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.

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Cartilage

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. [1]

Synovial fluid

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.

Osteoarthritis

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. [29]

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. [2]

Mechanism of Action

Glucosamine is purported to prevent joint cartilage deterioration, but its efficacy is still under debate. Some proposed mechanisms of action for glucosamine include: [3][4]

  • 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. [5]

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.

Research Findings

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 Culture Studies

Some in vitro (cell culture) studies using equine joint tissue have shown promising results from applying a glucosamine treatment directly to articular cartilage. [6]

One study found that glucosamine-3-sulfate prevented cartilage degradation in cells taken from equine joints. [7]

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. [7]

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. [6]

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. [8]

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. [9]

Bioavailability

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. [11] This means that if you feed your horse 10 grams of glucosamine, only 600 mg is expected to enter circulati