Everything Explained Obesity
Katie Williams M.Sc. (Dist) R Nutr
The problem of obesity has received increased attention recently and with the latest predictions from the World Health Organisation suggesting that 700 million adults will be obese by 2015, it looks set to remain in the spotlight for some time. In the UK it seems that we’re also just as bad at regulating our pet’s diets as we are our own; the Blue Cross report that they now deal with more horses and ponies affected by obesity-related diseases than malnourishment.
How do we measure obesity in horses?
In humans, obesity is measured using the body mass index measurement which uses an individual’s height and weight to create a score that is directly correlated with body fat. This system can not be applied to horses as we know that certain breeds and types could be the same height but have very different “ideal” weights, for example, the bodyweight of an Arab and a Highland that are both 14.2hh could easily vary by 100kgs. Instead, condition scoring systems have been developed which should be used in conjunction with weigh taping to determine a horse’s ideal weight and condition.
Condition scoring uses the fat that can be seen to indicate total body fat. The key sites of fat stores are the crest of the neck, over the rib cage and the quarters as well as the shoulders and the tail head. Not all horses and ponies store fat in the same places and so it is important to assess all areas to determine whether a horse is overweight. What you can be sure of is that visible fat reflects the fact that fat is being stored around internal organs too.
Why are horses getting fatter?
There are a multitude of contributory factors including:
- Stabling and rugging horses in the winter months means that they don’t lose weight as they would naturally
- We’re conditioned into thinking that we must feed mixes and cubes which are much more energy dense than high fibre feeds
- More horses are grazed on improved pastures – particularly where dairy farms have been converted to livery yards
- There is greater use of haylage which is more digestible and so horses and ponies tend to do better on it
- Less exercise – unfortunately we all lead busier lives and often have less time to ride
- A culture of bigger is better has developed in the showing world
- Restricting feed is perceived to be “mean”
What are the effects of obesity?
Being overweight places additional strain on joints and organs such as the heart and lungs and increases the risk of diseases such as laminitis. Metabolic Syndrome is a term being used to describe horses that are overweight and insulin resistant. Insulin is responsible for regulating blood glucose and controlling food intake and if resistance develops, blood glucose and insulin levels will increase as more and more insulin is produced but has no effect. The action of insulin is compromised by the hormones produced by fat cells called adipokines. Whereas fat stores were once thought to be benign, it is now known that they can develop the ability to produce hormones. In humans, it is known that fat stored in specific places such as the waist area, is the cause of the problem. Anecdotal evidence suggests that fat stored on the crest may be the source of the problem in horses and ponies. If there is a link between Metabolic Syndrome and laminitis, this could explain why those with crests seem to suffer with recurrent laminitis.
Another effect that has received limited attention but is certainly on the increase in humans and possibly equines, is non-alcoholic fatty liver disease (NAFLD). Obesity increases the storage of fat in the liver in the form of triglycerides. Initially this doesn’t cause any significant damage but over time it can result in inflammation and eventually cirrhosis or permanent liver damage.
Beating Obesity
In human studies, a 5% reduction in weight was enough to significantly improve health. Although in a horse 5% equates to 25kgs rather than 5kgs in a human, it is achievable. The first step is to know how much energy your horse is consuming and how much he is burning. Energy can be measured in either calories or joules, they’re just different measures for the same thing just as Celsius and Fahrenheit both measure temperature. For horses we tend to use Mega Joules (a million joules) and in humans Kilo Joules (one thousand) joules.
Calorie Counting
It can be difficult to count all the calories a horse consumes as the staple components of their diet such as grass and hay vary in energy content. Although we all want our horses to be out as much as possible, it is important to consider that grass will be contributing lots of energy and so may have to be limited or even removed from the ration altogether to give you control over your horse’s intake. Even a short time at grass can contribute a lot of energy, for example, 1.5kgs of grass will supply your horse with about 3MJ which is just under 5% of a 500kg resting horse’s total energy requirement. The photo opposite shows how much 1.5kgs of grass actually is and although the speed with which a horse will consume this much grass will vary according to the pasture quality and other factors, it is likely to take minutes rather than hours to consume.
Calorie Burning
The National Research Council’s Nutrient Requirements of Horses states that 45 minutes of schooling utilises about 12.5MJ of Digestible Energy. To put this into context one scoop of a cool or pasture mix which weighs about 1.25kgs and contains 10MJ/kg of DE will supply 12.5MJ. So if you feed your horse just HALF a scoop of mix a day as a treat, you would need to give him at least 20 minutes of schooling exercise to utilise the energy it supplies. As cubes weigh more than a mix, a scoop would provide about 16MJ and so would require at least 55 minutes of schooling to use up the calories.
If you have any comments on the issue of obesity or are struggling with your horse’s weight then please let us know as we would love to share your thoughts with others in our next newsletter. Just e-mail us at feeds@dengie.com.
