Laminitis and Founder

This article describes laminitis and founder, with the following topics:

  • 1.0 What is Laminitis & Founder?
  • 2.0 Symptoms - Acute Laminitis
  • 3.0 Symptoms - Chronic Laminitis
  • 4.0 Diagnosis & Treatment
  • 5.1 Causes - Carbohydrates in Food
  • 5.2 Causes - Nitrogen in Food
  • 5.3 Causes - Mechanical Separation
  • 5.4 Other Causes
  • 6.0 Prevention
  • 7.0 References
  • 8.0 Emergency treatment

If you suspect that your horse has laminitis (acute laminitis, not chronic), we would suggest that you go straight to section 8.0.

For information on other equine illnesses, click on horse disease.

1.0 What is Laminitis & Founder?

Laminitis is a common and serious disease of the hoof. The term 'laminitis' refers to damage to the 'laminae', which is the connective tissue which connects the hoof bones to the hoof wall. Depending on the type and severity of damage to this tissue, possible problems include:

  • Rotation of the hoof bones within the hoof.
  • The hoof bones sinking down lower into the hoof.
  • Damage to various tissues and blood vessels, due to bone movement and/or inflamation and/or other hoof changes associated with damage to the laminae.
  • Permanent changes to the hoof growth mechanisms, resulting in abnormal growth patterns (e.g. flattened or convex sole, visible rings in the hoof wall, separation between hoof wall and sole).

After horse colic, lamantis is the main cause of pre-mature death of domestic horses. Such deaths are not directly caused by laminitis itself, but through euthanasia of horses who have an unacceptable amount of permanent damage to one or more hooves as a result of laminitis..

Laminitis has various causes (see below) but the two main causes are :

  • Toxins. The release of certain toxins (poisons) into the blood stream will result in damage to the liminae. Such toxins can result from external sources (e.g. what the horse eats), internal sources (e.g. toxins produced by an infection) and in some cases certain medications. 
  • Mechanical. Repeated shocks to the hoof (e.g. running over a hard surface for a long time) can damage the liminae.

When the damage first occurs, it is known as 'acute laminitis'. If a horse has only partial recovery from 'acute laminitis', the remaining permanent damage is known as 'chronic laminitis'. The term 'laminitis' is the medical term, whereas 'founder' is more a common use term. The term founder does not have a single agreed definition and consequently is used in different ways (even by veterinarians):

  • Some people use 'founder' as an alternative term for 'laminitis'. In other words, the two words describe the same condition.
  • Some people use 'founder' to mean severe 'laminitis', or a condition following on from 'laminitis'. Specifically, the term 'founder' is sometimes used to describe the condition where the hoof bone sinks into the hoof (reportedly associated with the nautical term founder, meaning to sink).
  • Some use the term 'laminitis' just to refer to an abnormal condition of the laminae (e.g. reduced blood supply, inflamation, tissue break down), the term founder to describe the condition where the bone moves. There are two common variations of this definition; one where founder is used to describe any bone movement and the other where founder is used to describe rotation of the bone and 'sinker' for the next stage where the bone 'sinks' (moves downward to the sole, or even through the sole).

Due to these differing definitions of laminitis and founder, there is sometimes disagreement and confusion over what is meant. For this article, we use the term laminitis in the fullest sense, to include not only the changes in the liminae but also the resulting medical condition (e.g. bone movement, abnormal hoof growth).

2.0 Symptoms - Acute Laminitis

The most noticeable symptom of laminitis is pain in the hooves. It can occur in one, two, three or four hooves. Indications of pain in the hooves include:

  • Lameness. Unnatural gait, reluctance to walk or move forward.
  • Stance. Standing so that weight is taken off the affected hooves. As laminitis is more likely to occur in the front hooves than the rear (or be more severe in the front hooves), a characteristic stance has the forelimbs stretched in front, with the hind legs brought forward underneath the horse to take weight off of the affected front hooves.
  • Increased surface sensitivity. In mild to moderate cases the horse may walk normally over soft surfaces (e.g. pasture) but show increased sensitivity to hard surfaces (e.g. concrete stable floor) or rough surfaces (e.g. gravel path).
  • Tenderness. If the horse walks 'as if on egg shells', this is an indicate of a hoof problem, quite possibly laminitis.
  • Easing of hoof. Repeated lifting of one or another hooves. While this is normal behaviour, an increase in this behaviour may indicate a problem. Likewise, lying down when it normally would not do so or remaining lying down longer than normal may be an attempt to ease pressure on affected hooves.
  • Reluctance to lift one hoof off the ground. Lifting a hoof off the ground places increased pressure on the other hooves (especially the hoof beside), which increases the pain in a laminitis affected hoof, making the horse reluctant to lift a hoof. The hoof which the horse will be most reluctant to lift will be the one beside the most affected hoof.

Other symptoms include:

  • Warm hoof.  A hoof which is warmer (the wall, sole,or coronary band) than it should be is an indication of laminitis. As the apparent warmth of the hoof varies depending on a number of variables (e.g. weather), the easiest way for the inexperienced person to check is to feel each of the feet to determine if one is warmer than others. It can help to feel two feet at the same time (one with each hand) to see if one is warmer; in this case comparing a front hoof (typically most affected) with a hind hoof (typically least affected) is the most effective. If one has more than one horse, with only one horse exhibiting symptoms, one can compare the temperature of the two horses (but only if they have been in similiar environments; the hoof temperature for a horse in the stable may well feel different from one that has just come in from pasture).
  • Increase in digital pulses. The digital palmar artery pulse is very faint in a rested horse (although easily felt in a horse who has just been exercised); if it is easily felt in a rested horse this is a sign of laminitis.
  • Response to sole pressure. If the horse shows pain in response to pressure on the sole of the hoof.
  • Coronet Sweling. Swelling at the cornet may also be visible.
  • General. There are a number of general symptoms of an unwell horse, which may indicate laminitis but could very easily indicate other illnesses. These include anxiety, trembling, flared nostrils, increased respiration or heart rate, increased temperature, sweating.

Note that a horse with laminitis may only display some of the above symptoms.

3.0 Symptoms - Chronic Laminitis

Chronic (or permanent) laminitis has most of the same symptoms as acute laminitis but typically less severe. In addition, there may be:

  • Hoof wall rings. The outside of the hoof may have visible rings.
  • Flat sole. The sole of the foot may have a flat or dropped appearance.

4.0 Diagnosis & Treatment

Diagnosis can only be done by a trained professional (e.g. a veterinarian). In the early stages, this would be done by observation and external tests (see symptoms in section 2.0 above). In chronic cases or severe acute cases, radiographs can be used not only to confirm a diagnosis but to evaluate the nature and extent of the damage.

During acute cases of laminitis, the damage occurs over a period of time. In many cases, the amount of damage is fairly minor when the horse first exhibites symptoms, and if promptly treated there is a much better chance that the horse will return to full and normal function. However, if untreated over the subsequent hours or days, the damage may increase to the point that the horse may be unable to resume its normal work and may even have to be put down. Consequently, any case of suspected laminitis should be treated as an emergency.

The treatment of acute laminitis will depend largely on the cause of the laminitis:

  • If it is food related (e.g. excessive carbohydrates or excessive nitrates), one must limit further consumption of carbohydrates until the existing excess carbohydrates or nitrates have been fully processed and eliminated by the horse's body. The use of a laxative (e.g. mineral oil) to purge the digestive system can remove remaining toxins before they are absorbed.
  • If it is related to an infection or toxin, these need to be treated immediately and aggressively. In addition to treating any infection (e.g. with antibiotics), there are treatements which can be used to remove toxins.
  • Changing hoof temperature and blood flow.
    • Some veterinarians believe that the breakdown of the laminae is caused by restricted blood flow resulting from toxins and that this reduced blood flow restricts oxygen and amino acids reaching the laminae and thereby causes its breakdown. They may use vasodilation drugs to dilate (expand) the blood vessels in the hoof in order to increase blood flow.
    • Other veterinarians believe that the restricted blood flow is the result of laminitis, not the cause. They believe that the restriction in blood flow reduces the flow of toxins to the hoof, and thereby provides some protection to the laminae. They recommend placing the hooves in cold water to further reduce blood flow until the toxins causing the laminitis are purged from the body. For discussion of this point, refer to Laminitis Medical Thearpy which is part of the Queensland Veterinary Science Laminitis Study.
    • At the moment, these two conflicting views have not been resolved, and the veterinary community remains divided as to which treatment is correct.
  • General drug treatments include anti-inflammatory drugs (both for pain relief and to reduce inflamation). These may increase blood flow (see discussion in above point).
  • Heart-bar, frogs or imprint shoes have been used in acute cases in an attempt to diffuse sole pressure and avoid pedal rotation. Because an improperly fitted shoe aggravates the pain, correct fitting is essential.
  • Do not force or allow the horse to walk in severe cases (use a horse transport instead). In mild cases, the horse can be walked to his stable (see next point).
  • Providing bedding where the animal can lie down will reduce the amount of pain it is suffering and may also reduce the amount of damage to affected hooves.
  • The acute phase may last for an extended period and it is unlikely that the horse will lay down for the entire time. If he goes into his paddock, a soft surface (e.g. sand) is preferable to a hard surface (e.g. gravel, dry ground).
  • It was previously advised to chill affected hooves (e.g. by immersion in a bucket of ice water), but this treatment has been challenged, with many veterinarians arguing that it is of little benefit and may in fact make the situation worse by restricting blood flow.

For chronic laminitis, treatment consists mainly of:

  • Care to avoid further occurence of acute laminitis (e.g. diet control), as each occurence of acute laminitis adds additional damage.
  • Trimming of the hoof to minimise pressure on sensitive points.
  • Orthopedic devices to provide additional hoof support.
  • Pain relief if neccessary.
  • If the lamintis has resulted in bone rotation, one can counter-rotate the bone back into position if the damage is not too severe. This is done through specialist hoof trimming and orthopedic devices, both of which require specialist expertise.
  • Depending on the extent of permanent damage, the horse may find it painful to stand on hard surfaces. Consequently, a paddock of sand or rotted wood chippings would be preferable to gravel. Likewise, soft bedding or a cushioned stall floor can be more comfortable.

There are a number of surgical techniques which can be used during the acute phase to minimise damage, or afterwards to repair damage. For details see equine laminitis. For research on treatment of acute laminitis, see Queensland Veterinary Science Laminitis Study and in particular the PDF files at that location.

A horse which has had laminitis is at greater risk of subsequent cases of acute laminitis. Consequently, one must take additional preventitive care to reoccurence of laminitis.

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5.1 Causes - Carbohydrates in Food

The  most common causes of laminitis is excess carbohydrates. This can result from:

  • Rich feed. If the horse is given large amounts of rich feed (e.g. grain) or breaks into the feed storage and eats a large amount of garin.
  • Rich pasture. Grass which is high in carbohydrates. This is typically the case in spring with the new growth grass. It can also occur (typically to a lesser extent) in the fall, or when there is rainfall after a long dry period. In each case the grass is taking advantage of suddenly favourable conditions (i.e. warmth and sunshine after the winter, water after drought) to produce and store large amounts of sugar and other carbohydrates, unfortunately in quantities which can be excessive for horses.
  • Combination. A combination of the two (e.g. continuing winter grain feed into the period of lush spring pasture) may result in excessive carbohydrates when either on its own may have been acceptable.

In simple terms, a horse which receives excessive amounts of carbohydrates is unable to properly digest all of them, resulting in toxins (poisons) being produced and released into the bloodstream, where damages the hoof, thereby causing laminitis. The detailed description of this, according to Wikipedia Laminitis, is: if a horse is given grain in excess or eats grass that is under stress and has accumulated excess non-structural carbohydrates (NSC, i.e. sugars, starch or fructan), it may be unable to digest all of the carbohydrate in the foregut. The excess then moves on to the hindgut and ferments in the cecum. The presence of this fermenting carbohydrate in the cecum causes proliferation of lactic acid bacteria and an increase in acidity. This process kills beneficial bacteria, which ferment fiber. The endotoxins and exotoxins may then be absorbed into the bloodstream, due to increased gut permeability, caused by irritation of the gut lining by increased acidity. The endotoxaemia results in impaired circulation, particularly in the feet. This results in laminitis.

The maximum amount of carbohydrates that a horse can safely eat depends on both the horse and circumstances.

  • Breeds which have evolved in harsh conditions with limited food have a lower genetic capacity to process carbohydrates; for this reason ponies are more likely than horses to get laminitis than horses, and some breeds of horse are more prone to laminitis than others. Such breeds are often insulin resistant, which further reduces their ability to process carbohydrate-rich foods. 
  • A suddent increase or change in carbohydrates can also cause laminitis. For example, if a horse has had continuous access to pasture, it is less likely to get laminitis with the spring grass than if it has not had pasture access and suddenly been given access. This appears to be due to two factors. One factor is that a horse which has had continuous access to pasture will have a digestive system (including bacteria) which is adapted to processing the associated carbohydrates and is more able to digest same than a horse which is suddenly introduced to it. Another factor is that a horse which has been deprived of pasture is much more likely to gorge itself when finally given access.

5.2 Causes - Nitrogen in Food

Another common cause of laminitis is excess nitrogen in the horse's food, which results in toxins being released into the bloodstream in much the same way as for excess carbohydrates. The main sources of excess nitrogen are lush pasture (which often occurs in the spring), pasture which has been fertilized with nitrogen-based fertilizers, or pasture which has a large quantity of nitrogen-concentrating plants (e.g. clover and certain weeds).

5.3 Causes - Mechanical Separation

Horses which are worked extensively on hard ground or other hard surfaces (e.g. roads) can have damage of the liminae due to the repeated shocks of the feet hitting a hard surface. This condition is also known as 'road founder', due to its frequent occurence in horses that are used a lot on roads (historically, this occured often with carriage horses). Examples of activities which are known for causing laminitis through mechanical separation are:

  • Racing horses on hard ground.
  • Jumping ponies during the summer (when the weather has dried the earth hard).

Aside from the above activities, other risk factors include:

  • Breeds which have heavy bodies and small hooves are at greater risk, due to the increased shock on a smaller surface.
  • Overweight horses and pregnant mares are at greater risk, as the increased weight increases the shock of impact on the hoof when it hits a hard surface.
  • Horses which are used in endurance activities without adequate training (exercise) to build up their fitness gradually.
  • Trimming hooves for long toes increases the risk of this condition. 
  • Pressure points due to incorrect hoof trimming or incorrect shoeing.
  • A horse which has lameness in one leg, resulting in additional weight on the contralateral leg, can develop laminitis in the leg bearing additional weight.
     

5.4 Other Causes

In addition to the three common issues discussed above (excessive carbohydrates, excessive nitrogen, mechanical separation), there are a range of other causes of laminitis. These include:

  • Toxins. The release of toxins into the blood stream is the most common cause of laminitis. Aside from toxins associated with excessive carbohydrates and nitrogen (see above), other sources of bloodstream toxins include bacterial, viral, plant, chemical, and fungal toxins:
    • Infections.  Infections, expecially those cased by bacteria, can release endotoxins into the blood. Infections which have been associated with laminitis include: pneumonia, pleurisy, diarrhoea, purulent metritis.
    • Other internal issues. If a mare retains internally part of the placenta after birth, this can release toxins. Colic (particularly following colic surgery) can also release toxins.
    • Chemicals. Exposure to certain chemicals (e.g. herbicide, nitrate fertilizer) has caused laminitis.
    • Froozen or frosted grass. Some cases of laminitis have occurred after ingestion of frosted grass. The exact mechanism for this has not been explained but sudden imbalance of the normal bowel flora can be surmised, leading to endotoxin production.
    • Lawn Clippings. Lawn clippings should not be provided to horses, partly because it allows them to ingest a large amount of grass in a very short time but mainly because they may have started fermenting, making them a risk for both laminitis and colic.
    • Fungal. Fungus in horse food has been known to cause laminitis (as well as colic).
  • Poor blood circulation. Inadequate blood circulation in the lower limbs can result in laminitis. Lack of sufficient movement (e.g. horse permanently confined to a box, or horse being transported a long distance without exercise breaks), alone or in combination with other factors, can cause this.
  • Extreme heat or cold. Some cases have been reported of laminitis due to extreme cold (e.g. standing in snow for long times) or extreme heat (e.g. standing on a hot surface or incorrectly-applied hot-shoeing).
  • Cushing's disease. Both Cushing's disease (Pituitary Pars Intermedia Dysfunction) and Peripheral Cushing's disease (Equine Metabolic Syndrome) have been associated with an increased predisposition to laminitis.
  • Drugs. Some drugs (e.g. cotricosteroids, thyroxine) have been reported to result in laminitis.
  • Stress. Some cases of laminitis have been reportedly associated with stress. It is known that stress results in the release of various hormones, some of which can constrict blood vessels and thereby reduce blood flow in the hoof (specifically the laminae). It is proposed (but unproven) that this is the mechanism by which stress can cause laminitis.

6.0 Prevention

The main cause of laminitis in developed countries (e.g. UK, USA) is food which is too high in carbohydrates or nitrogen. Consequently, one needs to avoid excessive amounts of rich feeds (e.g. grain) or lush pasture, with special care being taken with ponies or horse breeds which are most sensitive. For the most sensitive breeds (especially if there is obesity as well), even normal grass may be too rich and they may need to be kept on 'poor' pasture or be part-fed with feed that is low in carbohydrates and high in fiber.  In addition to restricting the absolute amount, one should also introduce horse gradually to rich feeds or pasture, both to allow their systems to adjust (note that there is a maximum limit to which they can adjust) and also to avoid the additional risk of gorging. One means to restrict the amount of grass eaten, while still allowing the horse access to pasture, is to use a grazing muzzle.

The second most common cause is mechanical separation. To minimise the risk of this:

  • Avoid use of the horse on hard surfaces. When it is neccessary to travel on hard surfaces, reduce the pace of the horse as a walking horse will have less shock to its feet than a running horse.
  • Ensure that feet are correctly trimmed. In particular, avoid over-trimming and trimming for long toes. If the horse has shoes, ensure that the shoeing is done by a competent professional.
  • Shock absorbing shoes and boots are being increasing used, even in competitions, to protect not only against laminitis but other shock-related injuries.
  • Avoid over-feeding your horse, as obesity increases the risk of laminitis and other illnesses.
     

The third most common cause is toxins:

  • Monitor your horse so that you can quickly identify and treat illnesses.
  • Ensure that their food does not contain fungus, mold, or chemicals (e.g. herbicides). Ensure that they are not exposed to any chemicals in their environment.
  • After a mare has given birth, ensure that none of the placenta (after birth) remains inside. 
  • Prior to any treatment involving steroids or hormones, verify with your veterinarian that the doeses do not pose a risk of laminitis.

General good horse care (e.g. shelter from extreme weather) is also advised. If your horse is at high risk (see earlier discussion), take special care to avoid circumstances that could lead to laminiits.

Some authorities advise soaking hay in water to reduce excessive water soluble carbohydrates prior to feeding to horses at risk of laminitis. However, more recent research shows that this is of limited benefit (especially if soaking is for short periods, in small quantities of water, with unchopped hay). Furthermore, the water removes not only carbohydrates but also required nutrients and minerals. Consequently, while this may be a usefull short-term practice, it is not a long term solution. A better solution would be to use hay from a source which has been tested for acceptable carbohydrate levels. The original report is: Longland, A. C., Barfoot, C. & Harris, P. A. (2009) The loss of water-soluble carbohydrate and soluble protein from nine different hays soaked in water for up to 16 hours. J.Equine Vet Sci 29(5): 383 - 384.

7.0 References

In addition to the references and links provided in the above article, other references of note include:

  • Liminitis Trust - Good general information. They also provide a list of feeds which they have evaluated and found suitable for laminitis-prone horses.
  • British Horse Society - General information on a number of topics; use their search facility to get their articles on laminitis.

8.0 Emergency Treatment

If you suspect that your horse has laminitis (acute laminitis, as opposed to the permanent condition) we suggest that you:

  • Call a vet for an emergency visit. The sooner acute laminitis is treated, the less permanent damage occurs. A matter of hours can make a big improvement to your horse's heath and future useability, as well as potential medical costs.
  • Allow your horse to lie down. Walking is painfull for a horse with laminitis, and may result in further damage to affected hooves. Provide comfortable bedding where it can lie down. If the horse needs to travel some distance to get to the bedding, use a horse transport (unless the case is very mild and the distance is moderate). In severe cases, it is probably best to provide bedding where the horse is rather than force it to travel, until the veterinarian arrives and can advise.
  • Do not feed the horse. The most common causes of laminitis are food related. Providing additional food will make the condition worse.
  • Inform yourself. If the veterinarian confirms that your horse has laminitis, discuss treatment options. Educate yourself on laminitis, especially since a horse that has had laminitis once is more likely to get it again, so one needs to take further steps to prevent a reoccurence.

These suggestions are not a substitute for professional veterinarian advice. We take no responsibility (legal, moral, or otherwise) for their completeness or accuracy. They are a personal opinion, based on our experience.