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In his response to a lengthy message from Jay Leimbach on Adrian Parry’s “tb_breeding_theory” group, Tony Morris has made an exceptional synthesis of the factors involved in molding the Thoroughbred of 50 years ago into the animal we have today. Clearly, they are not the same animals, and the squashy nexus of commerce (international stallions, etc.), politics (jockey clubs, etc.), and social pressures (synthetic surfaces, changing attitudes, urban growth, etc.) all worked to that end.

There was also one table in Leimbach’s commentary regarding average times for the Kentucky Derby that illuminates one other point of interest for those of us with a concern for the history of the breed, as well as its future.

For the past six decades, the average time for the 10 furlongs at Churchill Downs has hovered right on 2:02 1/5. There have been insignificant fluctuations up or down, but the times have stayed admirably consistent despite different climate conditions for the race.

Some point to this as evidence that the Thoroughbred has stagnated genetically — or even worse — has regressed because the blooded racing horse had steadily decreased the average time for running the 10 furlongs of the Kentucky classic over the preceding decades.

In contrast, I interpret the data to indicate two different things. For one, we have reached a level of stasis in the breeding population. No matter how badly we breeders plan our matings and no matter how oddly we manage our horses, there are a sufficient number of horses in the population capable of running 10 furlongs in about 2:02 early in May to ensure that the race will be won by something of that ilk. Regardless of pedigree or fashion or price or anything.

I believe essentially that there are enough good horses in the breeding pool that a reasonable number of horses capable of running 10 furlongs in solid time will be born every year and that enough of these will survive the rigors of training to compete in the classics. This is despite considerations of pedigree or planning and suggests the depth of the bloodstock pool, as well as the random manner that genetics works out the details for us.

And on a second and quite different point, there is a concept in physics called the “strength of materials” that helps engineers and builders judge how much wood, steel, or concrete is needed to create something that will perform a function (think of bridges, buildings, and towers, for instance). That is the concept we are dealing with in the construction of Thoroughbreds.

Unlike engineers, breeders cannot select a horse for legs of a specific diameter or density. But by using racing class as evidence of soundness and using the most capable trainers available, owners can maximize the potential of their racers.

If a horse’s legs cannot stand the stress of racing any faster, it becomes unsound. If a horse is built with too much bone, it isn’t as fast as the one with somewhat less. So racing is selecting the horses with the minimum strength of materials needed to race as fast as possible and win. Therefore, horses with extraordinary speed and a tinge of fragility (Mr. Prospector, Native Dancer, Northern Dancer) are the best breeding prospects because they are right on the borderline of the perfect proportion of bone to weight and power.

And from the data regarding the Kentucky Derby, a Thoroughbred possessing the norm for strength of materials to run 10 furlongs and survive will get you the distance in 2:02 or thereabouts.