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. | iStock

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