Laminitis is inflammation of the laminae in the horse’s foot (most often one or both front feet, but it can affect the hind feet as well) caused by a disruption of blood flow that can be intermittent, chronic, or temporary. The hoof is connected to the body via finger-like projections that grow inwardly from hoof wall to coffin bone (non-sensitive laminae) and outwardly from coffin bone to hoof wall (sensitive laminae) creating a zipper-like ‘Velcro’ structure that holds the coffin bone in place. If the laminae become inflamed, the structure loosens, which allows for movement of the coffin bone within the hoof capsule. This is very painful for the horse; think of what happens when you slam your finger in a car door. Your nail bed becomes black and very painful. Now imagine the pain of bearing 60 per cent of your weight on that finger!
Laminitis affects many horses and can be one of the most difficult diseases to treat as a veterinarian, because we still don’t have all the answers as to the exact mechanism for how or why disruptions in blood flow cause inflammation of the laminae. Research is ongoing to figure out the missing pieces of the laminitis puzzle.
Causes of Laminitis in Horses
There are a number of causes of laminitis, some of which veterinarians and horse owners can prevent, and some we can’t, such as a natural predisposition for the condition in some draft breeds, Morgans, ponies and donkeys.
Laminitis-causing situations that horse owners can watch out for or try to avoid include:
- bedding on shavings made with black walnut
- a retained placenta after foaling
- severe colic
- high fever
- illnesses such as Potomac Horse Fever
- blood poisoning from infections or toxins released into the bloodstream from plants or chemicals
- excessive weight-bearing on one leg due to severe lameness in the other
- overweight animals and older horses with equine metabolic syndrome (EMS) or pituitary pars intermedia dysfunction (PPID or Cushing’s disease)
- hoof trauma caused by riding on hard surfaces
- diet-based causes such as grass founder or grain overload
Grass founder, triggered by sudden access to lush pasture, can cause a disruption of blood flow to the feet. The mechanism behind this is due to the increased sugar in the grass. When the horse digests the grass, the increased sugar content causes an overgrowth of bacteria in the gut. These bacteria release endotoxins that travel to the bloodstream and damage the small blood vessels in the feet, leading to a disruption in blood flow and subsequently laminitis.
To reduce the negative effects of spring grass, there are a number of ways to limit how much your horse is eating. Grazing muzzles, allowing them to fill up on hay before limited turnout, and keeping overweight, older, or cresty-necked horses on sparse pasture or in a dry lot until the grass growth has slowed are some ways to reduce exposure. Similarly, if your horse or pony happens to be an escape artist, gets out of his stall overnight and helps himself to the grain supply, the sudden increase in sugars from the grain will have the same effect as the lush pasture to his digestive system. Ensuring that stall doors are secured with horse-proof bolts, having doors on the grain room or lockable lids on grain bins can save your horse or pony from a very upset GI system and very sore feet – or worse.
Signs and Symptoms of Laminitis in Horses
Clinical signs of laminitis can range from mild to severe and acute to chronic. Signs of acute or sudden-onset laminitis include warmth in the feet, increased digital pulse, a horse that appears to be walking on eggshells, lameness especially when turning, shifting weight while the horse is standing still and a “sawhorse” stance where the horse shifts his weight onto his hind feet with front feet stretched out in front. This stance helps alleviate pressure on the front feet by bearing more weight on the hind.
Visual signs of chronic laminitis can be observed in the hoof as rings in the hoof wall, bruised soles, and a widened white line.
Treatment and Prevention of Laminitis in Horses
Treatment for laminitis is mostly symptomatic once the primary problem is identified and removed. Depending on the cause of the laminitis, treatment options can include IV fluids, antibiotics, anti-endotoxic medications, pain medication in the form of NSAIDs such as phenylbutazone (Bute) or flunixin meglumine (Banamine), vasodilators and bedding your horse on deep shavings or even sand to provide sole support. In severe cases, lidocaine patches applied to the horse’s pastern and fetlock can provide some relief, as does lidocaine infused into the digital nerves via a perineural catheter.
Changing the shoeing of the patient can make a huge difference in comfort level of the horse. There are many different ways to shoe laminitic horses, from a simple shoe with a rolled toe to a wooden clog to cushioning pads. Working closely with an experienced farrier can be infinitely beneficial to the horse’s comfort.
A newer treatment option for horses that are known to be high risk (such as a mare with a retained placenta or a pony that you know has eaten a large amount of grain) is cryotherapy. Standing the horse in ice boots for the first 72 hours after insult has been shown to reduce the risk of laminitis. Although this is a huge undertaking for caretakers, it often pays off in reducing the severity of the condition.
Laminitis can be a horse owner’s (and veterinarian’s) worst nightmare, and a lot of the time the treatments are just playing catch-up to the condition. Frequently, treatments allow the patient to become more comfortable and even return to previous work; however, there are many occasions where no progress is made despite giving gold standard care and in severe cases euthanasia may be necessary. Speak to your veterinarian if you think your horse or pony may be at risk for laminitis, or if you want to learn more about prevention.