Laminitis in Horses with EMS and Cushing’s Disorder
By Dr. Jaini Clougher, President, ECIR Group Inc.
Equine laminitis has been with us for a long, long time. Fortunately, in the last 10 to 20 years there have been great strides in understanding the causes of this terrible condition. Laminitis is now regarded as a syndrome that occurs secondary to something else, rather than a discreet disease all in itself. This has allowed much more focused research and effort in treating the cause rather than treating just the symptoms that occur in the hoof. It doesn’t matter how great the trim is, or what shoes are used, or how deep the bedding. If initiating causes such as EMS (Equine Metabolic Syndrome – see Equine Metabolic Syndrome & Equine Cushing’s Disease, or PPID (Cushing’s disorder) are not addressed, the laminitis and the pain will continue.
In its broadest sense, laminitis is the failure of the connections between the hoof capsule and the coffin bone, accompanied by the death of some of the cells responsible for these connections. The weakening and distortion of the laminae, abnormalities in circulation, and loss of support inside the hoof can lead to severe pain.
In chronic laminitis, the laminae connections stretch, separate and break down, allowing the pedal/coffin bone and hoof capsule to rotate or sink in relation to each other. Photo: iStock/Groomee
It is estimated that 80 percent of all laminitis cases are due to endocrine dysfunction, specifically excess insulin in the blood. This can occur in Equine Metabolic Syndrome (EMS) and Cushing’s disorder (PPID). Uncommon contributors to EMS and subsequent hyperinsulinemia are iron overload and ovarian abnormalities in some mares.
Despite the “-itis” suffix, which is used to indicate inflammation, inflammation inside the hoof is minimal in endocrine laminitis. There may be some inflammation later on in severe cases due to blood and serum pooling as the laminar connections continue to tear. There is strain and oxidative stress in the muscles of a laminitic horse as they tense muscles, shift, and have abnormal stances in an attempt to get comfortable; however, endocrine laminitis itself is not an inflammatory event. This accounts for the observation that anti-inflammatories, such as phenylbutazone (Bute), have only a partial effect on the pain of laminitis. Anti-inflammatories can address the inflammation in the muscles, and provide some central pain relief via the brain, but the events in the hoof go unchecked.
Please note that in the case of the severe laminitis secondary to septicemia, such as retained placenta or severe colic, there is body-wide inflammation, and anti-inflammatories are entirely appropriate.
An estimated 80 percent of all laminitis cases are due to endocrine dysfunction, specifically excess insulin in the blood. Horses with EMS should never be grazed, and if inappropriate diet is a cause of laminitis, it should be addressed immediately. Photo: CanStock/DecHogan
Causes of Laminitis
- Septicemia, toxins, and weight-bearing laminitis are less frequent than endocrine disorders, but still very important and just as devastating.
- Hyperinsulinemia (high blood insulin levels): This can be due to EMS; Cushing’s disease (PPID); mare ovarian abnormalities; or associated with iron overload. These endocrinopathic disorders are thought to cause about 80 percent of laminitis cases.
- Lyme disease: Tough to say where this fits in with regard to insulin vs infectious disease, but Lyme can cause severe laminitis or ongoing, low-grade laminitis.
- Septicemia: This can be due to colic from a feed-room break-in (hind-gut bacteria are overwhelmed and die, releasing endotoxins); surgery; retained placenta; or some severe infectious diseases, such as strangles. These horses are clearly very ill, with fever, inappetence, pain, and often diarrhea.
- Some toxins: Black walnut shavings in contact with the horse or sweet alyssum in the hay can cause laminitis (mechanism unknown).
- Weight-bearing laminitis: This is what struck down the 2006 Kentucky Derby winner Barbaro in early 2007. Barbaro shattered a leg in the 2006 Preakness Stakes, ending his racing career and eventually his life. When one leg is virtually non-weight-bearing for a prolonged time, the other limb can suffer severe laminitis.
Acute laminitis is hard to miss. There may be a classic laminitic stance, where the horse is rocked back onto its haunches in an effort to take weight off the feet. The horse is reluctant to walk. When it does walk, it looks like it is walking on eggs or broken glass. I will never forget putting hay out for one of our horses, and having her creep up to it and stand on the flake instead of eating the hay.
Hoof testers don’t always elicit a response (assuming you can get the horse to pick up its foot for this test). A light tap on the front of the hoof with a hoof pick often gets a flinch. The hooves are very warm to the touch, and there will be a bounding digital pulse.
Low-level (subclinical, or occult) laminitis is much less obvious. It is easily mistaken for arthritic changes, especially in older horses. It manifests itself as tenderness on hard or stony ground; short strides; reluctance to move under saddle; reluctance to do sharp turns; rigid head carriage; and increased muscle tone in shoulders, back and rump. There may be mincing, short steps when the horse is turning. Even more subtle is evidence of back pain, and resistance to being saddled. This can, of course, be due to saddle fit or other issues, but hoof pain (or any pain) will produce the same signs. Body work (chiropractic and massage) will help for a day or two, but then the tense back and taut muscles come right back.
There may be “event lines” on the hooves – ridges on the hoof wall instead of a smooth surface. Event lines may not be present with subclinical laminitis. Also, not every event line is due to laminitis.
Other hoof pathology, which may be assumed to be “just the horse,” includes flat or thin soles, flared walls, and widened white line. These pathologies can also be due to faulty trimming or nutritional issues.
Event lines, or ridges on the hoof rather than a smooth surface, may not be present with subclinical laminitis, and event lines may be present for reasons besides laminitis. Photo: ECIR Group
Steps to Take when Confronted with a Horse Suffering Acute Laminitis
You go out to the barn or the paddock, and your horse is reluctant to move, appears to be walking on eggshells, or is rooted to the ground in the classic rocked-back laminitis stance. Here are the steps to take:
Step 1 – First, call your veterinarian and schedule an appointment. Next, make your horse more comfortable. If possible, slowly move your horse to a deeply bedded area, whether a stall or shelter. In very severe cases where the horse won’t move at all, you can put anti-fatigue mats under the feet. The horse will not want to pick up the hoof for any length of time, so you have about a nano-second to shove the pad under the foot before moving on to the next foot. It is helpful to have two people to do this.
The use of therapeutic hoof boots with pads can help enormously with the pain. Alternatively, taping blue Styrofoam™ to the bottom of the hooves will provide relief. Apply duct tape to the Styrofoam™ first, then apply to the feet. This can be done over shoes as well.
When horses are really reluctant to move, make sure they have food and water within reach.
Step 2 - The next step is to start the Temporary Emergency Diet. For a 1,000-pound horse, this consists of 20 pounds of grass hay daily (two percent of body weight), soaked to reduce soluble sugars. Soak for one hour in cold water or 30 minutes in hot water, and drain the water where the horses can’t get at it. You can find hay-soaking tips at the ECIR Outreach Group at Groups.io: https://ecir.groups.io/g/main. Add one to two tablespoons of salt; one-half to three-quarters of a cup of ground, stabilized flax seed (to provide omega 3 fatty acids); 2,000 IU of Vitamin E; and one teaspoon of magnesium oxide (available from the feed store). Vitamin E needs to be in contact with fat or oil for adequate absorption; if you are using powdered E, add a teaspoon of olive oil or flax seed oil and mix it in. (See the article Are You Feeding Enough Vitamin E?, Spring 2018 issue of Canadian Horse Journal. I find it easier to use natural Vitamin E capsules which usually contain soy oil (check the label). Most horses will eat the 400 IU capsules. You need a safe carrier in which to put the salt, magnesium oxide, flax, and Vitamin E. Unmolassed beet pulp (rinsed, then soaked, then rinsed again), soy hull pellets, or Ontario Dehy Timothy Balance cubes are all safe for EMS and PPID horses. If your horse flatly refuses any of these, you can sprinkle the salt and other supplements onto the hay. Don’t feed anything else at the beginning until you sort out exactly what is happening with your horse. Even one carrot or one apple per day can be enough to cause continued high insulin and ongoing pain and laminitis in these early stages.
Step 3 – Non-steroidal anti-inflammatories such as phenylbutazone, Previcox, or Banamine can be of some use at the beginning, but limit the use to four to five days maximum.
Step 4 - At this stage of acute laminitis, you can’t really pull blood to try to parse out the cause because severe pain can cause changes in the blood parameters. However, there are other things you can do while waiting for the pain to subside. Start with a hay analysis, so that you know what the sugar and starch levels are in the hay. Horses subject to endocrinopathic laminitis need to have all components of the diet below 10 percent ethanol-soluble sugar (ESC) plus starch, and the starch component needs to be below four percent. Some very sensitive horses will need ESC plus starch to be under eight percent. Get a full mineral analysis as well, so that you can balance your minerals to the hay.
Step 5 - Foot comfort, once the Styrofoam™ comes off, can be greatly aided by providing an area with four to six inches of round pea-gravel (the round, small pebbles you see in kids’ playgrounds). Depending on where you live, it should cost between $250 and $450 for a full truckload (10 cubic yards), which is enough to provide a nice, cushy area for your horse(s) to hang out. Be sure to get the washed, round pea gravel, rather than crushed (which has sharp edges). Laminitic horses love pea gravel – it allows them to shift and adjust their feet to the most comfortable stance. Sand is a distant second-best, because it compacts rather than rolling like ball-bearings the way pea gravel does.
To successfully deal with a case of laminitis, you need the owner, farrier, veterinarian, and barn manager (if your horse is boarded), all working together as a team. Dr. Eleanor Kellon of the ECIR Group has developed a successful protocol for dealing with cases of laminitis: diagnosis, diet, trim and exercise. All of these components need to be in place in order to succeed.
This is magnificent Samson, a Gypsy Vanner/Draft cross, with IR/EMS. He used to weigh 1900 pounds, and now is a svelte 1550 pounds. Photo: ECIR Group
Once your horse is more comfortable, it is time to diagnose the cause of the laminitic incident. If this is not a clear case of septicaemia, infectious disease, black walnut/sweet alyssum, or prolonged non-weight bearing on one leg, then look for the most common causes: EMS, PPID, and Lyme disease. Initial blood tests should concentrate on these conditions. Mare ovarian abnormalities are rare causes of hyperinsulinemia. Iron overload is a more frequent contributor, but if your horse is diagnosed with EMS and/or PPID, then the dietary implementations (especially mineral balancing) will help with this.
Blood should be pulled from a non-fasting horse (non-fasting means access to hay only for at least four hours prior to testing, and no grains) in a quiet barn. Trailering to the vet clinic should be avoided as this will affect the results. Sedation can also affect the results, so if the horse is having other procedures done at the same visit, collect the blood before the sedation. The tests to ask for are insulin, glucose, ACTH (to check for Cushing’s if your horse is older than 10 years), and Lyme Multiplex (depending on where you live). Leptin is useful as well, but the blood will have to be sent to Cornell University, either directly or via Guelph University Animal Health Laboratory. Idexx Laboratories can analyze insulin and glucose, and will send out the ACTH to Guelph, and the Lyme Multiplex to Cornell.
The blood for the ACTH goes into an EDTA (purple-topped) tube; blood for everything else goes into either a serum-separator or plain red-topped tube. The blood should be kept cool, and spun and separated as soon as possible (ideally within two hours). The separated plasma for ACTH should be frozen, and the samples sent to the lab on ice. The other samples can be either chilled or frozen and sent on ice.
Blood for diagnosing iron overload must be sent to Kansas State University, for serum iron, TIBC (total iron-binding capacity), and ferritin. It can be sent through Idexx. Use red-topped or serum separator tubes; spin and separate as soon as possible; freeze the serum and ship on ice.
If your mare continues to have high insulin levels despite an appropriate diet, then ovarian abnormalities should be suspected. These tests are expensive! Blood for diagnosing ovarian abnormalities must be sent to BET Laboratories in Kentucky for Follicle Stimulating Hormone (FSH), Luteinizing Hormone (LH), and progesterone. It can be sent through Idexx. Use red-topped tubes only, and spin and separate the serum as soon as possible. Chill and ship on ice.
Diet consists of forage fed at two percent of body weight, with ESC plus starch less than ten percent, and appropriate vitamins and minerals added.
Trimming the Laminitic Hoof
Various work by Pete Ramey, Dr. Bob Bowker, Dr. Debra Taylor, and others have demonstrated that the key to success in reducing pain and encouraging healing of the laminitic hoof involves trimming the foot to align with the internal bony structures. Radiographs are important to assess exactly where and how to trim the foot, as the external landmarks are often distorted. The toe is backed up, without removing sole from below, to bring the breakover back to a normal position. Heels are lowered as necessary to bring the coffin bone to about five degrees from ground parallel. The bony parts of the foot may have sunk to an abnormally low position within the hoof capsule and this is one really good reason for getting radiographs done, because there may not be much sole available for lowering the heels. The walls are bevelled to take them out of weight-bearing, and the horse must then be in padded boots, or standing on pea-gravel, sand, or deep bedding. Any flare is left alone until about two-thirds of the hoof wall is new growth. The toe area is taken completely out of weight-bearing function. Because of the abnormal growth of the post-laminitic foot, it is best to have trim intervals of four weeks or less. Although shoes can help improve comfort with some laminitic horses, the necessity of frequent trimming to maintain proper hoof form and promote healing makes the use of shoes much more costly and difficult, compared to using boots and/or a conformable surface like pea-gravel.
Because the hoof shape is often distorted, radiographs should be taken to assess where and how to trim the hoof to align with internal bony structures. Trim intervals of four weeks or less are recommended. Photo: ECIR Group
- Call the veterinarian, and deal with the immediate pain by using foot support, bedding, and the Temporary Emergency Diet.
- Diagnose the cause.
- Correct the cause (institute appropriate diet, weight loss, and medications for PPID if necessary, etc.).
- Institute the appropriate trim and trim cycle.
- Exercise: Allow the horse to move about on its own, and do not force exercise. No riding for nine to twelve months after laminitis.
Prevention is always best. If you are noticing event lines on your horse’s hooves; if your horse is ouchy on firm ground; if he takes mincing steps when turning a circle; or if he is obese, take steps before something comes along that can tip him over the edge into frank laminitis.
This article was originally published in the Summer 2018 issue of Canadian Horse Journal.
The abnormal stance of a pony with laminitis. Photo: iStock/Groomee