Horse owners often feed their horses various supplements in an attempt to improve some part of those horses' function, but very little scientific research has been done to prove or disprove their faith in these products. Hilary Clayton, BVMS, PhD, MRCVS, McPhail Dressage Chair in Equine Sports Medicine at Michigan State University's Mary Anne McPhail Equine Performance Center, shed some light on one product's efficacy in minimizing hock lameness with her presentation "Double-Blind Study of the Effects of an Oral Supplement Intended to Support Joint Health in Horses with Tarsal Degenerative Joint Disease" at the AAEP Convention.

The study looked at the effects of a joint supplement (Corta-Flx) on gait asymmetry caused by degenerative joint disease (DJD) of the distal intertarsal and/or tarsometatarsal joints of one or both hocks. "DJD is the most common form of joint disease in horses," Clayton stated. "The objective of this study was to objectively assess changes in gait variables in horses with tarsal DJD after administration of a joint supplement in a double-blind, placebo-controlled trial.

"DJD is a common pathology in older working horses, and the majority of affected horses show changes in more than one joint," she noted. "The horses used in this study were lame in multiple sites, leading to complex patterns of gait abnormalities and compensations, which are typical of the older working horse."

Eight horses were used in this study; all horses were treated with Corta-Flx and a placebo solution (with the same taste, smell, color, and consistency) in a randomized, cross-over design. The horses received either Corta-Flx or the placebo orally via syringe for two weeks, then there was a two-week period without any treatment, followed by the other treatment for two weeks. Treatments were given as loading doses (60 mL/day) for the first five days of each treatment period, then as maintenance doses (30 mL/day) for the last nine days.

The horses were taken off of all dietary supplements and medications for two weeks prior to the trial.

Gait analysis using joint markers and computerized video evaluation as the horses trotted in-hand on a rubberized runway was combined with force plate data to calculate several measures for comparing lameness between groups. Trotting speed was controlled so that horses moved at the same speed after treatment with Corta-Flx and the placebo. In horses receiving Corta-Flx, the left and right hind limbs showed significantly more symmetrical values for the peak vertical (weight-bearing) ground reaction force, vertical impulse, tarsal joint range of motion, and  tarsal joint energy generation during the stance phase. Thus, "This product produced a more symmetrical gait pattern," Clayton explained.

"The use of left-right asymmetries as a means of assessing the severity of lameness is well recognized," she said. A more symmetrical pattern is considered to be characteristic of a sounder horse.

As with any study, there are conditions for interpreting this one's results. "The results of this study are specific to the oral supplement used in this study, and would not necessarily apply to other similar products," Clayton cautioned.
Also, neither this nor any other product is a magic bullet. "It is unrealistic to expect that an oral supplement of this type will restore complete soundness," she explained, "but an effective product might be expected to improve the lameness so that the horse's gait pattern more closely approaches left-right symmetry."

About the Author

Christy M. West

Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.

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