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Do Horse Tendon Injuries Have A Genetic Component?By Kentucky Equine Research Staff · January 22, 2015

Injuries to the superficial digital flexor tendon can occur when horses take an awkward galloping stride, slip or get bogged down on soft ground, or are worked too long or hard for their stage of fitness. Recovery from a serious tendon injury usually requires months of rest, and not all horses can return to their previous level of performance even after healing is complete.

Some horses suffer tendon injuries even though they have been carefully conditioned and exercised, leading owners to wonder if another risk factor might be involved. Recent British research on tendon injuries in Thoroughbred racehorses has suggested that some horses may be genetically predisposed to tendon injuries. Supported by the Horserace Betting Levy Board, the research team compared the genetic makeup of 270 horses with inflammation of the superficial digital flexor tendon. Another 270 unaffected horses in a control group were also studied. Specifically, the researchers looked at single nucleotide polymorphisms, or SNPs, in the genes involved in equine tendon structure, function, and remodeling as well as a set of genes corresponding to human genes involved in Achilles tendon problems.

Results showed that sequence variants in specific genes known as TNC and COL5A1 were associated in various ways with tendon strains in racehorses. A SNP in COL5A1 significantly increased the odds of having tendon inflammation, and horses with two copies of the COL5A1 COL5A1_01 variant allele were almost three times more likely to have tendon problems than those with normal genes. On the other hand, horses with a SNP in the TNC gene were significantly less likely to have tendon injuries. TNC is an important part of tissue remodeling, responding to and regulated by mechanical loading.

Injuries to racehorses are often related to more than one precipitating cause, and a training program that ends in injury for one horse might prove to be completely safe for another horse in the same stable. More studies may help to define the significance of genetic factors in tendon injury. When these factors are better understood, it may be possible to identify at-risk horses and design training programs to minimize the likelihood of injury to the superficial digital flexor tendon.