Feeding Horses: Art, Science, or Both?

When feeding horses, two seemingly opposing aspects hold true: It's a little bit of art, and a little bit of science. On one hand, tradition reigns supreme when it comes to horse feeding. Many techniques have been passed down from generation to generation and, in some cases, remain in place despite new knowledge based on scientific research. On the other hand, the industry seems to be very susceptible to new fads that have dubious merit in terms of scientific validity, let alone a real benefit for the horse.

The fundamental question at hand in this article is: "What is the foundation for horse feeding? Is it art, science, or both?"

My argument is that a mix of both is needed for appropriate feeding management of horses. As the old adage goes, there is absolutely no substitute for experience--and this experience has driven evolution in the art of feeding horses. Through the years, horse owners have learned by trial and error what works and what doesn't work, and the results of these "mini-experiments" have provided the basis for advice passed on to others. We have learned to work with feeds plentiful in our region, sort through the plethora of products on the shelf (and even understand feed tags), figure out likes and dislikes of the horses themselves, and work feeding into a daily routine that is sometimes time-crunched. This is part of the art of feeding.

The problem is that sometimes the advice of our forefathers is simply wrong and needs to be thrown in the proverbial round bin. Consider the seemingly endless list of myths and wives' tales concerning horse nutrition--bran mashes prevent colic, corn is a "heating" feed, high-protein rations cause horses to lose it mentally, high-protein rations cause osteochondrosis in growing horses, first-cut hay is bad for horses, pellets cause horses to choke, alfalfa causes kidney damage--and so the list goes on. Most--if not all--of these perceptions can be debunked due to lack of scientifically valid evidence.

Taking a scientific approach to feeding horses is attractive. Nutrition is, after all, a scientific discipline. Nutrients are needed to support virtually all body functions and are therefore fundamental to health. And we need a scientific approach to generate new knowledge to extend our understanding of the discipline. We need to know which nutrients are essential, how much is needed at different life stages or physiologic states (growing horses, performance, lactation, etc.), and whether or not certain levels of intake might actually be harmful, i.e., toxic. It is also critical to consider the horse's physiology, particularly gut function, in developing recommendations for feeding management. This information, in large part, forms the basis for the National Academy of Sciences publication, Nutrient Requirements of Horses (by the National Research Council, or NRC). The results of studies on various aspects of horse nutrition are evaluated and compiled by a committee of equine nutritionists, who then develop recommendations on nutritional requirements including some practical aspects of feeding.

However, there are problems with a purely scientific approach. The Nutrient Requirements of Horses (there is a similar publication in other countries, e.g., Japan and Germany) is an extremely valuable document that provides a scientific basis for the development of any feeding program. But it is important to realize that these recommendations are minimums, which contrast with recommended daily allowances (RDAs) used in human nutrition. The latter are easily translated into daily meal plans (if we care to take notice!), while it takes a bit more expertise to transform the horse data into a practical ration.

These types of publications can also quickly become outdated. The last version of Nutrient Requirements of Horses was published in 1989, and there has been a considerable body of equine nutritional research over the past 15-plus years that is obviously not reflected in this document. Thankfully, a new committee is now working on a revision that will help shape feeding recommendations over the next decade or so.

Another problem with the purely scientific approach is the complete lack of data for a given nutrient. Even today, there are nutrients (e.g., boron and sulfur) for which we have no knowledge on requirements. More importantly, blanket recommendations fail to recognize that horses are individuals who have "not read the textbook!"

This point is epitomized when you consider daily digestible energy (DE) needs. Clinical experience shows that recommendations can often over- or under-estimate a given individual's actual needs by as much as 25%. This means that if we doggedly adhere to a published value for daily DE provision, the chances are the horse will either gain (the more common scenario) or lose weight. Although these numbers can serve as a starting point for a feeding program, it is obvious that ongoing evaluation of the horse's condition is needed for fine tuning--a merging of art and science.

Finally, a singular focus on the science of horse nutrition can ignore crucial aspects of feeding management, such as: "Will he eat it?" Determining likes and dislikes is definitely an art. If the horse consistently turns his nose up at a given feed, that feed is useless no matter how wonderful it seems on paper (see "Feeding the Finicky Eater" on page 45 for more information).

Ultimately, it is necessary to merge art and science when managing your horse's feeding program. On the side of science, it is important to provide a ration that meets nutrient requirements and feed it in a manner that is compatible with the horse's gastrointestinal physiology. On the side of art, a somewhat holistic approach to feeding management is equally important--feed palatable feeds, individualize feeding programs, and feed in such a way as to keep the horse happy and content.

We will now examine the art vs. science issue in the context of the some "hot button" horse feeding topics.

Buying Prepared Feed, Avoiding The "Protein-Centric" Approach

Buying a prepared horse feed definitely involves both art and science. It requires some knowledge of feed ingredients (e.g., are they suitable for horses?) and an ability to interpret the information on feed tags. Yes, there is some science behind the latter, but also consideration for individual preferences (horse and owner). For example, some horses, and horse owners, prefer grain mixes over pellets or vice versa.

Feed companies are required by law to stitch a feed tag onto every bag of horse feed, although in some cases the tag information is printed on the bag. This tag should provide a list of ingredients, directions for use, and guaranteed amounts of selected nutrients. This is important information, although sometimes there is a tendency for feed sales people to over-emphasize aspects of the tag, for instance, "Our feed is better than Company X's because it contains more copper." Suffice it to say, more is not necessarily better, and you should be wary of this type of sales pitch.

First and foremost, the feed tag provides the product name and a statement of purpose. The purpose statement should indicate the class or classes of horse for which the feed is intended, such as growing horses, maintenance horses, or performance horses. This information is of some importance in selecting the right feed for your horse. For example, a product labeled as a "maintenance feed" isn't suitable for weanlings. The name statement also indicates the category of horse feed; there are four:

  • Processed concentrates (pelleted, extruded);
  • Textured concentrates (sweet feeds);
  • Complete feeds; and
  • Supplements (various combinations that might include protein, vitamins, minerals, and/or trace minerals).

The term "complete" causes a fair bit of confusion. Some companies use the term "complete feed" to describe any concentrates that, when fed with an appropriate amount of good-quality forage, will meet the nutritional needs of horses for which the feed is intended. This must be distinguished from complete feeds that are designed to provide 100% of the horse's nutrition, meaning no other forage is needed. Such feeds must contain a large amount of fiber, both digestible and non-digestible, to do this job. More on complete feeds later.

The tag next lists the guaranteed analysis. By law (in the United States), the feed manufacturer must list minimum levels (as percentages) of crude protein, fat, and fiber, minimum and maximum values for calcium, and minimum values for phosphorus, copper, zinc, selenium, and vitamin A (vitamin E is often listed as well). This information is somewhat useful for selecting feeds, but on the whole horse owners tend to place too much importance on this information when selecting a feed. The guaranteed data can be used to determine whether or not a given feed will be suitable, but only when combined with knowledge of the type and amount of forage to be fed with this feed, and only if you are prepared to grab pencil, paper, and calculator and perform a few calculations so that nutrient amounts can be compared to recommendations. I hazard a guess that not many horse owners go to these lengths.

Instead, there's an unjustifiable emphasis on the crude protein percentage listed on the tag. How often have you heard, "I feed a 14%" in response to the question, "What type of concentrate are you feeding your horse?" For me, it's too many to count. I've also found that the purchase of concentrate feeds is often based solely on the crude protein percentage with little or no consideration for any other feature. This situation is a bit of a Catch-22. On one hand, it is very convenient to express protein needs and requirements on a percentage basis. On the other, this approach tends to focus attention on the crude protein percentage without regard for more important issues such as protein quality, particularly quantities of the essential amino acids (building blocks for proteins) such as lysine. Indeed, there is emerging evidence that when adequate quantities of the essential amino acids (lysine, methionine, and threonine) are in the diet, horses (even growing horses) can thrive when the crude protein content is considerably lower than current practices.

More work is needed in this area before the science can be translated to real-world horse feeding. For the moment, it must be realized that horses need certain amounts of protein (actually, the essential amino acids contained within these proteins), not a specific percentage. Growing horses, lactating mares, horses in training, and "senior" horses do need more protein than mature horses at maintenance, so it makes sense to feed concentrates with higher protein content (%). However, you need to evaluate the total ration (i.e., forage and concentrate or supplement), including amounts fed, before making this call (see "Think Quantity and Quality, not Percentage" on the previous page).

Also bear in mind that the tag number is a guaranteed minimum--the actual protein content might be considerably higher, and that figure gives you absolutely no clue regarding the quality. Perusal of the ingredient listing is a better guide. Look for feeds that contain soybean meal, milk proteins, or individual amino acids (lysine is the most common addition to feeds intended for growing horses).

Sometimes a game of "tag folly" is used for the purposes of marketing. In the past few years, so called 10/10 feeds (10% crude protein, 10% fat) have been popular in part because of the belief that higher-protein concentrates or diets make horses hot-headed (even though there is no scientific evidence to support this perception). Laboratory analysis of these feeds often shows that the actual crude protein content is closer to 12-13% than to 10%. This is definitely the art of horse feed marketing, not the science of equine nutrition.

The Magic--Or Not--of Bran Mash

Now we are down to some serious tradition--the feeding of a bran mash on a weekly basis is perhaps the most common of all horse feeding practices. The rationale is that wheat bran will impart a laxative effect and "keep things moving." An extension of this theory is that regular (no pun intended) feeding of a bran mash will help prevent colic. There are all sorts of secret recipes for mashes, but the basic formula calls for wheat bran that has been steeped in warm to hot (120-125ºF) water and mixed with various other ingredients (such as oats, sweet feed, flax seed).

Unfortunately, the results of controlled research don't support these beliefs. For wheat bran to exert a laxative effect, we would expect to see an increase in fecal moisture (softening of the manure) compared to rations that do not contain wheat bran. The results of research studies do not support this expectation--wheat bran is a not a laxative for horses. On the other hand, feeding a wet mix is one way to increase water intake. Whether or not the inclusion of wheat bran in horse diets prevents colic remains unknown as controlled studies addressing this issue have not been done.

Another rationale for feeding a wheat bran mash is that it helps to boost overall fiber intake, and fiber is beneficial for hindgut health and function. The latter is likely true, but wheat bran is not a real stand-out in the fiber stakes. Oats actually contain more fiber than wheat bran. Feed more good-quality forage or other good-quality fiber sources such as beet pulp shreds, soy hulls, and dehydrated alfalfa if more fiber is needed in the ration.

It is also important to know that the high phosphorus content of bran can be harmful if not balanced with adequate calcium. Most of the phosphorus in bran is in the form of phytates, which can decrease calcium absorption. A weekly bran mash is okay, but excess feeding of wheat bran without attention to calcium nutrition can lead to calcium deficiency and bone problems ("bran disease" or "Big Head"). Calcium deficiency can cause calcium to be metabolized from bones (such as the face, leg, and rib) and give rise to Big Head, in which fibrous growths are responsible for swelling on the facial bones of affected horses as fibrin replaces the area where the bone becomes less dense as calcium is removed. The same problem can arise when feeding rice bran, although most manufacturers add a source of calcium to their rice bran products to ensure an appropriate calcium to phosphorus ratio (at least 1:1).

Bran mashes, when fed in moderation, probably do no harm, but at the same time are unlikely to provide a huge benefit to the horse as their nutritional value is pretty average. However, they're very palatable on the whole, so they might help with water intake in some circumstances. Those feeding a hot mash likely derive considerable satisfaction in providing a palatable meal. Chalk one up for the art of feeding.

Hold the Hay or Pasture?

Horses are sometimes fed complete feeds--those in which all components of the diet, including fiber or "roughage," are incorporated into the single feed. Typical feeding rates for these feeds are in the range of 1.5% of body weight per day, or 15-17 pounds for a 1,000-1,100-pound horse.

There are some circumstances in which the feeding of this type of diet is desirable. First, horses with poor dentition can have difficulty properly grinding forages, the end result being poor digestion and assimilation of the nutrients and energy contained within the forage, and ultimately weight loss. Worse, an inability to chew and digest fiber can lead to impaction colic. These problems are relatively common in old horses and have provided the strongest rationale for the so-called "senior" feeds. Most feeds of this genre are complete in the sense that they contain enough fiber such that when fed in recommended quantities, it is not necessary to feed other fiber sources such as forage (hay and/or pasture).

Complete feeds are sometimes fed to horses with chronic inflammatory airway disease such as heaves because this allows elimination of dry forages from the diet and therefore better control of dusts and other allergens in the horse's environment. For overweight horses, complete feeds with low energy densities can be a way to gain better control over daily DE (calorie) intake and assist with weight maintenance.

From a nutritional standpoint, a well-formulated complete feed is fine, and might be life-saving for geriatric horses with poor or non-existent teeth. However, there is scientific evidence that the health and welfare of horses can be compromised when there is severe restriction of access to long-stem fiber, such as that provided by hay or pasture. Restricted access to forage has been linked to development of stereotypic behavior patterns such as wood and tail chewing, cribbing, weaving, and stall-walking. There also might be increased risk for gastrointestinal problems such as gastric ulcers and impaction colic.

For example, housed horses that are fed a complete feed without supplemental forage will tend to eat more bedding, and the increased consumption of this indigestible material can lead to impaction.

This discussion plays nicely into the art vs. science of horse nutrition. Consideration of the horse's gastrointestinal physiology and "programmed" patterns of ingestive behavior is important in feeding management, particularly in regard to complete feeds. Horses evolved to consume forages, searching far and wide for palatable forages and consuming a variety of different species. Contrast that scenario with the lot of a modern horse kept in confinement for much--if not all--of the day and fed two square meals (usually spaced by about 10-12 hours). Horses can consume their daily ration of complete feed in not much more than two hours. With little else to do and no contact with other horses, the chances are he will be bored stiff, and this might lead to development of undesirable vices.

Several strategies can help avoid these problems and still allow the use of complete feeds. First, the ration can be split into smaller, more frequent meals. Horses are "trickle" feeders, and regardless of diet, it is better to provide small meals several times per day compared to two large meals. Second, turnout that allows exercise and contact with other horses helps alleviate boredom. Third, it is recommended that at least some long-stem hay be fed when a complete feed is the principal component of the diet, e.g., a half-pound per 100 pounds of body weight daily. This will help satisfy the horse's motivation to forage, alleviate boredom, and promote healthy gut function.

Energy Without the Electricity

A common question from horse owners is: "What can I feed my horse to help him gain (or maintain) weight in the face of increased work weight, but not make him ditzo?" Many wives' tales and perhaps some truths surround the area of diet and behavior. The crux of this issue is whether or not specific dietary constituents influence behavior. High protein is often blamed in reference to the unmanageable horse. Alternatively, too much grain or sugar takes it on the chin for causing horses to lose it mentally--recall the old-timers' thought that "corn (or oats) is a heating feed."

This is an area lacking in science, mostly due to the paltry number of well-designed studies undertaken to date. Nonetheless, there is some evidence that feed type can influence the behavior of horses, particularly in regard to the relative amounts of starch/sugar and fat in the diet.

You are probably familiar with the term "cool" energy, often used to describe feeds with more fat (and often more fiber from beet pulp and/or soy hulls) and less starch and sugar when compared to a straight grain or typical sweet feed. Concentrates of this type do appear to moderate excitability, although it is unclear whether this effect is specifically due to the increase in dietary fat or the decrease in starch and sugar.

Setting aside this academic question, current evidence does suggest that adjusting the amounts of these energy sources in the diet is one way to keep your horse's mind in check. However, there is likely to be large variation between horses--for some horses a change diet composition will have little or no effect on behavior.

Fat--Fad, Bad, or Fantastic?

We can quickly dismiss the first two parts of this question. The practice of adding fat (mostly vegetable-based) to horse rations has been around for more than two decades, and the overwhelming conclusion based on research data and clinical experience is that a higher-fat diet (relative to a hay/straight grain diet) is beneficial. Students of human nutrition might harbor some concerns about dietary fat, largely because of the human health concerns (obesity, increased risk of cardiovascular disease, and type II diabetes mellitus) associated with diets high in saturated fat (the fats in red meat and dairy products). That dogma is currently under challenge, but in any event, this issue is not relevant to equine nutrition. In fact, the opposite is true; rations with supplemental fat provide health and possibly athletic performance benefits to horses.

Here are a few examples. The condition of the skin, hair coat, and hooves improves with the addition of even small amounts of vegetable oil to the ration, e.g., one-quarter to one-half cup per day. For hard keeper horses, adding fat is a safe and effective way to increase the energy density of the ration and is preferable to feeding more grain and other starch-rich concentrates that might adversely affect health. There can be an increased risk of gastrointestinal problems when horses consume high-grain diets because some of the grain starch can pass undigested into the large intestine, undergo rapid fermentation, and disrupt microbial populations.

For horses genetically predisposed to chronic exertional rhabdomyolysis (tying-up), there is scientific evidence that diets lower in starch and sugar (less than 15% of DE from these energy sources) and higher in fat (more than 15-20% DE from fat) helps prevent further episodes of muscle damage, and it allows many of these horses to continue functioning as athletes.

Sugar Bashing--Is it Justified?

Recently, there has been considerable focus on insulin resistance in horses. Insulin resistance is a feature of Cushing's disease, the syndrome associated with a tumor of the pituitary gland or pituitary dysfunction. In addition, there is limited evidence that insulin resistance is a component of so-called equine metabolic syndrome, which is characterized by obesity and chronic mild to moderate laminitis. Indeed, there is some speculation that insulin resistance might underlie development of some forms of laminitis.

The hormone insulin drives the entry of glucose into the cells of insulin-sensitive tissues such as muscle and fat. Insulin resistance implies that these tissues have become less sensitive to the effects of insulin and the body becomes less able to deal with glucose entering the body from the digestive tract. This is where diet comes in. Meals high in starch and sugar result in large increases in blood glucose and insulin, and over time there might be exacerbation of insulin resistance and worsening of secondary effects, such as laminitis.

More research is needed in this area. So far, there is some evidence that diets rich in starch and sugar do lower insulin sensitivity, and there is rationale for reducing or eliminating starch/sugar from the diets of horses with documented insulin resistance. This last point is important, since only a very small proportion of the horse population is insulin-resistant and in need of these dietary changes.

Take-Home Message

Today's horse owner is faced with more choices in types of feeds, ingredients, and variety of mineral contents and levels than ever before. Getting the right levels into your horse with minimal problems is the art; knowing what to pick for the horse's proper nutrition is the science. Talk to your veterinarian or nutrition consultant to make sure you are walking the fine line between the art and science of equine nutrition.

PROTEIN: Think Quantity and Quality, Not Percentage

Horses require the amino acids contained in protein for a plethora of body functions, including tissue growth and repair. Some quick calculations and a little nutritional knowledge can allow to ballpark your horse's protein needs.

For example, a mature 1,100-pound horse at maintenance (no work function) that is consuming approximately 18 pounds (as fed) of feed per day needs about 1.6-1.7 pounds of crude protein per day. This is a little less than 10% of the total ration (18 pounds x 0.10 = 1.8 pounds).

Feeding 14 pounds of average-quality grass hay that is 8.5% crude protein will provide 1.19 pounds of protein (0.085 x 14 pounds). Supplementing this forage with 4 pounds of a concentrate that is 12% crude protein will deliver an additional 0.48 pounds (0.12 x 4).

Alternatively, a smaller quantity of a higher-protein, lower-energy supplement could be fed, e.g. 2 pounds/day of a supplement that is 25% crude protein. The latter often contains high-quality protein sources such as soybean meal, which is a rich source of essential amino acids such as lysine. The amount and protein content of the supplement needed will be different if a higher-protein forage (such as alfalfa) is fed.--Ray J. Geor, BVSc, BVSc, PhD, Dipl. ACVIM

About the Author

Ray Geor, BVSc, PhD, Dipl. ACVIM

Ray Geor, BVSc, PhD, Dipl. ACVIM, is professor and chairperson of Large Animal Clinical Sciences at the College of Veterinary Medicine at Michigan State University

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