If I had to sum up the direction that feeding horses is going, it would be back toward the basics. Overall, I see a trend developing to feed horses as nature intended them to eat. Some of this movement is fad and exaggerated to a degree, but evidence is piling up from several different directions to support the basic observation that horses are supposed to eat grass.
As an example, obesity is certainly nothing new in the horse world. However, it's getting more attention lately because of the potential link with serious health problems, which is finally coming to the forefront. Fat ponies that will founder on grass have been around forever. But now we're recognizing that "easy keepers"-or, frankly, overweight horses-might be prone to laminitis, as well, and we understand that this propensity is linked to insulin resistance.
In 2007, veterinarians from the Virginia-Maryland Regional College of Veterinary Medicine studied 300 horses living on pasture that were owned by their field-service clients. They found that 51% of the horses were overweight, and that 19% of the overweight horses were obese. Of that 19%, 32% had elevated blood insulin levels, an indicator of insulin resistance. Of the 32% that were overweight but not obese, the numbers reversed, with 18% having high insulin.
The recognition of insulin resistance as a nationwide problem has led to an explosion in new bagged-feed choices that are lower in sugar and starch, the two simple carbohydrates that the horse digests into glucose.
Feeding meals high in sugar and starch is known to decrease sensitivity to insulin. In short, these new feeds are moving closer to what the sugar/starch profile of a horse's diet should look like-grass. This is an improvement, but there are some things you need to know:
• Feeds that are "low starch," "reduced starch," "safe," etc., aren't necessarily low calorie. In many cases, the calories that were coming from high-starch grains and molasses have been replaced by fat calories.
• Because they're not necessarily low calorie, you can't substitute these feeds for your current feed and expect your horse to lose weight.
• Fat increases or even causes insulin resistance in other species. It's known to cause insulin resistance in ponies; there's some evidence to suggest caution with feeding high-fat feeds to insulin resistant full-size horses as well.
• The new reduced-simple-carbohydrate feeds are always lower in starches and sugars than the more familiar grain-based feeds, but they're not necessarily low enough for an insulin-resistant horse, especially one dealing with laminitis, which makes him unable to exercise.
Hays vary widely in how much sugar and starch they contain, but typically they're well below 20%. For a horse that's actually insulin resistant, the target is no higher than 10% when he isn't being worked.
Items such as rice bran and many grain byproducts often contain 25% or more sugar and starch. Since most of these feeds don't provide information on the label about sugar and starch content, you'll have to call the manufacturer to find out.
For the best available comprehensive information on feeding an insulin-resistant horse, consider joining the Yahoo Cushing's and Insulin Resistance group (http://pets.groups.yahoo.com/group/EquineCushings/). This group is made up primarily of horse owners, but also includes veterinarians, researchers, and hoof care professionals. Membership was at 6,347 and growing steadily at press time.
The bottom line for feeding overweight or insulin-resistant horses is to keep it simple. A diet based on salt, a low sugar/starch hay, vitamin E, and minerals to supplement what's missing in your area will get the job done.