The Hidden Link Between High‑Protein Diets and Arthritis in Horses

One of the overlooked contributors to joint issues in horses is excess protein in the diet. Protein itself isn’t the problem, horses absolutely need it for muscle repair, immune function, and overall health. The trouble begins when the horse receives more protein than their body can comfortably use. When this happens, the liver must convert the extra amino acids into ammonia and urea, which creates an acidic internal environment. To buffer this acidity, the body pulls calcium from the bones, slowly weakening bone density and compromising the structural integrity of the spine, joints, and hooves. At the same time, uric acid, another byproduct of protein metabolism, can irritate joint tissues and contribute to inflammation. Over months or years, this combination of mineral loss and chronic inflammation can set the stage for arthritis and other degenerative changes.

This is something I see all the time in my osteopathic practice. It’s often the horses who have arthritis in multiple joints, or those who show restriction in several areas but have clean X‑rays. They may have intermittent lameness, stiffness that comes and goes, or a general sense of being “off” without a clear diagnosis. These horses frequently have underlying metabolic stress that isn’t being addressed  and diet plays a much bigger role in this than most people realize. This is why I am so dedicated to helping owners understand the holistic side of equine nutrition. Supporting the body from the inside out is essential, and it often means challenging the norm and thinking outside the box. We can’t keep feeding horses a certain way just because “it’s always been done that way.” We have to read the horse in front of us.

It’s also important to remember that too little protein can be just as damaging. Horses who are underfed protein may struggle with weak connective tissue, slow recovery, and compromised immune function. Both extremes too much and too little create stress on the body in different ways. This is why it is so important to know what we are feeding and why. Guessing rarely works over time, although you can sometimes get away with it for quite some time. Understanding the forage, the workload, the individual horse, and the balance of the whole diet is what allows us to support them properly.

When bones become weakened or unstable, the body tries to compensate by laying down extra bone in an attempt to create stability. Unfortunately, this “reinforcement” bone is not the strong, healthy bone we want. It’s reactive bone, lower in quality, less dense, and structurally inferior. This is the type of bone change we see in conditions like kissing spine, ringbone, sidebone, arthritis, and even EORTH. These issues don’t appear overnight; they develop slowly, often in horses who have been on high‑protein diets for long periods, especially when combined with stress, inflammation, or mineral imbalance. Many owners don’t realize that feeding extra protein “for muscle” can actually create the opposite effect over time by stressing the liver, weakening the bones, and increasing joint inflammation.

The encouraging part is that once we understand this connection, we can make better choices for our horses. Supporting mineral balance, reducing unnecessary protein, and focusing on high‑quality forage can dramatically reduce the metabolic burden on the joints. When the diet is balanced and the digestive system is supported, the body can rebuild stronger, healthier bone and maintain joint integrity more effectively. Arthritis isn’t just a wear‑and‑tear issue in many horses, it’s a metabolic one. And by feeding with intention, we can help prevent the cascade that leads to chronic joint changes and keep our horses moving comfortably for years to come.