The Lowdown on Laminitis
Laminitis is a disease that affects the horse's feet. It's a secondary condition triggered by metabolic disease processes or mechanical (physical) stresses.
By: Nicole Kitchener |
Laminitis is a crippling disease that affects the horse’s feet. It’s actually a secondary condition triggered by metabolic disease processes or mechanical (physical) stresses that cause inflammation of the laminae – the connective soft-tissue between the hoof wall and the coffin bone.
As laminitis develops, the laminae’s scaffoldlike structure, which helps support the weight of the horse within the hooves, loses its integrity and the coffin bone rotates and/or sinks toward the sole of the hoof. As the coffin bone descends, blood flow is cut off. The resulting decrease in oxygen delivery, as well as cellular waste material removal, ultimately kills the laminae’s live tissue. In the worst cases, the coffin bone can become completely detached and even protrude through the sole. Laminitis can affect all four feet, but most commonly strikes the two front feet.
Laminitis is generally considered to have three phases:
1. Developmental – when the triggers that lead to laminitis are at work. This stage lasts about 20 to 60 hours after exposure. Clinical signs are not noticeable.
2. Acute – pain and lameness become evident as the laminae become inflamed. Indications of laminitis include: short, choppy stride; a sawhorse stance (front feet forward, rocked back on their hind feet); shifting weight from side to side; an increased (frequently called “bounding”) digital pulse; heat in the hoof; and pain when pressure is put on the toe with hoof testers. The horse may also appear anxious, stop eating and show an increased respiration rate. This phase lasts 24 to 72 hours.
3. Chronic – when clinical signs have been present for 72 hours or when x-rays show coffin bone rotation. Some experts call this stage the sub-acute phase, and consider the condition chronic when permanent damage has occurred. Signs of long-term laminitis problems include: rings in the hoof wall; bruised soles; seedy toe; dropped soles; dished hooves; toe cracks; and flakey outer hoof wall.
While the words laminitis and founder are often used interchangeably, founder is actually when the coffin bone rotates – it’s the irreversible result of laminitis. “Unfortunately, we don’t know too much about laminitis,” said Dr. Nicola Cribb, assistant professor in the large animal department at the University of Guelph’s Ontario Veterinary College, who is currently working on studies focusing on laminitis that occurs when an animal overloads its foot.
“And there’s been lots of theories over the past few years that have come and gone and been proved and disproved.”
While researchers like Cribb are working hard to solve the puzzle of laminitis at the research level, horse owners need to be aware of this potentially fatal disease, know what to do if laminitis is suspected and how to prevent it from occurring in the first place.
First Signs – Urgent Action
If laminitis is detected early and dealt with quickly, a favourable outcome is more likely.
If you think your horse has laminitis:
- Call your veterinarian immediately.
- Remove the horse from the suspected cause (i.e. take him off pasture if grass is a possible culprit).
- If the horse is far from the barn, don’t make him walk, as this can cause further coffin bone rotation. If possible, trailer him home.
- Provide the horse with a soft, even area to stand such as a stall or confined paddock. A deep bed of shavings or wet sand works best, allowing the horse to get complete support under the frog and giving him the opportunity to self-adjust his foot angle – usually toes down, heels up – to relieve pain.
- Remove horse shoes.
- Support the heels and provide cushioning by applying a wedge of some type – it can be quite rudimentary at this point. Some experts encourage horse owners to keep industrial Styrofoam on hand as a quick and effective temporary support.
- Keep the horse quiet and still. Encourage him to lie down to relieve pressure on the hooves.
“One of the things that we always do in the hospital here when we have any suspicion that a horse is at risk of laminitis, even if it doesn’t have any clinical signs, is ice their feet,” explained Cribb. “It’s really been the only thing that’s been proven to help with laminitis – or help prevent it anyway.”
Clinical trials undertaken in 2004 by Dr. Christopher Pollitt of the Australian Equine Laminitis Research Unit, indicated cryotherapy (cold therapy) is very effective in preventing laminitis when applied during the developmental phase. Cryotherapy provides analgesic effects, helps to preserve tissues and is believed to slow the metabolism in the tissues. It has not been proven, however, to slow or stop damage to the laminae once it’s started.
Cribb said a lot of research is going into the best methods and means to provide cryotherapy, as it isn’t always a practical procedure, particularly when, as some experts recommend, affected horses should spend days at a time with their feet iced. “The way we do it is take some big bags and put ice in them and literally put the horse’s foot in the bag. But then, you know, you have a horse with these four big bags walking around the stall,” said Cribb. “But we find it’s an important thing to do.”
A recent study out of Cornell University showed crushed-ice-filled boots are more effective than boots with gel pack inserts. And James Orsini, director of the Laminitis Institute at New Bolton Centre, University of Pennsylvania, has developed a new technique that uses dry-cold compression therapy.
Initially, the veterinarian will attempt to diagnose and treat the primary problem.(So, in the case of grain overload for instance, the vet will likely clear the gastrointestinal tract of all grain using mineral oil via nasogastric tube to limit toxin absorption.)
The vet will likely administer some form of pain relief/anti-inflammatory medication such as acepromazine (ACP), phenylbutazone (bute) or banamine. Other drugs might include antibiotics to fight possible infection, agents to reduce bacterial toxicity, anticoagulants and vasodilators to improve blood flow to the feet. If the horse is very sick or dehydrated, intravenous fluids might also be given.
Blood work can help determine whether disease elsewhere in the horse’s system could be involved and can also test for abnormal endocrine (hormone) levels – insulin, glucose, Adrenocorticotropin hormone ACTH and thyroid, which are often implicated in laminitis.
While sourcing the base condition can be like putting together pieces of a puzzle, the actual diagnosis of laminitis itself is not difficult. Radiographs, digital radiography and magnetic resonance imaging (MRI) can provide a definitive diagnosis and show the level of disease progression. Another diagnostic tool, venography – or the radiographic examination of the hoof using contrast materials injected into the vein to show blood flow – has also found favour with many vets, as it is less expensive than other technology and relatively easy to perform.
After initial care and diagnosis, treatment then shifts to management strategies intended to prevent further coffin bone rotation and to provide pain relief. At this point, ongoing support and monitoring by the veterinarian and a skilled farrier is essential to the laminitic horse’s health and well-being.
Treatment depends on the suspected cause and will vary among horses. Preliminary plans could include dietary restrictions such as eliminating grain and exposure to pasture, exercise regimes and addressing hoof problems that appear to be a contributing factor.
Beyond correcting foundational hoof problems, continued therapeutic shoeing and monitoring involves supporting the laminae, promoting more weight bearing on the back of the hoof and moving the breakover from back from the toe. To achieve these results, farriers use a number of different trimming techniques to great success as well as various shoes such as reverse and heart bar shoes. Plastic shoes are also used, even plywood clogs.
The horse should be exercised as soon as he’s able to walk comfortably on soft, even ground, very gradually increasing time and intensity of workouts.
Surgery is sometimes recommended in situations where the coffin bone continues to rotate and is about to or has already penetrated the sole. Called tenotomy, the procedure involves cutting the deep digital flexor tendon that attaches to the bottom of the coffin bone to limit rotation and allow new hoof growth as well as reduce pain.
Although treating a laminitis-prone horse is a team effort, ultimately it is the daily caregiver who will see what helps the horse and what hinders his progress. You know your horse. Listen to your own instincts and to what your horse is telling you.
You might find keeping a journal helpful in tracking management techniques that work for your horse. Track factors such as weather, changes in feed and hay, stress, exercise, farrier visits, your horse’s mood, soundness – anything that could provide pointers to when things are going well and when your horse might be more susceptible to laminitis.
Dr. Don Walsh is one of the world’s most renowned laminitis experts. He’s also founder and president of the Animal Health Foundation, an organization with the mission to find the cause of laminitis and ways to prevent it through financial donations to research, and dissemination of information to owners.
In his article, “Laminitis Prevention and Managing the At-Risk Horse,” Walsh says, “After treating horses affected by this disease for the last 36 years, I can say that prevention is the best possible way to deal with laminitis.”
Prevention, however, can be difficult when the causes of laminitis are so elusive.
Obese horses are also very prone to laminitis. Endocrine disorders such as Equine Metabolic Syndrome, which is triggered by excess starch and sugar intake, and Cushing’s syndrome, caused by a tumour in the pituitary gland, lead to obesity. These horses have thick, cresty necks, fatty deposits on their shoulders, back and tailhead. They are prone to a condition called insulin resistance (IR), which leads to elevated blood insulin levels and is similar to human diabetes. Higher-than-normal insulin levels have been implicated in laminitis. A recent field study Walsh conducted out of Cornell shows the higher the insulin level, the more severe the laminitis.
Horses in these categories need restricted carbohydrates, limited grazing, particularly in spring and fall, and regular exercise to avoid laminitis. Regular glucose and insulin testing can help too.
Studies have shown the ingestion of sugars called fructans in grass increases the risk of a horse developing laminitis. Fructans are not digested in the small intestine, but in the hind gut. When large levels of fructans enter the hind gut, the population of bacteria proliferates in order to ferment the sugar. It’s believed the overload of bacteria damages the gut’s lining and, as the bacteria die, the resulting toxins escape into the bloodstream and travel to the hooves. Limiting or eliminating exposure to grass for obese horses at all times and for all horses during spring and fall when the grass is rich in sugars is important.
Other seemingly simple, but significant ways to prevent laminitis include:
- Securing feed room doors with locks and secure feed bins to binge eating
- Limiting carbohydrate intake
- Testing hay for sugar content
- Providing adequate exercise and feed for the amount of work your horse is doing
- Using a grazing muzzle, if necessary
- Avoiding/limiting use of corticosteroids
- Ensuring quick removal of retained placentas
- Avoiding temperature extremes
- Not using black walnut shavings in stalls
- Avoiding stressful situations
- Treating initial lameness quickly and using frog and sole support on the foot opposite to an injured one
- Making dietary changes slowly
The role of an experienced farrier in laminitis prevention shouldn’t be underestimated, said Walsh. Early changes in the way a hoof is growing can be detected when the farrier is trimming or shoeing. Walsh said these subtle changes are seen when abnormally high levels of insulin are in the blood, but before lameness occurs. Farriers noticing these changes should notify owners, who can have a veterinarian test insulin levels. If levels are high, a low-glycemic diet, increased exercise and medication can bring the levels back down to normal and possibly avert laminitis from developing.
At-risk horses should be checked daily for higher-than-normal temperatures of the foot and to feel for increased digital pulse that could indicate a problem. Regular x-rays will identify any changes within the hoof.
Unfortunately, despite care and treatment, many horses who have suffered a laminitis episode will relapse, sometimes seemingly in subsequent instances for no identifiable reason. The already damaged laminae seem to be at greater risk to any type of stress and blood flow could be compromised.
Nevertheless, some horses will go on to their previous level of soundness and performance. Others, however, will suffer such extensive damage within the foot that euthanasia becomes the most humane option. “It’s a disease that veterinary professionals and owners alike – actually, everyone associated with horses – is very emotional about,” said Cribb. “It’s a very devastating disease and that’s definitely what drives my research.”
The Mystery of Laminitis
Laminitis remains very much a mystery despite having become one of the most aggressively researched equine conditions of the past couple of decades.
Noted laminitis researcher, Rustin M. Moore of Ohio State University, has stated, “No horse, no matter how valuable or how well cared for, is immune to laminitis….Despite substantial research over the last three decades investigating multiple mechanistic pathways involving the onset and development of laminitis and important discoveries, a complete knowledge and understanding of this disease is lacking.”
Not only is it a baffling disease, there are other inherent difficulties involved in researching laminitis. “There are multiple challenges, obviously, with a 500-kg horse that you can’t tell to lie down and have a rest,” said Cribb, who went on to explain how frustrating a disease it is to those investigating the inner workings of the disease, treatments and prevention.
“I attended a conference in Florida a few years ago where one of the presenters showed a huge list of all the different treatments for laminitis and also gave a quote out of a book from about 100 years ago about how to treat horses with laminitis, which said they should stand in a cold river,” Cribb recounted. “And basically, putting ice on a horse’s feet is the only way that’s been scientifically proven to help horses with laminitis. So, the past 100 years we’ve done a lot of work on it as a profession, but it’s difficult still to say what the most appropriate treatment is.”
As Cribb explained, often research findings from human ailments and conditions are extrapolated for use in horses and vice versa, but in the case of laminitis, there are few, if any comparable diseases. “And so there hasn’t been millions of dollars of research thrown into it,” said Cribb. “[The veterinary profession] is kind of doing all the research itself and doesn’t have the research dollars.”
Nevertheless, several innovative studies are underway in various research centres around the world. Some interesting areas of investigation include gene therapy to prevent support-limb laminitis, the use of stem cell therapy, the role of enzymes in the disease progression and continuing work on the inflammatory processes involved in laminitis.
On the home front, however, it is up to horse owners to be aware of the causes of laminitis and to take every measure to prevent this potentially devastating disease.