Written by Abby Hookey BSc(hons) PGDip MSc RD
Working as a diabetes and obesity research dietitian in the NHS I am always translating evidence into practical advice for patients. Something that has become apparent since working to complete my masters in research in the equine field is the overlap of health consequences resulting from over nutrition in both humans and horses.
Following on from the previous article looking at the role of carbohydrates in equine metabolic syndrome (EMS), this piece is going to focus on one aspect of EMS and discuss the role of obesity in the welfare of the horse and the overlap between horse and human.
Prevalence of Obesity
In 2011, a pilot study estimated the prevalence of obesity in horses in the UK was 54%. However, the National Health and Equine Survey (2016) reported 18.6% of horses were reported by their owners as being obese. These figures suggest a decline in equine obesity.
However, it is documented, as in humans, that obesity is on the rise, this is also true in the equine world. It has been hypothesised that the large difference between reported figures (54% vs 18.6%) is a result of horse owners (and vets!) underestimating body condition scores rather than a decline in equine obesity. This is also common practice in humans; Diabetes UK found that half of adults underestimate their weight. In addition, in the showing ring, it has been reported that a degree of obesity has been seen as advantageous which puts obesity as a desirable quality.
Consequence of Obesity
Obesity, as in humans, is linked with a variety of health complications; insulin resistance, dyslipidaemia, altered reproductive cycles and high blood pressure.
Specifically, to horses, insulin resistance is linked with the development of laminitis which results in significant pain for the horse and can result in euthanasia. Although insulin resistance is associated with the development of type 2 diabetes in humans, this is rarely diagnosed in horses.
Other complications of equine obesity in horses are equine Cushing’s disease, orthopedic disease (osteochondrosis), acceleration of arthritis, and increased pressure on joints and soft tissue which can result in injuries. In addition, obesity also has an impact on the horses’ athletic ability due to increased need for oxygen.
Causes of Obesity
The causes of equine obesity are similar to that in humans; over nutrition and/or lack of exercise. The shift in the role of the horse from productivity to leisure/companion has resulted in an increase in equine obesity.
Evolutionarily, horses are designed to trickle feed rather than have starchy feeds several times a day, which is now more common practice. A high intake of carbohydrate has been linked in horses and humans with insulin resistance which can lead to a diagnosis of type 2 diabetes in humans and laminitis in horses. Carbohydrates are essential for energy but consuming too much carbohydrate without appropriate exercise can lead to weight gain.
The treatment for obesity is calorie deficit, this is true for both human and horses. This can be achieved by reducing the amount of dietary intake and increasing exercise. However, it is important to consider the nutritional balance of the diet whilst achieving a calorie deficit.
Slow feeders or small holed haynets can be useful for reducing intake and slowing down eating that can help with weight loss. Kentucky Equine Research recommend feeding an obese horse 1.5% of body weight (rather than the recommended 2.5%) in order to keep body condition score within an ideal range.
Whilst this can be challenging for some horses, particularly for ‘do gooders’, it is essential to keep body condition score within the healthy range to avoid complications of obesity. This is true in humans where it is advisable to keep body mass index (BMI) within healthy range.
In addition, research has suggested monitoring BCS every 2-4 weeks, particularly when imposing dietary restrictions to ensure the diet is adequate and weight loss is steady.
Providing your horse with feeds high in fibre and lower in fat can help reduce calorie intake.
It has come to light over the years that soaking hay can reduce the amount of carbohydrate (and therefore calories!) and steaming hay can cause an additional reduction in carbohydrate as well as providing hygienic hay. The current recommendation is a 9-hour soak followed by a 50minute steam. Further research is being carried out with Haygain in order to identify how much carbohydrate is lost during the soaking and steaming process.
To reiterate Dr David Marlin’s article, ‘Horse Nutrition Is Simple’, sources of carbohydrate are not problematic as long as they’re included appropriately. As every human is different, every horse is different and nutritional needs should be tailored appropriately.
Obesity in animals has been studied to a lesser extent than humans and so further research is needed. However, research documents that the treatment remains the same; calorie restriction and exercise. There is some overlap in the consequences of obesity between humans and horses. However, there are differences; horses are very rarely diagnosed with type 2 diabetes, resulting from insulin resistance, but are diagnosed with laminitis which may also be a result of insulin resistance.
There is also an accepted level of equine obesity in some situations such as the show ring as previously discussed. This, coupled with the evidence that equine obesity is under-reported can make it a difficult condition to manage. As a result, it is important to monitor a horse’s body condition score accurately and if unsure, to ask a trained individual who is practiced in the skill. This is vital if the welfare of horses is to be managed in order to prevent the associated complications of obesity. Complications can be costly, not just in a monetary sense but also from a health perspective.
Argo, C (2015) Equine obesity: beyond the equine metabolic syndrome. Acta Veterinaria Scandanavica. 57:K2
National Obesity Week – Half of adults in UK underestimate their weight
Accessed 19th October 2017
Johnson, PJ, Wiedmeyer CE, Messer NT and Ganjam VK (2009) Medical Implications of Obesity in Horses—Lessons for Human Obesity. Journal of Diabetes Science and Technology. 3(1)
Stephenson, HM, Green MJ and Freeman SL (2011) Prevalence of obesity in a population of horses in the UK. Veterinary Record. 168,131
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Becky James BSc MSc explains how we know that horses love steamed hay!