Is your horse a “hard keeper?” If so, you are well aware of how difficult it is to maintain adequate or desirable body condition in this type of horse. The reality is that no two horses are the same when it comes to the amount of feed (and number of calories) required to maintain body condition, which is a reflection of differences in genetics, digestive efficiency, and metabolism. Temperament is also an issue–a nervous horse often requires more calories than a calm horse to maintain the same body condition. Similarly, horses with certain stable vices such as stall walking and weaving will burn more energy and will therefore need more groceries.

Beyond this classic easy vs. hard keeper scenario, there can be many reasons for persistent poor body condition and failure to gain weight despite what appears to be appropriate nutritional and general health care. In this article, the possible causes of weight loss and/or persistently poor body condition are discussed. Nutritional strategies for weight gain in thin or under-conditioned horses are also considered.

What Is Thin?

The logical first step to solving this problem is to set the ground rules on “thinness.” Use of body conditioning scoring will provide the best guide to a horse’s overall body condition. Many of you will be familiar with use of the body condition scoring system, but to briefly recap, recall that this technique assesses flesh coverage over several areas of the body–including the tailhead, rump, back, withers, ribs, and neck–and that a scale of 1 through 9 is used. A body condition score (BCS) of 1 is classified as emaciated. These horses have little, if any, flesh coverage and are literally “bags of bones.” At the other end of the scale, a BCS of 9 indicates obesity–there is so much fat coverage (fat tissue) that virtually none of the horse’s skeletal structure can be discerned, even by palpation.

Of course, beauty, or more precisely appropriate body weight and condition, is in the eye of the beholder. For some athletic disciplines, such as endurance racing and three-day eventing, the trend is to maintain horses a bit on the thin side (e.g., a BCS of 4). On the other hand, a halter horse with a BCS of 4 would be considered very thin and would likely be given more “groceries” for weight gain. In general, a horse with a BCS of 3 or less is definitely thin, while for most horses a BCS of 5-6 is about right.

You should regularly assess your horse’s BCS. Measuring body weight using a scale or estimating weight by using a weight tape is also useful for monitoring the success (or failure) of any dietary weight gain strategies.

Why Is He Thin?

The most obvious reason for weight loss and failure to maintain or gain condition is a lack of feed–the diet simply doesn’t provide enough calories. Lactating mares and hardworking horses are particularly prone to this scenario because of their very high caloric needs. So, the first and most important step in determining why a horse is thin is to assess the amount and quality of the feeds he currently eats. Sometimes a calorie deficit is due to the quality of the feed consumed rather than the amount.

For most horses, daily dry matter intake is 1.5-2.5% of body weight (i.e., 17-28 pounds for an 1,100-pound horse, or 7.7-12.7 kg for a 500-kg horse), although this figure can go as high as 3% or slightly more in some situations (such as a mare in early lactation). A mature horse not in hard work requires approximately 16 Mcal of digestible energy (DE) and can often maintain body condition when fed at 1.5-2.0% of body weight just as hay (17-22 pounds for the 1,100-pound horse, or 7.7-10 kg for a 500-kg horse). However, this will depend on the quality of the hay. Poorer-quality forages such as mature coastal or Bermuda hay often have low protein and calorie contents (approximately 0.7 Mcal of DE/lb, compared to 1.1-1.2 Mcal/lb for early-bloom alfalfa hay). That means 17-22 pounds (7.7-10 kg) of this hay will provide only 12-15.4 Mcal of DE–probably not enough to maintain condition in this horse.

Another common weight loss/thin horse scenario involves horses fed as a group–horses at the bottom of the pecking order might not get a fair shake at feeding time. This is particularly common in groups of mixed-age horses maintained at pasture or in large dry lots, with the younger horses typically at the lower end of the pecking order. Ideally, the more timid horses in the group should be separated from the dominant horses. Alternatively, ensure that hay is well dispersed in the area available, thus providing better opportunity for the less dominant horses to eat. Grain buckets or feeders should also be well spaced.

Extreme cold can be another reason for decreased body condition. Research has demonstrated that maintenance energy needs increase 30-50% in horses kept at temperatures below 0°F (-18°C). For a thin horse, housing in a warmer environment and/or using a heavy blanket can help offset these effects and make weight gain possible once the diet has been adjusted.

It is also important to consider medical problems as a potential cause for failure to gain weight, particularly when the feeding program seems to be adequate and the horse remains in poor body condition despite a substantial increase in the calories provided. Weight gain in these horses can only occur once the problem has been identified and remedied. Step one in these instances is to call your veterinarian–he or she can perform a physical examination and determine whether a medical problem is contributing to the poor body condition.

Perhaps the most overlooked problem is poor teeth. Remember that fibrous feeds such as hay constitute the bulk of the horse’s diet, and normally functioning teeth (especially molars) are required to grind this feed material, breaking it down into small particles that can be properly digested by the microbes living in the horse’s large intestine. Fiber digestion will be poor if the hay or other forage is not chewed properly. In short, the horse will not be able to extract as many nutrients from the feed (they will pass out the back end) and he will lose weight. This situation also makes horses more prone to choke and impaction colic.

Poor teeth are common in older horses, often necessitating the use of a senior feed that provides a complete diet, including forage, in a more digestible form. However, even young horses can develop dental problems (e.g., retained caps, sharp points) that result in a painful mouth, decreased feed intake, and a failure to thrive. If your horse is thin and has difficulty gaining weight, your veterinarian will want to thoroughly examine the mouth. Treatment of dental problems such as sharp points might make all the difference. Alternatively, the identification of more permanent dental problems, such as wave mouth or tooth loss, will signal the need for diet adjustments such as the use of a senior feed.

Putting Weight on a Thin Horse

The following are suggested feeding strategies for weight gain in horses which do not have an underlying medical problem and have not been through a period of starvation. Horses which have been starved and are extremely emaciated require medical attention; rehabilitation should only be done under the guidance of a veterinarian because metabolic problems can develop during refeeding of these animals.

This discussion also assumes that the mouth and teeth are in good working order. As mentioned, in older horses with permanent tooth loss or other dental problems that severely limit efficient chewing, changing the diet to a complete senior feed will be a step in the right direction. If the teeth are particularly bad (or nonexistent), these feeds can be soaked in water and fed as a gruel or slurry. Horses soon learn how to cope with this style of meal. Although these complete feeds do contain enough fiber to meet the horse’s needs for normal gut function, many horses retain the desire to consume longer-stem fiber, such as that contained in hay, and consumption of this long-stem fiber can help to relieve boredom in stalled horses. Therefore, it is commonplace for some hay to be fed along with the complete feed. However, particularly for older horses with suspect dentition (teeth), no more than one or two flakes should be fed per day. Sometimes, the tendency is to feed more hay than the senior product, the result being further weight loss. Remember that many of these old guys are no longer able to derive much benefit from hay, and they need to obtain most of their nutrition from the specially designed senior feed.

For other horses, the simplest strategy for weight gain is to toss him an extra flake or two of hay per day or perhaps an extra scoop or can of grain, or you can feed one to two cups of vegetable oil. This approach will work in many situations. However, I prefer a more methodical approach to the problem–one that involves calculations of current calorie intake in relation to actual needs and the number of extra calories needed for a certain amount of weight gain.

To do the latter, you will need to weigh the current ration. Your veterinarian, nutritionist, or local feed dealer can help you figure out the approximate number of calories in the ration. Alternatively, the calorie content of the feeds shown in “Energy Contents of Common Feeds” on page 64 can be used as a general guide.

For light-breed horses such as Quarter Horses, Thoroughbreds, and Arabians, one BCS unit is the equivalent of 40-45 pounds (18-20 kg) in body weight. Clinical experience indicates that approximately 5-6 Mcal of DE above maintenance needs is required for each pound gain in weight. So, for an average-framed mature horse with a BCS of 3 and a desired BCS of 5, 80-90 pounds of weight gain is needed. This will not happen overnight; patience is a must.

From these numbers, you can begin to develop a feeding plan for weight gain. “Feeding for Weight Gain” on page 62 gives an estimate of the number of extra calories required to change the BCS of a horse from 4 to 5 in a desired time. Using the 60-day time frame, the 1,100-pound (500-kg) horse in this example will need about 3.3-4.0 Mcal DE per day over and above his
maintenance needs. If we assume that the horse is only in very light work (e.g., ridden two or three times per week), his daily calorie needs are roughly maintenance needs, or 16.4 Mcal DE per day, according to the National Research Council. Therefore, for weight gain (a one-unit increase in BCS over a 60-day period), the diet must supply about 19.7-20.4 Mcal DE per day.

The next question is how to supply the extra calories. Your choices are fiber (e.g. hay or beet pulp), starch (grain), or fat (vegetable oils or other fat supplements). The safest approach is to maximize the quality of forage and to feed more of it. Early-cut hay is a must because of its higher digestibility compared to more mature hay. Compare 20 pounds (9 kg) of coastal hay providing about 14 Mcal of DE (at best) to 20 pounds (9 kg) of an early-cut timothy/ alfalfa mix that provides 18-20 Mcal of DE (or even more energy if straight alfalfa is fed). This change alone will make all the difference in many underweight horses. Of course, not all early cut hay is alike–choose hays with very little stem and plenty of leaf.

You have other fiber options if good-quality hay is in short supply. Alfalfa pellets or cubes (cubes are sometimes a grass and alfalfa combination) are made from early-cut forage and therefore are good sources of energy. Similarly, you could add a few pounds of beet pulp to the diet. The fiber in beet pulp is more digestible than even the highest quality hay and will provide about 1.1-1.2 Mcal of DE per pound.

For very thin horses, and those with energy needs well above maintenance (e.g., horses in training, late pregnancy, or lactating mares), the extra energy from more and/or better-quality fiber might not get the job done. This is particularly true for horses (in the 1,100-1,200-pound, or 500-544-kg, range) already eating 20 pounds (9 kg) or more of hay (or a combination of hay plus other fiber sources like cubes and beet pulp). These horses might already be at their upper limit for daily fiber intake. So, step two in the weight gain plan is to add grain, or preferably a commercial feed that delivers balanced nutrition as well as calories from starch, sugar, and fat. Feeds that contain 6-10% fat are often in the range of 1.5-1.6 Mcal/lb. Other options include specially designed fat supplements that pack even more calories per pound or the addition of straight vegetable oil to the ration (one to two cups per day started slowly and gradually increased). If you use straight vegetable oil, also add vitamin E (for its antioxidant properties) at the rate of 250 IU per standard measuring cup of oil.

Most importantly, any diet change must be made very gradually. A rule of thumb is to not increase the amount of grain by more than one pound per day. If you plan to increase the amount of concentrate by a total of three to four pounds per day, make this change over a 10-day period. Changes in hay/fiber feeding should also be gradual and, if possible, plan on mixing some of the old hay with the new for a week to 10 days when switching to better-quality forage.

Some flexibility in approach is often necessary, particularly for picky eaters. For performance horses, it might be necessary to reduce the training volume until weight gain is achieved. However, by paying close attention to the amount, quality, and energy content of feeds in the diet, it is usually possible to achieve the desired weight gain in underweight horses.

FURTHER READING

Geor, R. How Does Your Horse Score? The Horse, November 2001, 93-98. Article Quick Find #2861 at www.TheHorse.com.

National Research Council. Nutrient Requirements of Horses, 5th edition. NRC-NAS, Washington, DC, 1989. www.nap.edu/books/0309039894/html/index.html.

DIGESTIBLE ENERGY CONTENT IN COMMERCIAL FEEDS

Is Your Horse’s Feed Providing Enough Energy?

When calculating how much of a given feed is required to meet a horse’s energy needs, a critical piece of information is the energy content of a feed, expressed as digestible energy (DE)–essentially the amount of energy in the feed that is available to the horse. Unfortunately, laborious digestion studies are needed to measure the DE of a feed.. Still, by knowing the chemical composition of the feed, it is possible to compute reasonable estimates of DE–these computational methods form the basis for the National Research Council’s values for DE (see “Energy Contents of Common Feeds” on page 64) and are also used by feed manufacturers in the development of recommended feeding rates for a given feed.

Current regulations don’t allow for the reporting of DE values on feed tags. However, the following values are a good guide for the energy content of a commercial grain mix or pelleted feed. Feeds without added fat are typically 1.4-1.45 Mcal/lb, while a feed with 6-10% added fat will contain approximately 1.5-1.6 Mcal/lb.–Ray J. Geor, BVSc, PhD, Dipl