You can't watch TV for more than half an hour these days without viewing at least one ad preaching the virtues of a balanced diet. Public service announcements emphasize the value of getting enough servings of fruits and vegetables. Cereal companies tout their boxes of sweet flakes and squares as "part of a balanced breakfast." Vitamin manufacturers target young and old for specially "balanced" nutrients. Achieving this balance of nutrients is the optimal way of ensuring that the human machine works as it ought to. The same can be said of your horse: If you want to encourage his growth, fuel his athletic performance, and support his health and well-being, you need to provide him with a balanced diet.
Accomplishing this task is a little more complicated than it might appear on the surface. Your horse's status as a herbivore makes his dietary choices somewhat more limited than for a human, but within the realm of forages (pasture grasses, hay, and/or other fiber sources) and concentrates (grains), there's still a daunting spectrum from which to select.
How do you choose what's most appropriate for your particular equine? How can you tell if his dietary needs are truly being met? Is there any danger in supplying far more of some nutrients than he needs?
You don't need to be a PhD nutritionist to answer these questions. It's true that you can wade deep into the murky world of dietary calculations, but fortunately, it's also possible to get a pretty good idea of the appropriateness of his feed without any convoluted math.
First, pay attention to your horse. He'll tell you if his diet is balanced by his shiny coat, good hoof growth, hearty appetite, healthy energy level, and pleasant attitude. If all of these qualities are in place and his body condition (weight) is appropriate for his size and build, then chances are good, but not guaranteed, that he's getting all the nutrients his body needs. However, sometimes looks can be deceiving. For example, a horse fed a low-calcium diet might develop bone problems before his appearance would indicate a calcium deficiency.
If your horse gets good-quality hay or pasture, his diet is probably reasonably well-balanced because horses are designed to function on the nutrients supplied in fibrous forages. That is the natural basis of their diets, so they generally shouldn't need exotic nutrients such as dairy products, kelp, or bee pollen (to name only three common supplement ingredients).
All told, there are about 40 nutrients your horse's diet should include--the appropriate amounts of energy, fiber, and protein, some 14 different vitamins and 15 minerals (some as macro-minerals, others in only tiny trace amounts), plus salt, fat (required only in tiny amounts, but often beneficial in larger quantities), and at least four amino acids that his body can't manufacture (lysine, methionine, tryptophan, and threonine). Although this sounds like a lot to keep track of, most normal equine diets supply the majority of these nutrients in more than adequate amounts.
Only a few of these nutrients need close monitoring--digestible energy (DE), protein, calcium, phosphorus, and selenium. (For young, growing horses, copper and zinc are two trace minerals that also need careful tracking, but they're generally present in forages in adequate amounts for adult horses.) Levels of the fat-soluble vitamins A, D, and E can be a concern for growing horses and those being used in high-performance sports, especially in the winter months when there's no access to growing forage. But B vitamins and vitamin C are manufactured in more-than-adequate amounts within the horse's system if he is fed a reasonable diet. However, if a horse is fed a poor diet, he might be lacking necessary vitamins, which could cause health problems.
Factors in Formulating
Before you proceed any further, you need to ask yourself a few simple questions about your horse:
In what stage of life is your horse? Do you have a growing foal, yearling, 2-year-old, adult, pregnant or nursing broodmare, or an older horse? The answer will have a major impact on the nutrients required.
What sort of work is he doing? Is your horse in light, medium, or intense work? Or is he basically a pasture potato? His energy needs, and the amount needed of some nutrients, will vary according to the demands placed on his body.
Is he carrying the correct amount of weight, or would you like to see him thinner or fatter? As a rule of thumb, a horse in "good flesh" should have ribs that are not visible to the eye, but can be felt under the coat when you apply light pressure with your hand.
Next, calculate your horse's body weight. The easiest way to do this is with a heart-girth weight tape, available for a few dollars from your feed dealer. A weight tape should deliver a ballpark number within a hundred pounds of your horse's true weight.
If you seek a more precise idea of his body mass, measure your horse's heart-girth (the circumference of the barrel, just behind the elbows), and the length from the point of his shoulder to the point of his hip, both in inches. Multiply the heart-girth measurement by itself, multiply that figure by his length, and divide the total by 330 to get his weight in pounds. (This formula will work for all light breeds of horses except foals under six months of age and pregnant mares.)
Third, estimate how much total feed your horse needs in a day. The total weight of his rations should be between 1.5% and 3.0% of his body weight--so if, for example, your horse weighs 1,000 pounds, he'll require between 15 and 30 pounds (6.8-13.5 kg) of feed on a daily basis. If he's on the thin side and you'd like to put some more weight on his frame, or if he's in hard work as, say, a ranch horse, you would lean towards the 30 pounds end of the spectrum. If he's an easy keeper who's barely being ridden and has developed dimples in his rump and ripples of flesh along his barrel, you would feed him not much more than 15 pounds of total feed per day.
Now, calculate how much of his total ration each day is hay, and how much is grain. A great many adult pleasure horses function very well on forage alone. But if your hypothetical horse is a high-goal polo pony or an event horse exerting himself to the maximum on a regular basis, he might need the concentrated calories of grain to help him maintain weight and have enough energy to meet his performance demands. At most, though, he should consume only half of his daily ration (by weight) in the form of grain.
The equine digestive system is optimally designed to process forage. Therefore, if you provide your horse with too much grain and not enough fiber, his system can overload, resulting in colic, gastric ulcers, or laminitis.
Let's say your Quarter Horse is an amateur-owner hunter mare which is eight years old, in good flesh, seems happy in her work, and is not currently in foal. She's currently receiving 15 pounds of mixed alfalfa/grass hay, and five pounds of commercial sweet feed per day. Is this diet going to meet all her nutritional needs?
Breaking it Down
The first consideration in analyzing any equine diet is energy. Does the ration in question supply enough calories for your horse to do the work you ask of her, and still keep her in good flesh?
Despite the importance of this question, it's a difficult one to answer in quantifiable terms. Although commercial feeds come with labels that outline their fiber, fat, protein, vitamin, and mineral content, their digestible energy (DE) is almost never stated. So, we have to generalize a bit.
Established wisdom from the National Research Council's Nutrient Requirements for Horses (online at www.nap.edu/books/ 0309039894/html/index.html) tells us that adult horses need .03 Mcal/kg (Megacalories/kg, 1 Mcal=1,000 kcal) of body weight for maintenance metabolism, between 2.5 and 2.9 Mcal/kg if they are working or being used for breeding, and 2.2 Mcal/kg if they are older.
Furthermore, we can generalize that most legume hays deliver between 2.2 and 2.4 Mcal/kg of digestible energy, grass hays range from 1.5 to 2.2 Mcal/kg, and most cereal grains (oats, barley, and corn, for example) contain between 3.3 and 3.7 Mcal/kg.
So, if your Quarter Horse mare is receiving an average-quality mixed hay, she's probably getting somewhere in the range of 2.0 to 2.2 Mcal/kg of digestible energy from the hay, and perhaps 3.5 Mcal/kg of digestible energy from her grain.
There are roughly 2.2 pounds in a kilogram. So, if you like, you can di tge calculations and estimate whether your mare's energy needs are being met. Considering that three-quarters of her daily intake is hay, and one-quarter is grain, chances are she's okay for the amount of work she's doing. But without a laboratory analysis of her hay and grain to generate their actual digestible energy content, it's guesswork to some extent.
Fortunately, while energy might be tricky to quantify, it's easy to assess on a gut instinct level. To really answer the question of whether your mare is receiving an appropriate amount of energy from her diet, assess her attitude and her performance. Is she maintaining a healthy body weight? Does she have enough energy to do all you ask of her in a schooling session or a weekend horse show?
If your mare's "oomph" flags before the end of her course of nine fences, or if the pounds are melting off her, chances are her energy intake is inadequate. You can increase the amount of energy in her diet by cutting back a little on the hay and providing her with more grain, preferably broken up into several small meals rather than one large extra helping. Or you can supplement her diet with a fat source, such as rice bran or corn oil. Fat supplies more concentrated energy pound for pound than the carbohydrates in grain, but it must be fed at a fairly low level (most nutritionists suggest between 6-10% of the total diet for a performance-enhancing effect).
If, on the other hand, your mare is bouncing off the walls, needs to be longed for three hours before you can safely get on her, or is blimping out before your very eyes, her total caloric intake needs to be cut back (and her exercise level increased). For such a horse, you should reduce or eliminate the grain portion of her diet, and perhaps cut back her total ration to 15 pounds of feed a day rather than 20 pounds. Supplementing fat for this horse would not be a good idea.
Protein is the next nutrient you need to assess, with the caveat that actual protein deficiencies are extremely rare in adult horses. Their crude protein requirement is so low (between 8-11% of the total diet) that even most straight grass hays, which average 6-10% protein, can meet it easily.
Protein provides the building blocks for growth and repair of body tissues, so it's needed in larger amounts by young, growing animals and gestating or lactating broodmares, but even their needs can usually be met by a good mixed hay with some legume content (alfalfa and clover generally contain between 15-24% protein). If you choose to feed grain to your horse, realize that the primary purpose for doing so is not to help meet his protein requirement; your hay is probably doing that already.
Although not all of the crude protein delivered by hay and grain is digestible--some of it passes through the horse unprocessed--you can still get a pretty good estimate of whether your horse is getting an appropriate amount of protein from her diet by getting an analysis done on your hay supply (or on your pasture, if your mare's fiber content comes exclusively from grazing), and choosing a grain ration to complement it. For example, if your 8-year-old, non-pregnant mare is eating 15 pounds of mixed hay with a crude protein content of 14.5%, and five pounds of commercial sweet feed with a crude protein of 12%, her overall daily protein intake is about 13.875%--more than adequate for her needs.
Calcium and phosphorus can be evaluated in much the same way. These two minerals, critical to the maintenance of strong bones and muscles, need to be in balance with each other, with at least as much calcium as phosphorus in the system, never the other way around. An adult horse's requirement for both is fairly small--only about 0.25-0.3% of the total diet for calcium, and 0.2-0.25% for phosphorus.
Most hays (especially legumes) supply good amounts of calcium and relatively little phosphorus, so it's particularly important to get a hay analysis done if your horse is not getting any grain in his daily diet. If the analysis tells you your hay contains at least 0.2% phosphorus, you're okay; if not, you might want to supplement this mineral. (To calculate exactly how much extra phosphorus to feed, consult with your feed dealer or agricultural extension specialist; the amount will vary depending on the supplement you use and the nutritional breakdown of your hay.)
If your horse is receiving hay and grain, chances are her calcium:phosphorus ratio is fine, because grains contain more phosphorus than calcium. To be sure, compare the numbers, and make sure that there is at least 0.2% phosphorus overall and 0.2% or more of calcium. For young horses, you might want to supplement both of these minerals to support healthy bone growth.
As for selenium, your horse's need for this important trace mineral will vary depending on where you live. In many parts of North America, soils are extremely selenium-deficient, so selenium must be supplemented in commercial feeds. There are a few areas where the soils are so high in selenium that they are toxic! In such places, feeding supplemental selenium could trigger a number of adverse effects in your horse, including colic, diarrhea, hair loss, and separation of the hooves from the coronary band.
Before you supplement this mineral, find out what the selenium situation is in local soils. As a rule of thumb, horses should receive no more than 0.3 parts per million of selenium in their daily diets. So, even if your local soils are selenium deficient, don't feed extra selenium if your grain already has this mineral added to it.
Fresh or dried forage is the most natural source of vitamins A, D, and E for your horse. You should keep in mind, however, that vitamins break down over time. In baled hay, the vitamin content gradually decreases until, a year after it was first placed in storage, there's no appreciable quantity of vitamins left. To ensure that your horse gets all his vitamins, feed the best-quality hay you can find (not over-mature), and never depend on hay that's more than a year old to supply his nutritional needs. If your hay is less than ideal, feeding a general vitamin-mineral supplement is a good idea; fortunately, most of these nutrients have a very high toxicity threshold, so you can safely feed somewhat more than he needs without any ill effects.
Likewise, if you're feeding young horses, you might want to supplement not only calcium and phosphorus, but also copper and zinc, which have been shown to improve bone growth. The simplest way to do this is to choose a grain ration formulated for young, growing stock, and feed it in the recommended amounts. You can opt to top-dress a supplement to boost the regular ration you're feeding instead.
A lot of nutritional guesswork can be eliminated if you choose a good-quality commercial grain ration for your horse. Regardless of whether it is a sweet feed, pelleted, or extruded formulation, it will have been designed to more than adequately supply the nutrients your horse needs when fed as directed.
Be aware that the word "complete" can be interpreted several ways. For some feed manufacturers, a "complete feed" is one which supplies both a horse's daily concentrate and vitamin/mineral needs, and his fiber requirement as well (i.e., you don't have to give the horse anything else except this feed). For other companies, a "complete feed" is simply one that contains grains and a spectrum of required vitamins and minerals. The latter type will not replace your horse's need for hay and/or pasture. If you're not sure which type you're looking at, consult your feed dealer.
When choosing a grain ration, steer away from the cheapest formulations; they are often based on a "least-cost" recipe, and their nutritional content will fluctuate with the grain markets. Instead, insist on a "fixed formula" feed, which contains exactly the same nutrition in every bag. The price of such feeds might be somewhat more, but the peace of mind and the health of your horse are well worth it.
In the vast majority of situations, the combination of a good-quality grass or mixed hay, plus a scientifically designed, fixed-formula feed for your type of horse will ensure that he's getting a balanced diet. That will free you from spending hours with your calculator trying to create the "perfect" feed. After all, it's nice when you can achieve some balance in your life, too.
About the Author
Karen Briggs is the author of six books, including the recently updated Understanding Equine Nutrition as well as Understanding The Pony, both published by Eclipse Press. She's written a few thousand articles on subjects ranging from guttural pouch infections to how to compost your manure. She is also a Canadian certified riding coach, an equine nutritionist, and works in media relations for the harness racing industry. She lives with her band of off-the-track Thoroughbreds on a farm near Guelph, Ontario, and dabbles in eventing.
POLL: University Equine Hospitals