Your horse’s nutritional requirements depend on his life stage and individual needs

All horses need the same essential nutrients—water for cellular, tissue, and organ function, carbohydrates and fats to fuel body functions, protein to build and repair tissues, and certain vitamins and minerals to promote and maintain normal physiological function. Feeding an appropriate diet, however, is not just a matter of tossing them some hay, grain, and supplements. Creating a diet for your horse involves a targeted plan that allows him to use nutrients more efficiently.

To figure out what your horse needs, realize that horses are grazers designed to eat little and often, says Amy Parker, MS, equine nutritionist and technical services manager at McCauley’s, in Versailles, Kentucky. Their natural diet is mainly grass, which has a high roughage content. So, their diet as domesticated animals should be predominantly fiber-based— whether it’s grass, hay, haylage, a hay replacement, or a combination thereof—to mimic their natural feeding pattern.

Parker says the right diet for your horse must reflect his individual needs, taking into consideration factors such as age, weight, body type and condition, health, level of work, and physiological state (e.g., growing, pregnant, lactating). Time of year and weather conditions are also important to consider when formulating the appropriate diet. For example, if the horse gets most of his nutrition by grazing good-quality pasture, then he needs alternative feed sources (i.e., hay) when grass isn’t available. “All of this information provides the foundation to develop the whole diet—forage and feed components,” says Parker.

The National Research Council’s Nutrient Requirements of Horses is the standard guide for feeding horses. Although this text provides much more information than the average horse owner might need, it also offers basic guidelines for energy, protein, and some macromineral (i.e., calcium, phosphorus) amounts based on mature horse body weight. “Once we have met these needs, then the rest is usually okay,” says Shannon Pratt-Phillips, PhD, professor of equine nutrition and physiology at North Carolina State University, in Raleigh.

From Foal to Juvenile

Horses have different nutritional needs depending on their stage of physical maturity. In general, provided a lactating mare is in good body condition and on a balanced diet, we don’t have to worry about feeding the foal because the mare’s milk includes all the nutrients he needs, says Parker. Rather, we consider and select the proper diet when the foal transitions to a weanling and begins consuming solid feed. Young, growing horses need extra energy, protein, and the correct amount of minerals, such as calcium and phosphorus for proper bone and tissue development.

Digestible energy intake greatly influences a young horse’s growth rate, says Pratt-Phillips. In general, the more energy fed, the faster the growth. She says you can adjust diets to accelerate growth in horses earmarked for sale or competition as well as slow growth rates for horses intended to be marketed at a later stage of maturity.

Horses 4 to 6 months of age are defined as weanlings, whereas those 12 to 18 months of age are considered yearlings. Depending on the average daily weight gain you desire for your growing horse, first choose the appropriate forage type to feed. We know pasture alone typically doesn’t meet a growing horse’s nutrient needs, says Laurie Lawrence, PhD, professor of equine nutrition at the University of Kentucky (UK), in Lexington. Further, season affects a pasture’s nutrient content. For the growing season of most legume/grass pastures, the energy and protein content is highest in spring and fall and lowest during the summer.

Lawrence says choosing a hay to match the horse’s needs is a good way to ensure adequate nutrition from the forage. Hay has the highest nutrient value (composition) when harvested in its immature state of growth. Legume hay (alfalfa or clover) is higher in digestible energy, protein, and calcium than grass hay (e.g., timothy or orchardgrass). So, if you are selecting hay, look for the stage of maturity to be between pre-bloom and mid-bloom (prior to the plant flowering) for legumes and pre-head (prior to the plant producing a seed head) for grasses.

Growing horses’ hay consumption varies depending on the hay quality (related to the hay’s maturity at the time of harvest) but usually ranges from 8 to 15 pounds per day for weanlings and 15 to 25 pounds per day for yearlings.

Because feeding growing horses is a balancing act where you don’t want to provide excess or inadequate dietary energy or protein, Lawrence suggests keeping the diet proportions at 30% forage to 70% concentrate for weanlings and between 55/45 and 50/50 forage to concentrate for yearlings.

Average Adult Horses

Mature idle horses can do well on good-quality all-forage (pasture or hay) diets with vitamin and mineral support in the form of a ration balancer, says Parker.

Base forage selection on the type necessary to meet nutrient requirements. For a mature idle horse, this is typically an early to late-head grass hay.

Senior Considerations

Aged or senior horses (18+ years) have additional dietary considerations. They are less able to process and absorb nutrients from feed and have a less efficient microbial population in the hindgut, says Pratt-Phillips. These horses need high- quality pasture and hay with at least a 60% legume content. Senior horses might also develop metabolic problems (such as pituitary pars intermedia dysfunction) that require a specialized diet low in soluble carbohydrates, including warm-season hays that are naturally low in insoluble sugars, such as teff or some species of Bermudagrass.

Pregnant and Lactating Mares

Broodmares’ digestible energy, protein, and macromineral (primarily calcium and phosphorus) requirements jump during late pregnancy (last trimester) and lactation (foaling to three months). For these horses to maintain a healthy body condition, Parker recommends selecting feed that complements the forage to meet the nutrient requirements. For instance, if you feed your pregnant or lactating mare legume/grass hay, add a concentrate feed with moderate protein (12-14%) that is fortified to meet her vitamin and mineral requirements. If you feed a straight grass hay, you’ll need to provide a higher-protein feed. Lawrence recommends offering early to mid-bloom stage legume hays and pre-head to early-head stage grass hays. In general, pregnant mares in late gestation and early lactation consume 70-80% and 50-60%, respectively, of their diet in forage.

Calculating Correct Amounts

Nutritionists generally base their feed recommendations on amounts per kilogram or pound of mature body weight. So your horse’s weight and body condition are essential pieces of information. A livestock scale will tell you the precise body weight of your horse, allowing you to make better decisions about how much feed to provide. You can also make body weight estimations using a weight tape or the body weight formula:

Body weight (lb) = heart girth (in)2 x body length (in)/330

Parker also recommends using the Henneke body condition scoring system (TheHorse.com/164978) on your horse. This system allows the user to evaluate the amount of fat deposition in various body regions, which can guide how much to feed.

Work increases digestible energy needs. The increase ranges from 25 to 50% above maintenance levels with horses in light to moderate work (working five hours or less per week) to 100% above maintenance in horses in heavy work (e.g., upper-level eventing, racing, endurance). Environmental conditions, such as heat and humidity, also affect horses’ dietary requirements due to replacement losses of minerals in sweat.

Choosing Forage Types

You can add forage besides pasture or baled hay to your horse’s diet. These include hay cubes, pelleted hay, chopped hay, dehydrated hay, and haylage. Each poses advantages and some disadvantages, says Parker, but all must be fed based on the product’s weight.

A variety of forage mixtures are avail-able as hay cubes, which are usually 2-by- 2 inches, and can be fed as a substitute for long-stem hay. Horses that waste a portion of their long-stem hay might benefit from consuming a cubed hay, says Robert Coleman, PhD, associate professor at UK. Cubed hay is cut uniformly, thus eliminating sorting issues. Another benefit of hay cubes is you can weigh and store them easily. Cubes are usually made from forage that was cut at an early stage of maturity, giving them a guaranteed minimum nutrient content, says Coleman.

Hay pellets are typically 3/16 to ¾ inch in diameter. They, too, are easily weighed and stored and can be fed as a 100% alternative to long-stem hay with a guaranteed minimum nutrient content. Because hay made into pellets has been ground to smaller particle sizes than hay intended for cubes, horses might consume them faster.

Whether you choose to feed hay cubes or hay pellets, Coleman recommends soaking them in water to soften them for senior horses as well as reduce possible incidence of choke from eating them in their dried state.

Chopped hay is usually chopped to a length of about 1 inch, and you can purchase it bagged. Because of its shorter stem length, this form of hay is easier to chew and might be a good choice for senior horses with poor detention or in a total mixed ration for horses consuming a complete feed.

Dehydrated hay is a chopped hay product that is dehydrated and compressed into a block. The advantage dehydrated hay offers over regular sun-cured hay is it retains its maximum nutrient value with storage. As with the cubes and pellets, this product comes with a guaranteed minimum nutrient content.

Another excellent forage option for horses is haylage, because it provides a high-quality product that is dust-free. Haylage has a moisture content of 20-30% compared to dry hay’s approximately 14% moisture content. In Europe, feeding haylage is common practice, says Coleman. “It looks like regular long-stem hay and has a sweet smell to it,” he says.

Because of the fermentation process involved in making haylage (which increases the level of soluble carbohydrates), this type of forage might not be appropriate for horses with metabolic issues or prone to laminitis. It’s also at risk of botulism contamination if the packaging is not airtight, so ensure horses eating haylage receive a botulism vaccine.

Concentrate Decisions

The final part of creating a diet for your horse is the concentrate. Concentrate, for all intents and purposes, is the nonforage portion of the ration (grains, protein supplements, oils/fats, molasses). Not all horses need a concentrate in their diets. If the horse is at maintenance, for instance, he likely needs only a vitamin/ mineral supplement (ration balancer), says Parker. A concentrate might be an appropriate addition to the diets of horses that cannot get enough nutritional sup- port to maintain optimum condition from hay alone or cannot consume enough hay to maintain optimum condition (growing horses, mares in late gestation or early lactation, horses in intense work, and aged horses).

Parker stresses that the amount of concentrate you feed should be no more than that necessary to provide the horses’ required energy and other nutrients. If your horse needs a concentrate to stay at a healthy weight and body condition, then each feeding amount should provide no more than 0.5% of his body weight.

Final Thoughts

Creating the right diet for your horse involves considering many factors, including the science behind what we feed and how current research and knowledge can help us tailor the horse’s diet to meet his specific needs. Work with your veterinarian or an equine nutritionist to ensure your horse is getting the right nutrients in the appropriate amounts for his lifestyle.