Feed Your Horse a Balanced Diet

Determining whether your horse is getting the right nutrients doesn't need to be complicated.

Your horse doesn’t seem as sharp as he did a few months ago, and his coat is losing its glow. Does he need a supplement? Should you change his feed?

Get an accurate picture of what your horse is eating every day by weighing his feed. | ? Stacey Nedrow-Wigmore

Before you can answer those questions, you need to answer two others: First, does he have a health problem? Second, is his diet balanced? The first one is easy?just call your veterinarian and schedule a visit for a complete checkup. But determining if your horse’s current rations provide the right amounts of the nutrients he needs may seem daunting. You’ll find reams of nutritional information in books and online, much of it highly detailed. The numerical data and technical jargon can deep-fry your mind.

The process doesn’t need to be complicated, says Sarah Ralston, VMD, associate director of the Rutgers Equine Science Center and a specialist in equine nutrition. You won’t even need higher math skills. In this article, you’ll find out how to balance your horse’s diet using some simple tools. Want instant gratification? See “Cut to the Chase” below for shortcuts.

What Does He Need?
All horses need the same essential nutrients?energy to fuel body functions, protein to build and repair body tissues and produce enzymes and hormones, and certain vitamins and minerals?but the amounts required by individual horses vary. To figure out if your horse is getting what he should from his diet, start with basic information about him:

Weight: Feed recommendations are generally based on amounts per pound or per kilogram of mature body weight, so this is essential information. A livestock scale will tell you your horse’s precise current weight, but a careful estimate with a weight tape (easily obtained from feed stores) will be fine.

If your horse is underweight or overweight, base his feeding program on optimum weight rather than current weight, Dr. Ralston says. A body-condition scoring system (such as the Henneke scale, online at www.equisearch.com and other websites) can help you decide if you should go with his current weight. Check the table of typical weight and height ranges for various breeds at www.equi-analytical.com (the website of Equi-Analytical Laboratories, which does hay and feed analyses) for an idea of normal weight for horses of his breed and body type.

Age: Horses have different needs at different stages in life. Young horses need extra energy, protein and the right amounts of minerals, such as calcium and phosphorus for bone and tissue development. Broodmares’ nutritional requirements jump during late pregnancy and lactation. Senior horses may develop metabolic problems that call for changes in diet.

Work level: Work increases energy needs. The increase isn’t very great for horses in light to moderate work (five hours a week or less), but a horse in very heavy work (upper-level eventing, racing, endurance) may need twice as many calories as a horse who just loafs in the pasture. Sweat losses associated with hard work dramatically increase the need for water and salt, too.

What’s He Eating?
You’ll also need accurate information about what and how much your horse eats every day, by weight (not volume). Get the big picture?not just his grain, but his hay, pasture and supplements as well. If you board him, you may have only a vague idea, so ask the barn manager about the kinds and amounts of hay and grain he gets. If you’re in charge of feeding, you know what you’re giving him, but weigh everything (including typical flakes of the hay you feed) to be sure of the amounts. If he leaves grain or hay uneaten, weigh and subtract the wasted amounts, if possible, to calculate how much he actually consumes.

An adult horse in moderate work typically consumes about 2 to 2.5 percent of his body weight in dry feeds, such as hay and processed grain, a day. For a 1,000-pound horse, that means about 20 to 25 pounds. Individual needs vary, though. An easy keeper or a horse who’s not in work may do with 1.5 percent total intake, while intense training may increase the intake to as much as 3 percent of body weight.

The information you collect will let you see how much of his diet each component makes up. Forage?pasture grass, hay (grass or legume) or hay substitutes?should make up the lion’s share, if not the total amount, with free access to salt and water. The horse’s digestive system is designed to process it, and the fiber in forage isn’t just bulk. Beneficial bacteria in your horse’s gut ferment it, producing fatty acids that he can use for energy. As a general rule, the more he meets his nutritional needs with forage, as opposed to grain, the better off he’ll be. If hay makes up less than half of his daily ration or less than 1.5 percent of his body weight, you’re inviting impaction colic and other serious problems.

Pasture can provide excellent nutrition. It’s especially nutritious in spring and fall when grasses are either growing rapidly or storing energy for the long winter months. Grass is also high in water so it helps maintain gut function and hydration, and grazing is good for your horse?he moves around and thoroughly enjoys munching. But you need acreage to maintain horses on pasture grasses alone, even in summer. In most of the East, one-and-a-half to two acres per horse will get you by from spring through fall if the horses are not working hard. “Subdividing pastures into sections and rotating their use will keep the nutrient quality up and allow optimal use of minimal acreage,” says Dr. Ralston. “But in the arid Southwest, where grass is sparse, even rotational grazing won’t maintain a horse on less than five to ten acres.”

It’s hard to estimate how much a horse eats at pasture (you can’t count and measure every bite of grass), but Equi-Analytical’s website outlines a way: Calculate his total daily dry-matter need (more on this in the next section), subtract the amount he’s getting from hay and grain and assume?provided he’s maintaining good weight?that he’s getting the rest from pasture. Given the opportunity, horses will consistently eat at least 2 to 2.5 percent of their body weight a day, without regard to nutrient content. “That’s why so many horses will get fat with free-choice access to lush pasture or high-quality hay,” Dr. Ralston says.

What about grain and other processed concentrates? They can provide extra energy, protein, minerals and vitamins, but they’re not necessary in every situation. “Horses have survived for centuries on forages, plain salt blocks and water, with grain added for extra energy only if needed,” Dr. Ralston points out.

Check the Guidelines
With information on your horse and his current diet, you can figure out if he’s getting the basic nutrients he needs. The National Research Council’s Nutrient Requirements of Horses, last revised in 2007, is the standard. It has tables for horses at various weights, ages and work levels, setting out the average needs for

  • dry-matter intake (DMI)?the amount of feed your horse needs minus the moisture content. The nutrients are all in the dry matter. Hay and grain are typically 10 percent moisture, so a horse who consumes 22 pounds of those feeds has a dry-matter intake of 20 pounds. Pasture grass is typically around 75 percent moisture, so he needs to eat more of it?about 80 pounds of grass to get the same dry matter he’d get from 22 pounds of hay and grain.
  • digestible energy (DE)?the energy he needs from feed, with amounts in megacalories. (One megacalorie equals 1,000 nutritional calories.) Energy needs are highest for horses in intense work and for lactating mares.
  • crude protein?the total protein required, in grams. Lactating mares have the highest needs.
  • lysine?an essential amino acid needed for growth and muscle repair. (Proteins are made up of chains of amino acids; essential amino acids must be provided in the diet.) “This is of high importance only in young, rapidly growing horses,” Dr. Ralston says.
  • calcium and phosphorus?important macrominerals. The total ration must provide them not only in adequate amounts but also in the right ratio: between 1.2 and 1.8 parts calcium to 1 part phosphorus.
  • sodium, chloride (together, those are table salt), potassium, magnesium and sulfur and other macrominerals essential for body processes.
  • trace minerals?cobalt, copper, iodine, iron, manganese, zinc, selenium?needed in very small amounts. Some of these (such as copper and zinc) are especially important for growing horses and pregnant mares.
  • vitamins A, D, E, thiamin and riboflavin.

“The NRC guidelines represent our best estimates, but realize that they aren’t law and that there is wiggle room,” Dr. Ralston says. The full guidelines (available through the National Academy Press) provide much more information than most horse owners need, she adds. “It is not necessary to balance rations to the nearest one percent for all known nutrients. If you make sure needs for energy, protein and some macrominerals [calcium , phosphorus, sodium, chloride] are met, the rest will usually be OK,” she says.

What about vitamins and minerals not listed in the guidelines? “If the nutrients are not listed, it is because the requirements are not known and signs of deficiency have not been documented in horses,” Dr. Ralston says. This means that if there are physiologic requirements, they are met by standard rations. “Indeed, for some of the nutrients listed, such as sulfur and magnesium, true deficits have never been documented in horses on normal rations,” she adds, “so it is not necessary to worry about balancing them with supplements.”

Other tables show the typical nutrient contents of different forages and feed grains, such as oats and corn. (The amounts and percentages are all figured on a dry-matter basis.) You can look up grass hay, for example, and find that on average it provides up to 0.9 megacalories per pound, contains 9 percent protein and a good balance of calcium and phosphorus, and meets your horse’s needs for other macrominerals with the exception of sodium.

Are the averages good enough to go by? Grains don’t vary much in nutrient content from batch to batch, so averages are fine. Hay’s nutritional content can vary more widely, and a lab analysis is the only way to know for certain what’s in it. Still, as long as you are feeding good-quality hay, you can use averages in most circumstances, Dr. Ralston says. “Have it analyzed if you are concerned about quality, for example, when a drought affects the availability of good hay” or if you are feeding horses with special needs (pregnancy and growth, metabolic problems and so on). Extension offices can help you get this done, and it usually costs less than $50. If you buy hay in small lots and analysis isn’t practical, ask your suppliers if they have had it analyzed. Or check with your Extension office for information on the nutrient content of hays grown in your region. (Find your local Extension office at www.csrees.usda.gov/Extension/.)

Correct the Balance
Once you add up the amounts of important nutrients in your horse’s diet, you can compare the totals to his needs to see if his diet is balanced. The process may end up saving you money, especially if he’s getting supplements, because you may be giving him more of certain vitamins and minerals than he needs. This isn’t just a waste of your money?it can be harmful. “Suppose your horse is getting quality hay, a commercial feed mix, a coat supplement and a multivitamin supplement. All these may have vitamin A, and when you add them together he may be getting toxic levels,” Dr. Ralston says.

Here are a few other situations that may call for adjustments:

His work level increases. More work means he needs more energy, but don’t worry if his rations provide a bit less energy than the average in a table, Dr. Ralston says. “Let his condition tell you. If his coat shines and he has energy for the work you ask him to do, he’s getting what he needs.” If he’s sluggish or losing weight or condition, get a health check and, if he checks out OK, add calories?if possible in the form of better-quality forage.

  • If good grass is available, increase his grazing time. It’ll be good for his brain, too.
  • Grains are packed with carbohydrates, which provide fuel for bursts of intense activity. There are limits to how much grain a horse can handle, though. Heavy loads of carbs in the digestive tract can trigger laminitis, colic and other health threats. Divide your horse’s grain into as many small feedings as you can?at least two and preferably three. “Do not offer more than half of one percent of his body weight in grain-based feed in a single meal. For a one-thousand-pound horse that would be five pounds maximum,” Dr. Ralston says. “If he needs more than ten pounds of grain-based feed a day [which would be highly unusual], three feedings are a must.”
  • Fat provides twice as much energy ounce for ounce as carbohydrates; research suggests it’s an especially valuable fuel for sports that call for stamina, like endurance. (It’s also a good energy substitute for the minority of horses who can’t tolerate carbohydrates.) Rice bran, vegetable oil and commercial high-fat feeds are good sources.

Exercise doesn’t change the need for protein or most other nutrients in the ration. “He needs more energy, so he consumes more food, which increases his intake of all nutrients as well as calories,” Dr. Ralston says. One exception to this rule is salt: If he sweats heavily, he needs more plain salt (preferably free choice) and water. But the percent of protein in the diet doesn’t need to change, says Dr. Ralston. Excess protein is broken down by the body and stored as fat, and the byproducts are excreted. A horse who consumes more protein than he needs may drink more water and urinate more to get rid of the byproducts, producing ammonia fumes and a mess.

He’s a top competitor. Elite athletes?horses training and competing at top levels in any sport and regularly shipped to competitions?are under stress. Besides increased energy, they may need additional antioxidants (vitamins E and C) and electrolyte replacement, Dr. Ralston says. Electrolytes are minerals (mainly sodium, chloride, potassium, calcium and magnesium) dissolved in your horse’s body fluids, and they’re essential for body function and muscle activity. They’re lost in large quantities when he sweats. Most horses get enough of these minerals in their diets and don’t need a supplement other than free access to a salt block, even in warm weather. Elite athletes are the exception.

He’s too fat. You may have read that obesity is linked to laminitis, but not every obese horse will founder. “Don’t panic if your horse is overweight,” Dr. Ralston says. “There are genetic and metabolic factors in laminitis.” Don’t starve the weight off, she adds. A drastic reduction in feed intake can lead to digestive problems.

To help him shape up:

  • cut out grain. If you are worried that he’ll be short on vitamins and minerals, give him a single vitamin-mineral supplement balanced to complement his hay.
  • give him enough hay to supply about 75 percent of the energy required for his ideal weight. Divide it into three or four meals spaced throughout the day to keep his digestive system running smoothly, satisfy his need to chew and relieve boredom. If you give him all his hay in the morning, he’ll finish it quickly and likely start chewing the barn.
  • try a grazing muzzle to reduce intake while on pasture. Research suggests that limiting grazing time works less well?horses just eat faster while they can.
  • increase his exercise.

He’s a senior. Horses’ nutritional needs may change as they age. The changes may be different for different horses, but they often mean that forage alone won’t be enough, even for a retiree.

  • Your horse may develop dental problems that make it hard for him to chew his hay. Look to substitutes like chopped hay, hay-replacer pellets and complete feeds that include forage.
  • He may digest food less well so he doesn’t absorb all the nutrients it contains. You’ll see him begin to drop weight. Try him on a commercial senior feed that’s complete or balanced to complement his hay. These feeds are processed in ways that make them easy to digest.
  • He may develop metabolic problems that cause him to put on weight and put him at risk for laminitis and other health problems. You may need to limit his grazing and keep him on a low-carb diet with special feed and steamed or soaked hay. Your veterinarian can help you identify and manage these problems.

If your evaluation suggests you need to make changes in the kind or amount of feed your horse gets, do so gradually. That gives the microbes in his gut a chance to adjust to the change and reduces the chance of digestive trouble. A hay switch isn’t as big a change as a new concentrate. As a general yardstick, change hay over three to four days, change or increase grain over five days to a week, and take up to two weeks to add large amounts of new fat sources such as vegetable oil and rice bran.

Sarah L. Ralston, VMD, PhD, DACVN, is an associate professor in the Department of Animal Sciences at Rutgers’ School of Environmental and Biological Sciences, specializing in equine nutrition. She is also Associate Director-Teaching of the Rutgers Equine Science Center.

This article originally appeared in the October 2012 issue of Practical Horseman magazine.

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