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Ten things you should know about feeding the mature horse

Quick facts

  • Always provide unlimited access to clean, fresh water.
  • Feed your horse 1.5 to 2.5 percent of their body weight in forage.
  • Don’t feed your horse more than 0.3 to 0.4 percent of their body weight in cereal grains per feeding.
  • Make sure your horse’s diet meets a calcium to phosphorus ratio (Ca:P) between 1:1 to 3:1.
  • Provide enough vitamins and minerals.
  • Balance your horse’s ration in this order: energy, protein, minerals, vitamins.
  • Monitor your horse’s body weight and body condition score (BCS).
  • Routinely care for your horse’s teeth.
  • Change feeds gradually.
  • Feed each horse as an individual.

Always provide unlimited access to clean, fresh water 

Water is the most important nutrient your horse needs. Always provide your horse access to a fresh, clean water supply. Most 1,000-pound horses will drink 10 to 12 gallons daily. Your horse will need more water when temperature, humidity or activity increases. Changes in the horse’s body, such as a mare going into lactation, can also increase the amount of water a horse needs.

Keep water between 45 and 65 F to encourage your horse to drink more. You can supply water through automatic waterers, buckets or water troughs. Clean waterers, buckets and troughs weekly, even in the winter. Keep troughs and buckets out of direct sunlight.

If a horse doesn’t get enough water, it can result in

  • Colic
  • Dehydration
  • Death


Horses can sweat up to 2 to 4 gallons per hour to control their body temperature. A sweating horse will need more water. A 1,000-pound horse can easily drink 12 to 16 gallons of water when working in the summer heat and grazing fresh forages. A horse will drink much more on a dried hay diet.

There’s no scientific basis to support that a hot horse shouldn’t drink water until it’s cool.


If a horses doesn’t get enough water it may become dehydrated. Although a horse may be dehydrated, it may not be thirsty. Encourage your horse to drink to prevent further dehydration. Ideally, avoid dehydration completely by allowing a working horse to drink every couple of hours.

Maximize the amount of forage your horse eats 

Fresh (pasture) or harvested (hay) forages are the ideal energy source for your horse. Forages, such as legumes and grasses should make up most of the horse’s diet. You should feed most mature horses at least 1 percent and ideally 1.5 to 2.5 percent of their body weight in forages daily. Eating 2.5 percent of their body weight in forage would near the most a horse would willingly eat. The horse’s gut would also maintain some fill at all times depending on the forage form.

Benefits of forages

  • Helps keep the gut working

  • Provides much of your horse’s energy needs

  • Keeps your horse busy

Provide harvested forages in a way that prevents horses from eating directly off the ground. Eating off the ground may cause horses to eat sand, dirt or parasites. But raising the hay too high can increase your horse’s intake of molds and dusts. These particles can lead to respiratory problems. Teeth and back problems may also occur in horses eating hay that’s up too high.  

Minimize the amount of concentrate your horse eats

Owners frequently feed cereal grains such as corn and oats at the expense of forage in the diet. They feed cereal grains when the horse needs more energy than forages can provide. But horses can only eat a limited amount of cereal grain before facing serious nutrient-related illness. Do not feed mature horses more than 0.3 to 0.4 percent of its body weight in cereal grains per feeding.

You may choose to substitute fats for a portion of cereal grains. Fats are an excellent energy source for horses. By feeding fat, you can increase the feed’s energy content without facing the health problems of overfeeding cereal grains. The total amount of fat in the diet should not exceed 20 percent. Fat is beneficial for growing, hardworking, special needs, and senior horses. Idle horses usually don’t need fat.

It is important to meet your horse’s energy needs but avoid overfeeding them. Overfeeding can result in an unhealthy, overweight horse.

Meet your horse’s mineral needs 

Your horse requires numerous minerals in their diet. Trace minerals are minerals your horse needs in very small amounts. If you feed a commercial grain product according to manufacturer directions, your horse is most likely receiving the correct amount of these minerals. However, if you feed grains such as oats or corn, you will need to supplement most trace minerals. While such feedstuffs may supply enough of some minerals, especially the major minerals, they will not contain all of the nutrients a horse needs to remain healthy.

The ratio of calcium (Ca) to phosphorus (P) is important in your horse’s diet. Calcium and phosphorus interact with each other and absorb in different areas of the gut. As a result, horses require a minimum Ca:P ratio of 1:1 and an ideal Ca:P ratio of 2:1.

Always provide free choice salt or sodium chloride (NaCl). Horses will regulate their own intake of salt.

Vitamin and mineral deficiencies may be more common in some geographical locations than others. For example, in many areas of the country, the soil is deficient in selenium. This results in hay that is low in selenium and in time, a horse that is deficient in selenium. In this instance, it would be appropriate to supplement your horse with selenium. Many selenium supplements also contain vitamin E, as these two compounds work together in the body.

Meet your horse’s vitamin needs

Vitamins are essential nutrients your horse needs in small amounts. Your horse may receive enough vitamins through natural feedstuffs, their own production, and microbial production in the gut. You may need to supplement some vitamins in your horse’s diet under certain conditions. For example, mature, rained-on, and/or older hay may lack vitamins. Most horses should receive a vitamin supplement unless they are being fed a commercial grain product according to manufacturer directions.

Establish a balanced ration for your horse: energy, protein, minerals, vitamins 

It is difficult to properly design a feed plan for your horse that is correctly balanced for their energy, protein, vitamin, and mineral needs. We strongly encourage working with an equine nutritionist or purchasing prepared commercial feeds that are professionally balanced to meet your horse’s exact needs. There are numerous products on the market that are tailored to specific classes of horses, including but not limited to growing, working, idle, or pregnant horses.

If you do wish to design a feed plan for your horse, consult a reference such as the National Research Council’s (NRC) Nutrient Requirements of Horses when developing a feed plan. This source provides the nutritional needs for horses of different sizes and physiological conditions (e.g. lactating mares). It also lists the nutrient content of common feedstuff. If you can, sample your forage to get the nutrient content specific to what you’ll feed your horse.

Use this information as a basic guideline. Based on your horse’s individual characteristics, you may need to modify their diet to maintain an optimal body weight and condition.

Monitor your horse's body weight and body condition score (BCS) 

When deciding your horse’s nutritional needs, you need to know their body weight and body condition score. Body condition scoring checks the amount of fat deposit under the horse's skin in certain areas. The ideal score for each horse differs based on their

  • Energy use
  • Size
  • Physiological condition
  • Diet history
  • Your personal preference

A BCS between 4 to 6 is ideal. It is important to actually put your hands on your horse and feel them rather than just look at them from a distance. Check your horse’s BCS score routinely to decide if you need to make changes to your horse’s diet. How much you need to feed your horse depends on changes in activity level, weather, and feed quality. See Kentucky Equine Research’s chart for more detailed scoring descriptions.

Routinely care for your horse’s teeth 

Your horse’s teeth continually erupt for 20 years. But they’re continually ground down as your horse chews feedstuffs, especially forages. Sharp points occur on the teeth because the upper and lower teeth don’t fully align with each other. Routine filing down or "floating," can remove these points and prevent painful or poor chewing. Severe pain may cause the horse to go off its feed. Learn more about caring for your horse's teeth.

Change feeds gradually 

Replace only 20 to 25 percent of your horse’s current feed every other day when changing their hay or grain type. This will allow you to make a complete change over a week or more. A gradual change from one feed to another provides enough time for microbes to adapt in your horse’s gut.  

The horse relies on microbes in the hindgut to process forages. For this reason, horses are known as hindgut, fermenting herbivores. The microbes are a mix of different organisms that work together to benefit the horse. If the horse’s feed suddenly changes, the microbes that process the feed may not have enough time to adjust to the change. As a result, many microbes will die while others do really well. In this case, toxins may absorb into the horse and cause digestive problems.

Feed each horse as an individual 

All horses have nutritional needs in common. They all require water, energy, protein, minerals and vitamins. But how much of each of these nutrients a horse needs and in what relation to each other will vary with:

  • Age
  • Activity level
  • Physiological condition

The NRC requirements are the minimum amounts of nutrients for normal health, production, and performance. Use them as a starting point to fine tune the needs of your individual horse.

Authors: Marcia Hathaway, professor emeritus of Animal Science, College of Food, Agricultural and Natural Resource Sciences, and Devan Catalano

Reviewed in 2021

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