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  Family Numbers Explained

  New Research Affects Traditional Organization of Female Lines

In the August 2002 edition of the journal Animal Genetics, Dr. Emmeline Hill and her colleagues at the Smurfit Institute of Genetics, Trinity College, Dublin, Ireland, published "History and Integrity of Thoroughbred Dam Lines Revealed in Equine mtDNA Variation," a ground-breaking study that changes much of what we thought we knew about the early history of the thoroughbred, and that affects the pedigrees virtually every thoroughbred now living. The study examined pedigrees of horses associated with the English Foundation Mares, and does not address the other families, but it is highly likely further genetic research will have an impact on these families as well.

The original article and a discussion of how the analysis of mtDNA in thoroughbred horses has affected the traditional Lowe families are in the Genetics section.



The Family Numbers commonly used to designate the various Thoroughbred female families were popularized by Bruce Lowe, an Australian pedigree researcher at the end of the nineteenth century. Lowe's work, Breeding Horses by the Figure System was published posthumously in 1895 by his friend and editor, William Allison. He had traced back the pedigrees of the complete list of winners of the oldest English classics, the St. Leger Stakes, Epsom Derby Stakes and Epsom Oaks, grouping them by direct lines of tail female descent, from dam to granddam and on back until the family was no longer traceable in the General Stud Book. He then tallied the number of classic winners produced by each family and listed them in declining order. The family with the most classic winners, the one descending from Tregonwell's Natural Barb Mare, was designated Family #1, the Burton Barb Mare second, designated Family #2, and so on. The resulting forty-three numbered families became the core of his study, and while few actually adhere to Lowe's resulting theory, many still use his family numbers as a convenient way to categorize Thoroughbred families. Herman Goos, who had first published a comprehensive collection of pedigree tables in 1885, expanded the number of Lowe families to fifty.

Lowe's theory went far beyond identifying female strains. Of these families, he found that nine in particular appeared to be indispensable in the breeding of top racehorses, and he divided these into two classes, running(family #s 1, 2, 3, 4, and 5) and sire (family #s 3, 8, 11, 12, and 14) or as Lowe preceived them, feminine and masculine. His theory, too complex to relate here, was based on balancing the "feminine and masculine factors" by using these two classes of families as core to good matings.

In 1931, The Tabulated Pedigrees of Thoroughbred Horses (the "Polish Tables"), published by the Society for Promoting Horse Breeding in Poland expanded the tabulation of successful racehorses on a global basis. These were expanded upon by Captain Kazimierz Bobinski and Count Stefan Zamoyski in the first volume of Family Tables of Racehorses (1953), which compiled the families and detailed their lines of descent. Supplementary volumes were published through 1963. Research revealed that that some of Bruce Lowe's families went back to a common female ancestor, and so they were linked. Other groupings of mares were added to incorporate the global nature of the Thoroughbred.

Families 1 - 50 Bruce Lowe's original numbered English families, with Goos additions, traceable to the earliest volumes of the General Stud book
Families 51 - 74 Can be additionally traced to General Stud Book mares
Families Ar 1 - Ar 2 Native to Argentina
Families P 1 - P 2 Native to Poland
Families A 1 - A 37 Native to America
Families C 1 - C 16 Native to Australia and known as "Colonial families"
Families B 1 - B 26 Designated as "Half-Bred" due to some impure crosses

In 1990 the Societe d'Encouragement pour l'Amelioration des Races de Chevaux en France published Volume III of the Family Tables of Racehorses, updating the information to encompass race results and the expanding female family line branches in the thirty years since 1963; it was compiled and edited by Toru Shirai.

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