What Is Laminitis and Founder?

Laminitis and/or founder are one of the most common lameness problems affecting horses and ponies. 

In this article, we’ll examine both these conditions to get a better understanding so you can better prevent it from happening.

What is laminitis?

Laminitis is a crippling disorder of the feet, resulting from damage to the sensitive soft tissues known as ‘laminae’, which connect the pedal bone to the inside of the hoof wall.

There are about 600 interlocking laminae in each hoof and they provide the support for the weight of the horse.

What is a founder?

The founder is the physical change that occurs within the hoof as a result of laminitis.

When the laminae are damaged, their supporting function is weakened resulting in the hoof capsule displacing proximally and the pedal bone sinking. 

This is an extremely painful condition for the horse, which can become worse as damaged laminae can lead to other conditions such as:

• Abnormal hoof growth with obvious ‘growth rings’
• Long toes
• Flat soles
• Separation of the sole from the hoof wall at the white line
• The development of ‘seedy toe’

What causes laminitis and founder?

The development of laminitis and founder can often be due to a variety of causes, sometimes acting together and sometimes individually.

One of the more common causes however is overeating of feeds high in ‘soluble carbohydrates’, also referred to as non-structural carbohydrates or NSC (mainly found in cereal grains and stressed pasture).

Metabolic disorders such as EMS (Equine Metabolic Syndrome) and Cushing’s Disease (pituitary pars intermedia dysfunction – PPID) are associated with increased risk of laminitis.

In the case of EMS, the underlying issue is a result of hormonal imbalance related to insulin metabolism.

Insulin resistance appears to be one of the criteria defining EMS, with clinical signs including obesity-associated laminitis and abnormal fatty deposits or regional adiposity.

PPID on the other hand is fairly common in older horses (generally over 15 years) and is a disease of the pituitary gland.

Clinical signs of PPID include:

• laminitis,
• shaggy coat (hirsutism),
• undue sweating,
• lethargy,
• loss of topline,
• increased thirst and urination (polyurea/polydipsia)
• gastrointestinal problems (such as colic or diarrhea), retained placenta after foaling, metritis, pneumonia, peritonitis, enteritis.

Laminitis can also be caused by certain drugs and management factors such as poor hoof care and shoeing and by excessive work on hard surfaces (e.g. hoof concussion from galloping on a road).

How does feed cause laminitis?

Feeds rich in starch, sugar, and fructan can cause a digestive upset in the large intestine if appropriate adaptation has not occurred.

Mammals have no enzyme to digest fructan so this passes undigested directly into the hindgut (caecum and colon).

An excess of grain consumption (containing mainly starch and sugars) will also ultimately overflow into the hindgut.

In the hindgut, excess starch or fructan will undergo rapid fermentation to lactic acid, with many normal bacteria dying due to the increasingly acidic and low pH conditions.

As the acid builds up, it damages the gut lining and toxic substances including bacterial endotoxins and other toxins are released and enter the bloodstream.

Once in the bloodstream, the toxins appear to either directly or indirectly stimulate increased production and activity of certain enzymes called matrix metalloproteinases (MMPs).

The overactivity of these enzymes destroys the laminae, resulting in the onset of laminitis.

Signs of horse battling grain or sudden pasture sugar/fructan overload include¹:

• High heart rate
• Rapid breathing
• Increased digital pulses
• Fever
• Sweating
• Colic
• Diarrhea
• Depression

Do only fat horses or ponies founder?

A common question related to feed-induced laminitis and founder is whether it only affects fat horses and ponies.

The resounding answer is definitely NO – all horses can develop laminitis and founder, although pasture-associated laminitis tends to be more common in ponies.

Certain breeds are known to have a higher risk of developing laminitis.

Obese horses and ponies are more likely to experience pedal bone rotation and permanent hoof damage due to the extra weight their feet have to support even in a relatively mild case of laminitis.

Surveys have shown that valuable show and equestrian horses are also at risk of developing laminitis even when consuming feeds with relatively small amounts of grain.

Research has shown that many racehorses have low-grade laminitis, which may only cause mild sore footedness, a scratchy gait and separation at the ‘white line’. Studies have shown that low-grade laminitis can significantly affect racing performance².

Can repeat attacks of the founder occur?

Yes – once a horse has foundered, it is likely to suffer from continued repeated attacks unless preventative management strategies are instigated.

Often, these are the horses and ponies that are very sensitive to carbohydrates in feed, which may trigger an acute laminitis episode with only small amounts of grain or pasture.

Symptoms of laminitis can also occur if the horse’s hooves are not kept correctly trimmed.

Laminitis is a distressing and potentially crippling disease that can affect the lifetime performance of your horse.

Once a horse develops laminitis and founder, they are more prone to repeat attacks, so prevention is definitely better than a cure in this case.

To learn more, read our Laminitis – Prevention is better than cure article.

Founderguard^® - A proven preventative for feed-induced laminitis

FOUNDERGUARD is a feed additive containing ‘Virginiamycin’.

When given to horses at high risk of laminitis due to consumption of grains or pasture high in NSC an antibiotic it can prevent laminitis from occurring.

Founderguard works by suppressing the activity of Streptococcus spp and lactobaccilus spp bacteria in the caecum and colon.

This reduces the formation of lactic acid preventing a drop in gut pH that can lead to laminitis.

 FOUNDERGUARD is a preventative rather than a treatment for laminitis. It cannot correct any physical damage that has already occurred in the feet.

However, FOUNDERGUARD can help prevent the ‘flare-ups’ that frequently occur in the recovery period, particularly when diet NSC levels are unknown.

FOUNDERGUARD is a useful addition to a diet to prevent low-grade laminitis where there are no outward signs.

If you suspect your horse may be suffering from laminitis, please call your veterinarian for advice.

The sooner you call, the more likely you will be able to successfully treat your horse’s laminitis and limit any lifelong effects.

1. K.A Watts and C.C. Pollitt (2010) Equine Laminitis, Managing Pasture to reduce the risk. Rirdc Pub. No. 10/063
2. Linford RL, O’Brien TR, Trout DR, (1993) Qualitative and morphometric radiographic findings in the distal phalanx and digital soft tissues of sound thoroughbred racehorses. Am Vet J 54: 1, 38-51.