SCIENCE SUPPLEMENTS Laminitis: Part 1

Laminitis is a condition that most horse owners will have come across but what actually causes it and what can we do to prevent our horses and ponies from getting it? Over the coming weeks we will discuss laminitis in detail and provide tips for avoiding and managing this painful and distressing disease. This week we discuss what laminitis is and what it looks like.

What is Laminitis?

The horse’s foot is composed of the pedal bone suspended within the hoof capsule by complex interlocking structures called laminae. Laminitis refers to inflammation of these laminae and is the end result condition caused by reduced blood supply to the sensitive laminae within the foot. Decreased blood supply starves the laminae of oxygen and damages these sensitive structures. Not only is this painful for the horse but it can also result in destruction of the laminae such that the pedal bone may begin to separate away from the hoof wall causing rotation and sinking (Fig. 1). Rotation refers to rotation of the pedal bone away from the hoof wall so the tip of the pedal bone presses on (or penetrates through) the sole. Sinking refers to dropping of the pedal bone from the coronary band within the hoof capsule.

Fig. 1: Sectioned laminitic hoof showing bleeding and separation of the laminae away from the hoof wall and rotation of the pedal bone. A: pedal bone; B: hoof wall; C: laminae; D: sole. Arrows show bleeding from laminae tearing away from the hoof wall.

Signs of Laminitis

  • Altered behaviour e.g. moving less, lying down, depression.
  • ‘Rocking horse’ stance where the weight is pushed backwards off the front feet (Fig. 2).
  • Heat in the feet, especially around the coronary bands.
  • Lameness of usually both fore feet or all four feet.
  • Bounding digital pulses (felt at back of fetlock).
  • A depression at the coronary band in severe cases.
  • Patchy sweating and increased respiratory rate if severe.

Some of the clinical signs of acute laminitis are easily recognised. The horse/pony will stand rocking back onto the heels to take the wait off the toe, or they will weight shift from one foot to another. The hoof will feel warm to touch and bounding digital pulses can be felt over the back of the fetlock. At its worst, the horse is in is extreme pain and may no longer be able to stand because their feet are so painful. Heart rate and respiratory rate are usually also very elevated in these individuals due to pain.

However, many cases are less acute and can be more difficult for owners to recognise. Some milder cases initially look stiff and walk with a stilted or ‘pottery’ gait, particularly when turned in a circle, or when walked or ridden on hard ground. Horses may be reluctant to lift a foot for shoeing or picking feet out due to the extra weight this puts on the opposite, painful foot.

Fig. 2: Horse with acute laminitis showing the ‘rocking horse’ stance where weight is pushed backwards off the front feet.

Unfortunately, these milder cases are often overlooked by owners. It is very important to identify laminitis in the early stages before destruction of the laminae has occurred.

Most commonly both front feet are affected, although laminitis can occur in all four feet. Occasionally horses present with hind limb laminitis only which can be trickier to diagnose, particularly in thick skinned, heavy feathered horses which makes digital pulses very difficult to feel. Laminitis in just one limb can occur from severe lameness in one limb (e.g. fracture) causing excessive weight bearing in the opposite leg.

Laminitis is very unpredictable and can present in a multitude of different ways, even in the same horse with recurrent episodes. The degree of pain is unacceptable even in mild cases. Tearing of the laminae is probably similar to the attachment of your fingernail to your finger being torn away.

NEXT WEEK: CAUSES OF LAMINITIS

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