What is Laminitis ?
Laminitis is an extremely painful condition of the feet in which there is inflammation and weakening of the sensitive tissues (laminae) that bond the bone within the hoof to the hoof wall. The sensitive laminae act like velcro to form a strong bond to support the bone within the hoof. Laminitis causes the sensitive laminae to stretch, weaken and become damaged which can cause the bone to move within the hoof.
If we break this down to a very basic explanation, you can think of the horse’s foot as the tip of your finger, you have a hard outer nail, a bone and some connective tissue in between which represents the laminae. Laminitis literally means “inflammation of the laminae”. The pain associated with laminitis would be similar if you jammed your fingernail in the door and felt a painful, throbbing sensation. In extreme cases, the bone can rotate and/or drop through the sole of the hoof (image below) which is very painful. In cases like this, euthanasia may be the only option to end the horse’s suffering.
What Causes Laminitis ?
There are a number of important known associations and risk factors for the development of laminitis. The most common cause of laminitis is attributed to endocrine disorders, particularly due to high levels of insulin (hyperinsulinemia) in the body. The pancreatic hormone insulin is critical in facilitating the uptake of glucose into cells, but higher than normal levels are associated with laminitis. Obesity (or excessive fat deposits) can also worsen the hyperinsulinemia by secreting hormones called adipokines which make the tissues more resistant to the effects of insulin.
Experimental studies have demonstrated that laminitis can be induced by administering high doses of insulin to normal horses. Further studies have also shown that high insulin concentrations are a reliable predictor of future episodes of laminitis. The exact mechanism by which hyperinsulinemia causes laminitis is unknown with a number of theories being developed. Most recently, it has been theorized that insulin may stimulate insulin-like growth factor-1 receptors within the lamellae of the hoof resulting in cellular proliferation, weakening and subsequent lamellar failure.
Reducing insulin concentration is therefore considered fundamental in the prevention of laminitis and the management of horses with endocrine disorders.
Laminitis is usually a consequence of an underlying hormonal disorders such as Equine Metabolic Syndrome (EMS) and Pituitary Pars Intermedia Dysfunction (PPID). Equine metabolic syndrome describes the propensity for certain horses and ponies to develop obesity, high levels of insulin (a hormone responsible to decreased blood sugar level), and laminitis.
Pituitary pars intermedia dysfunction (PPID) is a condition affecting aged horses and results from loss of dopaminergic inhibition at the pars intermedia. The link between PPID and laminitis remains unknown. Studies suggest that insulin dysregulation occurs in approximately 30-60% of PPID cases and those with concurrent PPID and hyperinsulinemia may be at a higher risk of developing laminitis.
A number of breeds are prone to developing obesity and hyperinsulinemia, including British native breed ponies (Welsh, Shetlands, Cobs), Andalusians, Arabians and Warmbloods. Unfortunately, sometimes despite excellent dietary management, some horses will continue to produce too much insulin which leads to repeated episodes of laminitis.
Signs of Laminitis
Laminitis usually affects the front feet more than the back feet, however in some instances all four feet could be affected. The signs will vary with the severity of the damage and the most common sign you will see is lameness which ranges from a mild head-nod to inability to weight bear and stand. The signs may include one or more of the following:
- Bounding digital pulse
- “Walking on eggshells” appearance
- Shifting weight from one foot to the next
- Rocking back on hindquarters
- Laying down more than usual
- Reluctance to turn
- Reluctance to walk on firm/gravel ground
Remember, horses are prey animals and will not show signs of pain unless severe.
The pain associated with laminitis poses a MAJOR welfare issue.
Please do not disregard the early signs.
Diagnosis of Laminitis
A diagnosis of laminitis is based on the clinical signs and history.
Blood tests to measure your horse’s insulin levels are crucial so prompt treated can be initiated. Horses may present with three different types of insulin dysregulation. There are several tests which can be perfomed and your veterinarian will determine the most appropriate test for your horse. We recommend performing dynamic testing to measure insulin levels in horses and ponies at high risk for laminitis. Timing of testing is very important and we will schedule an appointment to help us catch the “peak” insulin concentration for your horse.
The test we choose will be tailored to the individual horse and what we feel will give us the most information whilst still being cost-effective for the owners. For horses that require ongoing monitoring, we offer tailored equine metabolic testing packages.
The metabolic testing we perform is tailored to the individual horse to provide the most information whilst still being cost-effective for the owner.
Contact us on 0427 072 095 or book online here to enquire about our metabolic testing packages.
Digital radiographs (x-rays) can provide a lot of useful information on the severity of the condition, how long it has been going on for and also offer important measurements for your farrier to implement a suitable corrective shoeing/trimming regime.
Treatment of Laminitis
Prompt veterinary intervention is imperative for a successful outcome. Any treatment should be performed alongside metabolic testing and include dietary modification, pain relief and mechanical support.
Dietary restriction: Dietary management is critical in limiting hyperinsulinemia and thus the prevention and management of laminitis. At the onset of clinical signs, the patient should be removed from pasture and placed on a diet low in non-structural carbohydrates (NSC) with the aim of preventing elevations in insulin levels in response to high dietary sugars. It is important to not starve horses! We will provide you with a full diet plan based your horse’s requirements that will be practical and simple to implement.
Pain relief: Failure to adequately control pain is one of the primary reasons laminitic horses are subjected to euthanasia. Pharmacological intervention should provide analgesia without encouraging excessive movement. Non-steroidal anti-inflammatories (NSAIDs) are the most commonly used, first-line analgesics for horses with laminitis but other therapies may also be required.
Confinement: Strict confinement in deep bedding or provision of alternative solar support is essential to minimise stress placed on the dorsal lamellae during movement and to prevent further pain associated with progressive lamellar pathology. Turning increases shearing forces between the lamellae and the consequences of excessive movement cannot be emphasized enough. Stabling or confinement to a small fenced-off section of the paddock is required for the acutely laminitic horse.
Mechanical Support: Remedial farriery of the laminitic patient focuses on improving comfort and providing mechanical support to prevent or limit displacement of the p3 (pedal bone). Peer-reviewed data documenting the efficacy of different farriery interventions is lacking. The greatest chance of a successful outcome relies on a cohesive team-based approach between the owner, the veterinarian and the farrier. The farriery plan has to be adaptable and a degree of trial and error is often required depending on each patient’s comfort levels.
The greatest chance of a successful outcome relies on a cohesive team-based approach between the owner, the veterinarian and the farrier. The farriery plan has to be adaptable and a degree of trial and error is often required depending on each patient’s comfort levels.
In addition to dietary management, medical interventions may also hasten the recovery from laminitis in selected cases. The use of pharmaceuticals as a treatment for obesity and insulin dysregulation has traditionally been a last resort but as evidence increases for the potential welfare benefits of accelerated weight loss and reduced laminitis risk, so the use of these drugs has increased. In a recent study of UK native ponies, the risk of laminitis occurring within 3 years was 9.9%; the risk in animals that had a fed serum insulin concentration of > 21.8 u/l was a staggeringly high 21.5%.
With the risk of laminitis being so high in certain populations it seems entirely appropriate that a more pro-active approach to management is taken to prevent unnecessary suffering.
Currently, no registered medications are available for the treatment of hyperinsulinemia in horses.
Metformin (a human medication) has historically been used in an attempt to limit hyperinsulinemia but oral bioavailability in horses is poor and studies showing its effectiveness at improving insulin sensitivity have yielded inconsistent results. Given the newer treatment options which are now available and the lack of compelling evidence of the benefits of metformin we do not recommend the use of metformin in horses or ponies with laminitis.
Ertugliflozin belongs to a class of human antidiabetic drugs known as sodium-glucose cotransporter 2 inhibitors (SGLT2i). These medications offer a novel treatment option for hyperinsulinemia. SGLT2i promote urinary glucose excretion, thereby lowering blood glucose levels and reducing the stimulus for insulin secretion from the pancreas.
A recently published case series from our practice was the first to document that ertugliflozin was effective at reducing insulin concentration (Figure 1) and lameness grade (Figure 2) in 51 horses and ponies with chronic laminitis that did not respond to diet and management alone.
You can read the full paper here: https://beva.onlinelibrary.wiley.com/doi/full/10.1111/eve.13738
A video summary of our study can be viewed here:
Despite ertugliflozin being well tolerated in the current study all but four of the horses exhibited hypertriglyceridemia (high circulating fat levels) following 30 days of treatment, however clinical signs of hyperlipemia were not observed. Medication with SGLT2i should be temporarily discontinued if horses are being fasted to prevent hyperlipemia and water should always be available to prevent volume depletion. Our ongoing work would also suggest that lower doses of ertugliflozin may be equally effective at reducing insulin concentration without increasing circulating triglycerides (Sundra, unpublished data).
Despite no adverse events being reported, we still recommend horses are closely monitored whilst on treatment with ertugliflozin. Our equine metabolic treatment packages offer a cost-effective and hassle-free way for horses receiving ertugliflozin to receive appropriate monitoring and properly timed blood tests.
It is important to highlight that whilst the potential welfare benefits for ertugliflozin may prove to be huge, we still need more studies to investigate the long-term safety in horses. More importantly, treatment with SGLT2i is not a substitute for proper diet and management. Owners must still ensure they are restricting dietary calories/sugar and maintaining a regular farrier schedule for high-risk horses.
The psychological impact of laminitis
It should, in theory be straightforward to manage the weight of domestic horses and prevent the development of laminitis, however owners understandably find traditional approaches to weight management (such as dietary restriction) difficult to implement as they perceive these interventions to have an immediate negative impact on their horse’s welfare and the horse-human relationship.
We must also consider the psychological implications for horses who spend the majority of their lives locked away in small pens as any access to grazing triggers a laminitic episode. People are often quick to say “just lock them off grass!” Whilst this may spare them the physical pain associated with laminitis there are other factors to consider. The chronic frustration from isolation, lack of social interaction and lack of environmental enrichment will almost certainly have a negative impact on their mental-wellbeing and also goes against the Five Freedoms outlined in the Animal Welfare Act.
In human medicine, doctors are much more proactive at medical intervention to prevent the development of heart attack and stroke in patients who are considered high-risk. Why then do we wait for our horses to develop excruciatingly painful episodes of laminitis before medical intervention is considered? We now have good evidence that close monitoring and metabolic testing can predict your horse’s risk for laminitis and medications are available to manage these high-risk horses and improve their recovery.
Many veterinarians are hesitant to use drugs in the treatment of obesity and hyperinsulinemia, however more evidence is emerging that medications (like ertugliflozin) have the potential to reduce suffering through accelerated recovery from laminitis and suggests that pharmaceuticals should no longer be considered a last resort.
Whilst diet and management should always form the basis of preventing the development of obesity-related endocrine dysfunction, ertugliflozin offers owners a new therapy in cases which have failed to respond to conventional management. Further studies investigating the pharmacokinetics, pharmacodynamics and long-term safety of ertugliflozin in horses are warranted. However, when used appropriately, with close monitoring and testing, medications like ertugliflozin have the potential to rapidly ameliorate suffering in horses with laminitis.
Please contact us to schedule a consultation for your horse online here.
If your horse is being treated with ertugliflozin, please take the time to read our information sheet.
Laminitis is an extremely painful disease which can be life threatening to your horse.
Identifying the risk factors, performing metabolic tests and taking measures to prevent laminitis is far more effective than trying to treat the condition once symptoms are already present.
Please contact us on 0427 072 095 if you wish to discuss your case book an appointment.
You can also schedule a consultation for your horse online here.