A Guide for the Basic Principles of Horse Nutrition

With so many feeds, supplements, and hay choices available, it can be difficult to be certain about what is essential for your horse's health and nutrition. This guide helps clarify the nutritional requirements of your horse, outlines general feeding principles, and assists in evaluating whether your horse's dietary needs are being met. Learn about making informed decisions to create a good, solid nutritional program for your horse.

Overview of the Gastrointestinal Tract

The horses digestive system is large, complex and very sensitive to change. The primary function of the digestive system is to transport food from the mouth to the anus and to break down food into particles that can be absorbed. In horses, the digestive system is divided into two main parts: the foregut and the hindgut. The foregut includes the oral cavity, pharynx, esophagus, stomach, and small intestine, where enzymes and acids work to break down feed components such as proteins, fats, and hydrolyzable carbohydrates. Horses have a distinctive stomach with a capacity of only 2 to 4 gallons for an average-sized 1000 lbs horse. This stomach produces hydrochloric acid and pepsin to start breaking down food. Unlike some animals, horses lack a gall bladder to regulate acid production, leading to constant acid secretion. As a result, horses have evolved as grazers, spending approximately 16 hours a day grazing on pasture grasses. This grazing behavior creates a protective layer over the acid to prevent it from splashing up and causing ulcers in the non-glandular parts of the stomach.

Materials that remain undigested then proceed to the hindgut, which comprises the cecum, small and large colon, and the rectum. Horses are classified as hindgut fermenters, with a variety of microbes breaking down this material. These microorganisms primarily utilize the fiber from the horse's diet to generate approximately 75% of the horse's daily caloric requirements. Forage typically contains more fiber than other feeds, making it crucial for maintaining the health of these microbes. Therefore, providing a forage-based diet is essential for the horse. Imbalances or feed that disturb these microbes may result in hindgut acidosis, ulcers, displacements, or gas accumulations, all of which can lead to colic.

Basic Nutrients

Horses need six essential nutrient groups to thrive and maintain optimal health: carbohydrates, proteins, fats, vitamins, minerals, and water.

Water

Water is a crucial nutrient for horses for many reasons, such as aiding digestion, regulating body temperature, supporting biochemical reactions, waste elimination, and milk production in broodmares. The water requirements of a horse can vary based on different factors. A healthy horse typically consumes 15-25 (or more) litres of water daily, depending on environmental conditions and activity level. It is essential to provide clean water daily and ensure continuous access for the horse. It is worth noting that snow is not a suitable water source for horses as they cannot consume enough snow and it requires significant energy to warm it to body temperature.

Carbohydrates

The horse's diet will primarily consist of carbohydrates. These can be categorized into two groups: structural (fiber) and non-structural (sugars and starches).

Nonstructural carbohydrates are mainly present in grains such as corn, oats, barley, molasses, and certain commercially available feeds (concentrates). Spring and autumn pastures are also rich in sugars. They offer a denser source of energy compared to structural carbohydrates. It is crucial to understand that the horse's digestive system has adapted to handle a roughage-based diet. As a result, concentrates should be utilized solely as a supplement to the forage regimen to fulfill nutritional needs that cannot be satisfied by forage alone.

The primary source of structural carbohydrates in a horse's diet is roughage like hay, grass, and beet pulp, which are effectively broken down in the horse's digestive system. Fiber is crucial for maintaining your horse's digestive health as it promotes the movement of food through the digestive tract and serves as a significant calorie source when utilized by microbes in the hindgut. One common type of fiber found in all plants is lignin, which is indigestible by a horse's microbes. The concentration of lignin increases as plants grow older. Therefore, providing high-quality, mold-free hay or forage that is cut at the right length and maturity stage is essential. Hay with excessively coarse or fine stems lacks nutritional value and can lead to digestive issues such as the development of a hay belly and increases the likelihood of impactions. This highlights the importance of prioritizing a forage-based diet for horses.

It is crucial to provide a horse with at least 1 percent of its body weight in forage (on a dry matter basis), with the optimal range being 1.5 to 2 percent. Failing to feed enough roughage can result in health problems like colic and ulcers.

Protein

When evaluating different feeds, most people usually concentrate mainly on the protein content and deem it adequate. It is essential to evaluate the protein level by analyzing the crude protein, which provides an estimate of the protein quantity in the feed. However, many horse owners do not fully understand quality protein, a nutrient essential for physical development and maintenance. Protein is needed for horses because it consists of amino acids. Once proteins are broken down in the small intestine, they are recombined into 21 amino acids which are essential for muscle formation, tissue repair, and the quality of hair and hooves. While certain amino acids can be synthesized by the body's tissues, ten of them, referred to as essential amino acids, must be obtained by horses through their diet. These amino acids are arginine, histidine, isoleucine, leucine, lysine (muscle growth and development), methionine (hoof, hair and coat quality), phenylalanine, threonine (tissue repair), tryptophan, and valine. If one amino acid is deficient, it can impede the synthesis of proteins using the remaining amino acids and the absorption of minerals. In grass hay, lysine is typically the first limiting amino acid, whereas in alfalfa, it could be threonine or tryptophan.

Overall, when evaluating the protein content in your horse's diet, take into account both the quality and quantity of protein. Having a good understanding of the forage type you are providing your horse is key for determining the appropriate supplements needed to enhance your horse's diet.

Fats

For certain groups of horses, feeding diets high in fat can be beneficial since fat is a easily digestible source of energy. While forage does have a small amount of fat, rich in omega 3 fatty acids, nowadays, many commercial feeds add 6 to 12 percent fat in the form of stabilized oil. By adding fat to the feed, the energy density rises, potentially decreasing the amount of feed needed by the horse. Before introducing fat into a horse's diet, it's important to ensure that all essential nutrients are adequately provided to meet their requirements. While commercial feeds are usually nutritionally complete, if you choose to boost the fat content in your horse's diet by including oil or fat supplements, it's crucial to confirm that you are meeting all their nutrient needs, not just their energy requirements.

Vitamins

Vitamins play essential roles in the body, supporting essential reactions necessary for an animal's survival. They are classified into two groups: water-soluble and fat-soluble. Water-soluble vitamins, such as B-complex vitamins and Vitamin C, are easily excreted through urine. On the other hand, fat-soluble vitamins, including Vitamins A, D, E, and K, are stored in the body and pose a higher risk of toxicity due to their accumulation. While some vitamins can be synthesized internally by horses, others like A and E must be obtained through dietary supplementation. A balanced forage program along with a well-formulated vitamin and mineral ration should adequately fulfill your horse's vitamin needs.

Minerals

Minerals are essential inorganic substances required in sufficient quantities for the proper functioning of the body. Without minerals, horses would be unable to metabolize fats, proteins, or carbohydrates, leading to abnormal nerve and muscle function and insufficient bone strength to support their weight. Minerals also play a crucial role in facilitating oxygen transportation in the blood, regulating the body's acid/base and fluid balances, and serving as vital elements in nearly all enzymes necessary for the horse's daily metabolism.

Minerals can be categorized into two primary groups: Macrominerals and microminerals. Macrominerals are needed in larger quantities and are found in greater quantities in the body. Examples of macrominerals are: Calcium (Ca), Phosphorus (P), Magnesium (Mg), Sulphur (S), Sodium (Na), Potassium (K), and Chlorine (Cl). On the other hand, microminerals (also known as trace minerals) are required in minute amounts and are present in very small quantities in the body. Microminerals include Copper (Cu), Zinc (Zn), Iron (Fe), Iodine (I), Selenium (Se), Manganese (Mn), Fluorine (Fl), Chromium (Cr), Cobalt (Co), Molybdenum (Mb), and Silicon (Si).

When feeding these minerals, it is important to consider a few key points. Maintaining a proper balance of mineral intake is essential to ensure optimal mineral absorption and prevent exceeding the recommended levels. Some minerals have interconnected relationships, where the presence of one mineral can impact the absorption and utilization of another. For example, Calcium and Phosphorus need to be in a specific ratio (with calcium equal to or higher than phosphorus) to effectively promote bone health and regeneration. The interaction between Copper, Zinc, and Iron is also critical, although these mineral needs can vary based on the horses age and overall health condition. To make matters more complicated, in addition to vitamin/mineral supplements, essential minerals can be found in basic forage and other supplements. Therefore, be cautious about excessive mineral intake, which could result in toxicities or hinder mineral absorption. While excessive doses of any mineral can be harmful, there is usually a significant safety margin. Providing the minimum required amount of a mineral can be just as effective as supplying the maximum amount.

So where do you start when feeding vitamins and minerals? To begin with, when it comes to providing vitamins and minerals for horses, it's important to consider the the specific mineral requirements based on their individual needs. Many feed companies tailor their products to meet these requirements. If your horse doesn't consume commercial feed and is on a forage-only based diet, it may be necessary to supplement with extra vitamins and minerals through a ration balancer. Another approach to ensure they receive the necessary vitamins and minerals is by offering a loose salt-vitamin-mineral mix for them to have freely. Choosing a loose salt mix is crucial because horses struggle to effectively use salt blocks, often resulting in injuries to their teeth and TMJ when trying to consume them. Mineral blocks are mainly salt and do not provide enough sufficient vitamins and minerals. A loose vitamin/mineral premix or a ration balancer is a suitable option for horses on pasture or a diet primarily consisting of forage. When offering a loose mix, a general recommendation is to anticipate horses consuming between 1.5 to 3 oz. per day.

Conclusion

To ensure that your horse's nutritional requirements are being met, start by assessing its body condition and determining its weight in order to calculate the amount of forage needed (1.5-2 percent of body weight). Understanding your forage regimen (pasture and hay) is key in identifying the nutritional gaps. Depending on any deficiencies in the forage plan, you can then select a suitable grain, commercial feed, or vitamin and mineral supplement. Each horse has unique nutritional requirements, so it is important to be able to analyze the quality of forage and feed tags to determine if they meet your horse's needs. For a thorough evaluation of your feeding regime, it is advisable to seek advice from a certified Equine Nutritionist.