This article is from the September 2020 Horse Deals magazine.
What is EMS?
Equine Metabolic Syndrome (EMS) is a disease process associated with the dysfunction of insulin, ie. insulin isn’t working correctly. Insulin is a protein used to transport glucose out of the bloodstream and into individual cells. Glucose is a key energy source for cell growth and function, therefore it is important for the health of the horse to have functioning insulin. EMS is similar to type 2 diabetes in humans.
In healthy horses without EMS, when they are fed feeds containing high levels of non-structural carbohydrates (NSCs - ie sugars, starch etc), as the glucose concentration in the bloodstream increases, the production of insulin increases. Then insulin moves the glucose out of the bloodstream and into the cells.
In horses with EMS, when they are fed feeds containing high levels of NSCs, as the glucose concentration in the bloodstream increases, the production of insulin increases. Because in horses with EMS, their insulin doesn’t work correctly, the glucose in the bloodstream slowly starts to reduce, however high levels of insulin are produced for a prolonged period of time.
How is EMS diagnosed?
Horses with EMS have the following physical appearance:
• Presence of regional adiposities, ie. fat pads. Fat pads can form behind the shoulder, rump, hamstrings, crest of the neck, and in males around the prepuce
• Tend to be overweight, ie. body condition score greater than 7 of 9
• May have evidence of laminitis
To confirm a diagnosis of EMS, an Oral Sugar Test is a practical and accurate way to diagnose EMS. An Oral Sugar Test requires the horse to be fasted overnight, a blood sample for glucose and insulin to be collected in the morning. Then the horse is fed a glucose mix, after which blood is collected for glucose and insulin two hours after the glucose feed. This test challenges the horse’s insulin response. If after two hours the horse’s insulin is still high, it means the insulin is not working correctly and the horse has EMS. A baseline insulin alone rarely identifies cases of EMS, as without a glucose challenge, horses tend to keep their insulin level within a normal range.
An example of regional adiposities.
How is EMS managed?
Once a diagnosis of EMS has been made, management is aimed at diet, exercise, drugs and hoof care. Hoof care will be discussed later in the article.
As mentioned earlier, when horses are fed high levels of NSCs in their diet, they increase production of insulin. This is a problem for horses with EMS. As you can imagine, diet is a very important factor in managing cases of EMS.
The major components of the diet to consider are:
• Hard feed
Most hard feed that has been milled comes with the nutritional information on the bag which is helpful in determining the amount of NSCs in the feed. Recently, horse hay producers are starting to provide nutritional information with their batches of hay, particularly if they are marketing their hay as ‘low sugar hay.’ When looking for low sugar hay, a NSC percentage of less than 10% is ideal.
The biggest dietary variable for a horse with EMS is likely pasture. The NSC in pasture can vary widely from season to season and in some cases, even throughout the day such as after an early morning frost. Ideally, testing your pastures NSC levels each season would be a great idea - especially because many pastures along the eastern sea board of Australia are improved pastures, geared to be high in NSC for stock forage.
Seasonal testing is not always possible, or perhaps the pasture is improved and there are periods throughout the year when the NSC is quite high. In these cases, reducing the horse’s access to pasture is very important. One question I’m asked regularly is, ‘is my horse with EMS ever able to eat grass again?’ My answer to this is usually ‘it depends’. When the horse has access to low NSC pasture and is in consistent exercise, I think the chances of having the horse on pasture is much higher. If the horse has access to high NSC pasture and isn’t being regularly exercised, I think the chances are very low.
It is important to consider that whenever modifying the diet of your horse, to balance it correctly with vitamins and minerals.
There are a number of options out there such as:
• Using the FeedXL programme online where you can formulate your own diet
• Using a feed or horse health company and their onsite nutritionist such as Ranvet or Jenquine
Exercise, like human patients with type 2 Diabetes is very important. Exercise helps to sensitise insulin and reduce body fat. This is essential in the case of EMS. The difficulty however is exercising horses with EMS and an active episode of laminitis - this will be discussed later in the laminitis section.
There are 2 drugs that are used to manage EMS that are currently available to the Australian horse community - Levo-Thyroxine and Metformin. Levo-Thyroxine (ie Thyro-L) can be used to increase the horses metabolism and mobilise fat. Metformin is a human drug commonly used to treat type 2 diabetes in humans. It can be used in cases of EMS in horses with varied success. These drugs will only be effective if the diet is controlled.
Hoof care will be covered later in the article.
What is PPID?
Pars Pituitary Intermedia Dysfunction (PPID) or Equine Cushings Disease is the benign growth of an area of the pituitary gland. The pituitary gland is responsible for the signalling and production of many of the important hormones produced by the body. Although PPID was discovered many years ago, we are still investigating how the body responses to the effect of PPID. PPID is linked to EMS and laminitis. One hormone that is produced at high levels is Adrenocorticotropic Hormone (ACTH). Broadly speaking, ACTH stimulates the adrenal gland to produce cortisol. Cortisol has effects on metabolism, in particular effects on hair, skin and hoof growth.
How is PPID diagnosed?
Horses with PPID have a typical appearance:
• Long hair coat (only present in ~60% of cases with PPID)
• Presence of regional adiposities (fat pads) similar to horses with EMS
• Chronic infections - typically dental disease, eye conditions, skin disease and a high susceptibility to intestinal worms
Typically PPID can be diagnosed from a simple blood sample to test the levels of ACTH. ACTH levels vary throughout the seasons in the healthy horse, however high levels of ACTH are associated with a diagnosis of PPID. Horses with PPID can be diagnosed as young as six years of age and they may not have a long hair coat, therefore if you suspect your horse has PPID, it is important to determine the level of ACTH.
In many cases of PPID, these horses also have EMS. ACTH and cortisol can have effects on insulin, therefore in a case of PPID, it is also a good idea to perform an Oral Sugar Test.
A long hair coat is a typical appearance of a horse with PPID.
How is PPID managed?
Similar to managing a case of EMS, diet, exercise, drugs and hoof care are important considerations.
Horses with PPID and EMS need to have a diet low in NSC, particularly if the horse is overweight.
Dietary management of the elderly horse with PPID is more difficult. Elderly horses with PPID, particularly in winter, can be difficult to keep adequate weight on. In these cases, diets containing higher levels of fat, oil and protein are essential.
In these cases, you may also be able to use a higher level of NSC in the diet, compared to the EMS case.
Exercise is important in a case of PPID - as we have mentioned there is a link between ACTH, cortisol and insulin, so if we can keep these horses active, that is very important in managing these cases long term. Again, we’ll discuss the role of exercise in the laminitic case later in the article.
The drug used to manage PPID is called pergolide. It is given once a day orally as a tablet or a liquid. Once your horse has been confirmed to have PPID through testing with a high level of ACTH, pergolide works to reduce the level of ACTH. It is very important to use pergolide on a regular basis to ensure it is effective. If you consistently miss a day, it will not be as effective. Over time, horses become resistant to the use of pergolide and the dose may need to be increased. To determine if the dose of pergolide needs to be increased, it is important to perform another blood test for the level of ACTH.
In addition to these management strategies, as mentioned before, horses with PPID can also have other health issues. PPID horses are prone to dental disease, so it is important to consult with your veterinarian on having a dental examination included in the 6 or 12 monthly health check. As well as regular dental care, quarterly faecal egg counts to determine your horse’s worm burden is very important in the PPID horse. By checking your horse’s egg count, your veterinarian can help you determine the most effective wormer. Once again, regular hoof care is important and will be covered later.
What is laminitis?
Laminitis is the inflammation and subsequent instability of the lamellar attachment within the hoof.
The lamellae are finger like projections that attach the pedal bone to the hoof wall. This allows the pedal bone to be suspended within the hoof capsule.
When laminitis occurs, the lamellar attachment becomes inflamed and damaged. This causes a change in the hoof growth patterns. In cases of severe laminitis, the hoof growth stops all together, causing widespread lamellar damage. Once the lamellae are damaged, the pedal bone is no longer suspended within the hoof capsule and can rotate within the hoof capsule.
A pony with chronic laminitis.
The timeline of laminitis is as follows:
• Developmental phase: horse hasn’t developed any signs of laminitis, however has been exposed to risk factors for laminitis
• Acute phase: starts when the horse develops signs of laminitis and last for 72 hours
• Chronic phase: starts after 72 hours since the horse developed signs of laminitis
How is laminitis linked to EMS and PPID?
There are three categories by which horses develop laminitis:
• Hormone associated: occurs in horses with EMS and PPID
• Sepsis associated: occurs in horses that are clinically sick such as pneumonia, colitis/diarrhoea, retained foetal membranes
• Overload: occurs in horses that have sustained a significant injury to the opposite limb and are overloading the lamellar attachment on the supporting limb in horses with PPID and EMS, changes in their metabolism and hormone levels, alter the lamellar attachment. Researchers believe that this alteration to the lamellar attachment, increases the chances of laminitis occurring. Also, horses with EMS and PPID appear to be in a pro-inflammatory state - this means that their immune system is over-reactive to even minor problems. Due to the high vascularity within the hoof capsule, inflammatory mediators tend to accumulate in the hoof, further fuelling an inflammatory reaction.
How is laminitis diagnosed?
Horses with laminitis have a typical appearance:
• Increased intensity of the digital pulses to one or more limbs
• Frequently shifting weight from one foot to the next
• Reluctant to stand on one or more feet when limbs are lifted
• Lame at the walk, trot or canter
• Increased periods of time laying down
• A stretched white line in the case of chronic laminitis, along with divergent growth rings in the hoof capsule (ie a growth ring wider at the heel than
Divergent growth rings at the heel.
The important aspect to remember is that laminitis is a spectrum, ranging from mild to severe. That means not all cases will be obvious. Subtle signs such as reduced performance, low grade lameness, and poor hoof growth between trimming/shoeing cycles are all part of the disease process.
How is laminitis managed?
The mainstays of managing laminitis include:
• Identify and manage the cause of the laminitic episode - 90% of all laminitis cases are associated with a metabolic condition such as EMS and/or PPID, therefore it is very important to diagnose and manage these conditions. If they are not managed, the horse will continue to have laminitic episodes despite any other treatments
• Provide hoof support - this comes in many forms and will be discussed later
• Confinement and then exercise once stabilised - we can’t start exercising all cases of laminitis. In some large breed horses with a fragile lamellar attachment or horses with either sepsis associated laminitis or overload associated laminitis, exercise needs to be gradual and after the foot has started to stabilise. In smaller breeds, particularly with EMS/PPID, exercise can be very helpful early in the management of the case
In terms of hoof support in the case of laminitis, it will change based on the severity, phase of the laminitic episode and the overall hoof conformation and health, however the below principles should be followed:
• Stabilise the hoof capsule - this could be with a cast, a glue on cuff shoe etc
• Shift load to the back part of the foot, particularly the frog - this can be done by utilising dental impression material over the frog
A rocker shoe to provide heel elevation.
• Reduce tension on the deep digital flexor tendon, which is responsible for contributing to the pedal bone rotation seen in many cases of laminitis
Supporting the laminitic limb.
A heartbar shoe.
These principles can be achieved with many different types of boots and shoes available on the market. After any modification to the mechanics of the hoof, it is a good idea to x-ray the hoof to see how this has changed the conformation of the hoof. It is also important that towards the end of the trimming or shoeing cycle to x-ray the hooves to see the change in hoof growth. That can help us decide what and how to manage the horse moving forward.
Overall, EMS, PPID and laminitis need to be managed together and require a team of people to ensure a positive outcome. Communicating with your veterinarian, farrier and nutritionist are very important when dealing with cases of EMS, PPID and laminitis.
Article by Dr. Luke Wells-Smith
Luke is a veterinary podiatrist providing a high level of service to the Australasian horse industry through affiliated veterinary practices and an online consultancy portal. Luke is the founder of Motion Equine Podiatry Consulting and is available by appointment in multiple locations along the east coast of Australia.
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