Negative and Positive aspects of starting a (thoroughbred) horse at the age of two for racing

Question
I am writing a term paper on an issue affecting the animal industry. I chose to write about starting thoroughbreds as young as two for racing. I have to present both sides of the argument for its positive and negative aspects. I have had a difficult time finding anything on this issue. Could you please answer my question or  direct me to any sites or magazines that can provide me with the information.
Thank you,
Sara  

Answer
-Sara

There are, as you have pointed out, both pros and cons to the early conditioning of two year olds.  Done properly, with careful attention to undue stress on the young body, early conditioning is very beneficial.  Done improperly, it can lead to permanent serious damage.
A two year old horse could be compared to a 14 - 16 year old human.  At three, he could be compared to a 25 year old or so.  Human athletes are well aware of the problems associated with waiting too late in life to train for a particular discipline, and so it is with horses.  Young bone, tendon and muscle is far more resilient than it will be at a later age.  Just as most world class athletes have to begin training at a young age in order to maximize their potential, so do horses.

Studies done by The Animal Health Trust in England have shown that by age three, tendon and cartilage development in the horse has basically stopped.  As a two year old, you can increase tendon and cartilage strength and resilience with proper conditioning, but by three, all changes tend to become degenerative, rather than adaptive.  Bone development is much the same.  Dr. Nunamaker at New Bolton Center did the definative study on shin development in the young horse several years ago, which showed that proper training methods in the young horse could completely prevent the incindence of tiny microfractures of the cannon bone, known as "bucked shins".  This is very important, because bucked shins can often lead to saucer fracture leter in life.  Young bone adapts and grows stronger more easily in response to stress than bone in an older horse.  Older horses have a greater risk of fracture, instead of remodeling in response to the stresses of training and racing.

Oddly enough, the New Bolton study showed that proper bone conditioning was achieved by adding speed early on in the training process, as opposed to long slow mileage.  The bone only develops to withstand the amount of strain put on it by training, so by giving the young horse long slow gallops, the bone never develops enough to withstand speed work.   The key is to add short bursts of speed at the end of the gallop a few times a week during early training, and gradually increase the amount of work done at speed as training progresses.

As with anything else, too much of a good thing is detrimental.  Too much stress on young growing bone and tendon will cause them to fail, and result in fracture or worse.  Careful attention to any signs of overwork is essential, and a light racing schedule as a two year old is certainly in order, if you want the horse to continue running well into adulthood.

I'm sorry that I don't have time to look up any reference materials for you, but a search on Dr. Nunamaker, New Bolton Center, and the Animal Health Trust should likely come up with something helpful.  The University of California at UC Davis often has some great stuff, and often a search if the archives of TheHorse magazine will be helpful, as regards new research.

--Stephanie Frost
www.alchemybloodstock.com