Putting the Brakes on Horse Weight Gain

Every horseman has seen, at one time or another, the telltale signs of a thin horse: the disproportionately skinny neck, the protruding spine, the row of ribs, and the jutting hipbones. Thanks in part to advances made in feeding management, veterinary care, parasite control, and dentistry, compassionate horsemen can fatten horses safely and with relative ease. But when is it time to switch from a “weight-gain” diet to a “maintenance” diet?

How can the diet be altered in the safest way possible for the horse?

With a little forethought on the part of its owner, a horse can move seamlessly from one diet to another without problems.

The Goal

Most equine veterinarians and nutritionists use a body condition scorecard to determine a horse’s need to lose or gain weight. Scores range from 1 to 9, with 1 denoting extreme emaciation and 9 signifying obesity.

Most healthy horses have body condition scores between 4 and 6. This is not to say, however, that healthy horses cannot be thinner or heavier, and certain life stages may prompt scores outside this range. Examples of horses that are typically thinner than ideal include athletes that are frequently asked to perform strenuous exercise, aged broodmares in the first two to four months of lactation, and horses recovering from illness. In such cases, horses are usually being offered full, nutritionally balanced diets yet are still unable to maintain appropriate body condition.

In these cases, the horses are incapable of consuming sufficient calories to fuel both weight gain and work, regardless of whether the work involved is actual performance, growth, lactation, or tissue repair. Yet once the workload is reduced (less strenuous exercise or weaning of a foal, for example), weight gain can be accomplished.

For most horses, a body condition score of 5 seems to be most appropriate. Horses in this state have sufficient fat cover so that ribs cannot be seen but can be felt. There is also no excessive fat deposition around the shoulders, over the withers and topline, or around the top of the tail. As researchers dig deeper into the metabolic issues that influence body weight, it is becoming obvious that maintaining horses in moderate body condition may be much healthier than keeping them even slightly overweight.

Switching Diets

Diets formulated for weight gain often contain high-quality forages and concentrates that are rich in energy. As with any species, horses gain weight when more calories are consumed than are used. Once a horse has reached its target weight (and a condition score of near 5), it is time to rethink his ration, as a continuation of the “weight-gain” diet may eventually lead to obesity.

The first components of a weight-gain diet that should be removed are any high-calorie supplements. Feed additives rich in fat such as vegetable oils (corn oil, canola oil) and rice bran are widely used to pack on pounds, but as the horse reaches an ideal weight, their inclusion in the diet should gradually be tapered off. The next consideration is the concentrate, as it delivers more calories per pound than forage. Owners should carefully read the feeding instructions that appear on the feed bag or the tag that is sewn onto the bag. In order to ensure the horse receives optimal vitamin and mineral nutrition, he should consume at least the minimal amount indicated.

For instance, if an owner is feeding a formula designed for mature horses in light to moderate work and the feeding instructions state explicitly that the horse should be fed six to eight pounds (2.7 to 3.6 kg) per day, the absolute minimal that can be fed is six pounds without risking nutritional deficiencies. If less than six pounds are given per day, a well-formulated vitamin and mineral supplement can be added to make up for nutrient deficiencies caused by a low grain intake. If this horse were eating eight pounds of the grain in order to gain weight, reducing his consumption by one-half to one pound (.45 kg) per day (accomplished over the course of several days) should lead to a slower rate of gain, or even equilibrium.

At this stage, body condition evaluation becomes a waiting game, as changes in weight often take several weeks. If the horse maintains his body condition on this new amount of feed for several weeks, further reduction by another half pound (.22 kg) per day is warranted. If more weeks elapse and he still remains in desirable body condition, another reduction can be made. As mentioned previously, if owners are feeding less than the recommended amount, feed manufacturers can suggest a low-calorie feed that will supply the horse the protein, vitamins, and minerals he requires.

The final part of the diet up for review is the forage. For most horses, a combination of hay and pasture make up the forage allotment. It is not unusual for horsemen to add alfalfa to a diet when weight gain is desired, because the legume contains more calories per pound than grass hays. However, once moderate body condition is achieved, the alfalfa can be removed from the diet and good-quality grass hay can be fed. If alfalfa cubes were supplemented, these can be reduced slowly until they are no longer fed at all.

Depending on the situation, horses might have access to lush pasture. As long as the pasture is introduced slowly (increasing by half-hour increments per day, to be safe), calorie-rich pasture grasses can do much to increase body weight. As the horse reaches a desirable body condition, grazing might have to be limited if he continues to gain weight. Many easy-keepers have been known to get extremely fat on pasture alone, and this might also occur in horses that have been on an increasing plane of nutrition. Reducing grazing time or using a grazing muzzle might be appropriate for a horse that tends to get too fat on pasture. If the pasture provides little in the way of nutrition, then most calories must be derived from a ration of concentrate and good-quality hay.

Make Changes Slowly

All changes made to a horse’s diet should be accomplished over a period of several days. The horse’s gastrointestinal tract is a fragile organ system. If abrupt changes are made, health problems such as diarrhea, colic, or laminitis may ensue. A step-by-step approach to instituting changes in a diet will help horse owners keep their formerly underweight charges in moderate body condition.

If a particular nutrition question or problem arises, horsemen should have on hand the number of a reputable equine nutritionist for consultation. A veterinarian might be able to assist with some nutrition-related questions as well.