The Changing Face of Laminitis
New research and more educated horse owners have resulted in many changes to the way laminitis, a devastating hoof disease, is triggered and treated.
By: Nicole Kitchener |
Essentially defined as inflammation in the horse’s feet, laminitis is mysterious, multi-factorial, painful, sometimes life-threatening, and, in some ways, according to British Columbia veterinarian and animal welfare advocate, Dr. Bettina Bobsien, it’s not quite the disease it used to be.
Inside the horse’s foot, the scaffold-like structure of the sensitive laminae – the soft-tissues connecting the hoof wall and the coffin bone – supports the horse’s weight within the hooves and keeps the coffin bone suspended in the hoof capsule. It’s believed a complex set of events in the horse’s body interrupts blood flow within the laminae, resulting in inflammation and swelling. Eventually, the live tissue dies, causing the coffin bone to detach and rotate due to the pull of the attached deep digital flexor tendon at the caudal end. In severe cases, the front of the coffin bone even protrudes through the sole.
When Dr. Bobsien first began practicing equine medicine in the 1990s, most of the laminitis cases she saw presented acutely – very dramatically and suddenly – and resulted from either overwhelming infections such as colitis or from carbohydrate overload after a horse pigged out on lush grass or a feed-room raider gorged on grain. Other factors that predispose a horse to laminitis are: stress, temperature extremes, abrupt changes in activity level, exposure to various toxins and certain medications such as corticosteroids. Physical trauma and mechanical issues can also cause laminitis, including repeated concussion from heavy work and supporting-limb laminitis, where the opposite foot to an injured one is forced to bear extra weight.
The telltale sign of acute laminitis is the backward “sawhorse stance,” where the horse tucks his hind legs underneath his body, setting his front feet unusually forward, as he tries to relieve pain in the front feet by rocking back onto his hindquarters. He may also shift his weight from foot to foot and react when hoof testers are applied.
A strong digital pulse, often described as pounding, will be felt at the back of the fetlock and there will be heat in the hoof wall and at the coronary band. The pain may also cause anxiousness, increased respiration and pulse, elevated hoof temperature, trembling, reluctance to move and a lack of interest in food. “Frequently, they have tremendous difficulty turning. Turning torques the laminae a little bit, causing pain,” noted Dr. Bobsien. “In some cases, they will be down and unable or unwilling to rise.”
While acute laminitis cases certainly still occur, they’re not quite as common, said Dr. Bobsien. This is partly because horse owners are more educated about the importance of proper equine nutrition, avoiding obesity, not feeding too much grain and slow introduction to pasture. Plus, dedicated research has brought much to light about causative factors, prevention and treatment.
“A lot of laminitis I see in my practice now is associated with underlying metabolic diseases that are developing as a result of aging.
Laminitis and Aging Horses
Dr. Bobsien is referring to equine metabolic syndrome (EMS) and pituitary pars intermedia dysfunction (PPID), formerly known as Cushing’s disease.
Both involve insulin resistance. Produced by the pancreas, the hormone insulin triggers the body’s cells to take up glucose from the bloodstream for energy. In horses with insulin resistance, the cells don’t take up as much glucose, so more remains in the bloodstream. Because the body isn’t using insulin properly, it responds by creating extra. This overproduction lowers a horse’s threshold for developing laminitis.
EMS is largely found in genetically predisposed breeds such as Morgans, Paso Finos and many types of ponies. These so-called easy-keepers have regional adiposity or “body fat in the ‘dangerous’ places, for lack of a better word,” said Dr. Bobsien. “Along the topline typically, along the crest, on the rump, around the shoulders, sometimes above the sheath and filling of the sockets above the eyes.”
With PPID, a malfunctioning pituitary gland causes insulin resistance and also releases other hormones such as cortisol that have been implicated in laminitis. Mainly a disease of the elderly, it’s characterized by unusual shedding patterns, a pot belly and regional adiposity, among other signs.
Horses are living longer for a number of reasons, including better dentistry, improved nutrition, preventative medicine and because more people are retiring their horses and “aging them out” rather than sending the animal to slaughter or euthanizing them at the end of their career, explained Dr. Bobsien. “The demographics of the horse population is not far off the baby boomers. Just like in people, we’re getting the opportunity to see [certain] diseases more. PPID or equine metabolic syndrome are creeping up on susceptible horses as they age. They retire, they’re gradually getting heavier. They are at risk for developing metabolic laminitis.”
What’s tricky about laminitis occurring secondarily to PPID or EMS is it’s usually slower to start and is “much more subtle,” said Dr. Bobsien. “Silent” or “sub-clinical” at this stage, horse owners might not notice any signs or symptoms while the disease is first at work. “Owners may think it’s some kind of minor traumatic injury or infection. The laminitis will sometimes start in one leg, so people will think the horse has a sole abscess or a bruise. It doesn’t get better and then five or 10 days later, the horse is lame in both front feet and the owner’s really scratching their head. And within two to three weeks, they may have laminitis in all four feet.”
However, there may be some physical clues of deformities occurring in the hoof capsule such as dropped soles, a depression at the coronary band and a dish-shaped hoof wall. Rings on the hoof wall surface also indicate small laminitic episodes. The horse may also be more prone to abscesses, hoof infections and white line disease as a result of changes in the hoof health and structure. These problems are also worsened by a suppressed immune system, which is another feature of PPID.
Another difficulty? Testing for PPID or EMS can be “elusive” said Dr. Bobsien. “You can have normal lab results and the horse is going through bouts of sub-clinical laminitis.”
No matter what the initiating cause, there’s good news. Laminitis isn’t as much of a death sentence as it was when Dr. Bobsien began practicing 30 years ago. “We used to lose a lot of them. With good diagnostics, educated horse owners and very skilled farriery, we don’t lose that many anymore. Many horses now can recover and go back to being relatively normal horses, able to do a job, although perhaps at a reduced level, and may even be allowed grazing again.”
My Horse Has Laminitis: Now What?
Early detection, intervention and aggressive treatment are critical in reducing inflammation and mitigating deterioration within the hoof. Veterinary intervention is key.
“I’ve had prudent horse owners who thought their horse had laminitis. We started the horse on medication and achieved a rapid turnaround. Within weeks those horses were relatively pain free,” said Dr. Bobsien. “If you wait too long, and allow the structural damage to get going, that horse may be in pain – not just not useful but actively sore – for a year or more, and develop permanent foot deformation and a compromised hoof structure”
If you suspect laminitis, first attempt to identify and remove the possible cause; for example, take your horse off grass if that might be a factor. Limit the horse’s movement and put him in a small stall or paddock, preferably with soft, even footing. Deep bedding such as shavings or sand can help support the frog and allow him to self-adjust his feet for pain relief. You can apply commercial frog and frog-sole combination wedges or fashion temporary ones yourself using Styrofoam™, impression putty or pads. Or put him in therapeutic boots. Encourage the horse to lie down as much as possible.
Research has shown that ice therapy can be effective as a preventative in pre-laminitic stages of carbohydrate overload or bacterial infections so long as the horse isn’t already showing clinical signs. “Pre-emptively they will now put those horses in ice baths or ice boots,” said Dr. Bobsien, explaining the action likely prevents inflammation and potentially reduces the chance of toxins reaching the laminae.
When the veterinarian arrives, they will assess the horse to determine if the problem is truly laminitis or another condition, said Dr. Bobsien. Then they will work to treat the primary condition, if necessary, and will administer anti-inflammatories and pain relievers to make the horse more comfortable.
Dr. Bobsien takes a blood sample to test for insulin resistance and will ask the owner for a full evaluation of the horse’s diet, exercise, housing and overall hoof care regimen. Radiographs are also recommended to determine the amount of coffin bone rotation.
Another, newer diagnostic tool is the venogram, in which contrast dye is injected into the blood vessels of the foot, then x-rayed. Normal vessels show up in a certain pattern, which is altered in a laminitic horse with compromised laminae. Ideally, a venogram is performed within 48 hours of the onset of lameness and then again four days to three weeks after treatment has been initiated in order to monitor subtle changes. Dr. Bobsien noted, however, that “the value of venograms in establishing prognosis and treatment has been debated.”
Longer term, working closely with a qualified farrier is “critical to a positive outcome of a case,” stressed Dr. Bobsien.
While the hoof will likely never be restored to its original condition, the farrier’s goal is to relieve stress on the laminae and support the coffin bone and sole through careful and gradual therapeutic trimming and often shoeing. They want to take pressure off the soles and promote weight bearing of the frog.
Traditional farrier solutions include application of heart-bar shoes or even a regular shoe nailed on backward. Custom-made wooden or leather shoes can also prove beneficial. Shoes are sometimes glued or screwed on when nails might prove painful. Farriers also use a variety of pads, packings and wedges for managing their laminitic patients.
The farrier may also have to resection (remove part or all of the hoof wall) to access abscessed or separated areas, relieve pressure and promote blood flow.
If disease progression isn’t hastened or ceased, a veterinarian might opt for a surgical procedure called a tenotomy, which involves cutting the deep digital flexor tendon to reduce the pull on the coffin bone. Research also suggests Botox injections can relax the tendon to the same effect.
Management and Prevention of Laminitis
Feeding a low- or no-grain diet along with regular exercise reduces the chances of laminitis and helps prevent obesity.
Don’t know what a too-fat horse looks like? Dr. Bobsien represented the Canadian Federation of Humane Societies and the BCSPCA on the development committee of the recently revised Canada’s Code of Practice for the Care and Handling of Equines. Available at
nfacc.ca/codes-of-practice/equine, the code’s valuable diagrams and information on the body condition scoring system offer a visual weight blueprint.
Good quality hay is also a staple, but Dr. Bobsien warns against jumping on the current low-sugar content bandwagon “just in case.” Most healthy horses are fine on regular hay, which may be more digestible and taste better, she said. “Some people are feeding all their horses low-sugar hay and it becomes unavailable or unaffordable for people whose horses truly have a medical condition. It makes sense if you have a horse that has other presenting signs [of laminitis], a breed that’s prone to metabolic syndromes or an aging horse.”
The owner must also monitor sudden changes in pasture growth and quality and limit access at those times when fructans, or sugars, are at their peak, not only in the spring, but fall too, especially after a summer drought.
The traditional strategy of permanently putting laminitic horses in dry lots with little to no grass access is no longer recommended, particularly for those with PPID and EMS because, the horses tend to just stand around. Instead, get the disease and the horse’s weight under control, then turn them out with careful pasture management and/or the use of a grazing muzzle. “So, be careful with fertilizer, keep the pasture mowed if needed. Try to find the sweet spot – the pasture size where the horse can keep it looking like a golf green. Then these horses can have a relatively normal life. They can walk, graze and burn off some calories. They are much happier because they’re moving and eating, even though it is a small amount.”
Routine blood screening for EMS and PPID is part of an annual wellness exam for many at-risk horses. If these conditions can be identified and corrected before the horse shows symptoms of laminitis, the animal can be saved both the suffering of the laminitis episode and the potentially long recovery period.
Laminitis remains one of the most serious diseases that affects horses, but improved understanding of the underlying causes and more effective treatments have improved outcomes for horses in recent years. Ongoing research into risk factors, genetics and management of clinical cases will, hopefully, continue this trend of improved survival and quality of life of affected horses.
Canadian Laminitis Studies
Laminitis is the focus of intensive research as experts around the world attempt to unravel the disease processes, and develop and improve treatment outcomes and prevention strategies. Here are a few Canadian projects:
- Dr. David Wilson of the Western College of Veterinary Medicine (WCVM) and other researchers have developed a vaccine that protects horses against laminitis resulting from grain overload. Bacteria proliferate to ferment the grain in the hindgut and produce an exotoxin that escapes into the bloodstream, causing a systemic inflammatory response that triggers laminitis. The vaccine prevented laminitis onset in 80 per cent of test horses.
- WCVM researchers have shown placing a screw into the coffin bone for two to three days, to anchor it to the hoof wall, prevents rotation and is shown to be well tolerated. The screw is removed after inflammation goes down.
- Soaking or steaming hay lowers the carbohydrate content, which can help reduce blood glucose – a good thing for insulin-resistant and obese horses that are at risk for laminitis. Equine Guelph’s Dr. Katrina Merkies is investigating the nutritional and feeding effects of soaking and steaming timothy and alfalfa hay.
- Work being done by Dr. Luis Arroyo, also at Equine Guelph, with co-investigator, Dr. Emma Allen-Vercoe of the University of Guelph’s Department of Molecular and Cellular Biology, uses a laboratory model that mimics the horse’s own gut. It examines how disturbances in the microbial ecosystem of the hindgut, where complex sugars are broken down, can lead to potentially life-threatening disorders such as colitis and laminitis.