Fascinating new research suggests there may be limited benefits in giving joint supplements to older horses. Peter Green MRCVS looks at the evidence

Older horses stiffen up — their joints become less flexible, their tendons and ligaments lose their elasticity and things begin to creak.

Alongside this, a massive market promotes joint supplements to keep the spring in the step of these ageing horses. Apart from herbal painkillers like devil’s claw, most of these supplements contain “neutraceuticals” such as chondroitin sulphate and glucosamine.

Millions of people take these daily as capsules or powder, and thousands give them to older horses in the hope or belief that they keep them flexible, reduce joint ageing and prolong working life.

Vets in the Netherlands assessed 24 horses in their late 20s for lameness. The horses were trained to walk and trot on a laboratory treadmill, so stride length and joint flexibility could be accurately measured. Any obviously lame horses were rejected from the study, but those with barely perceptible and intermittent lameness were admitted. This was thought to be acceptable for old, stiff horses.

The horses were divided into 2 groups balanced for size and type. 1 group was fed a commercial chondroitin sulphate and glucosamine joint supplement for 3 months; the other a placebo that looked and smelled identical. The grooms and vets did not know which horses had received the active supplement and which the dummy.

During the experiment, the horses were turned out to pasture by day and stabled by night. All 24 horses were analysed again after 3 months. If the true joint supplement was going to have any effect, the vets expected stride length and joint flexibility to be increased.

The results, published in the Equine Veterinary Journal (EVJ), revealed that the supplement had made no difference. There was no increase in stride length in treated horses. Individuals in both groups showed increased joint flexibility, which was simply a result of the limited treadmill exercise. In fact, the horses receiving the placebo actually had slightly better knee flexion than those given the supplement.

The conclusion? Exercise keeps old horses more supple than joint supplements.