Catastrophic breakdowns: Drugs may be the real culprit in injuries to young horses

The training and racing of two-year-old horses are supported by the findings of a just-published scientific review, but the authors pose an uncomfortable question: Is the prolific use of pain-relieving substances the real culprit in many catastrophic injuries?

Alyssa Logan and Brian Nielsen, writing in the journal Animals, acknowledged the common debate among equine professionals and enthusiasts alike over whether entering race training at two years of age is harmful or beneficial to the animal’s career and growth.

Conflicting research and anecdotal evidence have created disagreement over the question, they said.

Logan and Nielsen, with the Department of Animal Science at Michigan State University, evaluated a range of studies to better determine the impact of training and racing on young horses.

The evidence suggests that two-year-old horses are not at greater risk of injury compared to older horses, the pair reported. “Horses which enter race training at two years of age are, in fact, found to have greater earnings and longer race careers.”

They also explored data relating to equine bone, joint cartilage, and tendons to determine the impact that exercising an animal at two years of age or younger has on these tissues.

“Numerous studies on growing animals have found confinement to be detrimental to normal musculoskeletal growth,” they said.

“However, exercise of dynamic nature in moderate distances, such as that attained with pasture access or prescribed sprints, is beneficial to musculoskeletal development and may prevent injuries when entering race training.”

Based on scientific evidence, the research examined in the review supports the training and racing of two-year-old horses, they said.

“The evaluation of numerous studies on the topic provides evidence that a horse which is trained or raced as a two-year-old has a lower risk of injury and better-adapted tissues for the rigors of racing.

“Unfortunately, the current prolific use of pain-mitigating substances in the racing industry does place horses, including young cohorts, at greater risk of injury, and should be used with caution.”

The researchers, who cited 65 scientific papers in their paper, noted that, despite clear scientific evidence that training horses, while they are young and growing, is beneficial for producing a strong musculoskeletal system that is better prepared to handle competition, many in the horse community are quick to condemn the practice.

“The belief is that waiting until a horse is skeletally mature is the best approach to avoid injury.”

Indeed, a recent poll on the Facebook page of Feed XL Nutrition Software found that 79% of their followers believed that horses should start work when almost mature (4 years of age or older), and 21% felt that work should start when horses are young (less than 2 years of age).

This survey did not specify racing horses only, and could have encompassed individuals involved in many different equine sports, they noted.

Turning to injuries and their prevention, Logan and Nielsen discussed the risks of well-intended treatments that mask the pain but do not cure the injury.

“When a problem develops in training, pain-mitigating medications such as corticosteroids are often provided instead of rest or a reduction in training load,” they said.

The authors noted that Thoroughbreds and Quarter Horses that died as a result of race training had five times greater odds of having hyaluronic acid injections compared to animals that had not died during race training.

In Kentucky, horses who sustained a catastrophic musculoskeletal injury had greater levels of non-steroidal anti-inflammatory drugs.

“Horses administered a local corticosteroid injection up to 398 days before a race had a greater hazard for musculoskeletal injury compared to untreated horses. Subsequent corticosteroid injections increased the risk of injury.”

Corticosteroids have potent anti-inflammatory effects, they said, but their repetitive use during racing and training alters the articular cartilage’s mechanical integrity.

“Though there can be disagreement as to whether corticoid steroids have beneficial or detrimental effects on cartilage, few can argue that corticosteroid administration can result in a rapid decrease in the degree of lameness, presumably by decreasing pain.”

However, as detailed by Nielsen and others in earlier research, joint pain is a signal that is useful to warn an animal that care must be taken to avoid causing further damage.

“When that signal is removed, performance is improved (for instance, faster speeds are achieved) as the animal is no longer protective of the joint, but unfortunately the damage is still present.

“Even if corticosteroid administration has benefits to joint pain and subsequent performance, articular cartilage cannot be repaired within a matter of days.

“Thus, it is highly likely that the use of these drugs is a culprit in many of the catastrophic injuries that have been seen on the track.

“While the age of horses entering training has been blamed for catastrophic injuries, the real culprit may be how we manage horses that are developing injuries.”

The pair noted that, in young animals, the optimal amount of exercise which is ideal for musculoskeletal strength and performance of function during maturity is not entirely known.

“Given that this optimal amount of exercise is not yet determined, prescribed exercise during growth is controversial to many.

“However, it has been shown in numerous studies that confinement and the subsequent lack of loading, lead to weaker tissues and potential loss of function of bone, articular cartilage, and tendons and that exercise during growth aids in the longevity of animal health and performance,” they said.

“Medical attempts to decrease pain to allow a horse to train through an injury, instead of providing adequate time to allow an injury to heal, may greatly increase tissue damage — putting horses, and riders at risk.”

Logan, A.A.; Nielsen, B.D. Training Young Horses: The Science behind the Benefits. Animals 2021, 11, 463. https://doi.org/10.3390/ani11020463

The review, published under a Creative Commons License, can be read here.

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