Your horse’s joints are the linchpins of his athletic ability and longevity, so keeping them healthy should be a vital component of your care routine. Most of the major joints involved in movement contain cartilage, the tissue that creates a cushion between the bones of a joint. Over time, cartilage wear and tear can lead to effects on soundness and comfort. Although many people feed horses oral supplements to help protect their joints from such damage, scientific evidence supporting these products is often lacking. However, a recent study suggests that using a combination of three specific ingredients supports horses’ joints, even in the face of possible negative effects seen in cell cultures with antibiotic use.

Studying the Effects of Antibiotics on Joints

Two common routes for administering antibiotics into horses’ legs are intravenous regional limb perfusion and intra-articular injection. Intravenous regional limb perfusion involves a veterinarian injecting an antibiotic into a vein in the horse’s leg to locally treat a wound and/or infection in that leg. An intra-articular injection is performed by a veterinarian injecting a substance directly into the joint. Because introducing a needle into the sterile environment of a joint when administering other substances, such as hyaluronic acid or steroids, raises the risk of infection, most veterinarians also incorporate a small amount of antibiotic medication into these injections as a preventative.

This study, which was conducted by scientists at Michigan State University, Mississippi State University and Nutramax Laboratories, Inc., investigated the pathway by which antibiotics may cause adverse effects on joint health. They also tested to see if the pathway could be affected in cartilage cells by a combination of three compounds: glucosamine and chondroitin sulfate, which are both components of cartilage, and avocado/soybean unsaponifiables (ASU), which comprise of an extract from avocado and soybean oils. The researchers collected chondrocytes (cartilage cells) from healthy knee (carpal) joints of 12 horses for the laboratory study.

Part 1: Measuring Effects of Antibiotics on Cartilage Cells

In the first part of the experiment, the chondrocytes were exposed to two different types of antibiotics at increasingly higher levels. When the antibiotic concentrations were comparable to the doses that horses would experience in the above-described injection techniques, the cartilage cells began to die off. The higher the antibiotic levels went, the more cells died.

Part 2: Measuring Effects of Supplement Ingredients on PGE₂

In the second part of the experiment, researchers observed that the chondrocytes produced a substance called prostaglandin E₂ (PGE₂) when they were exposed to one of the antibiotics. PGE₂ is known to contribute to cartilage breakdown and joint discomfort by inhibiting the synthesis of cartilage building blocks and stimulating the production of substances that lead to inflammation. This inflammatory mediator also likely played a role in the antibiotic-involved cartilage cell death researchers observed in this study.

Next, the scientists assessed the effects of the combination of ASU, glucosamine and chondroitin sulfate on PGE₂ levels in antibiotic-exposed chondrocytes. Indeed, this mixture of ingredients significantly reduced the production of PGE₂ levels stimulated by the antibiotic.

The researchers concluded that the combination of ASU, glucosamine and chondroitin sulfate, the primary ingredients found in Cosequin® ASU and Cosequin® ASU Plus, could serve to potentially influence production of mediators associated with the undesirable effects that some antibiotic medications might cause in equine joints. This adds to the growing evidence that suggests this blend of ingredients may help to maintain joint health and inhibit inflammatory mediators that can lead to cartilage breakdown.

“The ever-expanding body of research surrounding ASU, glucosamine and chondroitin sulfate continues to serve as support of their use in any horse,” said Stacey Buzzell, DVM, R&D technical services veterinarian for Nutramax. “The more we learn about common treatment modalities, in this case, antibiotics, and their effects, the more we see an opportunity for compounds such as these to support positive effects and minimize drawbacks for the benefit of the patient. I believe it is never too early or too late to start giving your horse these supplements.”