen rotation and sinking. Let the horse decide how much he wants to move, if he does not want to move never force him too. Make sure his feet are supported by boots and pads.
3. Initially follow your vets advice on the amount of pain relief needed. But reduce and then cut out bute as soon as possible by stabilising the horse with dietary changes and padded hoof boots. Vets commonly prescribe phenylbutazone (bute), which is a pain killer and anti-inflammatory. However, high doses of bute over a period of time will result in ulcerations of the stomach and intestinal lining. Remember part of the cause of laminitis is damaged intestinal wall, so it makes no sense to give bute for longer than is absolutely necessary. The other danger of bute is that you and your horse will not know how the feet are doing and may do too much, possibly causing further damage.
NUTRITIONAL SUPPORT OF THE LAMINITIC HORSE.
To improve a laminitic horse the diet must be as low in non-structural carbohydrates as possible. This is the most important part of the process. No trimmer or farrier can improve a laminitic horse while its diet is too high in sugar.
1. NO GRASS.
2. SOAK HAY FOR AT LEAST 1- 2 HOURS. This will leach out 18-30% of the sugar. Rinsing the soaked hay in clean water and changing the water part way through soaking helps too. Long term if hay can be sourced that tests below 10% NSC this can be safely fed to most laminitics without soaking. If hay has not been tested it must be soaked.
3. BALANCE MINERALS. The best way to do this is to identify mineral imbalances and deficiencies in the hay by having it tested in a lab. Then have a bespoke supplement made up to balance to the analysis results. If this isn’t practical then a quality commercial supplement is better than nothing.
4. Use UNMOLASSED SUGAR BEET as a carrier for the mineral supplement. This can be rinsed in clean water before and after soaking to further reduce sugar.
5. A PROBIOTIC will help to stabilise the hind gut.
DEALING WITH THE AFTERMATH/TRIMMING THE LAMINITIC HOOF.
When trimming a laminitic hoof my aim is to return the rotated pedal bone to a normal angle and position relative to the other bones of the limb, and the ground. And to maintain this relationship whilst the blood vessels heal, and blood supply and growth return to normal. This requires regular trims because of the way the damaged hoof grows.
To illustrate how the laminitic hoof grows I have highlighted the growth rings in red (below left). The rings are closer together at the toe and widen towards the heel. The heel grows downward and gets higher, the toe grows forward and gets longer (below right).
The high heel raises the back of the pedal up, tipping the front of the bone down so that it presses into the sole. If this is not corrected then over time the pressure at the tip of the pedal bone causes bone erosion (below). Bone that is under constant pressure remodels – bone is removed, and a large part of the pedal bone can disappear. It is common for the pressure to cause the pedal bone to develop a ski tip at the end. With the pedal boned tipped up shearing forces are created between the pedal bone and hoof wall, tearing them apart and delaying or preventing healing and the growing in of hoof wall that is well connected to the bone.
It is important that at each trim the heels are shortened to a normal length. Note: "normal" is individual to each horse. There is no set formula, or measurement in centimetres or degrees, that can be universally applied to every horse. An experienced natural hoof care practitioner works to several "landmarks" visible on the hoof. If you want to know about trimming the laminitic hoof in detail study Pete Rameys instructional DVD series "Under The Horse" available from www.hoofrehab.com
Below left: the yellow lines are the projected new hoof capsule position, this is what we want to grow. Below right: the pink lines are the actual trim we would do on this hoof. We do not remove all the excess hoof wall as that would weaken the hoof.
For a severe laminitis case study CLICK HERE
SHOULD A LAMINITIC BE SHOD OR BARE?
When a horse is bare everything on the base of his foot plays a part in supporting the weight of the horse. Most of the weight is born centrally, directly underneath the pedal bone. When a horse is shod the foot is lifted off the floor by the shoe, the weight is born peripherally via the hoof walls - the weight of the horse is suspended from the laminae. This is unnatural but the foot of the horse is designed to withstand huge pressures, eg when galloping over rocky terrain. So it can withstand peripheral loading, although all to often developing hoof deformity and lamness.
In laminitis the connection between the pedal bone and hoof wall is weak and damaged and yet a shoe is still used, suspending the weight of the horse from the damaged laminae. This makes recovery a long and painful process and may prevent it altogether. A heart bar shoe is often used for laminitics. The idea is that the frog plate supports the pedal bone and prevents rotation. However, the frog plate doesn’t reach far forward enough to do this. And if there is rotation the sole corium becomes pinched between the pedal bone and frog plate causing pain.
Another misconception is that the deep digital flexor tendon pulls on the pedal bone causing it to rotate. In reality the pedal bone and pastern bones are held securely in place by a series of ligaments and what we are actually seeing in capsular rotation. This misunderstanding leads to the idea that reducing the tension of the tendon will stop rotation. To achieve this the heels are left too long. But as explained above, this raises the back of the pedal bone, so that the tip presses painfully into the sole and delays or prevents healing.
Having said all that, if the trim is good and diet is addressed, horses can return to soundness in shoes, but my experience is that you halve recovery time by using natural hoof care.
DORSAL WALL RESECTIONS.
Here the hoof wall is removed down to the dead area of laminae (below left). The belief is that this relieves pressure, allowing the hoof wall to grow down connected to the bone.
The negatives with this procedure are;
1. Increases chance of infection (the black dots on the photo left are flies).
2. Exposes the living dermal laminae beneath to knocks and damage.
3. Weakens the structural integrity of the hoof.
4. A shoe is still applied resulting the horses weight being born by the damaged laminae at the quarters.
The natural trim positions breakover so that pressure is reduced in the same way without having to thin or remove hoof wall (below). It gives the benefits of a dorsal wall resection, without any of the negatives.
LONG TERM MANAGEMENT OF THE LAMINITIC HORSE.
Once a horse or pony has suffered from laminitis it will always be susceptible to another attack. It is very likely to be insulin resistant and will always need to be carefully managed on a low sugar diet to avoid further bouts of laminitis. This means a lot of work soaking hay, using grazing muzzles, setting up grass free paddocks, exercising the pony to keep its weight down.