Microdamage to the bones in the joints of racehorses has been detected in multiple studies, but a cut-and-dry answer on how to prevent this damage is not clear. The accumulation of subchondral bone microdamage in the forelegs of racehorses is thought to lead to more significant bone damage, including fractures, which can be life-threatening.
A study done by the University of Melbourne set out to quantify subchondral bone microdamage in the third metacarpal bone of Thoroughbreds in different stages of their training to be a racehorse. The results suggest that extending rest periods or decreasing training intensity may reduce bone damage, but a specific length of time or degree to which training should be lessened is not known.
For the study, Dr. Chris Whitton analyzed bone samples of 46 racing Thoroughbreds port-mortem. Of those, 26 horses were in training at the time of death and 20 horses were resting from training. No limbs were used that had catastrophic injuries that required euthanasia; other than that caveat, all other limbs were chosen at random for analysis.
The bones were examined using micro computer tomography (microCT) to determine if they had microcracks; light microscopy was used to determine other microcracks in the subchondral layer of bone, which serves as a shock absorber in joints that bear weight. Racing histories were also obtained on all of the horses.
The researchers reported that subchondral bone microcracks were seen in every horse using at least one method of detection. The damage was greater and more-dense in older horses. Reports indicate that the damage accumulates throughout a horse's racing career.
Not taking into account the age of the horse, microdamage was lower in resting horses. From these results, the study team proposed allowing racing Thoroughbreds adequate rest periods during training and training at a lower intensity to reduce the rate of microdamage. The length of rest or decreased intensity of exercise deemed “adequate” is not known.
Read more at HorseTalk.
Read the full study here.
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