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Laminitis Causes in Horses

11th January 2017

Laminitis in horses is one of the commonest causes of lameness.

It can be one of the most devastating and debilitating diseases that can pose a major threat to the wellbeing of any equine.

Laminitis can cause permanent lameness and, unfortunately in some cases, euthanasia is necessary due to unrelenting pain within the hoof.

Therefore it should always be considered a veterinary emergency once symptoms are apparent.

Early appropriate treatment will give the best chance of recovery and in very mild cases, appropriate treatment will resolve the problem with no lasting effect.

However if the inflammation is more severe and progressive, the effects can be much more serious.

What is Laminitis?

Laminitis is a complex disease of the equine foot which we are starting to slowly piece together the puzzle of how and why it occurs.

Structure of the Hoof

fellowes-farm-shop-laminitis-in-horses-hooves

An appreciation of the anatomy of the normal foot is important in understanding the processes and changes that occur in the abnormal laminitic foot.

It also explains why laminitis is such a painful condition. The pedal or 'coffin bone' - the bone at the bottom of the foot that sits inside the hoof capsule, does not rest on the sole of the hoof as our foot does inside a pair of shoes; rather it is suspended a few centimetres above the ground within the hoof.

It is suspended here by laminae [sometimes also referred to as lamellae], which are a very specialised structure within the hoof which resemble the leaves of a book.

Here, the ‘sensitive’ underlying layer (containing blood vessels and nerves) interlocks with a series of leaf-like ‘insensitive’ laminae on the inside of the hoof wall, which lacks blood vessels and nerves.

It is this interlocking of the two sets of laminae, where they act like biological Velcro - many many small attachments together forming a strong bond that is difficult to break.

This helps suspend the pedal bone within the hoof and it is this interface between the two layers of structures where laminitis strikes.

Laminitis inflammation

Laminitis causes the sensitive laminae become inflamed and painful - ‘itis’ is a suffix that denotes inflammation i.e., appendicitis (inflammation of the appendix), colitis (inflammation of the colon).

The inflammation causes the interface between the two sets of laminae to ‘weaken’, resulting in instability of the pedal bone within the hoof.

inflammation and varying degrees of pain, from moderate discomfort to excruciating pain, causing obvious lameness.

Laminitis Prognosis

In some cases, by the time that clinical signs of pain and lameness are noticed, irreversible damage within the hoof has already begun.

In severe cases, the damage may become so that they are no longer able to suspend the pedal bone in its normal position and the entire weight of the horse is  suspended on the painful laminae.

Long term changes in the anatomical position of structures within the hoof can occur as the pedal bone ‘rotates’ or ‘sinks’ within the foot; crushing soft tissues and damaging blood vessels.

This can also cause adverse changes in hoof horn growth.

In severe cases penetration of the sole by the tip of the pedal bone can follow, with fatal consequences.

Even in chronic cases, gradual rotation of the pedal bone can occur and cause irreparable damage to this bone with increasing levels of pain and discomfort and more chronic distortions in the shape of the hoof.

Once the feet have undergone chronic laminitic changes a full recovery is often no longer possible, leaving the horse with permanent foot impairment, which requires ongoing management to prevent further degeneration.

What causes Laminitis in horses?

For a long time laminitis was presumed to be a disease of the foot that affected small, fat native ponies mainly when they ate too much grass.

For some of these ponies the laminitis was mild, and taking them off the grass with anti-inflammatory painkilling medication was all it took to resolve.

However, over the last 5-10 years however our understanding of this complex and often devastating disease has changed.

We have come to understand that in the majority of cases the laminitis is a symptom, not the disease itself.

By recognising laminitis as a symptom we have much more scope for treating the condition.

Treating the sore feet which the horse presents is still important but we now understand that, in order to resolve laminitic episodes and minimise the risk of recurrence, it is vital to identify the underlying cause.

Cushings Disease

Recent studies show that over 90% of laminitic cases are the result of an underlying hormonal disease or imbalance; namely Cushings Disease, sometimes referred to as PPID or Equine Metabolic Syndrome (EMS).

This is the reason that equine vets will now normally recommend blood testing your horse to check for these endocrine disorders very early on in an episode of laminitis.

Cushings disease is tested for by a single blood sample to check ACTH levels. EMS requires a dynamic blood test where we check both resting starved insulin levels and those 2 hours after giving the horse or pony a measured dose of glucose.

Once we understand the underlying problem we can target treatment for these conditions to help us control and hopefully prevent future laminitis episodes.

For Cushings cases this is a drug called pergolide (Prascend, Boehringer Ingleheim) that is a small tablet taken once daily.

Obesity

EMS is similar to type II diabetes in people and is generally associated with obesity and unfortunately this makes it a much more complex and difficult disease to manage.

The mainstay of treatment is weight loss so we will advise a strict diet in order to maximise weight loss.

Often we will use a drug called metformin to help in the early stages, especially when the horse is unable to exercise because its feet are too sore.

Grass has traditionally been blamed for causing laminitis because horses were eating too much of the water soluble sugars (fructans) contained in grass.

Since most horses will eat a similar amount per kg of body weight, this did not explain why you can turn a thoroughbred and a Shetland out on the same field and one would have a problem while the other was fine.

We now realise it is because laminitis-prone horses are super-sensitive to the sugars in the grass, meaning they can eat far less than a non-laminitic prone horse and still induce laminitis.

Overweight horses, or animals that have gained weight, are at a higher risk due to access to lusher grass following a period of wetter weather in the autumn.

This grass often contains higher level of soluble sugars which are enough to tip the balance in a horse or pony that is on the brink of a laminitic episode.

In addition, we know that later into the autumn, frost can also cause a short lived flush in fructans levels in the grass, enough to spark off an episode of laminitis.

These are the main causes of Laminitis, but there are others to watch out for:

  • Stress

Equines are prone to stress and a sudden change in their environment or, for mares, after giving birth, can trigger laminitis.

  • Infection

Blood poisoning (also known as Toxaemia) can cause severe bacterial infections which can lead to laminitis.

  • Concussion

Concussion of the limbs can also trigger laminitis if a horse has been worked fast and for prolonged periods on a hard surface.

fellowes-farm-shop-horse-gallop

How to spot Laminitis in horses

Acute laminitis

The horse will be unable or reluctant to walk or move around properly. It could also lie down with an unwillingness to get up. The animal will be visibly lame with an increased digital pulse in the foot.

When standing the horse will lean back on to its hind feet to relieve the pressure on its front feet. Pain in front of the point of frog will make it put heels down first rather than toes when walking. There can also be symptoms that are similar to colic.

Chronic laminitis

A horse with chronic laminitis will show signs of ongoing symptoms that are generally a result of a relapse from previous attacks.

The horse’s hoof will have the appearance of growth rings around the hoof wall, which generally indicates that it has suffered from laminitis in the past. However, these should not be confused with hoof rings, which are due to changes in nutrition or to stress.

The heel will often grow faster than the toe and the white line in the hoof will have widened. The horse may well have a large crest, which runs along its neckline.

Treatment of Laminitis

Veterinary assessment is important to determine the severity of the condition, underlying issues, and initiate appropriate treatment.

The position of the pedal bone is often assessed by X-rays. This information can also be given to the farrier when shoeing.

Specific treatment regimes vary form patient to patient but almost always comprise of :

1) Non-steroidal anti-inflammatory drugs (NSAIDs) which help reduce the inflammation and therefore the pain

2) Sole support in the form of pads, special shoes or a deep bed to help prevent / reduce rotation and sinking

3) Strict box rest to reduce movement which reduces the forces trying to pull the laminae apart each time the horse takes a step

4) Changing your horse's diet will reduce the intake of non-structural carbohydrates (i.e. - cutting out cereals and feed soaked grass hay only). Use a high quality balancer for minerals, vitamins and protein

5) Treatment of any underlying endocrine problem identified by clinical signs or a blood test thereby reducing / eliminating the initialling cause of the laminitis

fellowes-farm-shop-laminitis-in-horses

Prevention of Laminitis in Horses

To prevent relapses of laminitis, it is important to be vigilant when making changes to the daily management of your horse or pony.

Although you may need your vet's advice, there are easy steps you can take yourself:

  • Using electric fencing to divide pasture and restrict access to grass particularly at the critical times of rapid grass growth when the sugar levels are likely to be at their highest
  • Turning your horse out onto sand if no other turnout is available
  • Preventing access to frosted paddocks
  • Restricting exercise on hard surfaces
  • Exercising your horse or pony daily

Your vet can advise you on other important preventative measures which include:

  • A diet that provides adequate nutrition including minerals, vitamins and protein but without excess carbohydrate
  • Weight loss if your horse is overweight: use a weigh tape for accuracy
  • Routine foot care, including regular hoof trimming
  • Improving parasite control and vaccination protection to keep your horse in good health
  • Nutritional supplements to promote healthy hooves

If you are concerned about laminitis in your horses or ponies, contact the Fellowes Farm Equine Clinic for more advice. We also offer a wide range of hoof care and laminitis products at the Fellowes Farm Shop.

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