Equine Metabolic Syndrome (EMS) is a condition that’s become increasingly recognised in the equine world and for good reason. Much like Type 2 diabetes in humans, EMS is a hormonal disorder that affects how a horse’s body regulates insulin. Left unmanaged, it can lead to serious complications, most notably laminitis, a painful and potentially debilitating hoof condition.
In recent years, growing research and awareness of equine health issues has highlighted conditions that can significantly affect a horse’s quality of life. Among these, EMS stands out as a complex and increasingly common concern.
In the first instalment of this two-part blog, Lisa Elliott, MSc from Equine Nutrition Solutions explores what EMS is, why it matters to horse owners, what it does to your horse and how its diagnosed.
What Is Equine Metabolic Syndrome?
EMS is not actually a disease in itself but more like a cluster of risk factors that include:
- Insulin dysregulation: The horse’s body either produces too much insulin or doesn’t respond to it properly.
- Obesity or abnormal fat deposits: Especially around the neck (a “cresty” neck), shoulders, and tailhead.
- Increased risk of laminitis: A painful inflammation of the tissues (laminae) bonding the hoof wall to the pedal bone, causing severe discomfort and lameness.
Ponies, and certain breeds like Morgans, Arabs, warmbloods, Paso Finos, alongside donkeys seem to be more genetically predisposed to EMS and associated risk factors, which can be defined as more of an EMS ‘Phenotype’. This is often thought to be due to their “thrifty” metabolism, which evolved to survive in harsh environments with limited food. Ongoing research seeks to characterise the genetic basis for the EMS phenotype and associated laminitis risk which could lead to the development of more sensitive and specific laboratory tests.
What Does EMS Do to the Horse?
The most significant characteristic of EMS is predominately, insulin resistance, where horses or ponies with insulin dysregulation lose their sensitivity to the hormone insulin – which helps regulate the movement of sugar in the blood into cells – and become insulin ‘resistant’. As a result, the body produces more insulin to compensate, leading to increased levels of insulin circulating in the blood and potential hyperinsulinemia – where the blood has higher levels of insulin than normal. This hormonal imbalance can lead to:
- Chronic or recurrent laminitis
- Difficulty losing weight
- Lethargy and reduced performance
- Increased thirst and urination
- Infertility in mares
However, whilst EMS is closely associated with obesity, even horses that appear to be at a healthy weight can suffer from EMS if they have regional fat deposits and insulin dysregulation.
Diagnosing EMS
Current criteria for a diagnosis of EMS have been identified as three main characteristics
- Generalised or regional obesity (fat deposits, especially around the neck)
- Insulin dysregulation, including resting hyperinsulinaemia or an exaggerated response to oral or IV glucose challenge
- A predisposition to laminitis including both current and historical evidence.
EMS can be diagnosed through a range of tests, performed by a vet, including
Resting Insulin Concentration – a blood sample is taken, usually in the morning before feeding, to measure baseline insulin levels. Elevated insulin levels can be indicative of EMS.
Oral Sugar Test (OST) – The horse is given a measured amount of sugar (e.g., corn syrup), and blood samples are taken before and after to assess insulin response. This test is particularly useful for detecting early insulin dysregulation.
Insulin Tolerance Test (ITT) – Evaluates tissue insulin resistance by measuring the reduction in glucose levels after insulin administration.
Combined Insulin-Glucose Tolerance Test – A more in-depth dynamic test where both glucose and insulin are administered intravenously (IV) and blood samples are taken at specific intervals to monitor glucose and insulin levels.
EMS and the link to the Microbiome
In addition to the established diagnostic markers for EMS, recent studies indicate that horses affected by EMS exhibit distinct hindgut microbial populations compared to horses without EMS.
Research has shown that horses with EMS had reduced microbial diversity, significant differences in microbial community structure and lower numbers of beneficial fibre-digesting bacteria, alongside overrepresentation of a certain type of bacteria that is receiving increased attention as a potential early stage biomarker of metabolic disease.
Further research is needed to explore the exact relationship between gut microbiota and metabolic dysfunction, but understanding the differences between the hind gut microbes of horses EMS and non-EMS horses could be key within diagnosing, management and potential prevention of EMS.
So, what if your horse has been diagnosed with Equine Metabolic Syndrome? In part 2 of this series of blogs we will look at managing EMS through the right diet, nutrition and lifestyle, alongside taking a proactive approach to prevention.
If you have any questions about creating the best diet for your horse and keeping your horse healthy through the right nutrition, please contact Coligone – 0333 0503785/07986 183616 or sales@hbradshaws.co.uk
