Laminitis (Laminar = layers, Itis = inflammation)
Laminitis is an inflammatory
condition of the laminae (the structures within the hoof that connect the
external hoof wall to the internal coffin bone) and is one of the most
distressing conditions that can face horses and their owners. It occurs most
often in the front feet although it can affect the hind feet as well. Sadly it
is also common, reportedly affecting 7.4% of horses and ponies at some point in
Founder (= Send to the bottom)
Founder is a progressive
condition following acute laminitis, where the weakened basement membrane is
detached within the hooves to allow the deep flexor tendon to pull (rotate) the
toe of the coffin bone (sometimes known as the pedal bone) downwards to separate
the laminae. Without the distal phalanx properly attached to the inside of the
hoof, the weight of the horse and the forces of locomotion drive the bone down
into the hoof capsule, shearing and damaging arteries and veins, crushing the
corium of the sole and coronet, and causing unrelenting pain and a
Main causes of founder
• Poor digestion - Acids and
toxins are produced which end up in the blood stream damaging blood vessels.
• Hard ground “Road Founder” - Increases the concussion on the horse’s feet.
• Lush pasture “Grass Founder” - Horses consume too much and their digestive
system becomes shocked by the excess non-structural carbohydrates.
Retained placenta by mare after foaling - Either from toxicity or bacterial
• Various primary foot diseases and Infections - Produce enough
toxins to damage blood vessels.
• Grain overload can lead to severe colic -
Endotoxins and exotoxins are released and absorbed by the bloodstream which
results in reduced circulation, primarily in the feet.
• Black Walnut
Bedding - Laminitis can occur through exposure to Black Walnut (Juglans nigra L)
shavings used as bedding in stalls. As little as 10 percent of the total
shavings, by weight, may result in clinical signs of toxicity in horses. Sadly
research has yet to determine if the problem is caused through ingestion or
• Consumption of cold water by an overheated horse
Cause of Grass Founder
Good winter and early spring
rains and the onset of sunnier weather can result in a ‘flush’ of lush, rapidly
growing grass pasture containing a high level of carbohydrates (starch, sugars)
and protein. Under ideal moist, sunny conditions after cold nights, the rapidly
growing early spring grasses can produce large amounts of fructal sugars (a
non-structural carbohydrate, composed of glucose and varying fructose molecules)
stored in the stem. In Ohio April has higher levels of non-structural
carbohydrates than in other months.
Horses do not have an enzyme that can
break down fructose sugars in their small intestines, so that large amounts of
undigested food move into the caecum and large intestine. In the large bowel,
fructans are fermented by particular gram-positive lactic acid producing
bacteria that proliferate rapidly, generating large amounts of lactic acid,
including non-metabolised, damaging D-lactic acid that lowers hindgut pH. The
decreased in hindgut pH (acidosis) results in the death of large numbers of
digestive microbes. When the fructose intake reduces, the excess bacteria run
out of fructan ‘feed’ and die in large numbers to liberate damaging vascular
toxins (endotoxins). The high acid concentration damages the gut wall, allowing
the endotoxins to enter the blood stream.
In the horse, the vessels of the
feet are particularly sensitive to these toxins, which cause profound
vasoconstriction. Clinically this condition is referred to as laminitis, or
inflammation of the sensitive lamina of the foot.
These changes occur 24-48
hours prior to clinical signs of laminitis.
These toxins act to devitalise
the basement membrane which loads the laminae within the hooves, producing
chemical damage to the bonding sites. They also act to reduce blood circulation
to the laminae by opening ‘shunts’ to circulate blood away from the laminae and
‘starve’ them of nourishing blood.
Which pasture grasses are safer?
Research suggests that safer
grasses are those with lower levels of non-structural carbohydrates. Warm season
grasses like prairie grasses, native grasses and Bermuda grass generally have
lower levels of non-structural carbohydrates while cools season grasses like
timothy, orchard grass, brome, fescue and clover have higher levels.
levels of non-structural carbohydrates are found with higher temperatures,
higher radiation (photosynthesis) and are lower with increased humidity.
Which horses are prone to grass founder?
If the horse is in working
condition it is very unlikely to founder on new grass.
The overweight horse,
on the other hand, are particularly prone to “laminitis triggers” and can
founder on spring grass, good quality hay or summer grass that has gone to seed.
The heavy horse has a threshold where it is safe. This is when its nutrient
intake matches the energy needs of its body.
Horses with a previous history
of laminitis, and horses with Cushing's disease are predisposed to “grass
Certain breeds like Morgan, Arabian and Welsh ponies seem
Also the risk is increased with the condition called Equine
Metabolic Syndrome. EMS is an endocrine and metabolic disorder, where Insulin
Resistance (IR) is the primary problem encountered. Affected animals will either
suffer from generalized obesity and have an overall overweight appearance, or
look more normal in appearance but have enlarged fat deposits in the neck and
tailhead regions. The presence of enlarged fat deposits in these locations is
referred to as regional adiposity and the thickened neck region is often called
a “cresty neck.”
Signs of laminitis
If just the two front feet
are affected, the horse will stand in the "founder stance" with his hind legs
well up under the body carrying as much weight as possible, and the front legs
placed forward with the weight on the heel. He will be reluctant to walk and
will turn by leaning back and pivoting around on the rear legs.
If all four
feet are affected, the horse will lie down for extended periods and may refuse
to get up. If forced to stand, he will pull his hind feet and fore feet in
toward each other under the centre of his body.
Other symptoms include heavy
breathing and glazed eyes due to pain. The feet will feel hot and the digital
artery, located over the fetlock joint, will have a pounding pulse.
• Short stilted gait with a
“heel first” footfall
• Shifting of weight from one leg to another
Repeated lifting of alternate feet
• Gait worse on hard ground
Reluctance to stand on a hard surface
• Often worse when turned sharply
Heat in feet, especially near the coronary band
• Increased digital pulses
• Acute onset lameness
affecting one or more feet, usually both front feet
• Reluctance to move
May be impossible to lift feet
• Increased digital pulses
• Heat in feet, especially near the coronary band
lies somewhere in between with varying degrees of the above signs/symptoms
Each attack of acute laminitis can leave a ring formation on the hoof. A horse
suffering from chronic founder will have multiple rings on his hooves. He might
also have seedy toe, a separation of the hoof wall from the sensitive laminae in
the toe area. If left untrimmed, the hoof wall also overgrows to form a "slipper
Due to the speed with which laminitis can progress and the severe
sequelae that can result many regard laminitis as a medical emergency. As an
owner the ability to recognise the signs of laminitis will enable earlier
intervention and often greatly improve the eventual outcome.
Prevention of grass founder
Start the eating of spring
grass slowly. Let horses graze for 30 minutes a day, and then increase the time
allotted over the course of a few weeks, as long as they handle the new diet
Feed low non-structural carbohydrate grain. Grain can contain from 10
to 35% non-structural carbohydrate. Oats, corn and barley are usually high in
Use a grazing muzzle while the horse or pony is in the
pasture. The muzzle only allows the eating of the top of the grass (the best
part), reduces the amount eaten, while providing the same opportunity for
The sooner laminitis or founder
signs are detected in a horse, the more likely the horse can make a full
recovery without long term complications. Call your vet and follow his/her
If you have any suspicion of laminitis then the horse or pony
should be ideally be placed on a deep shavings bed and given only hay and water
whilst you seek veterinary attention. However if the horse or pony is severely
affected whilst out at grass it may be better to leave the horse where it is
until your vet arrives but prevent it from grazing. Spreading a bale of shavings
around the horse and getting the horse to stand on them may also offer some
Restricting movement by confining to a small yard, and standing the
horse on wet sand to maintain ‘cool’ feet can help control inflammation and
provide support to help limit downward rotation of the pedal bone.
hooves in ice at the earliest stage of laminitis and founder. Repeat ice packing
every 15-20 minutes for 24-36 hours or application of ‘icing boots’ can
significantly reduce the immediate damage to the laminae. Research suggests that
horses, unlike humans, do not regard extremely cold feet as uncomfortable and
can tolerate having their feet in iced water for 48 hours without effect.
The distal phalanx (coffin) bone is connected by tendons to the rest of the leg.
These tendons run from that bone up the back of the leg to various muscles.
These same tendons are the ones flexing the leg when the horse walks or runs so
we can see how strong they are. Each time the foot makes contact with the ground
the tendons are drawn tight. Normally this gives spring to the step as the
distal phalanx bone is firmly attached to the hoof wall. But with inflammation
of the foot, the tendons actually add to the discomfort by pulling the distal
phalanx bone away from the hoof. The longer the toe of the hoof, the greater the
break over a period of time, which keeps tension on the distal phalanx bone
longer. A shorter toe allows the foot to break over more quickly and before the
tendons are drawn tight.
As soon as the horse has been treated for the acute
phase of founder, trimming the toe very short will allow more comfortable
walking. Trim every 3-4 weeks and maintain heel support.
In more severe
cases, shoeing with a flat shoe and preferably one with a worn toe, will protect
the foot from contact with the ground. Additional doses of pain reliever or
local nerve blocks may be necessary before the farrier can work on one foot
while the horse supports all its weight on the other.
Give the horse a well
formulated calcium, trace mineral and vitamin supplement with organic selenium
and chromium to help laminae bonding and limit insulin resistance. During
recovery, provide a daily source of good quality protein, such as lupins or
soybean meal (30g/kg of food) to the feed to help laminae regeneration.
Reduce non-structural carbohydrates in hay by soaking in hot water for 30
minutes or in cold water for 60 minutes. Pour water out after soaking.
For further in-depth reading search on:
Christopher C. Pollitt, BVSc, PhD
Australian Equine Laminitis Research Unit
University of Queensland, Australia
Article composed from information found on the internet.
– April 2009