An Updated Look at Hemp: A Powerful Alternative to Soy in the Equine Diet

Updated to reflect current research on hemp nutrition, fatty acids, and concerns about soy-based feeds

by Juliet M. Getty, Ph.D. 

Look at the ingredient label on commercial horse feeds and supplements and you will likely see soy listed as a primary ingredient. Soybean meal is commonly used as a concentrated source of protein, and soybean oil is often included as a fat supplement. For decades, soy has been a staple ingredient in equine feeds because it is inexpensive and provides a concentrated source of protein.

However, horses did not evolve eating a single concentrated plant ingredient. In nature they consume a wide variety of plants, each contributing different nutrients that together create a balanced diet. As our understanding of equine nutrition continues to evolve, it is worth taking a closer look at whether commonly used feed ingredients truly support the horse’s natural physiology.

Today, however, horse owners are reconsidering soy as a routine component of the equine diet. Increasing numbers of feed manufacturers are introducing soy-free formulations, and interest in alternative plant-based protein sources continues to grow. This shift reflects a broader trend toward feeding horses in a way that more closely resembles their natural diet—one that emphasizes a variety of whole plant foods rather than heavy reliance on a single concentrated ingredient.

Several factors contribute to this change.

Concerns About Soy in the Equine Diet

Genetically Modified Soy and Herbicide Exposure

Most soy grown in the United States is genetically engineered to tolerate applications of glyphosate, the active ingredient in the herbicide Roundup®. Approximately 95% of soybeans produced in the United States are genetically engineered for herbicide tolerance (USDA ERS, 2024). This allows farmers to spray fields to control weeds without harming the crop, but it also contributes to widespread glyphosate use in soybean agriculture.

Concerns have been raised about potential health effects associated with glyphosate exposure. There are studies that suggest glyphosate may disrupt beneficial gut bacteria and interfere with mineral metabolism, which may contribute to broader metabolic and inflammatory disturbances in animals and humans (Shehata et al., 2013; Myers et al., 2016; Mesnage & Antoniou, 2020; Vandenberg et al., 2023).

More recent reviews have continued to examine glyphosate’s potential effects on biological systems and microbiomes (Mesnage & Antoniou, 2020; Vandenberg et al., 2023).

In 2015, the International Agency for Research on Cancer classified glyphosate as “probably carcinogenic to humans” (Guyton et al., 2015). While regulatory agencies continue to debate the level of risk associated with dietary exposure, the widespread use of glyphosate in agriculture caused increased interest in avoiding genetically modified soy.

It is important to note that organic soybeans are not genetically engineered and are produced without the use of glyphosate-based herbicides, which reduces some of the concerns associated with conventionally grown soy.

Anti-Nutritional Factors

Raw soybeans naturally contain compounds known as trypsin inhibitors, which interfere with protein digestion by reducing the activity of digestive enzymes. These inhibitors must be destroyed through proper heat processing, but feed labels do not always specify the degree of processing used (Liener, 1994).

Phytoestrogens

Soybeans also contain isoflavones, a class of phytoestrogens that can interact with hormone receptors in the body. Because phytoestrogens can mimic or modulate estrogen activity, many horse owners prefer to limit soy intake in the diet (Messina, 2016).

Fatty Acid Imbalance

Soybean oil is particularly high in linoleic acid, an omega-6 fatty acid. Linoleic acid is essential because the horse cannot synthesize it, but excessive omega-6 intake relative to omega-3 fatty acids can promote the production of pro-inflammatory signaling molecules in the body (Calder, 2015). Because soybean oil contains far more omega-6 than omega-3 fatty acids, heavy reliance on soy-based feeds can contribute to an imbalance in the dietary fatty acid profile and may promote inflammatory processes affecting tissues such as joints, skin, hooves, and the digestive tract.

For these reasons, it has become commonplace for horse owners to explore alternative plant-based protein sources. One seed in particular is gaining attention for its exceptional protein quality and beneficial fatty acid profile.

Why Protein Quality Matters

Horses require nine essential amino acids, meaning they must be supplied in the diet because the body either cannot produce them or cannot produce them in adequate quantities to meet physiological needs (National Research Council, 2007). Arginine is sometimes described as conditionally essential, particularly in young growing horses, because their metabolic demand for this amino acid may exceed the body’s ability to synthesize it.

Protein quality depends not only on the percentage of protein, but on the balance of essential amino acids. In horses, lysine is typically the first limiting amino acid, meaning that if lysine is present in insufficient amounts, the other amino acids cannot be fully utilized for tissue repair and growth. For this reason, you will find equine supplements that are formulated to provide the three most commonly limiting amino acids—lysine, methionine, and threonine—to help improve the overall amino acid balance of the diet.

Once the limiting amino acids are depleted, there will be amino acids that remain unused. The body cannot store these excess amino acids. Instead, they are broken down in the liver, where the nitrogen portion is converted to urea and excreted in the urine. The remaining carbon skeletons may be used for energy or, under certain metabolic conditions, converted to glucose through a process known as gluconeogenesis. Providing protein sources with a balanced amino acid profile helps ensure that dietary protein is used efficiently rather than unnecessarily metabolized.

Why Horses Benefit from Diverse Plant Proteins

Most horse owners rely on forage as the primary source of protein in the diet. While hay often provides adequate crude protein, the crude protein value alone does not indicate protein quality or the balance of essential amino acids. Grass hays in particular can be limited in certain essential amino acids, especially lysine.

To compensate, a concentrated protein source such as soybean meal is added as a convenient way to improve amino acid balance. Other horse owners will do this by adding alfalfa hay, which typically contains more protein than grass hay. While alfalfa can improve overall protein intake, its amino acid profile is still limited in certain essential amino acids and may not provide an optimal balance on its own.

In nature, however, horses do not rely on only one or two protein sources. Instead, they graze on a wide variety of grasses, legumes, herbs, flowers, and other plants throughout the day. Each plant contributes its own unique nutrient profile, and together these plants provide a broader spectrum of amino acids, fatty acids, vitamins, and minerals.

Modern feeding practices often move away from this natural diversity by relying heavily on one concentrated protein source. Incorporating a variety of plant proteins more closely mirrors the horse’s evolutionary diet and can help create a more balanced nutritional profile. Ingredients such as hemp seeds, along with forage sources like grasses and legumes, and a source of essential fatty acids such as ground flaxseeds or chia seeds, can help provide a broader range of amino acids and beneficial nutrients that support overall health.

Hemp Seeds: A Nutritious Alternative

Hemp seeds are gaining popularity as a feed ingredient for horses because they provide high-quality protein, beneficial fatty acids, and valuable micronutrients.

Although hemp and marijuana belong to the same botanical genus (Cannabis), they are quite different varieties. Hemp is bred to contain extremely low levels of the psychoactive compound THC and does not produce intoxicating effects. Hemp seeds themselves do not produce cannabinoids such as THC or CBD. These compounds are found primarily in the flowers, leaves, and stems of the plant. Any cannabinoids detected in hemp seed products typically result from trace contamination during harvesting or processing rather than from the seed itself (Callaway, 2024).

High-Quality Hemp Protein

Hemp seeds contain all essential amino acids and provide a well-balanced amino acid profile, making them a valuable component of a diversified plant-based protein supply. Their primary storage proteins—edestin and albumin—are highly digestible globular proteins that provide a balanced spectrum of amino acids.

Research evaluating hemp seed protein quality has demonstrated favorable digestibility and a balanced amino acid composition compared with other plant proteins (House et al., 2010; Tang et al., 2006). More recent reviews continue to confirm the strong nutritional profile and functional benefits of hemp seed proteins (Wang & Xiong, 2019; El-Sohaimy et al., 2023; Wang et al., 2025).

Beneficial Fatty Acids

Hemp seeds contain both essential fatty acids—linoleic acid (omega-6) and alpha-linolenic acid (omega-3)—in approximately a 2–3:1 ratio of omega-6 to omega-3. While this ratio is more moderate than that found in other vegetable oils commonly used in horse feeds, it still provides more omega-6 than omega-3, which is opposite of what is typically found in fresh pasture grasses. For this reason, hemp seeds should not be relied upon as the sole source of essential fatty acids in the diet.

Soybean oil contains 7 to 8 times more omega-6 than omega-3, while oils such as corn or cottonseed oil provide prominent levels of omega-6 with trace levels omega-3 fatty acids. Because excessive omega-6 relative to omega-3 can promote inflammatory processes throughout the body, relying heavily on these oils can contribute to an imbalanced fatty-acid profile.

For optimal fatty acid balance, hemp is best combined with omega-3–rich seeds such as flaxseed or chia, both of which contain approximately four times more omega-3 than omega-6, similar to the fatty acid profile found in fresh pasture grasses.

Hemp seeds also contain gamma-linolenic acid (GLA), a unique fatty acid belonging to the omega-6 family. Unlike linoleic acid, which can contribute to inflammatory processes when consumed in excess, GLA plays a role in regulating inflammatory responses and supporting immune function. This makes hemp seeds somewhat unique among plant oils, as they provide both essential fatty acids along with this beneficial anti-inflammatory component.

In addition, hemp seeds provide stearidonic acid (SDA), a less common omega-3 fatty acid that serves as a metabolic precursor to longer-chain omega-3 fatty acids involved in anti-inflammatory pathways. Because SDA is more readily converted in the body than alpha-linolenic acid alone, its presence further enhances the nutritional value of hemp as a source of beneficial fats.

Additional Benefits of Hemp Seeds

Hemp seeds offer practical advantages when included in the horse’s diet.

• Naturally free of enzyme inhibitors and can be fed raw
• Highly digestible
• Highly palatable, even for picky eaters
• A natural source of vitamin E and beneficial minerals

Hemp Products are Available in Several Forms

Different forms allow horse owners to choose the option that best fits their horse’s nutritional needs.

Hemp seed meal is produced by grinding whole hemp seeds and removing a portion of the oil. This product typically contains about 30% protein and retains a significant amount of fiber from the outer hull.

A second option is the hemp seed heart, which is the inner portion of the seed after the fibrous hull has been removed. Hemp hearts provide a high-protein, high-fat whole food, making them an excellent choice for horses that can benefit from additional calories supplied by fat.

A third option is a concentrated protein product such as Organic Hemp Protein 74%, which is made by grinding the hemp seed heart and removing most of the oil. The result is a highly concentrated source of amino acids with little fat or fiber.

In addition, hemp seed heart oil is available as a fat supplement. Because it is pressed from the seed heart rather than the whole seed, it lacks the bitterness sometimes associated with oils pressed from seeds that still contain the outer hull.

Amount to Feed

The amount fed will depend on the horse’s size, body condition, and the rest of the diet. For an average 1,100-pound horse (approximately 500 kg), about ½ to two cups of a hemp product (meal, hearts, or protein) per day will provide a meaningful contribution of protein and beneficial fats. Horses needing additional calories may benefit from the higher-fat options such as hemp seed hearts, while those requiring additional protein without additional fat can be fed hemp protein 74%, which is a protein isolate supplying concentrated amino acids with truly little fat.

Bottom Line

Soybean meal has long been used as a convenient source of protein in commercial horse feeds. However, growing concerns about genetically modified soy, herbicide exposure, and the potential inflammatory effects associated with soy-based ingredients have led an increasing number of horse owners to explore alternative protein sources.

Hemp seeds provide a nutritious whole-food option that supplies high-quality protein, beneficial fatty acids, and valuable micronutrients. When combined with forage and other plant-based ingredients, hemp can help create a more diverse and balanced diet that better reflects the way horses are naturally designed to eat.

Ultimately, feeding horses according to their natural physiology means emphasizing forage, variety, and whole plant ingredients. Including nutrient-dense foods such as hemp seeds is one way to move closer to the type of diet horses evolved to eat—one built on balance, diversity, and the wisdom of nature.

References

Callaway, J.C. 2004. Hempseed as a nutritional resource: An overview. Euphytica.

Calder, P.C. 2015. Functional roles of fatty acids and their effects on inflammation. Journal of Parenteral and Enteral Nutrition.

El-Sohaimy, S. et al. 2023. Nutritional composition and functional properties of hemp seed proteins. Food Reviews International.

Guyton, K.Z. et al. 2015. Carcinogenicity of glyphosate. The Lancet Oncology.

House, J.D., Neufeld, J., & Leson, G. 2010. Evaluating the quality of protein from hemp seed. Food Chemistry.

Liener, I.E., 1994. Implications of antinutritional components in soybean foods. Critical Reviews in Food Science and Nutrition.

Mesnage, R., & Antoniou, M. 2020. Facts and fallacies in the debate on glyphosate toxicity. Frontiers in Public Health.

Messina, M. 2016. Soy and health update: Evaluation of the clinical and epidemiologic literature. Nutrients.

Myers, J.P. et al. 2016. Concerns over glyphosate-based herbicides and risks associated with exposures. Environmental Health.

National Research Council. 2007. Nutrient Requirements of Horses. National Academies Press.

Shehata, A.A. et al. 2013. Effect of glyphosate on beneficial and pathogenic bacteria. Current Microbiology.

Tang, C.H. et al. 2006. Physicochemical and functional properties of hemp protein isolate. Journal of Agricultural and Food Chemistry.

USDA Economic Research Service. 2024. Adoption of genetically engineered crops in the United States.

Wang, X., & Xiong, Y. 2019. Processing and nutrition of hempseed protein: A review. Comprehensive Reviews in Food Science and Food Safety.

Wang, Q. et al. 2025. Hemp seed as an emerging source of functional ingredients. Critical Reviews in Food Science and Nutrition.