Designing Your Horse's Diet

A step-by-step approach to ration-balancing

To some, listening to fingernails on a chalkboard sounds more pleasing than sitting down to balance a horse’s diet. But it’s an important part of horse ownership. The National Research Council’s (NRC) Committee on Nutrient Requirements for Horses (who authored a document of the same name in 2007), states that the goal of any equine diet is to “provide nutrients that efficiently maintain a horse’s body and well-being and support functions related to growth, production, and work.” The committee advises the government on the nutrients required by all equids.

Whether building a plan for feeding a new horse or troubleshooting a current horse’s diet to see what could be missing, ration evaluation is key to health and performance. With the NRC’s requirements as our guide, we’ll take on ration-­balancing one step at a time. So embrace your inner mathematician, and let’s get started.

Step 1. The Steed Deets

First things first: Gather information about the equid you’re feeding. The NRC publishes tables of data (available here: listing daily requirements for energy, protein, vitamins, and minerals based on a horse’s weight and physiological class (think growing, pregnant, lactating, or performance). But creating a balanced diet depends on more than just science. There’s an art form to feeding horses—the “equine factor” will play an influential role and must be considered on a case-by-case basis, including:

A successfully balanced diet must also take into account factors such as feed palatability (Does the horse prefer sweet feed over pelleted?), mealtime behavior (Does he bolt feed?), and management practices (How many meals does he get per day?).

Keep the appropriate NRC tables of nutrient requirements for your horse on hand as you evaluate his diet.

Step 2. The Feed Deets

We all know our horses need forage to keep their complex digestive systems working properly. Although researchers have yet to establish an official “forage requirement” for horses, we know to use this feedstuff to provide most of the nutrients in the diet to reduce the horse’s risk of developing hindgut acidosis (increased acidity in the large intestine that alters its natural population of microorganisms), colic, and gastric ulcers. Because forage makes up the largest part of the diet, it can have the biggest influence on overall nutrient balance. If you can accurately assess the energy, protein, vitamins, and minerals your horse’s forage provides, you’ll understand what gaps, if any, you need to fill with supplemental feed.

With conserved forage, better known as hay, a quick visual inspection can give you some idea of quality, but this isn’t an accurate way to estimate its ­nutrients.

“The only way to really know the nutrient value of the hay is to test it,” says Sarah Fessenden, PAS, business ­development manager for Equi-Analytical Labs, a subsidiary of Dairy One, in Ithaca, New York. Taking a representative hay sample is fairly easy. “To pull a sample, we recommend using a hay probe (a long, hollow metal cylinder with a sharp tip that you can either drive or twist by hand or with an electric drill into a bale of hay),” she says. “We have them available to order or you can contact your local extension office or feed mill.”

Use the hay probe to core sample at least 12 to 20 square bales from various sections of your supply to get the best representative sample. With round bales, take three to five core samples from each. Combine all samples into one, mix them thoroughly in a resealable plastic bag, and submit them to a lab for nutrient analysis.

Don’t have access to a hay probe? Buying hay in small batches? In some instances, pulling a core sample doesn’t make much sense. Resources such as the Dairy One Forage Lab keep a large database of hay analyses you can use to estimate nutrient content in these ­situations.

“If you know precisely the type of hay, you can look at the average values in our interactive feed library,” says Fessenden. Use the same feed library to look at nutrients in pasture grasses and grains, too.

As for grains and concentrates, you can secure a list of the nutrients in single grains (corn, oats, barley, etc.) from several sources, including the NRC or Dairy One’s interactive feed library ( But what about that commercially mixed ration balancer for an easy keeper? Or the high-fat fortified pellet fed to a barrel racer?

For bagged commercial concentrates you can find nutrient values in the guaranteed analysis printed on the bag or tag. In the U.S. most analyses list protein, fat, fiber, calcium, phosphorus, copper, selenium, zinc, and vitamin A values for their products as either minimum or maximum amounts. Individual states regulate how nutrients are listed on the guaranteed analysis. Depending on where you live, the labels probably won’t supply all the information needed to balance a diet. 

“I always call the manufacturer for more detailed information, because what is on the tag is in some cases the bare minimum,” says Clair Thunes, PhD, independent equine nutritionist with Summit Equine Nutrition LLC, in Gilbert, Arizona. She says some companies share the independent analysis they’ve had completed on the feed in question, while others just give expected levels based on formulation.

Another option is to have the feed analyzed yourself, but this can be timely, expensive, and less accurate. “The data you get back from such a sample is not going to be as representative as a sample that includes feed taken from multiple bags in a batch,” says Thunes. 

But if you want to go this route, laboratories like Equi-Analytical can test grains, mineral mixes, and finished feeds.

The supplements you mix into your horse’s grain every day might not seem like much. But you’d be surprised how a small amount of a few supplements could tip the balance of micronutrients such as selenium. Therefore, it’s important to properly capture the nutrients being delivered in all supplements. As with concentrates, the label’s guaranteed analysis ­provides some information, but for the most accurate nutrient values, contact the supplement ­manufacturer.

Estimates of Voluntary Dry Matter Intake*

  Estimated Intake Per Day
Pasture  1.5 – 3.1% of body weight
Hay, grass type  2% of body weight
Hay, alfalfa type  2.4% of body weight

*values from NRC, 2007


Step 3. Weights and Measures

It’s been drilled into our heads to feed horses by weight, not by volume—scoops or coffee cans. And there’s a practical reason: Nutrient levels included in a hay analysis report or feed tag are listed as a concentration, such as percentage or grams per pound. So, without knowing the exact amount being fed in pounds (or kilograms) per day, it’s impossible to calculate these nutrients.

Feeding a large round bale or free-choice hay? Grazing pasture? We can’t easily measure our horses’ free-choice forage intake, but science can help us guess intake levels (see Table 1). Many factors play a role in these estimates; number of horses on pasture, season, drought, or overgrazing can negatively affect pasture intake. Certain grass species, such as Kentucky bluegrass and orchardgrass, can positively impact intake (Hayes et al., 2011). Equid type and class affect intake, too. For example, lactating broodmares grazing pasture consume well above ­average—around 2.8% of their body weight per day vs. 2% (Marlow et al., 1983). Ponies grazing pasture can consume almost 50% of their total daily dry matter in about three hours (Ince et al., 2011).

Have a horse that naps in his hay? Feeding outside in a muddy pasture? Not all feed, especially hay, gets eaten on a daily basis. For complete ration evaluation accuracy, weigh and subtract from the total amount fed any feed refusals (what’s left in the feed bucket) or wasted feed (like soiled hay in a stall).

Step 4. Doing the Math

With your nutrient information and quantities in hand, it’s time to do the math. Simply calculate the amount of each nutrient being provided in each feed. Some calculations will be simple, such as for digestible energy. Here’s an example:

(per lb)
(per day)
 Total Calories
(per day)
1,000 Calories   MULTIPLY BY 15 pounds 15,000 Calories

Nutrients such as selenium require more steps. The selenium amount on the feed tag reads 0.3 ppm (parts per million) or milligrams per kilogram of feed. If your horse eats 5 pounds of that feed a day, how much selenium is the feed providing?

First, convert pounds to kilograms (there’s about 2.2 pounds in 1 kilogram):

(per day)
(per kg)
(per day)
5 pounds   DIVIDED BY 2.2  2.27 Kilograms

Next, multiply this amount by the selenium concentration:

Selenium     Amount     Total Selenium
(per day)
0.3 mg/kg   MULTIPLY BY   2.27 Kilograms  0.68 Milligrams

Each feedstuff contributes different nutrient amounts based on the amount fed, so it’s important to capture those values correctly. Here’s an example with calories:

Feedstuff  Amount
(per day)
(per lb)
Total Calories (per day)
Hay (in stall half of the day  10 lb  1,000 Calories  10,000 Calories
Pasture (out half of the day)  12 lb  900 Calories 10,800 Calories
Concentrate (ration balancer)  2 lb  1,200 Calories  2,400 Calories
TOTAL      23,200 Calories

Step 5. Waving the White Flag

Is all this math making your head spin? An online search can lead you to ration-balancing programs available for free or purchase. If you want to talk to someone, consider seeking out an independent equine nutritionist. Most feed companies also employ a nutritionist capable of evaluating rations and analyzing hay, and they might provide this service free to customers. Inquire with your feed company about this service and its cost.

Local extension offices can provide hay and pasture analysis help and might evaluate your horse’s diet for free or a small fee.

Summing It Up

Developing a ration involves more than just tossing together nutrients. It’s the art and science of creating meals that meet all your horse’s daily ­requirements.