The use of herbs in horse feeding has increased over recent decades, yet the topic continues to raise many questions. Are herbs simply part of traditional horse management, or is there scientific evidence supporting their use?
According to current research, the answer lies somewhere in between. Many herbs used for horses contain nutritionally interesting compounds, and some plants have also been investigated in scientific studies. At the same time, researchers point out that the effects of many herbs have been studied far less extensively in horses than in humans or livestock species.
One thing is fairly clear, however: in nature, a horse's diet is far more diverse than simply hay or pasture grass.
Horses Are Naturally Diverse Plant Consumers
Wild horses utilize dozens of different plant species throughout the year. In addition to grasses, they consume herbs, shrubs, tree leaves, bark, seeds, and roots.
This means that horses naturally ingest a wide variety of plant-derived compounds. In modern stable environments, feeding programs are often much less diverse, which is one reason why many researchers consider the inclusion of herbs a biologically relevant way to increase dietary diversity.
What Do Herbs Contain?
The interest in herbs is not based solely on their vitamin or mineral content.
Plants naturally contain compounds such as:
- Fiber
- Polyphenols
- Flavonoids
- Carotenoids
- Essential oils
- Mucilage compounds
- Various organic sulfur compounds
These substances are a natural part of plant structure and metabolism. Their presence is one reason why plants have attracted growing interest in animal nutrition research.
What Has Research Found?
One of the best-known reviews on herbal feeding in horses was published in 2008 by Carey Williams and Emily Lamprecht, who examined commonly used herbs and plant-based feed ingredients.
The review included:
- Garlic
- Ginger
- Echinacea
- Ginseng
- Yucca
- Various plant-based feed supplements
The authors concluded that many plants contain biologically active compounds, but relatively few studies have been conducted specifically in horses. The use of most herbs is currently based on a combination of traditional use, known nutritional characteristics, and research conducted in other animal species.
In recent years, however, more studies have been published, particularly concerning digestion, antioxidant compounds, and plant bioactives.
Rosehip – One of the Most Studied Plants in Horses
Rosehip (Rosa canina) is among the few plants that have been investigated in controlled equine studies.
Researchers have been particularly interested in its content of:
- Polyphenols
- Flavonoids
- Carotenoids
- Vitamin C
- Pectin
- Fiber
In 2010, Winther and colleagues conducted a randomized, placebo-controlled, double-blind study investigating the effects of rosehip on the immune system, work capacity, and behavior of horses.
The study found differences between horses receiving rosehip and those receiving a placebo in several measured parameters. The results suggested that compounds naturally present in rosehip may influence certain physiological responses.
In 2012, the same research group studied the absorption of natural vitamin C from rosehip and markers related to antioxidant capacity in trotters during a three-month feeding period.
The researchers observed changes in antioxidant-related measurements compared with the control group. According to the authors, rosehip may serve as a natural source of antioxidant compounds in equine nutrition.
Garlic – One of the World's Most Studied Herbs
Garlic (Allium sativum) is one of the best-known and most extensively studied plants in horse nutrition.
The compounds that attract the most scientific interest include various organic sulfur compounds such as allicin, along with numerous other naturally occurring plant constituents.
Studies in horses have focused particularly on:
- Respiratory parameters
- Mucus production
- Blood values
- Long-term safety
In a study published in 2019, horses received dried garlic for more than 80 days. Researchers observed changes in certain respiratory findings and in the composition of tracheal mucus compared with the control group.
At the same time, research has shown that very high levels of garlic intake may affect red blood cells. For this reason, researchers emphasize the importance of appropriate dosing and the use of garlic as part of a balanced feeding program rather than in excessive amounts.
Garlic is a good example of a plant whose use is supported by both a long history of traditional feeding and scientific research.
Mucilage-Rich Plants – Interesting Because of Their Physical Properties
Not all herbs are of interest because of their bioactive compounds.
Some plants contain high levels of mucilage, a group of polysaccharides that form gel-like structures when mixed with water. The significance of these plants is primarily related to their physical properties.
Well-known mucilage-rich plants include:
- Marshmallow root (Althaea officinalis)
- Slippery elm (Ulmus rubra)
- Psyllium (Plantago ovata)
- Flaxseed
- Fenugreek
- Chia seeds
When mucilage compounds come into contact with water, they form a gel-like structure.
Researchers are particularly interested in:
- The structure of digesta
- Soluble fibers
- Gel formation
- Natural mucilage compounds present in plants
Marshmallow root and slippery elm are especially known for their high mucilage content. Psyllium is one of the most extensively studied mucilage-rich plants in horses, and its use is based on its ability to absorb large amounts of water and form a gel-like mass.
In chia seeds, researchers are additionally interested in the naturally high content of omega fatty acids.
The use of mucilage-rich plants is primarily based on their well-known composition and their content of soluble fiber and mucilage compounds.
Can Horses Select the Plants They Need?
In recent years, researchers have also become interested in a phenomenon known as zoopharmacognosy.
This term refers to an animal's ability to select particular plants or substances from its environment.
In studies where horses have been offered a range of different plants simultaneously, researchers have observed considerable individual variation in plant selection.
Although current research does not demonstrate that horses can "self-medicate" using specific plants, it does suggest that horses make far more complex and varied plant choices than previously believed. Horses are also highly capable of recognizing and avoiding many plants that are unsuitable for them.
Herbal Feeding and Summer Grazing – The Same Idea in Different Forms
Summer grazing provides an excellent example of how a diverse range of plants naturally forms part of the horse's diet. Well-managed pasture often contains multiple species of grasses and herbs, offering variation along with a wide range of nutrients and naturally occurring plant compounds.
In nature, a horse's diet is not based on just one or two plant species. Instead, horses utilize a broad variety of plants that change with the seasons. From this perspective, the inclusion of herbs in the diet can be seen as a way of increasing dietary diversity, particularly when a horse's daily ration consists primarily of hay and other conventional feed ingredients.
Whether the plants come from summer pasture, wild herbs, or carefully selected herbal supplements, the common denominator remains the same: a diverse plant intake has been a natural part of the horse's diet throughout its evolutionary history.
References
Williams CA & Lamprecht ED (2008). Some Commonly Fed Herbs and Other Functional Foods in Equine Nutrition: A Review. The Veterinary Journal.
Winther K et al. (2010). A Randomised Placebo Controlled Double Blind Study on the Effect of Subspecies of Rose Hip (Rosa canina) on the Immune System, Working Capacity and Behaviour of Horses.
Winther K et al. (2012). The Absorption of Natural Vitamin C in Horses and Anti-Oxidative Capacity: A Randomised Controlled Study on Trotters During a Three-Month Intervention Period. Comparative Exercise Physiology 8:195–201.
Mazan MR et al. (2019). Effects of Feeding Garlic (Allium sativum) on the Respiratory Health of Horses.
Pearson W et al. (2005). Effects of Dietary Garlic on Blood Parameters in Horses.
Elghandour MMY et al. (2018). Plant Bioactives and Extracts as Feed Additives in Horse Nutrition.
