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Fashionable diseases or metabolic disorders?

What are they anyway?

For some years now, more and more horses with metabolic ‘syndrome’ diseases have been appearing.
These include Equine Metabolic Syndrome (EMS), which is often referred to as ‘equine diabetes’, and Equine Cushing Syndrome (Cushing’s disease).

Twenty years ago, EMS and equine diabetes (insulin resistance) were completely unknown in veterinary literature.
Cushing’s was described as a very rare disease occurring in very old horses. Today, almost every second horse over the age of 18 is diagnosed with Cushing’s disease.
However, not every horse with EMS symptoms necessarily has insulin resistance and not every horse with Cushing’s symptoms has a pituitary tumour.

Therefore, we should take a closer look at these diseases in order to understand where the symptoms come from. To do this, you need to take a closer look at the horse’s hormone (endocrine) system.

The hormone system – a highly sensitive and selfregulating system

The body has various hormone glands which interact together like an orchestra – the conductor of which is the pituitary gland.
It controls all the other endocrine glands such as thyroid, adrenal glands, sex glands (ovaries and testicles), pancreas and others.
All these glands in turn control the pituitary gland and affect each other.

The endocrine system connects distant areas

The thyroid gland controls (amongst other things) the adrenal gland. The adrenal gland regulates itself and the pituitary gland.

This complicated system means that any disturbance in one part of the hormone system can affect the opposing part of this system. Hormones are substances that the body produces which regulate the metabolism. They are effective even in the tiniest amounts and work very specifically in the way that only certain cells have receptors for the respective hormone. Cells without such receptors are virtually ‘blind’ to the hormone. In addition, the receptors of different cells have different sensitivities.

Control of blood sugar by insulin

The receptors of muscle and liver cells are the most sensitive to insulin, which also serve as large sugar stores in the body when blood sugar levels rise. After a sugar-rich meal, the pancreas secretes insulin, which then binds mainly to the liver and muscle cells so they will absorb the sugar and store it temporarily. Blood sugar levels then return to normal level. If the blood sugar levels drop further, the liver releases sugar again.

Sugar-rich feed reduces sensitivity of insulin receptors

Horses need a long time (up to six hours) for their blood glucose levels to return to normal after eating concentrated feed.
The less the horse is exercised, the longer the regulation takes.

If there is a constant oversupply of sugar – e.g. due to an abundance of concentrated feed, fruit and/or vegetables – the receptors lose their sensitivity because there is always a high insulin level. The consequence is that these cells no longer absorb sugar from the blood, and the blood sugar level consistently remains too high. This is called insulin resistance or, in humans, type 2 diabetes.

The role of selenium in hormone regulation

Selenium plays a crucial role in the cell when it comes to absorbing sugar in the blood. Until the 1990s, selenium deficiency in horses was unknown because there was no routine testing. After selenium deficiency had been found in high-performance cows, screening tests were carried out in horses, where selenium deficiencies were also found.

Researchers were looking for the most obvious explanation as to why horses of different breeds and management conditions consistently suffered from a ‘selenium deficiency’; they concluded that it must be due to the selenium-poor soils. For this reason, selenium is now added to practically every horse feed and has also been added to fertilisers for about ten years – a fatal development since:

A selenium analysis in the horse says nothing about the supply of selenium.

The problem with selenium evaluations in horses is not only that there is a whole range of possible maximum values (depending on the manufacturer and the test) from different laboratories, but the blood plasma value, which is usually what is determined, does not tell us anything about the actual supply of selenium to the horse.
The blood value is the first to drop whilst there is still sufficient selenium in the tissues, especially in the endocrine glands and the liver.

Conversely, when selenium is fed to the horse, it is first stored in the endocrine and liver tissues and lastly circulated in the blood. As a result, most horses today suffer from chronic and harmful selenium poisoning due to the high levels of selenium in feed.
This is because there is a very fine line between selenium’s effectiveness and toxicity

What is the effect of an over-supply of selenium?

If selenium accumulates in the liver and thyroid gland (which can happen if there is a selenium deficiency in the blood count!), too much of the normally bound thyroid hormone is released. This ensures that the pituitary gland regulates the production of thyroid hormone via the natural regulatory mechanisms and the horse can develop an undetected hypothyroidism (under active
In many cases, the high level of free thyroid hormone leads to an up-regulation of the adrenal hormones, the so-called glucocorticoids. This endogenous cortisone is now responsible for converting the body’s own proteins into sugar on a large scale in order to gain energy, as the hormone system suggests an obvious lack of energy.


This leads to all the visible symptoms that we see in EMS and Cushing’s horses: muscle breakdown, weak immune system, brittle tendons, laminitis, poor hoof quality, poor skin, and the fluffy coat that does not shed in spring.
In many horses, the blood sugar levels rise because they have plenty of sugar in their feed, although these amounts of sugar cannot be used effectively at all.
This in turn can cause insulin resistance which often accompanies EMS or Cushing’s disease.

The body sometimes reacts by converting this sugar into fat and forms conspicuous fat pads, while at the same time the muscles in the back steadily decrease.
Alternatively, the sugar is metabolised inefficiently and
broken down into acids, which are temporarily stored
in the connective tissue and lead to a ‘fat’ (but actually
bloated) appearance of the horse.

What makes the diagnosis difficult

Which metabolic pathway is taken, and which symptoms appear at what time, varies depending on the horse, making the determination of the disease rather difficult. If Cushing’s is suspected, ACTH is usually measured. This is a hormone that is also secreted by the pituitary gland under stress in order to activate the adrenal glands. It only shows whether the adrenal regulation is disturbed and is subject to major natural fluctuations during the course of the day.

An elevated ACTH level is, therefore, by no means proof of a tumour on the pituitary gland. The adrenal gland is controlled by the thyroid gland, but also by stress – meaning most horses with typical symptoms and abnormal blood results do not have ‘real Cushing’s’ but a pseudo-Cushing’s. This pseudo-Cushing’s is caused by disturbances in the hormone system. EMS, pseudo-Cushing’s, and insulin resistance are therefore ‘fed’ civilisation diseases.

What can you do about EMS, Cushing´s disease or insulin resistance?

The first priority must always be to check and optimise the feeding and housing conditions. Poor intestinal activity due to too little hay and feeding haylage, or structured muesli’s, favour the development of metabolic stress and thus triggers the body’s own stress. This can lead to an increase in ACTH and can cause hormonal disorders.

Reduce concentrated feed and ‘sweets’

The feeding of concentrated feed, flaked cereals, generous feeding of carrots, apples, bananas or treats, encourages insulin resistance.

Viele Karotten
© bennyartist / Adobe Stock

No selenium supplements

It is fatal to feed selenium supplements when there is a noticeable selenium deficiency in the blood count; this
is usually the ‘straw that breaks the camel’s back’, so to speak. Selenium supplementation above the physiological levels can cause insulin resistance even if the feed is otherwise normal.

Dietary fibre and intestinal restoration

After changing the feeding to plenty of hay, grazing, and none or only little (performance-adapted) concentrated feed, an intestinal restoration should be followed to reduce the strain on the immune system and detoxification.

Back to natural metabolic regulation

The administration of OKAPI PankrEMS forte increases the insulin sensitivity of the muscle and liver cells, so that the blood sugar levels can be regulated again. This is followed by the normalisation of cell activity so that the metabolism can be regulated, and the muscles rebuilt.

To help the muscles rebuild, you can use targeted detoxification with OKAPI Spirulina (as pellets or powder) and deacidification with OKAPI Prodic as well as OKAPI Lymeth which has additional amino acids.
Furthermore, craniosacral therapy, which affects the hormone system, is useful.

As a long-term alternative to concentrated feed we recommend OKAPI Vierjahreszeitenfutter, a pure herbal feed. It contains herbs that are suitable and supportive for the season and is a healthy alternative to concentrated feed. Even unpalatable ‘extras’ can be fed to the horse using this. For horses with severe muscle loss as part of Cushing’s symptoms, OKAPI Sainfoin (soaked as cobs or ready to use as fix&fertig pellets) can be given as a grain free restorative feed.


With correct feeding and sensible therapies, horses with EMS or pseudo-Cushing’s – like any metabolic disorder – can go back to their ‘normal values’ again.

Team Sanoanimal