Laminitis is a prevalent, extremely painful condition in horses that has significant welfare implications for owners. It is an inflammatory condition of the tissues (laminae) bonding the hoof wall to pedal bone in the hoof. It is often recurrent for individual horses.

In excess of seven percent of equine deaths are linked to the laminitis, with many animals being euthanased. There are a number of risk factors associated with the development of laminitis including the spring and summer months, obesity, being a pony rather than a horse, older age and hormonal diseases such as equine Cushing’s disease (pituitary pars intermedia dysfunction; PPID) and equine metabolic syndrome (EMS).

Because the hoof wall is rigid, the sensitive laminae within hoof cannot expand with swelling and therefore it can become excruciatingly painful and debilitating. The condition can result in the pedal bone sinking or rotating within the hoof under the weight of the horse and in extreme cases this can result in penetration the sole of the foot by the pedal bone.

Causes

Laminitis can arise in three general situations:

1) Diseases associated with inflammation
e.g. certain types of colic, diarrhoea, retained placenta, severe pneumonia

2) Endocrine (hormone) disease
e.g. Equine Cushing’s disease (pituitary pars intermedia dysfunction; PPID), equine, metabolic syndrome, excessive pasture consumption

3) Mechanical overload (supporting limb laminitis; SLL)
e.g. associated with a fracture or infected joint the other leg which is bearing all of the weight is at risk of laminitis

The precise sequence of events leading to laminitis is still unclear. In diseases associated with inflammation, the exact identity of the laminitis trigger remains elusive, but there is activation of inflammation throughout the body which results in turn in lamellar inflammation. The end result is failure of the adhesion between the cells and laminitis. The hormone insulin appears to be important in laminitis associated with endocrine disorders, but again the exact sequence of events remains unclear. Finally in mechanical overload laminitis, it is thought that there is inadequate blood supply to the lamellar tissue associated with excessive and continuous weight-bearing.

Clinical signs

  • Lameness affecting most commonly at least two limbs
  • The horse leans back onto its heels
  • The lameness is worse when the horse walks on hard ground or turns
  • Shifting weight between feet when resting
  • Increased digital pulses
  • Pain with use of hoof testers at the point of frog on the foot

Diagnosis

  • A diagnosis is based on the clinical signs usually
  • X-rays may be taken if there is concern that the pedal bone has sunk or rotated, or if the animal is not improving despite appropriate therapy
  • Blood tests may be performed in cases where an underlying endocrine disease is suspected.

Treatment and management

Laminitis is a medical emergency and horses should be treated as soon as possible. Various medicine can be given to control the pain. Vets may give non-steroidal anti-inflammatory drugs (NSAIDs) such as phenylbutazone or flunixin and opiates like morphine and pethidine.

Foot support is a vital part of the treatment to limit movement of the pedal bone and to reduce the pain experienced by the horse. The can be achieved in a variety of ways including providing a deep bed which extends all the way to the door, frogs supports attached to the feet such as Lilypads or TLC frog supports, or frog and sole combined supports such as dental impression material or Styrofoam.

Acepromazine has been traditionally used to increase the blood supply to the feet as it was thought that all laminitis was a consequence of decreased hoof perfusion. However it’s beneficial effect is probably more related to its sedative properties which will result in the horse standing still or even lie down taking the weight off their feet. In cases of laminitis associated with inflammation, the use of ice to cool the feet may be beneficial.

Box rest along with dietary changes are important. Rather than grass, horses should have poor quality hay and no or minimal concentrates. Roughage rich foodstuffs like unmollassed sugar beet and the Hi-Fi feed product can form part of a revised diet.

If the laminitis is the result of an underlying condition, such as an endocrine disorder, that disease should be treated accordingly.

Prevention

Laminitis associated with inflammation can be prevented by prompt treatment of the underlying disease and use of ice to cool the feet in horses at risk of inflammation-associated laminitis prior to its occurrence.

Endocrine disorder-associated laminitis can be prevented by appropriate treatment of the underlying endocrine disorder and by reducing consumption of non-structural carbohydrates found in the pasture.

Mechanical overload laminitis can be prevented by using frog or frog and sole supports in high risk animals prior to its occurrence.

Key points

  • Laminitis is extremely painful and debilitating for horses 
  • There is a failure of the tissues bonding the hoof wall to the pedal bone in the hoof. This can result in the bone rotating or sinking within the hoof. 
  • There are a number of underlying conditions that can lead to laminitis
  • Horses with suspected laminitis need to be assessed by an equine vet and treated as quickly as possible 
  • Various medicines may be used for pain control and diet can be altered to reduce factors likely to cause or contribute to the condition 

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