by: Nancy S. Loving, DVM
July 01 2007, Article # 9918
n this age of plenty, it is not uncommon to see horses carrying too much body fat. Such an individual exceeds what we might call pleasingly plump; in other words, he is fat. When running your hands across the horse's sides, you won't feel any ribs beneath his flesh. Often a fat horse has developed a cresty neck, and if you can stand on a fence rail and peer down on him from above, an overweight horse might appear to have a "rain gutter" along his back. When the girth or cinch is tightened, it makes a distinct dent in the underlying flab. Some might think such a horse is solid and in full "bloom," ready for the show season ahead. But such a body condition is dangerous to the health and athletic future of the horse.
Where to Start?
Philip Johnson, BVSc (Hons), MS, MRCVS, Dipl. ECEIM, professor of veterinary medicine and surgery at the University of Missouri, has explored hormonal aberrations that result from overfeeding, particularly as related to what he describes as equine metabolic syndrome (EMS, see sidebar on page 66). His recommendations to treat the problem of obesity are based on common sense and a healthy approach to dietary management. First, an owner must recognize that a horse is, in fact, overweight or obese. He urges, "To improve metabolic health, a philosophical shift is necessary. An acceptable and desirable body condition, as perceived by a horse owner, should be a horse that is fit and trim."
Johnson suggests using measurements with a weight tape and with body condition score (BCS) to evaluate how your horse measures up to ideal body weight. Then he urges owners to implement a sound nutritional program in consultation with a veterinarian.
A starting place in feeding an overweight horse is to take a realistic look at what your horse has previously been ingesting. Sometimes it is easy to think that a horse in a herd is only eating a specified amount when, in fact, he might be driving others away from their feed and consuming a double ration. In that case, it is important to isolate the horse during feeding time so there is no question about how much he eats.
Restricting calories is key to success--if your fat horse has previously been on pasture, put him into a dry paddock with restricted access to measured portions of food or confine him to a portable pen that can be moved around the pasture to restrict grazing, or attach a grazing muzzle to a breakaway halter.
How Much and What to Feed?
The next step is to critically evaluate exact amounts and types of material fed. The only accurate way to determine this is to weigh the ration with a feed scale.
" 'Guesstimating' how much something weighs is fraught with error and limits how well you are able to fine-tune the diet," states Johnson. "Getting an accurate weight on your horse is invaluable. A lot of people take their horse to the feed distributor and weigh the horse and trailer at their weigh scale, then weigh the trailer empty the next trip to town." Weight tapes can be used, but they are rough estimates geared to measuring adult light horse breeds.
As a general rule, most horses consume about 2% of their body weight each day for maintenance, with a 1,000-pound horse getting along fine on a daily ration of 18-20 pounds of grass hay. To assist a fat horse in losing weight, you might need to cut his hay back to a total of around 15 pounds for the day.
Johnson remarks, "It's important to feed to a desirable target weight. Your veterinarian should evaluate the horse's current weight and body condition score (BCS) and make a recommendation as to what the weight and BCS should be. Different breeds and types may have different standards." (Learn more about BCS at www.TheHorse.com/emag.aspx?id=7205.)
All recommendations should be in conjunction with the caloric content of the hay based on lab analysis, when possible.
In concocting a dietary plan, Johnson recommends, "Remove as much grain and supplement feed as possible, including complete or senior feeds containing high starch or sugar." In most cases of a fat horse, you need offer nothing more than hay, salt, and water.
Concentrate feeds, especially with those that are carbohydrate-rich, elicit large surges in blood glucose. In response, insulin hormone concentrations peak to facilitate storage of glucose as glycogen in the muscles and liver. Obese horses are often insulin-resistant, which means higher amounts of insulin are released in response to a standardized sugar or starch challenge than is considered to be normal (hyperinsulinemia). Their blood glucose might or might not be elevated, too (compensated or uncompensated insulin resistance, respectively). Hyperinsulinemia has been associated with increased risk of laminitis.
[...more - Timing of Weight Loss, Weight Loss for Laminitic Horses, Feeding Recommendations, EQUINE METABOLIC SYNDROME AND INSULIN RESISTANCE