Breeding Facts

Question
There is a popular belief out there that today抯 thoroughbred is more brittle than the thoroughbreds of the recent past from say 30-50 years ago. I read in places things like "the primary goal in thoroughbred breeding has been to decrease bone mass while increasing muscle mass". How true is that statement? If true when did this start to take place and which sires that past on heavier bone mass were fazed out? Are the actual bones in horses legs today less dense, and more brittle?  

Answer
Morgan

I am familiar with the theory that you mention about breeding for less bone and more muscle.  I don't think that this is actually fact.  Today's Thoroughbred is being bred more for speed than stamina though, and that does lead to a more muscular, less streamlined horse than produced in the past.
This is due mainly to economic factors.  Years ago, racing really was the "sport of kings".  If you weren't independently wealthy, you couldn't afford to breed or race.  Racing was mainly an extremely prestigious hobby, rather than a way to earn money.  Today, most breeders and owners are in the business to make money, and in order to do that, they need to get a more rapid return on their investment. That accounts for the rise in two year old racing.  It also leads to breeding for more speed, because earlier developing horses are usually speedballs.  Distance horses tend to mature later, and run longer.

Todays Thoroughbred is bred for a different type of body than in years previously. Earlier Thoroughbreds had more long, lean slow twitch muscle fiber, while today's Thoroughbred tends toward bulkier fast twitch muscle.

Stephanie Frost
www.alchemybloodstock.com