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.
Why has this become a problem?
In previous articles I have regularly mentioned that horse have evolved to spend life literally on the hoof! In the wild they would travel several kilometres a day, and Brumbies in Australia have been tracked covering distances of around 17 km daily. Their time is spent searching for food, and they have evolved to consume a forage based ration with a specialised hind gut acting as a fermentation vat of bacteria to break down the fibrous content of the plant consumed. The grassland where wild horses evolved would be covered by poor quality, low carbohydrate, fibrous grasses and so horses became efficient converters. They are actually hormonally regulated to gain weight over the summer in readiness for a sparse winter diet.
It is well known that certain breeds and types, notably native ponies and cobs are especially good doers and it is surmised that these animals carry a thrifty gene. Man first domesticated horses as beasts of burden – for centuries we rode them and drove them both as a means of transport and to work on the land. During this time it was realised that grassland alone would not be sufficient to fuel the London to Brighton Express Coach horses or the hard working heavy horse which was ploughing all day. The feeding of higher energy concentrate rations was therefore introduced, initially as straight grains.
Over the years pasture has changed as agriculture has developed; the grasses now having a higher energy concentrate for higher yielding dairy herds or for more efficient maturation of animals raised for meat. With the introduction of the internal combustion engine and the motor industry horses were no longer working animals and are now kept predominantly for pleasure, leisure and sport. In the thirty odd years that I have been qualified there is no doubt that welfare standards have improved beyond all measure, and our horses are regularly living well into their thirties. Who would have predicted back in the 1970s that Nereo would win Badminton aged 17?!
A lot of this has to do with advances in equine nutrition as well as veterinary care. The first compound feed was introduced in 1958 but the Industry has ballooned and nowadays there are innumerable diets available for every imaginable type of horse and in every conceivable type of work. Feed balancers and supplements abound for every situation you can imagine. All this has been carefully researched and there is a lot of science behind it but in my opinion the marketing has been a little too good and horse owners can get confused as to what is necessary for their horse. In most situations feeding at manufacturer’s recommended rates will be too many calories for the majority of leisure horses resulting in weight gain. Also do not underestimate the calorific value of good grass. In the spring, it can be nutritionally equivalent to oats!
So how do you know if your horse is overweight?
I would probably not advise comparing your horse with its stablemates due to the problem of common perception described earlier. Body Condition Scoring (BCS) has been devised for evaluation of condition in order to standardise measurements and excellent advice can be downloaded from the websites of World Horse Welfare (Right Weight Guide) and the Blue Cross (Fat Horse Slim). Both Charities have produced easy to read charts and diagrams which I would recommend pinning up in the feed room! For most leisure and low level competition horse a score of 3 is ideal, whereas a thoroughbred in training maybe a BCS of 2 and a three star eventer 2.5.Veterinary health professionals are now beginning to realise that it is as cruel to have a horse in BCS of 5, (which is obese) as a score of 0 (emaciated) as both have severe implications for welfare, and people can now be prosecuted for neglect and cruelty in both situations.
The key to this time bomb of a welfare disaster is owner education, and we, as equine veterinary surgeons, are trying hard to spread the word. However, most people are very sensitive if it is suggested that their horse is overweigh, little do they realise that they are being negligent at least, if they let their horse pile on the pounds, and cruel at worst should the horse develop severe health complications. If you are worried that your horse may be overweight, do not crash diet him as this can result in the fatal disease of hyperlipidaemia where the fat stores are mobilised into the blood stream and effectively clog everything up. Rather restrict his access to fresh grass, and ask your veterinary surgeon to help you formulate a diet based on 1.5% of his body weight where he receives the majority of his calories in low carbohydrate forage.
Your veterinary surgeon will be able to test for EMS if thought necessary and prescribe medication to help if this is diagnosed. In my experience vets are always very happy to help and advise and would much rather prevent disease than treat the dire consequences of obesity.
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