Glucosamine and chondroitin sulfate are two of the most common ingredients found in equine joint products.
These natural supplements are purported to promote mobility and joint comfort in hard-working performance horses and aging seniors.
But despite their commercial success, there is limited research to support the efficacy of glucosamine or chondroitin in horses.
Although studies in humans, other animals and cell cultures suggest potential benefits, the results are not as promising when these supplements are fed to horses.
The poor results in horses are likely because these compounds are not well absorbed from the gut and are typically used at much lower doses than the amounts used in cell culture studies.
In this article, we will review the science behind glucosamine and chondroitin supplementation for horses and discuss alternatives that provide more effective support for your horse’s joints.
Glucosamine & Chondroitin for Joint Health in Horses
Glucosamine and chondroitin are generally purported to improve joint health in horses by supporting and protecting cartilage.
Both glucosamine and chondroitin are natural compounds found in high levels within cartilage tissue and synovial fluid.
But as we will discuss later on in this article, this doesn’t necessarily mean that feeding glucosamine or chondroitin sulfate will help keep your horse’s joints healthy.
Cartilage is the soft tissue made of collagen and elastic fibres, located at the end of your horse’s bones. This flexible connective tissue encapsulates joints, providing padding and allowing smooth joint movement.
Cartilage is one of several components of your horse’s joints that can become damaged from wear and tear as horses grow, age, perform work, or become injured.
Cartilage is produced by cells called chondrocytes. But as horses age, these cells lose their capacity to generate new cartilage. Chondrocytes can also start to produce factors that break down cartilage and cause inflammation. 
Synovial fluid is found within the joint capsule and is critical for maintaining healthy joints. It provides lubrication and reduces friction between the bones of the joints.
Changes in the composition of synovial fluid can decrease its lubricating properties, stimulate cartilage degradation and cause pain.
With significant cartilage degradation, your horse can begin to experience pain and a loss of normal joint function, potentially leading to a diagnosis of osteoarthritis.
Osteoarthritis is the most common form of degenerative joint disease in horses and the leading cause of lameness. Osteoarthritis is also characterized by synovial membrane inflammation and subchondral bone sclerosis – a condition in which the bones under the cartilage thickens.
Over 50% of horses aged 15 years or older experience osteoarthritis, and the prevalence is as high as 80-90% in horses over the age of 30. 
Given the high rates of equine joint disease, it is no surprise that there is significant demand for joint supplements that work for horses.
Let’s take a closer look at glucosamine and chondroitin and their purported effects on joint health in horses.
Glucosamine for Horses
Glucosamine is an amino sugar compound naturally produced by the horse’s body.
It is an important building block for larger molecules called glycosaminoglycans (GAGs), which are essential components of cartilage, joint fluid, vertebral disks, and other soft tissues.
Nutritional supplements are often made with glucosamine harvested from marine shellfish or produced synthetically in a lab. Commercially available forms include glucosamine hydrochloride, glucosamine sulfate, and N-acetyl-D-glucosamine. 
Mechanism of Action
- Exerting a chondroprotective effect to inhibit cartilage degradation or promote cartilage synthesis
- Preventing cartilage breakdown by inhibiting proteolytic enzymes
- Promoting the synthesis of GAGs to support connective tissues
- Reducing inflammation by regulating pro-inflammatory signals (such as cytokines)
Benefits for Horses
High quantities of glucosamine are naturally present in your horse’s connective tissues, and this compound is essential for healthy synovial fluid and joint cartilage, and .
Proponents of glucosamine supplementation claim that providing this nutrient in the diet might help to prevent or slow down cartilage degradation. 
Theoretically, this could help to promote soundness and potentially slow down the progression of osteoarthritis symptoms.
However, research into the benefits of glucosamine supplementation for horses has produced mixed results.
Scientists have extensively researched glucosamine for its potential benefits for joint health in humans, other animal species and cell cultures.
While there is evidence of efficacy in other species, there is limited data available to determine efficacy in horses.
Cell Sulture Studies
Some in vitro (cell culture) studies using equine joint tissue have shown promising results from applying a glucosamine treatment directly to articular cartilage. 
One study found that glucosamine-3-sulfate prevented cartilage degradation in cells taken from equine joints. 
However, there are significant differences between testing a supplement in cell culture studies and in living animals. While cell cultures can be used as a preliminary testing strategy, animal studies must be conducted to demonstrate therapeutic efficacy.
Furthermore, the dosages administered in the cell culture studies were significantly larger than the amount of glucosamine typically provided by commercial supplements. These dosages would be impractical for everyday use. 
Studies in Horses
Scientific studies in living animals consistently produce mixed results for glucosamine, with literature reviews often casting doubt on the usefulness of this ingredient as a joint supplement for horses. 
Positive results have come from studies with small sample sizes, unclear criteria for lameness evaluation, and no blinding or control group. These low-quality studies make it difficult to interpret the validity of their results.
The few higher-quality studies available yield poor results for glucosamine. One trial of yearling Quarter Horses found no reported differences between horses provided daily glucosamine supplementation and a control group. 
Another study involving young Standardbreds also found no significant results from supplementing 4 grams of glucosamine every 12 hours over 48 weeks of training. This protocol did not change any biomarkers for joint health. 
One of the reasons that glucosamine supplementation may not be effective for horses is the low oral bioavailability of this compound. Bioavailability measures how much of a substance is absorbed into the body.
According to independent research, the oral bioavailability of glucosamine is less than 6% in the horse.  This means that if you feed your horse 10 grams of glucosamine, only 600 mg is expected to enter circulation and exert a therapeutic effect on joint tissue.
Joint supplements that use glucosamine as an active ingredient often provide a lower dose than the amounts used in studies with positive findings.
When one study evaluated the glucosamine levels in commercially available equine joint supplements, they found that most contained significantly less than their label claimed. 
Chondroitin Sulfate for Horses
Many equine joint supplements are formulated with a combination of glucosamine and chondroitin sulfate to promote chondroprotective benefits.
Chondroitin sulfate is a sulfated glycosaminoglycan that is found in joint cartilage. It is composed of a chain of alternating sugars and is an important component of the extracellular matrix of connective tissues.
Bovine (cow), porcine (pig), or marine (fish) sources of chondroitin are commonly used in horse supplements. Chondroitin is usually combined with glucosamine because it is difficult to synthesize in the lab and formulate as a single-ingredient product.
While chondroitin is generally regarded as a safe feed additive, it is relatively expensive because it is difficult to extract. It also has varying absorption rates, depending on the source. 
Mechanism of Action
Chondroitin is purported to support joint health by the following mechanisms: 
- Supplying building blocks necessary to synthesize new components of the extracellular matrix, including stimulating cartilage synthesis
- Reducing inflammation by inhibiting the synthesis of inflammatory intermediates like COX-2, nitric oxide synthase, and certain prostaglandins
- Increasing hyaluronic acid (HA) concentrations in synovial fluid
Benefits for Horses
Chondroitin sulfate is believed to help manage pain, enhance mobility and promote joint health in horses.
It is purported to help delay the progression of osteoarthritis due to its anti-inflammatory and chondroprotective properties.  However, limited research in horses is available to support the claims made about this ingredient.
Chondroitin is also well-researched in humans, other species and in vitro lab studies, but has limited research in horses or equine cell cultures. Most studies evaluate chondroitin in combination with glucosamine, so it is difficult to isolate the efficacy of chondroitin on its own.
Cell culture studies
One study examined the effects of chondroitin on articular cartilage cells taken from the metacarpophalangeal joint of 13 horses. 
The researchers administered concentrations of chondroitin sulfate to approximate the dosages used in oral supplements. They observed no effect on mediators of osteoarthritis. 
Studies in Horses
Several studies have examined the effects of supplementing horses with a combination of glucosamine and chondroitin sulfate.
In one study, horses received one of the following treatments at each feeding for 15 days:
- 5.5 grams of glucosamine and 2 grams of chondroitin sulfate
- 8.5 grams of glucosamine and 3.5 grams of chondroitin sulfate
On both dosage regimens, the researchers failed to observe any change in blood concentrations for either glucosamine or chondroitin sulfate. This suggests that these compounds are not well-absorbed from the gut and are unlikely to have a therapeutic benefit to the horse. 
There is abundant scientific literature investigating the potential benefits of glucosamine and chondroitin for joint health. However, there is limited high-quality research on their use in horses.
Evidence from in vitro cell culture studies suggests potential benefits. But these studies use unrealistically high doses of glucosamine and chondroitin that would be prohibitively expensive or impractical to feed daily.
In vitro results must be validated with real-world clinical studies showing that glucosamine and chondroitin produce benefits when they are fed to horses.
So far, this has been a challenge likely due to the low oral bioavailability of glucosamine and chondroitin sulfate products. 
Low-Quality Equine Studies
Some of the in vivo studies that reported positive results had faults or flawed methods that made their data inconclusive. Examples of low-quality clinical equine studies include:
- Trials with small sample sizes
- Trials that did not include a control group to compare with the treatment group
- Trials that used subjective efficacy measures, such as subjective flexion responses and lameness grades. 
In contrast, studies with objective measures such as blood serum concentrations generally produced negative results. 
Given the mixed results and the lack of high-quality research data, there is insufficient evidence available to evaluate the efficacy of glucosamine and chondroitin for horses.
More research is needed to determine whether these supplements can help to support equine joint health.
Supporting Equine Joint Health
Other research-backed ingredients have been clinically studied and shown to support equine joint health. Below, we will discuss some of these alternative supplements and general management principles to help keep your horse’s joints healthy.
Always check with your veterinarian about specific health concerns. If your horse shows signs of osteoarthritis or another joint problem, consult your veterinarian to obtain a diagnosis and treatment plan.
Some key factors to support your horse’s joints include:
- Establishing an appropriate exercise program
- Supporting normal growth in young horses
- Providing a balanced diet with adequate vitamins & minerals
- Maintaining a healthy body condition
- Identifying lameness early
- Maintaining healthy hooves
If your horse is exhibiting joint stiffness, swelling, lameness or showing signs of pain consult with your veterinarian about potential causes and solutions.
Alternative Equine Joint Supplements
Before adding any supplements to your horse’s feeding program, ensure that their overall diet is balanced and that there are no vitamin or mineral deficiencies. You can work with our nutritionists to formulate a balanced feeding program for your horse for free.
Once you have addressed your horse’s core nutritional needs, consider adding nutraceutical supplements targeting joint health. These can work through a variety of mechanisms including:
- Inhibiting factors that break down cartilage
- Increasing the ability of chondrocytes to produce cartilage
- Reducing inflammation and/or oxidative stress
- Supporting other soft tissues including ligaments and tendons
- Improving synovial fluid composition
Here are five effective alternatives to glucosamine and chondroitin for horses.
1) Methylsulfonylmethane (MSM)
MSM is a highly bioavailable form of sulfur, which horses uses to synthesize cartilage and collagen found in soft tissues.
Although small amounts of MSM are naturally present in forage and grain, supplements are necessary to provide the amounts required to support joint health.
Research shows that MSM is effective against cartilage degradation and inflammation in horses. One study found that feeding 8 mg/kg of MSM daily for five weeks protected competition horses from exercise-induced inflammation and oxidative stress. 
To learn more, read our article on the Top 9 Benefits of MSM for Horses.
2) Omega-3 Fatty Acids
Most horse owners know that feeding omega-3 fatty acids can promote anti-inflammatory benefits.
In one study, feeding the omega-3 fatty acid DHA (docosahexaenoic acid) to arthritic horses decreased inflammation in the joints and normalized certain parameters of joint health. 
Omega-3 fatty acids have the highest quality evidence for protecting joints from the clinical signs of osteoarthritis in horses and other domestic animals. 
However, not all omega-3s are the same. ALA (alpha-linolenic acid) is a plant-based omega-3 found in flax and camelina oil. DHA and EPA (eicosapentaenoic acid) are omega-3’s found exclusively in marine sources.
Research shows that only DHA and EPA have anti-inflammatory effects, whereas ALA needs to first be converted to DHA and EPA to be effective.
Because only 10% of ALA is converted to EPA and less than 0.1% is converted to DHA, it is more effective to supplement with EPA and DHA directly. 
Comparison studies have found that supplementing DHA and/or EPA is more effective at lowering pro-inflammatory factors than supplementing with ALA and may also slow down cartilage degradation. 
Mad Barn’s w-3 oil provides 1,500 mg DHA per 100 ml serving along with high levels of natural vitamin E to support joint health.
3) Hyaluronic Acid
Hyaluronic acid (HA) is another vital component of connective tissue and cartilage. Joint injections often use hyaluronic acid injected directly into the joint to treat osteoarthritis and other conditions.
Oral supplements that contain hyaluronic acid are increasing in popularity as research demonstrates this compound is bioavailable, effective, and safe for horses.
Hyaluronic acid can also support horses with osteochondritis dissecans (OCD). One study found that feeding 100 mg of HA per day resulted in decreased effusion (swelling) in the affected joints of yearling Thoroughbreds with OCD. 
Resveratol is a natural polyphenolic compound found primarily in grapes and berries.
It has potent antioxidant effects that may benefit joints. Antioxidants protect tissues from oxidative damage by neutralizing free radicals.
Equine studies have found positive results using resveratrol in horses with mild lameness. Feeding 2,000 mg of powdered resveratrol for 10 days reduced markers of oxidative stress and cartilage degradation. 
5) Avocado/Soybean Unsaponifiables (ASU)
Avocado/Soybean Unsaponifiables, also known as ASU, are natural extracts from soybeans and avocados. They include a combination of triterpene alcohols, vitamins, and plant sterols that promote healthy joints.
ASUs stimulate collagen synthesis and inhibit molecules that lead to inflammation and degradation of cartilage. 
Human clinical trials of ASU supplements consistently show reduced pain associated with osteoarthritis. 
Research in horses is ongoing, but one equine study showed that ASU effectively prevented cartilage degradation and increased cartilage synthesis. 
- Despite the popularity of glucosamine and chondroitin supplements for horses, there is limited high-quality research to back up the efficacy of these ingredients for joint health.
- If you’re looking for an equine joint supplement, consider research-backed alternatives, such as MSM, omega-3 fatty acids, or hyaluronic acid.
- Joint supplements are just one part of a comprehensive approach to supporting your horse’s soundness and mobility. Review our 8 Principles for Healthy Joints for more tips.
- A balanced diet with adequate amino acids, vitamins, and minerals is also essential to bone and soft tissue development.
You can help to ensure that your horse’s diet is providing everything they need to support healthy joints by submitting their infromation online. Consult with our equine nutritionists for free to learn more about feeding for optimal equine joint health.
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