Horse people are an opinionated lot. Racing settles these differences on the track, as everyone believes they have the fleetest horse. But visit any feed mill and you will find that, in spite of the wide variety of commercially prepared feeds (as well as the mill's own feeds), many managers and owners like to use their own "custom" mix. A little more biotin for the weanlings, a little less corn for the mares. These personal formulas usually are based on an older mentor's recipes and then modified in response to new ideas and the farm's location and soils, tempered with what worked in the past. But fed by the right hands, either commercial feed or custom mix will produce a good horse.
As any reader of horse publications is aware, each issue contains numerous advertisements for a host of feeds and supplements that make a wide variety of claims. Just as in human nutrition, some of these products are very useful under the proper circumstances, while others will do no harm other than significantly raise the value of the horse's urine. But some supplements can, if used improperly or in conjunction with other supplements, actually degrade performance or potentially harm the horse.
But how can the average owner learn to sift through these products, short of earning a degree in equine nutrition? While personal education is an ongoing process with no set endpoint, an understanding of the nutritional requirements of the horse, as well as how these requirements were arrived at, can help an owner begin to make more informed choices at the feed mill.

All flesh is grass
Humans have been aware since antiquity that the food chain begins with plants. But it is only with the advent of microbiology that the full story of how herbivores utilize the stored energy of pasture that is unavailable to humans. As Major Sean O'Grady recently learned, while a diet of grass (and the odd ant) may fill the stomach, it lacks sufficient nutrients for even a sedentary man waiting for the Marines to arrive.
To take advantage of pasture plants, horses, after a fashion, have developed into mobile breweries. Unlike ruminants (such as sheep and cows), the equine fermentation tank is simple. In the normal horse, a variety of bacteria and yeast have taken up happy residence in the horse's hindgut (colon and cecum) and are content in that warm and steady environment. Anyone who has spent an afternoon watching horses will remember that they spend the majority of their time eating. In fact, this continuous grazing is perfectly suited to providing the beneficial bugs with a constant source of fermentable fiber.
In man-made breweries, yeast are cosseted in vast tanks and the temperature, pH, and food sources are carefully controlled. And for our trouble, the yeast ferment hops and malt. More simply put, yeast consume the simple sugars in the tank and excrete alcohol. (This has never been pursued in the advertising; thus no "Made from only the finest yeast excreta.")
In the hindgut, the various species of bacteria excrete a potpourri of volatile fatty acids (VFAs) similar (though not inebriating) to alcohol. Both alcohol and VFAs are relatively energy dense and easily absorbed by the intestine. As anyone nearing middle age can attest, it does not take very many beers to achieve that lovely "body by Budweiser" look. It is also why horses can grow fat on pasture that would only gag us and send us running off to an ant hill for sustenance.

So what?
There is significance to all this, beyond "Alex, I'd like Hindgut Digesters for $200, please." Because every time the horse is removed from the pasture where it is allowed to graze continuously, it is his life that is in Double Jeopardy. Colic, laminitis, chronic ulcers, developmental orthopedic disease, and a host of other maladies are essentially man-made problems that result from paying insufficient attention to the grazing heritage of the horse.
This is not to advocate that all horses should be returned to pastures and left alone. Our relationship with the horse is now based on either altering their diet and exercise to sculpt a desirable appearing animal (as with halter horses and sales yearlings), or altering the same parameters to effectively turn a sedentary grazer into a high-performance vehicle for unusually short men and women. It can be done, and usually without harm to the horse, but the key is to always keep the health and happiness of the microbes in mind.
Once the horse is removed from its natural setting and we begin to make our various demands on its behavior, we have assumed stewardship of its life. But how do you supply the energy that our new performance objectives demands, while at the same time restricting intake of the primary and natural source of food, pasture? These questions were discovered through trial and error when horses were first domesticated. Early on, energy-dense cereal grains were found to be, if fed in small, well-spaced meals, an excellent way to supply sufficient firepower to the working horse. But it was not until the disciplines of chemistry and physiology became increasing scientific in the late 19th century that the horse's requirements for protein, calcium, phosphorus, and a host of other nutrients began to be explored.

Of Limeys and big heads
Human nutrition was advanced largely as the result of severe maladies, such as "scurvy," being studied, and their cause found to be deficiencies in the diet. In the case of scurvy, bleeding gums and prostration were relieved when fresh citrus fruits were added to the diet of English sailors (hence the term "limeys"). Vitamin C was later found to be the necessary nutrient, and threshold levels for health could be inferred.
Equine nutrition has been marked by similar discoveries. The horses of feed mill operators were found to develop bony malformations, particularly of the head, which became large although the bone itself was brittle. This "miller's" or "big head" disease was found to result only when the horses were fed rations very high in bran, a byproduct of the milling process when white flour is produced. Later investigation revealed that bran was high in phosphorus, and that this condition will be evident in horses if their ration has more available phosphorus than calcium. With refinement, a proper calcium/phosphorus ratio was established, again as a result of a pathology first noted due to aberrant feeding protocol.

Performance by the pound
The National Research Council (NRC) was established to coordinate data for all domesticated species and determine requirements of important nutrients. However, horses differ from other domesticated species in one significant way. In all the other species, farmers are interested in how quickly and efficiently these animals turn one pound of feed into one pound of chicken or cow. With all horses not destined for the tables of France, these criteria are not important; performance is.
It is relatively easy to monitor weight gain per pound of feed. You feed an animal for a given period of time, weigh it daily, and chart the growth. Once a breed of chickens conversion of feed to meat is established, you can begin to alter other components in the diet and see how the conversion rate is affected. This new research can then be used to propose new recommendations.
But what do you do in the case of horses? Once you get beyond the maladies caused by gross deficiencies, excesses, or imbalances of certain nutrients, the fine tuning that has occurred in other domestic species becomes more elusive. So many other variables influence performance-training, breeding, environment, and injury, for example-that isolating the significance of a given nutrient becomes much more difficult.

Applied research
Economics drives all research, and horses are particularly expensive to house and study, compared to a chicken or cow. While increasing feed conversion has a direct economic benefit to the farmer who underwrites the research, nutritional improvement of performance is difficult to study and hard to capitalize on. As a result, almost all of the requirements in the NRC are based on trials done on draft animals, mules, and ponies in the early part of this century.
"If this is so," you may be thinking, "then what about the various claims made for a whole host of supplements?" The answer to this is twofold. First, nutrition and its effect on performance has been studied extensively in one species, human beings. Many of the products and performance-enhancing foods (such as carbo-loading, milkshakes, and the like) have been imported from human exercise physiology research and no small amount of conjecture. Between the Olympics and intercollegiate sports, a tremendous amount of research has been done on all aspects of human physiology, including the effect of various nutrients on performance. But there is a tremendous difference in how the two species react to training, much less nutrients. Hundreds of years of selective breeding has produced a unique animal in the racehorse. Imagine if all humans were Chris Everts or Michael Jordans. And it is not wise to simply infer that what works in people will work in horses.
The other factor that tends to lead to product exaggeration by some is the fact that few manufacturers are asked to verify their claims by any governmental body. In the few instances where they are brought to task, the instigator of the investigation is often a competitor seeking to tone down their rival's claims. Neither the Federal Drug Administration nor the United States Department of Agriculture seem too concerned if horse owners use their discretionary income to purchase powdered bat wings, if the owner feels better about themselves after feeding powdered bat wings.

A better way
There are many feed and supplement manufacturers that have taken the time and considerable expense to actually field-test or otherwise determine through legitimate experimental means the validity of their product. The advent of high-speed treadmills (HST) capable of traveling at near racing speeds (while the horse is attached to a variety of scientific monitoring devices) has greatly enhanced the prospects of evaluating the efficacy of nutritional supplements on performance.
Attempting to measure what effect (positive, negative, or neutral) on performance of a given additive was extremely difficult before the high-speed treadmill. Riders found it difficult to work horses at the same speeds on different days. Between tests it was hard to achieve the identical training regimens necessary to ensure that no other factor beside the supplement had an effect. But with an HST, speed, distance, and intensity of workout can be precisely recorded and replicated each time. In addition, measurements of important parameters, such as heart rate, blood chemistries, and temperature, are all greatly facilitated by the horse running in one place within arm's length of the researchers. Finally, the good footing offered by the belt of the treadmill greatly reduces the chance of injury, which not only is safer for the horse, but yields more consistent and meaningful data.

What to do?
There is currently no Consumer Reports that owners can turn to help them evaluate the claims of feed supplements and other performance enhancers. As always, sophisticated advertising will often lead to erroneous conclusions if the buyer does not beware. The key to being a wise consumer is to ask the sales representative of a given product to back up his claims with actual research. If he replies that the research has been done "at a highly respected university," ask to see the resultant paper. If he does produce research, you may not feel competent to evaluate the merits of either the facility where it was performed or how the trial was conducted. But your veterinarian will, and most practitioners will gladly look at such a paper and offer an opinion on its merits. How many horses were in the trial? (The one-horse experiment is not considered valid in the real world.) What was the intent of the trial? Is this the same as those purported by the salesman? Is the conclusion similar to the salesman's or advertised claims? Where was the trial conducted? (Beware of obscure institutions in the former Soviet Union.) Looking for satisfactory answers to these questions will not only help make this a better informed purchase, but will also help spur the entire industry to higher standards.