Laminitis

This meshing together of both layers ensures that the internal structure of the hoof and the outer wall bond together, thus supporting the pedal bone within the hoof.

During a bout of laminitis, an inflamation, and a disturbance of the blood vessel network in the hoof generate a deterioration of the laminae. The pedal bone is no longer supported by the laminae, and is no longer bonded to the rear wall of the hoof, it then rotates downwards due to tension from the deep digital flexor tendon. If the damage to the lamellae is severe, the 3rd phalanx (pedal bone) can sink in the hoof : this is known as founder. In the most severe cases, it can result in perforation of the sole. In some extreme cases, the horse can lose the hoof.

Laminitis is always a consequence of other disorders. Since the causes are multiple we will only discuss the main causes in this fact sheet.

Feed causes

Laminitis due to overfeeding is the most frequent. Over half the cases laminitis are observed when horses are turned out to graze. Overloading in grain and cereals is responsible for 10 % of cases.

Endocrinal disorders

Insulin resistance in horses with Cushng’s disease (PPID= Pituitary pars intermedia dysfunction) and EMS (Equine metabolic syndrome), gives rise to increased risk factors in horses. According to several studies, laminitis is prevalent (between 50 % and  80%) in horses affected by PPID (Cushing’s disease).

Mechanical causes

Horses can also develop laminitis after intense excercise, especially on hard ground : this is termed exercise laminitis. It is especially noted in endurance horses.
When a horse is lame through injury, e.g in the case of a fracture, the other front hoof becomes the main weight bearing limb, and laminitis can develop in this hoof. This is termed static laminitis. In this case it occurs only in one hoof.

Colic and infections

Laminitis can also occur after a serious bout of colic, severe diarrhea, or following infectious diseases, such as postpartum metritis (infection of the uterus after foaling), pneumonia….. Toxins are produced and create vascular damage in the hooves. It is therefore important to check the hooves (digital pulses, excessive heat)

Laminitis is more often than not  located in the front feet. It can also be present in all four hooves, in the hind feet, or in just one foot.

Signs of acute laminitis

An pain-relieving posture

A horse whose front feet are affected, will adopt a characteristic stance when resting : the horse is camped out in front (front legs placed in front of a vertical line) and bring its hind legs underneath ( hind legs also in front of a vertical line).
This position relieves pain : the weight is displaced towards the heels. It is an analgesic position. At rest the horse will also shift its weight from one foot to the other.

Difficulty moving

• The horse shows signs of a stilted gait
• The horse walks very tenderly as if on egg shells, and resists when asked to lift a front foot ;
• Moves reluctantly, and refuses to lift a foot when asked
• The horse is recumbent.

Take care ! A horse who remains recumbent for too long, may tie-up, develop colic or pressure sores.

Other general signs of pain

Other non-specific signs of pain may also be noted :

• Horse standing away from the herd
• Loss of appetite
• Signs of anxiety
• Visible trembling
• Increased breathing rhythm
• High temperature (T=>38.5°C).

Inflammed feet

When in doubt, there are two signs to look for in the feet :

• An elevated digital pulse (this factor can only be assessed if the pulse is measured regularly, in order to ascertain a normal pulse)
• The walls of the hoof are hot (the heat should be compared to the heat in a healthy foot).

Signs of chronic laminitis

The chronic phase of laminitis prolongs the acute phase. There is sometimes a depression on the ridge of the coronet, which indicates a sinking or rotation of the pedal bone (distal phalanx).
Because of the rotation or sinking of the pedal bone, the coronet ridge is stuck behind the wall of the hoof. Hoof growth is dirupted, it grows faster around the heel, and grows more slowly, and abnormally on the toe and sides. The hoof appears deformed with characteristic horizontal rings.

Call your treating veterinarary surgeon

Laminitis is a major medical emergency which can lead to euthanasing the horse in the most serious cases. It is therefore important to call the veterinarian immediately.
While waiting for the vet, it is recommended not to move the horse to avoid worsening the damage. The more pain the horse is in, the more the tendons will retract, especially the deep digital flexor tendon, which then pulls the distal phalanx, and provokes its displacement.
If there is a suspicion that the laminitis is due to feed, the horse should be put on a strict diet, if necessary by using a grazing mask. Cryotherapy can help to limit the consequences of a bout of laminitis, and can be undertaken while waiting for the vet (see below). The efficiency of cryotherapy will be greater when implemented quickly. The horse can also be placed in a sandy area or a thick comfortable bedding so as to improve comfort.

How does the vet establish a laminitis diagnosis ?

Clinical signs are characteristic and will quickly direct the vet towards a diagnosis. Testing    the hoof  around the toe area with hoof testers shows soreness in this area.

An X-ray examination (front and side X-rays) enables :

• Confirmation of the laminitis suspicion, and indicates the position of the pedal bone in relation to the hoof wall. There can sometimes be transparent X-ray areas (black) which indicate a seperation between the epidermal (keraphyll) and dermal (podophyllous) layers.
• Fine tune the prognosis : sinking of the pedal bone (drop of the bone in the foot)  always  gives a poor prognosis
• Follow the evolutionof the disease in the case of chronic laminitis

A venogram shows the vascular network in the hoof, this si carried out with an X-ray taken after injecting a contrasting agent. This method is rarely used in the field.

What treatment for acute laminitis ?

Look for and treat the cause.

Laminitis is always the consequence of another affliction, therefore the cause should be treated first. For example : an obese pony with laminitis should be put on a strict low carbohydrate diet.

Pain management and prevent any worsening of the damage.
There is no miracle cure for laminitis. The purpose of any treatment is to relieve pain and keep the consequences to a minimum.

• The use of NSAIDs (non steroid anti-inflammatory drugs) or aspirine (which has an effect on the vascularisation of the hoof) are necessary to relive pain.
• Prolonged cryotherapy, consists in cooling the hooves to fight inflammation in the lamellae, thus avoiding worsening of damage to the foot. It should be implemented as soon as the symptoms appear. Several techniques can be used :
  • Using boots (available in tack shops) with asystem of continous cooling by circulating a cold gel, this cools the leg and foot without direct contact
  • A more low-tech method, consists in placing the horses hooves in a bag filled with 5 litres of crushed ice, and taping the bag around the pastern.

This technique is effective, but time and labour consuming, as the bags need replenishing with ice every two hours, and treatment should be continued until 24 hours after the disappearance of the symptoms. The temperature of the hoof should be maintained at -5° to – 7° horses tolerate this temperature easily. (Nocold burns)

• During an acute phase of laminitis, the horse should not be shod or unshod, this is to avoid any mechanical stress to the interdigitating epidermal and dermal layers. However, support can be given in the heel area, so as to reduce muscular tension, and the tension in the deep digital flexor tendon. This can be given by using plaster or resin heel-lifts.
• The horse is immobilised and strictly confined, ideally in a loose box, with deep comfortable bedding for a minimum of two months. If the horse needs to be transported for intensive care, then the use of a plaster cast for transport will reduce mechanical stress on the hoof.
• Massaging the  flexor and extensor muscles of the forelimb, can reduce swelling of the leg and increase blood circulation to the hoof, without walking. An analgesic effect has been noted. 

The role of the farrier is to improve the horse’s comfort.

• In serious cases of laminitis, the coronet lip is stuck behind the hoof wall, which is very painful for the horse. In some cases drastically thinning the wall of the hoof in the toe area may relieve the pressure and the pain for the horse
• The distal phalanx (pedal bone needs to be supported at the rear of the hoof (through the frog and digital cushion). On the contrary, presure in the toe should be reduced, and the shoe should help the overbreak : M shaped shoes are particulary well adapted. When resuming work heart bar shoes may be used.
• Using polyeurathane pads protects the front part of the sole, which is extremely sensitive, and can help in promoting horn growth
• Shoes with embossed design on the lower side, have been specially designed to promote continuous small movement of the foot, and have a beneficial massaging effect : they improve blood circulation in the hoof. An example of this type of shoe is the « Rock and Roll rail shoe »
• It is also necessary to ensure horn growth in laminitic horses. A recent study has shown the effectiveness of supplementing with biotin for hoof growth in healthy horses. ( Equ’idées article, March 2016)

Endocrinal disorders should be addressed with the collaboration of the treating vet.
For horses prone to obesity, it is important to implement an appropriate low calorie, low starch diet : Here are a few major guideleines :

• Isolate from the grain store to avoid accidental binging ;
• Restrict access to grazing during the critical periods (Spring and Autumn);
• Restrict high energy feeds : the ration can essentially consist of hay with a poor energy level, e.g hay that has been harvested late in the season. Avoid hard feeds as much as possible. If energy needs are high, the horse can be supplemented with oil;
• Fence off fruit trees during the  fruit production period ;