Equine Metabolic Syndrome and Equine Cushing's Disease

Equine Metabolic Syndrome

and

Equine Cushings Disease

Equine Metabolic Syndrome (EMS) and Equine Cushings Disease (ECD) are common disorders of the endocrine system of horses/ponies that manifest with a variety of clinical signs. They are of importance because they can cause considerable discomfort to your horse/pony, especially if the horse/pony develops laminitis (founder) – a very painful disease.

Early detection and management can help improve the quality of life of your horse or pony.

Equine Metabolic Syndrom (EMS)

Some breeds of horse are genetically predisposed to EMS and it is most commonly seen in Morgans, Paso finos, Norwegian fjords, American saddlebreds, Donkeys, Shetlands, Riding ponies, Miniatures and Welsh ponies. Those at risk of EMS are typically known as ‘Easy keepers’, have a history or current signs of obesity, are often fed higher concentrate diets, have low levels/lack of exercise, with or without previous history of laminitis. EMS is characterised by the development of Insulin Resistance.

Clinical Signs of EMS

• Generally seen in mature horses/ ponies around the age of 8- 14 years. Younger horses can avoid developing this disease with careful management.
• Typical appearance (phenotype)
• Fat deposits around the neck, sheath, tail and head

–        A ‘cresty’ neck is the most classic sign 

• Predisposition for laminitis +/- abnormal hoof growth
• ‘Easy keepers’

–        These are horses/ ponies that are genetically programmed to maintain body condition regardless of environment. If these horses/ponies are overfed, have a diet high in soluble carbohydrates and have a lack of exercise then EMS can develop.

What is INSULIN RESISTANCE:

Insulin Resistance (IR) is where the organs in the body fail to respond to appropriate levels of insulin, which is produced following ingestion of feeds containing carbohydrates (sugars). Insulin is required for the breakdown and utilisation of glucose. As a result the body has higher levels of glucose, and attempts to produce excessive amounts of insulin. Both high levels of glucose and insulin can become toxic, especially to the sensitive laminae of the hooves.                             

Fat deposits

Testing for EMS

• Helps to identify the condition early and enable management to prevent laminitis episodes.
• Baseline Insulin levels: Checking for ‘Insulin Resistance’

–        Held off grain and fresh pasture for 12 hours prior to having the blood sample taken. This sample should show an insulin level less than 20µU/ml if the horse is normal.

Further sampling procedures are occasionally required and will be discussed with the veterinarian if necessary. Stressed and painful patients may falsely elevate readings and as such, the horse/ pony to be tested should be free of pain caused by laminitis.

Treatment of EMS

• PREVENTION of predisposed individuals developing laminitis
• EARLY RECOGNITION of clinical signs
• MANAGEMENT

–        Management through diet plays an important role in treating EMS.

Feeding

Most horses only need 1-1.5% of their bodyweight per day in fibre (pasture/hay). 

i.e. a 500kg horse = 5-7kg hay per day. However not all hay is created equal.

• The vet may recommend a forage based diet for those that have greater energy requirements, using a feed with the Laminitis Trust Approval Mark. ie Hygain Ice, Speedi Beet
• Ideal hay being fed to a horse/ pony suffering from EMS is low in sugars/starch. The ideal concentration of non structural carbohydrates (NSC) is <12% and hay can be tested to determine these levels, however each different batch of hay may have a different nutrient profile and will require retesting.
• Soaking grass hay by submerging it in cold water for 30mins before feeding can reduce the amount of soluble carbohydratyes (sugars) in the hay making it safer. Do not feed the water to the horses/ponies.
• Alternatively lucerne hay/chaff may be fed as it has different storage sugars to grass hays. 
• Limiting the grass intake can be accomplished by using a grazing mask or muzzle or by restricting the area available for grazing or strip grazing. This is especially important in Spring/ Autumn.

• Avoid grazing on frosty mornings when the fructan levels in the grass are higher.
• There are certain environmental conditions that increase the risk of pasture laminitis. For more information see the following website: www.safergrass.org
• Ideally body condition should be maintained so there is not a fat depot along the crest or at the tail head, around the sheath or udder or over the loins. You should be able to feel the ribs easily by running your hand along their side.
• Any feed changes need to be gradual, animals should never be starved to make them lose weight, this can be dangerous causing a disease called hyperlipaemia.
• Once the animal has recovered from a bout of laminitis a combination of diet and exercise should be used to control body weight.
• If feeding sugar beet pulp – ensure it is PLAIN, without molasses added.

• DON’T FEED

–        molasses

–        Soybean meal

–        Corn oil

–        Rice bran

• AVOID

–        Corn/maize

–        Oats

–        Barley

-        Excess treats 

A little exercise (10-15 mins) several times a week can assist as, insulin sensitivity improves quickly, however the effect doesn’t last long when exercise stops. Exercise can only start when horses/ ponies are not suffering from laminitis. Laminitis must be treated/ managed prior to the start of an exercise regime.

Prevention is better than cure for breeds that show a predisposition to EMS. Avoid high risk horses/ponies becoming obese. For those suffering from EMS, try to maintain exercise, monitor with regular insulin levels in high risk patients and avoid rather than try to manage laminitis!

Equine Cushings Disease (ECD) (Sometimes called PPID)

This is a condition caused by an abnormality of the pituitary gland in the horse's brain. The disease sends abnormal signals to the adrenal glands which produce the hormone cortisol. This results in high levels of ‘stress’ hormones entering circulation. Horses fail to shed their winter coat, the coat becomes long and curly, they may drink and urinate excessively and are very prone to developing laminitis or founder.

Clinical signs of ECD include

• Curly coat
• Sweating
• Muscle wasting
• Fat deposits
• Lethargy
• Increased thirst/urine production
• Predisposed to infections
• LAMINITIS

Who is affected by ECD

• Older horses/ ponies

–        Usually +15yrs

–        Young horses can be affected, it has been infrequently reported in horses 3-4 years old.

• Morgans and ponies most commonly but all types of horses can be affected
• It is possible to have both Cushings and Equine Metabolic syndrome

Reasons for Testing for ECD

• Need to test horses/ ponies with typical signs before they develop laminitis
• Treatment early may prevent laminitis
• Horses/ ponies with unexplained laminitis
• Monitor response to treatment

Testing for ECD

• Easiest and most reliable tests

–        Baseline ACTH level

• The advantages of measurement of the ACTH concentration is that it requires only a single sample and there is no risk to the horse. The disadvantages are that it is less sensitive than the DST, there are sample handling issues, and there are seasonal effects on test results.

–        Dexamethasone suppression test

• The advantage of the dexamethasone suppression test (DST) is that it is the best validated antemortem diagnostic test. The disadvantages of DST are that it is not sensitive in early cases, it requires two farm visits, there is a perceived risk of laminitis, and there are seasonal effects on test results.
• The standard protocol for the overnight DST is as follows. A blood sample is drawn for serum cortisol measurement between 4:00 and 6:00 pm; Dexamethasone is administered intramuscularly, and a second blood sample is collected the following morning, ~19–24 h after dexamethasone administration.
• Pitfalls

–        Stress/concurrent disease may falsely elevate levels

–        Autumn – normal animals may have falsely elevated ACTH levels due to seasonal variation.

Management of ECD

• Drugs

–        Pergolide

• Best and safest treatment
• Oral, once a day dosing (either as a liquid or tablet form)
• Other options available if poor response
• General health care

–        Dentistry, deworming, clipping thick coat

–        Regular hoof trimming

• Good quality food

–        Especially important for older kids with missing/worn teeth

–        Often will need a complete feed, low in sugar but higher in fat/protein, easily digestible and high in fibre.

–        See feeding recommendations for EMS.