One of the most significant health challenges that the leisure horse population has to cope with is insulin sensitivity, or perhaps more accurately, insulin dysregulation (ID).
If you have ever experienced the heartbreak and management concerns that come along with dealing with a horse or pony with insulin-linked issues such as laminitis, or Equine Metabolic Syndrome (EMS), you’ll appreciate how distressing and challenging it can be.
For affected horses, issues with insulin sensitivity and dysregulation of how insulin works in the body can seriously impact on their overall health and wellbeing, as well as their ability to live as full a life as possible with minimal restrictions.
For caregivers, looking after a horse with health issues linked to their metabolism and normal insulin functioning can be worrying, time consuming, expensive and stressful.
But what do we mean by the term ‘insulin sensitivity’ and what should we be aware of in terms of management of affected and potentially affected horses? How can we best manage and support the health of these animals affected by insulin dysregulation?
What Is Insulin Sensitivity?
The hormone insulin is a critical signalling molecule in the body that helps to keep everything in balance. This is called homeostasis, where the body systems are effectively working in harmony with each other, and this helps to support overall health and wellbeing.
Insulin is produced and released from the pancreas; an organ intimately linked with the digestive system. Insulin is released in response to circulating levels of glucose in the blood. Glucose is the simple carbohydrate sugar that is essential for normal functioning and energy production in the body. However, the levels of glucose within the bloodstream do need to be carefully managed and regulated, to prevent overall metabolic and systemic dysfunction.
Under normal conditions, blood glucose levels are detected by molecular signalling mechanisms. At the most basic level, when circulating levels of glucose are high, insulin is released to support the absorption and utilisation of glucose. This is important for energy output, glucose being a key ‘fuel’ within the body.
Insulin sensitivity then describes how well the body responds to circulating insulin levels.
When a horse is described as insulin sensitive, they have a better capacity to manage levels of glucose effectively and efficiently within the bloodstream than horses that have impaired insulin sensitivity. This helps in the maintenance of their homeostasis and overall health and wellbeing.
Conversely, insulin insensitivity (or insulin resistance) means that the ability to respond to elevated levels of glucose in the circulating is impaired. Insulin resistance means that the body stops being responsive to circulating levels of insulin, leading to issues with normal metabolic functioning and overall health.
Consequently, blood glucose levels can remain artificially high and this can impact negatively on a wide number of body systems, directly affecting the health of affected animals.
In addition, circulating levels of insulin can remain high (termed hyperinsulinemia), and if there are prolonged high levels and dysregulation of insulin, this can be linked to an increased risk of laminitis and EMS in our horses.
Indeed, ID is recognised to be a key component of EMS, the array of metabolic and endocrinological problems linked with the occurrence of laminitis and other conditions in affected horses and ponies. Notably, obesity and ID are also linked to other health concerns for our horses including digestive disturbance, colic and conditions such as osteoarthritis. This is why acknowledging the importance of normal insulin functioning and supporting overall health is so critical for our horses and ponies.
What Can Cause Problems With Insulin Sensitivity?
A number of factors appear linked to concerns with insulin sensitivity. Interestingly, it is not just horses that are affected, and a number of studies have found parallels between issues with insulin sensitivity in humans, horses and a number of other affected species too.
There does appear to be a genetic predisposition to developing issues with insulin and metabolic functioning. Some breeds and types of horse and pony do seem more likely to develop signs and the clinical consequences of ID, notably many of our native breeds and types.
Genetic predisposition, combined with access to modern management which often includes access to highly nutritious and energy-dense feedstuff as well as limited exercise, can create significant challenges in maintaining the health of some horses and ponies.
Diet is a significant factor and in horses, diets that are high in soluble, non-structural carbohydrates (NSC – includes sugar, starch and fructan) are significant risk factors in developing issues with sensitivity to insulin. For this reason, restricted diets for ‘at risk’ or diagnosed animals are essential. These diets should be carefully managed to keep dietary levels of NSC low – ideally lower than 10% NSC for symptomatic animals – those with laminitis, EMS and insulin dysregulation.
Soaking forage is typically an easy way to reduce levels of NSC, while also having the benefits of supporting respiratory health. However, there is a balance to be struck between time of soaking, removal of NSCs and the hygiene of the forage too – avoid soaking for longer than 12 hours and use fresh water on every soak.
Animals with restricted exercise potentially as a result of grazing or turnout restrictions, illness or injury may also be at risk of developing ID, especially if exercise is restricted for prolonged periods. Indeed, in human medicine, exercise and movement is recognised as being integral in the management, and in some cases even reversal of symptoms associated with ID, highlighting its value. This appears to be linked to how exercise encourages the body to utilise and respond to glucose levels, in addition to how hormones such as insulin function too.
Bodyweight is also a significant risk factor. Excess dietary energy is linked to the development of overweight and obesity in our horses, so overfeeding or allowing free access to energy rich feeds and feedstuffs is a major problem.
How Can We Best Manage Insulin Sensitivity In Our Horses?
Where a horse has been diagnosed with ID and/or EMS, essential management centres around careful dietary provision of nutrients to maintain a lean body condition with minimal levels of fat. Typically, this takes the form of restricted dietary provision, especially free access to rich grazing. Managing dietary levels of NSCs is important too and this is achieved through careful access to grazing, selection of feed materials and ensuring any forage fed is as low in NSC content as possible, especially for symptomatic animals.
However, it is critical to note that a restricted diet refers to the amount of energy being consumed (i.e. calories) and the levels of NSCs provided in the diet. Horses and ponies still need adequate fibre intake for digestive and overall health – never be tempted to starve your horse as a form of dietary restriction.
Because animals on a restricted diet may have reduced intake of key nutrients required to support normal bodily functioning, the use of a suitable vitamin and mineral supplement or feed balancer such as those in the WellHorse range would be ideal options. In addition, where there is an inflammatory challenge, additional dietary provision of antioxidants may be advisable. Typical antioxidants of potential value often include vitamins C and E, although the omega-3 fatty acid, docosahexaenoic acid (DHA) also has antioxidant potential and has been identified as having potential benefits for supporting insulin sensitivity.
Ensuring that ‘at risk’ and symptomatic horses also undertake regular, gentle exercise can also go a long way to supporting health and reducing the potential for harmful consequences. This might be met through turnout on limited grazing, use of track systems, hand walking, long reining or being ridden when possible.
Finally, ensuring that stress levels are minimised can be useful in the management of affected animals. This would apply to situations of training, stabling, transport and even your horse’s day-to-day life.
Potential Future Treatments For EMS
It is important to note that while management is a critical factor in supporting horses with metabolic issues relating to ID, veterinary advice and guidance should always be sought. Management is integral to supporting horses and ponies that are either affected or at risk, but veterinary intervention and input is also critical and might provide targeted approaches in some cases.
There are also some new, potentially valuable treatments being explored for EMS affected horses, including medications which can help to manage levels of insulin by inhibiting glucose reabsorption in the body. Many such compounds are already used in human medicine to support metabolic, cardiac and renal health. It seems likely that with further experimentation and trialling, they might become a critical part of our armoury in being able to support the wellbeing of our equine friends also.
Science Supplements offer a premium range of high specification equine supplements that are carefully formulated by nutritionists and veterinary surgeons to support your horse’s overall health and wellbeing.
You can find out more and explore our equine supplement range here, including our WellHorse feed balancers specifically formulated according to NRC (National Research Council) and BASF (Animal Nutrition) guidelines, or contact us to speak to one of our experienced nutritional advisors.