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It is widely accepted that thoroughbreds have been selectively bred for speed over the decades. However, there is a lot of debate as to whether thoroughbreds are getting faster or not. One study found that over the past 100 years, winning times in top races have not changed, suggesting that thoroughbreds have not got faster. This could be because we have bred thoroughbreds to go as fast as they possibly can without breeding for other traits which may also improve speed.
Stallions which have a successful racing career often become very popular breeding stallions. However, these stallions may not be the fastest stallions. During a race, horses race against each other and often use tactics to win. It could therefore be argued that the winning horse might not be the fastest horse. So the most successful stallions may not be the fastest, but they will have other (possibly more important) traits which make them successful.
Maybe the racing industry, by selecting successful horses to breed, has been selectively breeding for these other traits all along. There is no doubt that horses like Frankel and Secretariat were faster than their rivals, but they weren’t just faster. Frankel’s stride is 2 foot longer than the average thoroughbred and Secretariat had a huge heart and 2 moments of suspension in his stride. All of these things would improve their performance and top speeds.
It is hard to say whether thoroughbreds are getting faster or not. There is not enough good evidence to suggest either way. However, when you look at this years Triple Crown winner American Pharaoh race against Secretariat, Secretariat is considerably faster.
Is this because Secretariat is faster? Or could it be because modern day horses, such as American Pharaoh, lack the motivation to leave the pack behind and reach their top speeds? It would be interesting to see if racehorses were encouraged to race ahead of the pack, if we would see faster winning times or not.
Unless we start racing horses against the clock, it will be almost impossible to find out exactly whether thoroughbreds are getting faster or not. If thoroughbreds are not getting faster, then I’m sure they will begin to improve in other ways.