Hardly a week passes without there being an article in the News about the obesity crisis in the human population.
Today’s young people may be the first generation not to have longer lifespans than their parents. There is a huge increase in Type 2 diabetes and obesity is linked to heart disease, numerous types of cancer and joint problems.
When it comes to our pets, it would be fair to say the same pattern is occurring. Small animal vets have been very concerned about obesity in dogs and cats for at least ten years and I am afraid the equine population is going the same way. Perhaps it is a question of perception and we are used to seeing a rounder outline as “normal”. Looking back, the most famous champion show pony of the time “Holly of Spring” would look poor in a line up nowadays!
So, is there a problem with our horses being a little on the plump side? – The answer is a resounding YES!!! Just as in human medicine where obesity is linked to numerous health problems, so is it in horses. Most people will be aware of the relationship between weight and laminitis, but far fewer will know that weight loss is at least as effective as drugs for pain relief in overweight arthritic animals. It goes without saying that the more weight the animal has to carry, the greater strain its muscles, tendons and joints will have to bear. Being overweight is therefore also a direct contributory factor in osteo arthritis. A fat mammal whatever the species will not just have external fat visible as a “spare tyre”, “cresty neck” or “pudgy bottom”; adipose tissue also accumulates inside the body cavities.
What problems are caused by carrying excessive weight? Overweight horses show exercise intolerance as fat accumulates in the thorax. They also struggle with heat regulation as there is a lower surface area to mass ratio which means that they have to sweat more in order to cool down, plus adipose tissue acts as insulation so they are prone to overheating. In the abdomen fatty lumps or lipomas can form in the mesentery which supports the guts. If the lipoma is on a stalk or pedicle this can wrap around the gut and cut off its blood supply resulting in a potentially fatal surgical colic, known as strangulating lipoma. Excessive fat accumulation in the liver can lead to a situation where the liver is overloaded, and severe, potentially fatal disease occurs. Obesity in mares has been known to affect their oestrous cycles and conception rates; it is also linked to lower fertility rates in stallions. Being overweight is known to be a predisposing factor for osteochondrosis (developmental orthopaedic disease) in youngsters.
We now know that adipose tissue secretes hormones which affect insulin regulation as in EMS (Equine Metabolic Syndrome) which is one of the major factors in laminitis and is the equine equivalent of Type 2 Diabetes in humans. Some researchers have suggested that laminitis in EMS ponies is equivalent to gangrene in the toes of severely affected diabetic people. Inflammatory precursors known as cytokines are also produced by adipose tissue and these will have a direct adverse effect on other body systems. Type 2 Diabetes is associated with high blood pressure in humans and studies have shown this to be the case in horses as well. However blood pressure is seldom routinely measured in practice.