Horse Feeding

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There are multiple opinions on the ways and options of feeding the horses since each horseman, trainer or groom has his own ideas and conceptions on how to feed them. Often not knowing the way the horse’s gastrointestinal tract works, improper feeding practices are carried out. It will generate problems that are mainly attributed to food. We will first review some anatomical and physiological aspects : the shape and function of the horse’s digestive tract to understand what is the best way to feed them, so that we can reduce or avoid problems.

In the natural conditions, the horse feeds on grass, grazing approximately between 12 and 20 hours a day since the capacity of its stomach is limited.  Comparing the size of the stomach with that of the horse, it is considered that the stomach is small (10% of the total digestive system). Horses must eat small portions several times a day. When the horse is in a stable, these habits are modified, depending on the animal’s conditions, training time, etc.

Horse’s digestive tract


It is the beginning of the digestive system. The mouth allows the capture and grasping of food thanks to the lips, mainly thanks to the upper lip, which is very vigorous, mobile and sensitive, and to the incisor teeth. The teeth are a very important part since they are in charge of grinding the food ingredients to allow the nutrients to be exposed and absorbed in the following sections of the digestive system. Likewise, they give the necessary size to the particle to avoid problems of colic. If the teeth do not receive adequate attention we will begin to notice that the food is excreted “whole” without undergoing major changes, the horse may begin to lose weight and its performance will not be the same.


It is a tubular organ endowed with movements called peristaltics, thanks to which food is forced to pass into the stomach.


As noted above, the stomach of horses has a very reduced capacity, from 15 to 18 liters, and usually only fills 2/3 which is 10 – 12 liters. This justifies the need to divide the food throughout the day. Enzymatic digestion begins in the stomach thanks to the active ingredients of gastric juice (pepsin and hydrochloric acid) that lowers the pH of the stomach content. If the food remains in the stomach for the proper time, these conditions are capable of starting the hydrolysis of plant proteins. Forages do not undergo major changes in the stomach because the conditions do not allow the proliferation of bacteria that degrade starches and easily fermentable sugars, which produce different types of volatile acids (which are used as an energy source). Therefore, it is interesting to increase the gastric digestion of the concentrates. Foods rich in cellulose (forage) will not be attacked by the fermentative microflora except at the level of the large intestine. For this reason, it is convenient to distribute the forage first followed by the feed and concentrates in the ration. The adequate production of saliva and the sufficient presence of forage of a good quantity will help to diminish and avoid gastric ulcer problems.

Small intestine

It has a length of 16 to 24 meters with a capacity of 60 liters. In it, nutrients are absorbed through the intestinal villi to pass into the bloodstream.

Digestion in the small intestine lasts only a few hours. It is enzymatic in nature and practically does not affect cellulose. Mainly, the constituents of concentrated foods are digested, sugars, lactose and starch, fats and nitrogenous materials (proteins in particular). The enzymes amylase, lactase, maltase, proteases and peptidases are those that release the different nutritional elements from food, providing energetic nutritional elements that can be used by the body. In general it is said that they can contribute 30 to 60% of the total energy absorbed, and nitrogenous nutritional elements (amino acids) that can provide 30 to 80% of the total nitrogenous matters. The percentages increase with the concentrate content of the ration. Minerals are absorbed from the small intestine, except phosphorus.

The Large Intestine

It is the most voluminous compartment, from 180 to 220 liters divided between the cecum, colon (major and minor) and rectum, and it is always full. Basically, the forage is digested in the large intestine.

Digestion in the large intestine lasts for at least 24 hours. In it, the digestion of the undigested constituents in the small intestine is ensured thanks to the prolonged fermentation carried out by the very active microbial population, present in the cecum and colon. The plant walls and a reduced fraction of the reserve sugars are transformed into energetic nutritive elements (volatile fatty acids) and nitrogenous (amino acids). Volatile fatty acids can provide up to 2/3 of the total energy absorbed in the digestive tract, in diets rich in forage. In addition, some vitamins of group B (B1, B6, B12) and vitamin K are synthesized here. Also in the large intestine phosphorus absorption occurs.

Now we will talk about the nutrients that we must provide to horses

Water, Energy, Protein, Carbohydrates, Fats, Vitamins and Minerals


Water is the most important nutrient. The horse can live several weeks without eating food, but two or three days without water can cause serious illness or even death. On average, a 500 kilograms horse consumes about 18 liters of water per day.

It is important to note that the horse should be offered a fresh, clean source of water at all times. Water consumption varies between horses, not all consume the same amount, in hot climates the consumption increases significantly, also in the case of horses that sweat a lot or lactating mares.

Supplementation with electrolytes will increase water consumption, generally this supplementation is not necessary unless the horse sweats heavily. Sweat contains large amounts of the main electrolytes such as sodium, chlorine, potassium, and low amounts of calcium and magnesium. These electrolytes must be replaced if the horse sweats heavily.

Some horses will not drink the water if the electrolytes are added (due to the change in taste), if electrolytes are added to the water. It is important to offer them water without electrolytes to avoid dehydration. White or common salt (also called cooking salt) can be offered freely at any time or, add a quantity to the food ration. The other electrolytes such as potassium, calcium and magnesium are normally present in adequate amounts in food, so there is no need to supplement them in horses that sweat normally.


Protein is made up of molecules called amino acids. There are 22 amino acids that make up proteins. When digested, proteins release amino acids which are absorbed. These amino acids are necessary for the construction of new proteins, such as muscle tissue. The amino acid lysine, also called essential, is very important, since it is necessary for multiple processes within the body, a 500 kilograms castrated horse requires an average of 23 grams / day.

The most important thing about protein is not its quantity but its quality, the quality is given by the amino acids that make it up. Using a concentrate with a certain percentage of protein (12% or 16%) does not really say much, since a certain amount of grams is required to cover the needs instead of a certain percentage. What you need to know is the total amount of protein you are providing, the amount (not the percentage) contained in the daily ration of grain and forage that your horse is consuming compared to its requirements. For example, a 500 kilograms neutered horse requires 665 grams/day of protein in the diet.


Carbohydrates can be simple (also called soluble carbohydrates or monosaccharides), such as glucose and other sugars, or complexes, such as starch, fiber, and the less soluble portions of grains. Grains have both carbohydrates, soluble (in the inner part of the seed) and insoluble (the outer parts of the seed and parts of the plant). Grain products are also called concentrates and are made up of more soluble carbohydrates than fodder.

Grain digestibility is also affected by processing. For example, rolled oats or broken corn have soluble carbohydrates that are more available to the digestive process than if they were whole grains. Most soluble carbohydrates are digested and absorbed in the small intestine, while insoluble carbohydrates pass into the colon and cecum to be fermented by bacteria that produce volatile fatty acids. Glucose and volatile fatty acids are used by the horse to produce energy or are stored in various tissues as fat reserves for later energy production.


Fats are digested and absorbed in the small intestine. Fats can be used for energy production or they can be stored as an energy reserve for a relatively long time. Recent research has shown that fats can cover up to 10-20% of the horse’s daily energy requirements. In the case of horses with muscle disease problems (such as spanking or Monday disease, etc.), they can benefit significantly by decreasing the amount of soluble carbohydrates (grain ration) in their diets by increasing the amount of energy provided by fat. The same amount of fat has the ability to produce twice as much energy as soluble carbohydrates or protein gram for gram.


It is important to consider vitamins in the horse ration, due to multiple factors it can decrease the vitamin content in horse feed. Some vitamins are sensitive to sunlight, heat, and oxidation (especially vitamins A and E). Hay stored for a year or longer, as well as hay that rained between harvest and packing, can have a large decrease in the concentration of these vitamins. Also the pelletizing process of many products involves heat and pressure, so it is important to know if vitamins are supplemented and how they should be added. The vitamins most commonly added to horse food are Vitamin A (important for reproduction), Vitamin E (a preservative and natural antioxidant, which ensures optimal functioning of the reproductive, muscular, circulatory, nervous and immune systems), Vitamin H (also called biotin, which helps improve the quality of the hoof and hair and is necessary for the synthesis of fats, proteins and glucose). Horses that do not have access to fresh pasture during the winter months (or all winter) have been shown to be significantly deficient in Vitamin E during these months.


Minerals are relatively stable during food processing processes, but the concentration of a particular mineral within a plant is proportional to the concentrations within the soil, for example, it is well known that selenium deficient forage is produced in some areas. It is important to know if you are in a geographic area that requires selenium supplementation. The minerals commonly added to balanced foods are calcium, phosphorus, copper, zinc and selenium.

Selenium deficiency can cause muscle disease in both young and adult horses. Check with your vet if you need to supplement selenium, because the difference between required levels and toxic levels is very small. Be careful and avoid using three or four supplements that contain selenium; this can inadvertently cause toxicity. This is true for all supplements, check carefully what it contains and how much it contains to provide it in the amounts that the horse requires.


Grain (%) Forage (%)
Young Horses 60 40
Maintenance Horses 30 70
High Performance Horses 50 50


The British Nutrition Society defines the word “Nutrition” as “the sum of all the processes that go from taking nutrients to absorbing them as well as their subsequent use” (BESM 1994).

This means that each horse can absorb and use nutrients more or less effectively. A diet that is optimal for one horse may not work for a different horse, since its systems do not use the calories provided in the same way.

Therefore, it is necessary to observe its health, energy level, weight and quality of the hair, the competitive performance of the horse, its physical weaknesses and adjust the diet when necessary.

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