And Can These Diets Be Acceptable for Active Horses?

By Madeline Boast, MSc. Equine Nutrition

Q: Fact or fiction? Horses require grains to be fed in their diet to meet their nutritional needs. 

A: Fiction! 

Grains are not a required feed ingredient for horses, and reducing the amount of grain-based products fed to horses has been a popular trend in recent years. 

Grains have developed a poorer reputation in equine nutrition due to their higher non-structural carbohydrate content. Most horse owners understand that forage is almost always the preferable energy source to promote gastrointestinal health; however, understanding optimal feed supplementation for the varying needs of horses is imperative to well-being. With “grain-free” becoming a hot topic, there are many misconceptions throughout the industry. Understanding what grain-free means is valuable when designing your own horse’s nutritional plan, especially for active horses.

Defining Grain-Free

The Association of American Feed Control Officials defines grains as “a seed from cereal plants.” A few examples of various grains are oats, corn, wheat, and barley. Where the confusion often begins is when a different part of the grain is used.

There are four distinct parts to a grain: the germ, the endosperm, the hull, and the bran. This can be confusing for horse owners to navigate as even though the product may not contain full oats, corn, barley, or wheat, the feed product may still contain the hulls, for example.

A product can be labelled as grain-free if the intact seed portion is not included. This means that other parts such as the hull may be used despite the product being labelled as grain-free. In equine nutrition it is extremely common for the hull and bran to be used as they are very fibrous. Therefore, even if a product is labelled grain-free, it may have parts of the grain used as ingredients.

Another popular misconception regarding grains for horses is that any product that is pelleted is commonly referred to as “grain.” Therefore, a key part of understanding grain-free diets is understanding what a grain is.

In addition, it is important to note that concentrate products are processed (e.g., extruded, pelleted, cracked) to improve digestibility, palatability, reduce the ability of the horse to sort ingredients, and eliminate dust.

Related: Are You Feeding Your Horse Enough Vitamin E?

Investigating concentrate products comes down to reviewing the guaranteed analysis and reading the ingredient list. There are a variety of products on the market that are pelleted or extruded concentrates and labelled “grain-free” but do contain the hull, for example. This does not tend to be problematic as those products are high in fibre and lower in starch and sugar than the grain-based products.

Nutrient Requirements 

Although grains are not required for a balanced diet, forage alone will not suffice. The majority of a horse’s diet is almost always hay, which is recommended for gastrointestinal health, but hay alone will not meet nutrient requirements. 

As forage alone will not meet your horse’s nutritional requirements, the first step to designing your horse’s nutritional pan is to have your hay analyzed to determine its nutritional value. Photo: Shutterstock/Anjajuli

The Nutrient Requirements of Horses, Sixth Revised Edition (2007), published by the National Research Council (NRC), has published recommendations to prevent nutritional deficiency. The six required nutrient categories for horses are water, protein, carbohydrates, fat, vitamins, and minerals. A quality forage will typically meet the energy and protein requirements of most inactive or light riding horses, but vitamins and minerals must be supplemented.

Carbohydrate Types 

It is impossible to remove all the carbohydrates from your horse’s daily ration, and prior to trying to remove the starch and sugar it is critical to understand the different types of carbohydrates. As mentioned, carbohydrates are one of the six essential nutrient classes for horses and are therefore required in the diet.

Carbohydrates are divided into two broad categories: structural and non-structural (NSC). Structural carbohydrates are the fibrous portion of the plant (hemicellulose, cellulose, polysaccharides); therefore, hay is a significant source of these. Structural carbohydrates will be the highest in mature and overly mature forages and lower in immature hay and pasture. In the foregut, structural carbohydrates cannot be digested. The horse relies on the microbial fermentation in their hindgut to break down these nutrients into a usable energy form (volatile fatty acids).

Structural carbohydrates, the fibrous portion of the plant, are high in mature forages and lower in immature hay and pasture. Non-structural or nonfibrous carbohydrates are highest in cereal grains and high in immature forages such as fresh pasture. Photo: iStock/Zbynek Pospisil

In contrast, NSCs are the nonfibrous carbohydrates (mono-, di-, oligo-saccharides, and polysaccharide starch). NSCs are the highest in cereal grains and will also be high in immature forages such as fresh pasture. This type of carbohydrate can be digested in the foregut by the digestive enzymes present. The energy from these carbohydrates can be absorbed by the horse earlier on in the digestive tract and therefore used immediately for energy.

Why is Grain-Free Gaining Popularity? 

It is well-known that horses do not thrive on high starch rations. When high NSC meals are fed, the horse is unable to digest and absorb all the starch and sugar in the foregut and therefore, some of it reaches the hindgut. When this occurs, there is a disruption of the hindgut microbial population and an increased risk of gastrointestinal upset.

Excessive carbohydrate intake has also been linked to equine obesity, equine metabolic syndrome (EMS), laminitis, colic, and undesirable behaviour. A high NSC diet can also exacerbate equine muscle conditions (e.g., polysaccharide storage myopathy). Therefore, if you are considering a grain-free diet for your horse, consider the reason. For example, does your horse require a low starch ration for health reasons? Are gastrointestinal issues arising?

Related: Chew Factor - Fibre Intake in Horse Hay

A horse owner may investigate a grain-free diet for a variety of reasons. Easy-keepers and horses at maintenance are quite simple to maintain on a grain-free ration. Chances are, they are already on one. Grain-free is an option for active and working horses too; however, before making the switch, educate yourself on other options for nutritional supplementation.

Hay Testing – Always Step 1

Hay testing is the critical first step when designing any balanced diet plan for a horse. It is impossible to be confident that your horse’s nutritional requirements are being met if you do not know the nutritional value of the hay. A hay analysis will provide you with a significant amount of information that can then be used to choose optimal products when formulating a nutrition program.

If your horse requires a low NSC diet, testing your hay to ensure it is low in NSCs is critical for safety. Your hay analysis will also provide information on how much protein and energy the forage supplies. This is key information as you can then rely on it as a base for supplemental product decisions. For example, if you have a senior horse being maintained on a vitamin and mineral supplement mixed with beet pulp, but new hay is much lower in protein compared to previous hay, you may need to add a quality protein source such as alfalfa cubes or pellets.

Easy-Keepers

If you have a horse that readily maintains weight on hay, it is easy to source a grain-free ration balancer. These products are designed to provide vitamins, minerals, and often supplemental protein as well to the horse without adding a significant number of calories. When investigating the ingredient list on pelleted ration balancers, the hulls of grains are commonly included. This should not be a concern, even for your easy-keeper, as they are fibrous and not high in starch or sugar.

If you are looking to curate a ration that does not have any grain, or even grain parts in it, a vitamin and mineral powdered supplement at a minimum is what you would need to feed your easy-keeper. These products work well for balancing a ration as long as the hay is meeting your horse’s protein requirements. For palatability, they are typically mixed with a soaked fibre source such as hay cubes or beet pulp. 

Active Horses 

Active and hard-working horses generally need additional nutritional supplementation above and beyond hay and a ration balancer. In these cases, a fortified performance feed that includes vitamins, minerals, protein, and additional carbohydrates and fats, is fed. These products are often pelleted or extruded and contain an array of various ingredients.

As previously mentioned, it is important to understand that just because a product is pelleted does not mean that it is high in starch or contains large amounts of grains. In fact, many of these products include fibre-based ingredients such as alfalfa meal, oat hulls, beet pulp, and fat sources like oils and rice bran. Of course, often there will also be grain ingredients such as steam-rolled oats or cracked corn to list a couple of the many examples. Therefore, if you are beginning to investigate grain-free due to concerns over starch intake or gastrointestinal upset, consulting an equine nutritionist to critically review the ingredient list of various performance products is recommended. To reiterate, just because a product is pelleted or processed does not mean it is high in starch and sugar. Low-starch feeds will generally rely on fat and fibre as the primary energy source, instead of NSCs.

Although there may be various situations in which a low NSC diet is recommended, it does not mean there aren’t benefits to including grains in the ration of working horses. Energy is a requirement for survival, and horses that are performing or working have a greater energy requirement. But it is important to note that not all energy sources are equal.

Related: Senior Horses Aging Gracefully

Different types of work have different types of fuel which relates to the primary muscle fibre type in the particular horse. Horses in fast work of a shorter duration (e.g., racehorses, showjumpers) will have more fast-twitch muscle fibres, which only utilize glucose for fuel. This work is characterized by a heart rate above 170 bpm. On the other hand, horses performing long-term work such as endurance will primarily make use of slow-twitch muscle fibres, which only utilize fat for fuel. This work is characterized by a heart rate below 170 bpm.

Horses performing long-term work (top photo) primarily use slow-twitch muscle fibres which utilize fat for fuel. Horses in fast work (bottom photo) of a shorter duration have more fast-twitch muscle fibres and utilize glucose for fuel. Photos: Clix Photography (top); Dreamstime/Amidchaos9 (bottom).

There are also trainable muscle fibres which comprise about 50 percent of the muscle fibres in horses. These muscle fibres can use both fat or glucose for fuel, and what they use for fuel will depend on the horse’s diet. With the training of these muscle fibres, it takes a minimum of three weeks to effectively change fuel sources.

Fat sources are higher in caloric content than starches/sugars but are not an ideal fuel source for work that relies on fast-twitch muscle fibres. If the horse is required to do short speed work at a high intensity, NSCs are a crucial energy source as they can be immediately available for the horse to use.

Horses do receive some NSCs from their hay, and in most cases our riding horses in light or moderate work can be well-maintained on a grain-free diet. However, horses in very heavy work that results in a heart rate over 170 bpm may benefit from some carbohydrate-containing grains.

Both grass and legume hay will contain a small amount of starch, about two to three percent, and the sugar content will vary greatly depending on a variety of factors such as harvesting conditions, drying time, cutting time, and plant species in the forage. The starch content of grains will vary depending on the type; for example, oats are about 40 to 50 percent starch, whereas corn is about 70 percent. 

A performance horse in moderate work can likely be maintained on a grain-free ration with a supplemental source of vitamins and minerals, additional protein, and fats for calories. For horses in very heavy work that relies on fast-twitch muscle fibres (e.g., racing), having grains incorporated into the diet is beneficial to increase the amount of NSCs available for energy.

Safely Feeding Grains 

If you have a horse in heavy work that benefits from the inclusion of some grains, there are ways to feed these high-starch products to minimize the risk of gastrointestinal upset. The first consideration is meal size. As previously discussed, when large meals high in NSCs are fed, starch will reach the hindgut as the horse is not able to digest it all in the foregut. This negative situation can be avoided by feeding any high NSC products in small amounts to prevent the excess starch and sugar reaching the hindgut. Additionally, opting for processed grains (cracked, pelleted, extruded) improves the digestibility of the starch and lessens the risk of the undigested starch reaching the hindgut.

Related: Feeding Horses with Special Nutritional Needs

Senior Horses

Senior horses are often unique as they do not require starch and sugar for heavy work requirements, but generally need additional calories and protein above and beyond what their hay offers. When designing a grain-free ration for a senior horse, of course you must always start with a vitamin and mineral supplement at the bare minimum. From there, rely on your hay analysis to decide how much protein to add to the diet. Alfalfa, or other legumes and clovers, can be used to increase the protein content in a ration without adding grains. Alfalfa cubes and pellets are readily available and can be a great option for many senior horses.

The senior horse’s diet should always be based on a hay analysis. In addition to a vitamin and mineral supplement, they usually need additional calories and protein. Inset: Soaked hay cubes for a senior horse. Photos: Clix Photography

Adding fat sources is also recommended if your senior horse requires additional caloric supplementation but you wish to feed grain-free. Oils such as flax or camelina are popular, and other fat sources include ground flaxseed or products such as rice bran. These diets with vitamin and mineral supplementation, a quality protein source, and added fat are often great options for senior horses struggling to maintain weight but diagnosed with PPID or EMS.

To summarize, carbohydrates are an essential component of equine nutrition and must be provided to our horses. However, grains are high in NSCs and when fed in large amounts or to horses that do not require the additional supplementation, they can have a variety of negative health implications. There are also various health issues such as horses diagnosed with PSSM or EMS that require low NSC diets. In these situations, designing a grain-free diet is recommended. Grain-free is an option even for senior horses and many active horses. Remember that grains are not all bad and there is a time and a place for them in equine nutrition; however, they need to be fed in a way that minimizes the risk of digestive upset for our hard-working performance horses. 

Related: How to Accurately Feed a Forage-Based Diet

Related: How to Choose Horse Feed Supplements

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Main Photo: Dreamstime/Vanessa Van Rensburg