The vast majority of a horse’s diet should be forage or roughage. Hay, however, is not enough for a complete nutritional profile. The addition of grains and concentrates will add critical minerals and nutrients but will also add calories. Below, see types of roughage, feeds, and concentrates—ordered from least to most “complete."
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Roughage and Fiber
A horse on anything but a complete feed should eat 1.5-2% of its body weight in good-quality roughage in the form of pasture, hay, or other types of fiber. This equals 15-20 pounds of hay per day for an average 1,000 pound horse. Because horses evolved to graze, it is the most natural to feed smaller, frequent meals throughout the day if your horse isn't on pasture.
Green grass is the most natural form of roughage and can be the most economical. However, it is important to routinely ensure pasture is free of any poisonous plants or debris that may injure the horse. Also, fresh green grass is very high in easily digestible sugar, so horses that are prone to obesity may need to have restricted pasture to prevent metabolic disease. In seasonal climates, pastures may not supply enough nutrition in the winter, so hay supplementation in colder temperatures may be necessary.
Hay is dried and baled grass (such as timothy, Bermuda grass or orchard) or alfalfa. There is no perfect hay; horses prone to obesity require a less nutrient-dense hay, while others may require those with more protein or easily digestible carbohydrates. Timothy, orchard, oat, and Bermuda are all grass hays. These are all high in fiber but lower in energy and protein than alfalfa. Hay is usually kept in either square or round bales, with the former being divided up into partitions, called flakes. Weighing a sample flake from each new batch will give you an idea of how much to feed; flake and bale weights differ considerably. Round bales may be more economical, but must be closely examined for wetness or mold which can harbor the dangerous toxin, botulism. Quality of hay, including low dust and absolutely no mold, is paramount to horse health.
Cubes and Hay Pellets
Hay and alfalfa also come in pelleted and cubed form. These can be easier to eat for horses with poor dentition because roughage is already broken down into small pieces to create the pellets and cubes. However, it is very important to soak hay cubes in water for at least 10 minutes and even break them up manually, as they can be a source of esophageal obstruction or choke. Horses that have airway diseases may benefit from being fed soaked hay, cubes, or pellets, as dust coming off soaked feeds is minimal.
Beet pulp is a byproduct of the sugar beet industry and is dried or pelleted. It is a source of fiber and carbohydrate without being massively high in sugar. It is also high in calcium and has moderate protein content. Soaking raw beet pulp makes it more palatable, increases your horse’s hydration, and reduces the chance of esophageal obstruction. Beet pellets do not have to be soaked. It is excellent as an additive for "hard keepers" that need to gain weight safely. Beet pulp cannot completely replace the need for hay but is a good option if you want to reduce the amount of hay you feed because of cost or increase water intake.
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Mineral and Vitamin Supplements
Minerals and vitamins are critical for horse health. Essential major minerals include calcium, phosophorus, sodium and others, while trace minerals such as iron and selenium are just as needed but in smaller amounts. These can be found in many fortified grains but can be added separately in the form of mineral salt blocks or commercial mineral supplements. The vitamin and mineral needs of a horse depends on its stage of life, what roughage it is being fed, and the geographic location.
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A ration balancer is a commercial mineral and vitamin supplement that is pelleted with a protein source, often soybean meal. They can be added to a diet if a horse needs more protein but is sensitive to feeds high in sugar.
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Concentrates are feed that can be used to supplement calories to a horse’s diet. Many horses don’t need anything other than roughage and a mineral supplement, but those in high levels of work such as racing or pregnant or lactating mares should be monitored carefully for low body condition and supplemented as needed. There are a few key things to know about the horse’s digestive system before supplying concentrates. Firstly, the horse digestive system relies on microbes to help digest food, and any change in feed, especially grain, will cause a shift in this microbial population and can potentially cause colic. Secondly, horses are very sensitive to some additives found in other livestock feeds. Only feed your horse equine-specific feed; cattle or poultry feed can be fatal.
It's important to read any feed bag carefully and follow instructions. Also, make sure any feed is stored in airtight containers and thrown away if mold develops or if pests such as mice or opossums are noticed to have gained access. Grains are especially tasty to horses, and horses may overeat if they themselves have been able to access storage. Call your veterinarian immediately if you notice your horse has overeaten any type of grain, as it can cause serious diarrhea and laminitis.
Cereal grains include corn, oats, and barley. These are very high in energy, with corn being the most energy-dense and oats the most-fiber dense. Mold on any grain can be poisonous to horses, but especially mold found on corn. Grains are usually mixed with pellets in commercial feeds to provide added vitamins and nutrients.
Grain Mixes with Pellets
Commercial mixes are fortified in minerals and vitamins in addition to the grains and pellets. Beet pulp may be added to increase fiber, and molasses increases palatability and decreases dust. The most classically known mix is “sweet feed,” which so named because it is high in sugars. These are best for horses in high levels of work, as they are made up of mainly easily digestible carbohydrates for fast energy.
Pelleted and Extruded Feeds
Pelleted feeds contain the same ingredients as grain mixes but are ground and formed into pellets so that horses can’t sift through to pick and choose ingredients. Extruded feeds undergo an additional cooking process to cut down on dust. Extruded feeds are also higher in fats, which help a horse gain weight and condition without some of the deleterious effects of sugar on the gastrointestinal system. There are myriad commercial options for every stage of life and level of work, with many higher in fiber and protein and lower in sugar than can be found in grain mixes.Continue to 5 of 5 below.
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Complete feeds are so named because they are made up of the roughage, mineral, vitamin, and caloric content needed for a horse’s entire diet. Senior horses who have completely ground down or lost their teeth often need a senior feed, as they instead gum hay into balls called quids and drop them rather than appropriately chewing and swallowing. Some types of horses that colic routinely may benefit from a switch to complete feeds from hay.
Other additives to a diet are called supplements; your veterinarian and/or farrier may recommend these if your horse has specific hoof or health needs. Otherwise, while the bulk of a horse’s diet should be made up of roughage with the addition of minerals and vitamins as needed, a small amount of grain can support overall health and provide a tasty treat. Make sure to always supply a source of clean, fresh water.
Calculating your horse’s dietary needs can be tricky. Feed stores have scales that you can use, and there are ways to estimate your horse’s weight. Make sure to ask your veterinarian for their advice and make any feed changes slowly for the best gastrointestinal health. The best resource for further reading for any equine caretaker is the National Research Council's Nutrient Requirements of Horses: Sixth Revised Edition.
National Research Council. 2007. Nutrient Requirements of Horses: Sixth Revised Edition. Washington, DC: The National Academies Press. https://doi.org/10.17226/11653.