Thoroughbred breeding theories

Thoroughbred breeding theories are used by horse breeders in an attempt to predict successful mating of racehorses to produce progeny successful in horse racing. They stem from the belief that careful analysis of bloodlines can lend predictability to breeding outcomes. Though a prestigious pedigree does not necessarily translate into racing success, there are, nonetheless, various theories, many of them implemented from other animal breeding stock practices. Some breeding theories are qualitative, relying on judgement. Quantitative breeding theories usually focus on statistical analysis of the sire and broodmare sires in particular. The best-known classification system for mares was developed in the late 1800s by an Australian named Bruce Lowe, who analyzed the statistics of major race winners and ranked the distaff or mare lines by their degree of success. This and similar ranking systems are still used by some breeders today.

The soundest breeding theory is the simplest one: "Breed the best to the best and hope for the best" is a phrase that probably originated with John E. Madden in the first half of the twentieth century. Studies have proven that, in general, good racehorses make the best breeding stock. While not all top male runners succeed as stallions, it is much more unusual for a poor racehorse to become a good proven sire. A poorly-raced mare does have a better chance to outbreed her own record on the track, especially when she has a good pedigree and is bred to good stock. On the other hand, statistics have shown that high quality racemares produce an inordinately high percent of high class runners.

"The Thoroughbred exists because its selection has depended, not on experts, technicians, or zoologists, but on a piece of wood: the winning post of the Epsom Derby. If you base your criteria on anything else, you will get something else, not the Thoroughbred."

The Racecourse Test means that the most important selection criteria for breeding the Thoroughbred is the ability displayed on the racetrack. The Racecourse Test measures a horse's ability to win, which requires a certain combination of speed and stamina depending on the race in question. The ultimate goal is to win elite races, especially the Epsom Derby in England or the Kentucky Derby in the United States, and the breed has evolved accordingly. Racing also tests the horse's strength, soundness and will to win. Horses that fail the Racecourse Test, either because they are poor athletes or lack racing spirit, are usually poor candidates as breeding stock. When an unproven racehorse becomes a good sire or broodmare, a further look usually shows that he or she showed tremendous potential in training and was retired due to some untimely circumstance, usually an injury. Such horses usually also have above average pedigrees.

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