Thoroughbred breeding theories
While not all top male runners succeed as stallions, it is much more unusual for a poor racehorse to become a good proven sire.
[1] "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.
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.
[2] An example of the danger of ignoring the Racecourse Test was Sunday Silence, who firmly established his ability on the racetrack as the 1989 Horse of the Year and thus would ordinarily have been given major opportunities as a sire.
[3] Because stallions can have hundreds of offspring, it is possible to do statistical analysis to measure their success, which in turn affects their future prospects at stud.
For context, the AEI should be accompanied by the Comparative Index (CI), which is a way of measuring the quality of the mares to which the stallion was bred.
Another statistic that is valuable to both the bettor and breeder is the Average Winning Distance (AWD), available through the Online Stallion Register maintained by The Blood-Horse and published in some Past Performance charts.
Major sires, called chefs-de-race, are placed in one of five categories: Brilliant, Intermediate, Classic, Solid, and Professional.
[7] As the Dosage Profile and Index are widely published, breeders may select mates for their mare with these figures in mind, especially if they are intending to sell the foal at auction.
As with Average Winning Distance, if the mare has a Dosage Profile oriented to speed, the breeder may look for a sire that provides stamina influences.
However, modern genetic studies have revealed that there are some cases where the haplotype in the mtDNA of modern Thoroughbreds, which should not mutate or alter, differs from the records in the General Stud Book, indicating that some female families contain deep rooted pedigree errors.
Lowe stated,The figures are derived from a statistical compilation of the winners of the three great English classic races, Derby, Oaks and St. Leger.
[16] They identified mares in several countries whose pedigrees had been lost or whose descendants were unacceptable to the GSB at the time of Lowe’s work.
For example, Family 1 refers to all horses who trace back in the female line to Tregonwell's Natural Barb Mare, foaled c. 1670.
It takes many generations for the most influential mares to be identified so most of these family branches date back to the 18th and 19th century.
[22] In the modern era, the most successful nick was Danzig with mares by Mr. Prospector, which produced 16 stakes winners from 53 runners, a rate of 30.2%.
The lines may become dominant for certain characteristics, but the offspring also tend to become weaker, less vigorous individuals than animals that are not as inbred.
In the thoroughbred industry, inbreeding is used to focus specific genes by using superior, prepotent individuals, usually within the fourth and sixth generations.
But inbred animals frequently make outstanding breeding stock because when outcrossed, superior hybrid individuals often result.
