Laminitis is a painful inflammatory condition of the tissues (laminae) that bond the hoof wall to the pedal (coffin) bone in the horses hoof. It can affect any horse, of any age or sex, at any time of the year. Although it is traditionally considered a disease of fat ponies, laminitis can be triggered by a variety of metabolic or physical causes in any horse as discussed in Causes of laminitis'.

Laminitis is caused by weakening of the supporting lamina within the hoof, leading to painful tearing of the support structure suspending the pedal bone within the hoof. If laminitis is not treated promptly, the pedal bone drops (these cases are described as "sinkers") or the pedal bone can rotate downwards.

Laminitis and Founder are not the same. Laminitis can, but does not always result in Founder. The word Founder describes the sinking of the horse's foot. The sinking occurs when the laminar bond fails. The laminar bond is made up of two layers:

The level of pain a horse demonstrates does not necessarily indicate either laminitis or founder. Some horses show tremendous pain while they are laminitic, and others show very little. The same may be true for foundering horses.

Causes of laminitis

Laminitis can be triggered by various causes. The most common causes are:

• Grain engorgement or excessive intake of pasture
• Sequel to infection. For example a mare that has recently foaled and has retained afterbirth
• Sequel to administration of excessive doses of certain drugs such as corticosteroids (e.g. Prednisolone)
• Cancer of the pituitary gland ("Cushings disease")

Less common causes include

• Concussion from riding on hard surfaces
• Excessive weight bearing by one leg due to severe injury or lameness in the opposite leg
• Stress from long distance transport

Effects of Low Grade Laminitis

Subclinical laminitis is the early stage of laminitis where structural changes have occurred within the hoof, without the horse being obviously lame or short in the stride.Subclinical laminitis is a likely cause of the following.

• Prominent growth rings on the hoof wall
• Dished hoof wall with flared out long toes (and often low compacted heals)
• Low grade seedy toe, sub solar haematomas that may lead to an abscess
• Crumbly white line
• Flaky soles and hoof edges broken away
• "Sore feet" in the front feet. More evident particularly on hard ground
• Shortened gait that doesn't improve with exercise and worsens with fast and hard work.

If you recognize any four of the above symptoms your horse may be suffering the effects of low-grade laminitis.

Diet and laminitis

Vets and horse owners alike have long been familiar with the association of lush pasture and laminitis in susceptible equines. Water soluble carbohydrates in grasses are implicated as triggers for dietary induced laminitis. Cereals (grain) contain high levels of starch. Starch has the same effect as the Water Soluble Carbohydrates found in grasses in causing laminitis.

Temperate grasses contain naturally large amounts of carbohydrate (sucrose, fructose, glucose, and fructans). It is the carbohydrate that is rapidly fermented that initiates the cascade resulting in laminitis. In most of Europe, USA & southern parts of Australia, temperate grasses are an important part of the diet of most equines, especially during the period Spring to Autumn. It is only recently that the association with high fructan levels and the onset of dietary induced laminitis was made.

Difficulties lie in predicting Fructan ( a soluble carbohydrate) levels at any given point in time. The content of Fructans in grasses is highly variable. The actual amounts of sucrose and fructans vary from 5-50% of total dry matter. Large changes can occur within hours. The accumulation of these sugars is a highly dynamic, variable and environmentally responsive process. Temperate grasses may store 10-13% of their total sugars reserves as starches. This leaves up to 90% being stored as sucrose or fructans. (Water-soluble carbohydrates)

Certain grass species seem to accumulate more fructans than others; perennial ryegrass may contain 12% fructans and cocksfoot only 2%. Temperature effects fructan accumulation, cold sunny days mean a high level of fructan accumulation. Grass stores more fructans in its stems than in its leaves so horses turned out on stubble after a hay crop can be eating a relatively large amount of fructans, conversely well managed fields which are grazed by sheep or cut will have a high leaf to stem ratio and potentially less fructans. Fertilisers should be avoided wherever possible

International research has shown that there is an interrelationship between diet, hindgut acidosis and low-grade laminitis.

Prevention of Dietary Induced Laminitis

"PREVENTION IS BETTER THAN CURE"

Restricting the horses intake of lush green grass and grain can reduce the rate of lactic acid production. Easy to say, however in practice a pony in a field as sparse as a pool table can still suffer dietary induced laminitis.

Digestion of carbohydrates in Equines and its relevance to dietary induced laminitis.

Lush green grass, which carpets the countryside particularly in spring and autumn, or feeding high levels of grain, can induce laminitis in horses. This information is well known amongst horse owners and riders.

The first step is to understand what components of the horses diet create the risk of laminitis. What do grains and lush pastures have in common? Cereal grains contain abundant amounts of Starch a form of carbohydrate that is broken down to simple sugars such as glucose in the digestive tract. Lush green grass can have high levels of sugars that are directly available in the digestive tract.

• GRAIN contains Starch that are converted to Simple Sugars
• LUSH GRASS contains readily available Sugars

How does the horse usually digest its food?

This question provides us with the key to the cause of dietary induced laminitis. The horse digests its food in two ways

• Simple digestion Once the food has been eaten it is digested by enzymes in the first part of the digestive tract. The nutrients are then absorbed from the digestive tract.
• Hind gut fermentation Excess sugars and complex carbohydrates which require longer to digest move onto the large bowel for fermentation.

Normally the bacteria ferment away slowly and horse absorbs the products from the bowel for use as an energy source. When the simple sugars arrive in the large bowel it takes the bacteria no time to ferment them producing large amounts of acid very quickly - more quickly than they can be absorbed. This leads to build up of lactic acid in the hind gut. This is the first step towards laminitis. The process that follows is complex and there is still research being conducted as to the exact mechanism. Suffice to say that the build up of acid is the primary trigger.

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Why is there so much variability in the incidence of laminitis?

• The amount of sugars present in pastures. Warm clear days and cool nights provide the ideal conditions for build up of sugars - particularly when there has been rain and growing conditions are good.
• Variation between animals. The risk depends on how much they eat, how quickly they eat and how efficiently they digest their feed prior to fermentation

Behavioural changes associated with feeding grain or lush green feed

Researchers discovered a connection between behavioural changes and the feeding of grain or lush green feed in 1998. The link was shown by using Founderguard to reduce the build up of hind gut acid during grain feeding. By keeping hind gut pH closer to normal there was a reduction of cribbing and wind sucking in stabled horses.

MANAGING LAMINITIS - Minimising the risk

(1) FEEDING GUIDELINES:

• Feed a forage based diet. Feed a mixture of mature grass and hay with alfalfa (Lucerne). Alfalfa contains essential minerals and proteins that the horse can utilise to improve hoof quality. Unless horses are in hard work they do not require hard feed. For extra calories use vegetable oils. Please ask our advice regarding quantities.
• Feed a high fibre diet e.g. hay made from mature flowering grasses but ensure that adequate water is consumed to avoid the risk of an impaction colic. Soaking hay for two hours will assist water intake and also leach out some of the protein and carbohydrate.
• Manage grazing carefully. Do not turn laminitics out in the frost or on very stressed or bare paddocks. Grass is safest at night when sugar levels are in decline. The later in the evening the better. Strip grazing may be a safe alternative. Pick up all droppings to reduce pasture spoiling and risk of infection with parasitic worms. Consider cross grazing with sheep.
• Avoid Bran. Due to its high phosphorus levels feeding over a long period will result in relatively low levels of Calcium, one of the important minerals for hoof health.
• Avoid lush grass pasture, cereals and coarse mixes.
• Use a quality Vitamin and Mineral supplement. If your pony has poor hoof structure the use of Farriers Formula should be considered.
• Changes to the diet need to be gradual. Feed little and often.

(2) BODY WEIGHT:

An overweight equine has a higher risk of laminitis. At ideal weight you should be able to feel your horse or pony's ribs but not see them and they should have no crest on the neck or gutter along the back. It helps to ensure that your horse or pony is in the correct bodily condition before you turn out in the spring as you cannot diet a horse on grass! If dieting is unsuccessful we can test whether your horse's thyroid glands are working properly. Never starve a laminitic horse as this can lead to death through hyperlipaemia.

(3) HOOF HEALTH:

Regular trimming and correct foot balance are essential for healthy feet. Specialist shoeing can assist - please contact us to discuss whether this is appropriate.

(4) GENERAL HEALTH:

• Monitor you horse following medical conditions such as colic or retained placenta in mares. These are high-risk causes.
• Turn out in sand arenas for exercise each day. Please note that ponies that eat sand may develop sand colic - a muzzle should be used on these cases.

(5) WORK:

As concussion can also cause laminitis avoid excess work on hard surfaces, such as hunters working on hard roads in winter and ponies working on hard surfaces during summer shows. Feed according to work. Any form of stress may predispose the horse to develop laminitis. When stressed, animals respond by releasing corticosteroids from their adrenal gland. Alterations in the blood flow to the feet can then lead to a laminitic episode.

Founderguard

As described earlier laminitis can be managed in part by controlling the diet. Minimising the intake of cereals and pasture containing high levels of sugars can prevent laminitis of dietary origin. Easy to say, however this can be very difficult to achieve in practice. An alternative is to control the pattern of fermentation within the gut to prevent acid build up. From scientific research carried out in Australia it was shown that the product Founderguard could be used to help reduce the acid build up during fermentation of starches and sugars in the hindgut. By controlling acid build up Founderguard can reduce the risk of laminitis.

Founderguard may be beneficial in the following cases.

• Horses fed high grain diets
• Horses grazing lush pastures
• Horses that have suffered from laminitis or founder in the past
• Horses with seedy toe, white line separation and poor quality hooves due to low-grade laminitis.

Founderguard contains a very small dose of Virginiamycin in a special pellet. When mixed into the horse or ponies ration the pellet releases the active ingredient in the large bowel to target the excessive bacterial attack on carbohydrates overloaded into the hindgut. It is only available under special licence in this country, please contact us if you would like to discuss whether it is appropriate in your situation.

Glossary of terms

Cellulose - A carbohydrate (sugar) forming the skeleton of most plant structures and plant cells.

Fructan - a collective of oligosaccarides, polysaccarides, chains of fructose molecules.

Hypothyroid - A medical condition where the thyroid function is less than normal.

Keratin - A protein that is the principle component of skin, hair and nails.

Lactic Acid - a compound formed in the body by metabolism of carbohydrates or by fermentation of carbohydrates.

Lactobacillus - a genus of gram-positive rod shaped bacteria. They produce lactic acid by fermentation. In doing so they play a part in the development of lactic acidosis in the hindgut of horses.

Laminitis - an inflammatory condition of the sensitive laminae of the hooves. Characterised clinically by mild to severe lameness especially of the front hooves. There is heat and pain at the coronets and in bad cases the pedal bone can penetrate the sole of the hoof.

Credits

Explaining Laminitis and its Prevention, Robert Eustace obtainable from The Laminitis Clinic 0870 444 0676

www.laminitisclinic.org

Dobson & Horrell Equitalk Newsletter

www.dodsonandhorrell.com

The Founderguard site

www.founderguard.uk.com

Hoofcare and Lameness Magazine -- Horseshoeing Information

www.hoofcare.com/info.html

Laminitis page

www.olympus.net