Hormonal Regulation of Feeding Behaviour: feeding to body condition
There are few things female humans are more sensitive about than our body weight. Where the rest of the world sees our gentle curves and happy smiles, we see lumps and wobbles and wrinkles. We generally have a far worse opinion of our own body condition than any of the people around us. I would hazard that this is because our friends and family care about us and see the best in us and recognize that while we may have a few extra curves we are healthy and happy, and that’s what counts. And if anyone ever said things about our friends that resemble what we have said about ourselves most of us would likely get pretty vocal about defending our friends! And so it is with our horses. Our emotional connection to our horses often blinds us to his/her extra ‘fluffiness’ and a plague on anyone’s house that dares suggest he/she needs to shed a few pounds!
The best way to steer clear of family feuds around your horse’s waistline is to apply a simple set of objective rules around assessing his/her body condition. “Feeding to body condition” is a strategy that celebrates the individuality of our horses. It recognizes that no two horses are the same, and the ‘rules’ for feeding are loose guidelines that undergo pretty rigorous refinement in the feed room. There are 2 scales commonly used to assess body condition – one goes from 0-5, the other from 1-9. A key similarity between both of these scales is that they assess the amount of fat on a horse. This is important because it accounts for the fact that fat is deposited preferentially on different parts of the skeleton. For example, a severely malnourished horse will, when weaned onto a healthy diet, deposit fat first along the lumbar spine. The very last place that fat is stored in a horse is over the ribs, so in most cases, the ribs are the tell-tale landmark of how well-conditioned a horse is. For a healthy body condition ribs should not be visible, but should be felt when you run your hand along the horse’s side. There should be some fat around the tail head, and the withers should be rounded with the shoulders and neck blending smoothly into the rest of the body (Figure 1). The ideal body condition is somewhere near the middle in both the 0-5 and the 1-9 scale, but it will vary with individual horses. Some horses will never achieve the ‘ideal’ body condition, preferring either to hover around thin-ish or plump-ish.
Regulating feed intake
One of the key factors in maintaining a healthy body condition in your horse is how much your horse actually eats. Let’s face it, some horses left to their own devices will literally pig out and be a poster child for Weight Watchers. But others, it doesn’t matter how much expensive high-fat grain you offer them they’ll just pick like sparrows and look suspiciously like they need a cheeseburger. Feeding behaviour is regulated, at least in part, by a hormone called ‘ghrelin’. In horses this hormone is produced more-or-less consistently throughout the day, with larger amounts being produced at night. It contributes to horses ‘trickle feeding’ behaviour, wherein they prefer to eat small amounts frequently throughout the course of the day. And many of us who offer hay to horses 24/7 can attest to the fact that horses eat considerably more at night than during the day. When we impose ‘meal feeding’ on horses, ghrelin gets produced in larger amounts during times of feed restriction. This can contribute to horses bolting their feed at mealtime and may predispose them to choke or colic.
Why is my horse too skinny?
Conscientious horse owners frequently turn to the published NRC guidelines for feeding horses. But all too frequently, despite the ration being optimized for a horse’s weight, age and workload the horse still carries a low body condition score. This can be because: a) the horse isn’t eating enough; b) the horse is not able to extract energy from his diet; or c) the diet isn’t offering the nutrients that the horse needs.
In cases where the horse isn’t eating the feed that he/she is offered, this may be attributed to poor dentition (teeth should be floated at least once a year), stress (the stress hormone cortisol reduces production of ghrelin thus inhibiting the drive to eat), or ulcers. Horses can be encouraged to eat more over the course of a day by providing smaller, more frequent meals. This is consistent with the way the horse is hardwired to feed and can actually encourage them to eat more by avoiding big variations in ghrelin production. It can also reduce stress by eliminating fasting between meals. And gastric ulcers can be dramatically reduced because the stomach is not left empty for long periods of time.
If your horse stays skinny irrespective of how much or how frequently you feed him/her, this can be an indication of not getting enough nutrients from the diet. Sometimes this can be fixed simply by conducting a nutrient analysis of the hay, then balancing the ration with concentrates. Hay is the mainstay of a horse’s diet and should always be considered the starting point for any complete ration. Other things to consider might be parasite burden (a simple inexpensive fecal analysis can tell you if you have an unhealthy parasite load), or gastric ulcers (which inhibit the ability of the gastrointestinal tract to digest and absorb nutrients). And again, increasing the frequency of feeding will often increase the total amount of nutrients consumed over the course of a day and can help put weight on a hard keeper.
Why is my horse too fat?
While it’s relatively easy for most of us to wag a disapproving finger at a skinny horse, we tend to be more forgiving of the excessively ‘fluffy’ of our equine friends. But carrying too much weight can be even unhealthier for a horse than carrying not enough weight. Health conditions that plague overweight people, including arthritis, insulin resistance, heart disease and circulatory problems are equally prevalent in overweight horses. Insulin resistance has reached almost epidemic proportions in pleasure horses, and is frequently associated with obesity and laminitis. Insulin sensitivity and glucose metabolism are involved in the complex endocrine regulation of feeding behaviour. In its most simple explanation, insulin resistance decreases activity of enzymes that degrade ghrelin; thus ghrelin remains high in the blood and the stimulus to eat prevails. Controlling insulin resistance can be very challenging for horse owners as there is little in terms of a ‘cure’ that we can rely on. Feeding compounds that can increase insulin sensitivity (eg. Fenugreek and cinnamon) can help control irregularity in plasma ghrelin.
Feeding a fat horse can be very difficult as often they look at a bale of hay and put on 20 lbs. The key is to reduce energy intake without sacrificing nutrient intake. This can be achieved by feeding hay that has been soaked for 24 hours to reduce sugar content, and offering this in small amounts frequently over the course of a day. The diet can then be balanced with a ration balancer (such as Enhancer, Optimal or Equilizer), which contain balanced nutrients without additional energy. Just providing a balanced ration can be enough to reduce excessive feed intake in overweight horses.
Feeding to body condition score is an excellent strategy to maintain a healthy body weight in horses. It recognizes the fact that all horses are individuals and they must therefore be offered a diet that meets his/her unique needs. Your horse will thank you for it.
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