Grains and Horses - How Much to Feed and When

Horses have evolved over millions of years to live on grassland, with their main food consisting of grass and some herbs. This means that their diet consists of relatively low-energy food and high fiber, which consequently they must eat in volume to compensate. Compared to this natural horse diet, grain is the exact opposite. It is much higher in energy, much lower in volume, has much less fiber (especially if the hull has been removed) and a day's worth of food can be eaten in a very short period of time. In addition, the minerals and other nutrients of grain are very different from grass both in the absolute amounts and in terms of the ratios (e.g. ratio of calcium to phosphorous). Consequently, grain is an unnatural food for horses, which can lead to a variety of physical and mental issues when fed in excessive amounts(see Horse Feed and Grain Types for further discussion).

That being said, grain can be a useful supplement. Situations in which grain is of benefit include:

  • Old or Sick Horses. Eating and digesting grass (or hay) takes a lot of time and energy. Horses which are old or sick may not be able eat enough grass to meet their energy needs, which can result in excessive weight loss. To prevent this, one needs to feed a high-energy, easily digested food such as grain. Depending on the grain type, one may wish to process it (e.g. crushed, hulled or cooked) to make it more digestible.
  • Chewing or Digestive Problems. Horses which have dental issues may be physically unable to grind hay (or even grass) sufficiently. Likewise, older horses often have problems in the jaw joint, which makes long periods of chewing either difficult or painful. Some horses (usually very old horses) may also have limited digestive capabilities. In such cases, grain is often fed to reduce weight loss. One may also want to consider one of the other feed types, such as soaked hay pellets, which can address these problems with a more natural diet.
  • Working Horses. Horses with moderate to high amounts of exercise require more energy and depending on a variety of factors may require some high-energy food such as grain as a supplement. In addition, grain provides a quick source of energy, which may be more convenient than the horse stopping work for hours to graze on grass.
  • Sport Horses. Grain may be fed to sport horses for the same reason as working horses. In addition, horses which are fed high-energy foods don't get a 'hay belly', which is of benefit when competing in sports or show.
  • Financial and Practical. Aside from the above health considerations, there are a number of economic and practical advantages for the horse-owner and stable-owner. Provided that grain is not fed in excessive amounts, it is reasonable to supplement a horse's natural diet (e.g. grass, hay) with grain for these purposes. See below for further discussion.

Economic and Practical Considerations

Although prices of grain and hay vary from one region to another, in many places the cost of grain is cheaper than hay on a weight basis (i.e. per pound or per kilogram). Furthermore, grains have more energy they hay. For example, in terms of digestible energy (the energy that a horse gets from the food, which excludes the bits they don't digest), Timothy Hay has 0.8 Mcal/pound whereas oats has 1.3 Mcal/pound and corn (maize) has 1.54 Mcal/pound. This means that even in areas where grains are slightly more expensive on a weight basis, they can still be cheaper because a horse gets more energy from grain than from the same amount of hay. For this reason, many horse-owners or stable-managers feed grain to horses, thereby reducing their overall feed costs.

In addition to grain being cheaper to buy, it uses up far less space they hay. For example, hay bales have only about 0.2kg per liter (and much less when unbaled) whereas grain has 0.4 to 0.75kg per liter (see horse grains).  In combination with the higher energy density, this means that the space requirements for grain is far less than for hay, which can result in savings in terms of transport, storage and feeding. This of course depends on individual circumstances (e.g. grain stored inside will have a higher storage cost than hay stored outside).

Stable managers will often find that some clients (horse owners) see grain as 'value added' and believe that their horse is getting something 'extra' if they receive a daily measure of grain in addition to their normal feed. Consequently, stable managers may feed grain as part of their standard horse boarding package in order to justify the price, or they may charge an additional fee per horse for clients which want the horse to receive grain. In either case, feeding grain can help stable mangers increase revenue and profit. In areas where grain is cheaper than hay, this results in the happy situation for stable owners, where they can feed cheaper food and get paid more for it.  

Quantity

As can be seen from above, grains can be beneficial to horses in terms of health (see list of specific health considerations above), as well as having economic and practical advantages. The disadvantage is that they can increase the risk of physical illness (e.g. colic, laminitis) or behavioral issues. Consequently, determining the amount of grain to feed is a matter of balancing the benefits against the risks.

Although the benefits of grain (e.g. financial, weight gain) are often relatively easy to calculate, determining the associated risk is often more difficult as it varies from horse to horse depending on:

  • Race. Certain breeds are more tolerant of grain than others. For example, ponies are more likely to develop laminitis and horses.
  • Circumstances. Individual circumstances are very important. A horse with field access most of the day and part of a herd is far less likely to develop behavioral issues when hay is replaced by grain than a horse which is confined to its paddock much of the day. Likewise, horses are less likely to develop laminitis during winter than when eating spring grass.
  • Individual. Like people, horses are individuals, both physically and psychologically. Consequently, given two horses of the same breed which are kept in exactly the same way, one may be able to safely eat much more grain than another.

Due to this complexity, it is advisable to take specialist advice (e.g. a veterinarian specializing in horses) in terms of how much grain is appropriate for a given horse and given circumstances. In addition to veterinary advice, here are what I would consider reasonable guidelines:

  • Feed as much grass and hay as possible, rather than high-energy foods such as grain.
  • For horses with special needs (e.g. old, sick, hard working) which cannot get enough energy from grass and hay or alternatives (e.g. soaked hay pellets for horses with dental problems) feed enough grain to maintain an acceptable weight. For this, I prefer lower-risk grains (e.g. oats, barley) rather than higher risk alternatives (e.g. wheat, commercial musli mixes high in sugar/starch/molasses).
  • From a mental health perspective, restrict the horses grain intake to a third of its energy requirements. One can measure a horses energy requirement by observation (e.g. if it is totally hay fed and maintains its body weight with a 15kg bale of hay per day, this is its energy requirement) or by rough calculation (e.g. an relatively idle horse needs 2% of its body weight in hay, so a 600kg horse would need 12kg hay per day). I then use the rough calculation that 1 pound of grain equals almost 2 pounds of hay. For example, if a horse gets a maximum of one third of its energy from grain, then a horse which needs 12kg hay per day would instead get 8kg hay and about 2.5kg grain.
  • From a physical health perspective, avoid feeding any grain to high risk groups (e.g. pony breeds or individual horses with a history of laminitis) or during high risk periods (e.g. spring time for grass fed horses). For low risk horses, I would suggest a maximum of 1kg (for uncrushed whole grains, this would be about 2 liters or 2 quarts) of low-risk grains (oats, barley) per horse and per day (this is for an average size horse, with large or small horses adjust proportionally). If the grain is split over 2 or more feeds, this amount could be doubled.
  • In any case, when changing (especially when increasing) the grain ration, one should closely monitor the horse for side effects (in particular, laminitis).
  • Note that the above are my personal guidelines only, one should take specialist advice and consider individual circumstances. For example, we occasionally get horses which are dangerously underweight (e.g. rescue horses, old horses with dental or digestive issues), where I feed a higher grain supplement than I would otherwise.

That being said, many horses have diets which are more than 50% grain. In particular, competitive sports horses have high grain diets, often with no obvious problems. However, one needs to keep in mind that research indicates that over 90% of competitive race horses have ulcers in their stomach or intestines, probably due to this high-grain (and consequently low-fiber) diet.