Equine laminitis is a common yet complex disease involving the inflammation, swelling, weakening and eventual death of the soft tissue structures (laminae) within the hoof wall. In severe cases, as the supporting laminae become weak and loosen, laminitis can result in rotation and/or sinking of the coffin (or pedal) bone causing a permanent and painful internal deformity known as founder. Unfortunately, laminitis can occur before symptoms become obvious and treatment can be exceptionally difficult. It is important as a horse owner to be aware of the causes, early signs, treatment and prevention of laminitis in order to avoid the serious complications that can arise.
What is laminitis?
Laminitis literally means inflammation (-itis) of the laminae. The laminae are the sensitive and insensitive structures within the hoof that
interdigitate to secure the coffin bone to the hoof wall (Image 1). Laminitis causes these interdigitating structures to become weak and often results in the loss of the tight adherence between the hoof wall and the coffin bone. Consequently, the coffin bone rotates and/or sinks downwards altering the distribution of weight onto the toe of the hoof and causing significant pain (Image 2). The terms “laminitis” and “founder” can be used interchangeably, however founder usually refers to severe chronic cases, wherein the prolonged distribution of weight causes permanent remodelling of the pedal bone and hoof (Image 3).
Clinical signs of acute equine laminitis may include:
- Lameness (most commonly affecting at least two limbs)
- Abnormal stance or positioning of feet. Horses with laminitis will often try to walk or stand on its heels (leans back) to avoid putting pressure on the painful toe/s. This stance has been described as “sawhorse stance”
- Reluctant or hesitant gait with worsening lameness when walking on hard ground or turning
- Shifting weight between feet when resting
- Increased digital pulses. To check your horses pulse place two fingers in front of the sesamoid bones at the level of the fetlock.
- Pain with the use of hoof testers at the point of frog on the hoof
- Heat in and around the hoof
Clinical signs of chronic laminitis may include:
- Rings in the hoof wall. These might appear even in the absence of clinical lameness if a mild chronic form of laminitis is occuring.
- Dropped soles or “flat feet”
- Dished hooves resulting from unequal rates of hoof growth (the heel grows at a faster rate than the rest of the hoof) (Image 4).
Causes and predispositions
The exact pathogenesis of laminitis is poorly understood, however there are three general situations by which laminitis can occur.
Diseases associated with inflammation:
While the precise sequence of events resulting in laminitis is unknown, it is clear that diseases associated with inflammation (i.e. certain types of colic, rapid changes to diet especially in cases of grain overload or rapid exposure to lush grass (resulting in endotoxaemia), diarrhoea, retained placenta, severe pneumonia etc.) can activate inflammatory factors throughout the body resulting in lamellar inflammation.
Endocrine or hormone disorders such as Pituitary Pars Intermedia Dysfunction (PPID; also known as Equine Cushings Disease) and Equine Metabolic Syndrome (EMS; also referred to as “easy keepers”) are commonly associated with laminitis. Again, the exact mechanism remains unclear however it is evident that insulin dysregulation as a consequence of obesity associated with endocrine disease results in increased insulin in the horses blood. In higher concentration than normal, insulin alters messages or signalling within lamellar cells of the hoof and causes them to change their structure resulting in laminitis.
In mechanical overload laminitis it is thought that an inadequate blood supply to the lamellar tissue associated with excessive and continuous weight bearing results in the activation of inflammatory factors within the lamellae. This can refer to a variety of situations including a fracture or joint infection causing a mechanical overload on the compensatory limbs, obesity, or excessive concussion to the feet (often referred to as road founder).
How can I prevent laminitis?
As with most diseases the best treatment for laminitis is to prevent it from happening in the first place. In cases of laminitis of an inflammatory origin such as retained placenta, or pneumonia prompt veterinary care to alleviate the inflammation may prevent or allow early treatment of laminitis. In horses prone to mechanical overload laminitis, prevention measures include using frog or frog-and-sole supports prior to laminitis occuring. In horses and ponies that are predisposed to laminitis due to being overweight or obese, have EMS, insulin resistance and/or PPID, treating the underlying endocrine disorder alongside pasture management and diet changes remain an important preventative measure.
What can I feed a horse that is predisposed to laminitis?
If your horse is predisposed to laminitis it is important that they have restricted access to lush green pasture (particularly in the spring and autumn). Limit the amount of turnout time each day (1-3 hours) and only turn out late at night (after 10pm) or early in the morning. Ensure to remove your horse from pasture by midmorning as this is when grasses contain the most sugar. Alternatively, limit the size of available pasture by using temporary fencing to create smaller paddocks that can expand depending on feed availability.
It is important that you do not put your horse on a “starvation ration” by severely limiting access to all nutrients. Remember that your horse still requires maintenance nutrition achieved through low sugar forage (including native warm season grasses such as Kangaroo or Mitchel grass, lucerne hay that has been soaked to remove excess sugar, and grass hay), and highly digestible fibre sources such as beet pulp. The addition of a small amount of ration balancer that is low in sugar can ensure that all of the horses nutrient requirements are being met. This ration should be fed at a maintenance amount of 1.5% of their body weight in kilograms. If your horse is overweight, feeding them a ration 1.5% of their body weight and reducing this to 1% of their body weight is ideal. Grains and treat foods such as carrots and apple high in sugar should be avoided.
I think my horse has laminitis, what should I do?
Laminitis is an incredibly painful condition and requires prompt veterinary intervention. If you suspect your horse has laminitis please call your vet immediately and bring your horse in from the field for box rest. Supply deep bedding, fresh water and feed your horse a diet of poor quality hay.
How is laminitis diagnosed?
Your vet will conduct a thorough physical exam and may be able to diagnose laminitis through observation alone. Radiographs may be taken if it is suspected that the coffin bone has sunk or rotated, or if your horse is not improving despite appropriate therapy. If an underlying endocrine disorder is suspected, blood tests may also be performed.
How is laminitis treated?
Treatment for laminitis will vary depending on the cause of the disease. If the cause of laminitis is obvious, appropriate treatment can begin concurrently. If the cause of disease is not obvious, laminitis can be treated symptomatically while diagnostic investigations occur simultaneously.
As laminitis is a painful condition your veterinarian will begin a pain relief protocol as soon as possible. This can be achieved through the use of non-steroidal anti-inflammatory drugs or opiates depending on the severity of the condition. Rare cases may require a sedative to encourage the horse to stand still or even lie down to relieve the pressure on the affected hooves. In cases of laminitis with an inflammatory origin, temporary cooling of the feet may be beneficial.
A vital part of treatment for all laminitis is foot support to limit movement of the coffin bone and therefore reduce the pain associated with that movement. This can be achieved by providing deep bedding whilst the horse is on box rest, boots can be used to cushion the soles allowing the horse to be turned out into the paddock sooner. Dietary changes as described above, and allowing adequate box rest is also an important component to treatment.
Frequently asked questions
Should I walk my horse with laminitis?
No, whilst your horse has painful feet they should be box rested. Talk to your vet about introducing controlled exercise once the laminitis is controlled.
Can a horse with laminitis go barefoot?
Yes, if both your vet and farrier believe this is appropriate for your horse.
How long does it take for a horse to recover from laminitis?
It can take weeks to months for a horse to recover from laminitis. As there are multiple causes of laminitis this will depend on how well the underlying issue is being managed and how accepting and responsive your horse is to treatment.
Can a horse with laminitis be cured?
Once your horse has laminitis, it is likely to reoccur. It is important that you implement appropriate pasture management and dietary changes to reduce the risk of laminitis in the future.
My horse does not like to be stabled and cannot be box rested, what should I do?
Discuss with your vet to decide on an appropriate course of action. Providing adequate enrichment and ensuring the stable is free from distressing stimuli will help your horse feel more relaxed. Discuss with your vet the use of boots to provide adequate cushioning for your horses soles to minimise the time needed in the stable. If your horse is seriously affected by stabling, sedation may be appropriate.