Originally appeared in the June 7, 2008 of Thoroughbred Times
by Jason Hall

Aside from mare selection, no other decision impacts a breeder’s chances for long term success than choosing the right stallion. Even in scenarios where breeders make prudent decisions in all other aspects of their program, it can be all for nothing if the wrong stallion is being utilized.

There a dozens of variables that go into selecting stallions, ranging from the more practical (such as conformation) to the arguable more theoretical (nicking or dosage), all of which have been hotly debated for generations. Certainly though, two of the more intensely debated variables are the importance of racing ability versus a strong female family.

Few will argue that both of these variables are important and desirable. Where the debate begins is when breeders are asked to differentiate the two variables according to importance. At one end of the debate, pedigree pundits, by their very nature of being intrigued by genetic patterns, argue that a strong female family will take a stallion further than just racing credentials. Conversely, those breeders who tend to stick with the first 1-2 generations of a pedigree are likely to gravitate towards a stallions racing credentials.

The late Joe Estes, a former bloodstock editor and ardent student of statistical genetics argued incessantly through out his writing career that prospective bloodstock should be evaluated primarily as a function of their own racing and conformation credentials. In the 1999 compilation of his writings and speeches “The Estes Formula for Breeding Stakes Winners”, Estes writes “…regarding pedigree selection… it should usually be a minor accessory to individual selection, being permitted to sway the balance in making decisions which are fairly close on individual merit.” Estes was a staunch believer in acquiring stallion prospects with solid race records, with female families and pedigree being minor considerations.

On the other side of the debate, current icons in the industry like Seth Hancock argue for strong female families, more so than racing class. In Edward L. Bowen’s book “Matriarchs: Great Mares of the 20th Century”, Hancock in scripts in the forward: “Generally, I believe in the old saying that the family is stronger than the individual. Connected to that line of reasoning is the fact that the racing record alone is not always a true measure”. Although not quite as one-sided as Estes in his beliefs, Hancock clearly makes his argument for individuals with blue blood in their female families.

Perhaps the most one-sided theorist advocating the importance of the female family was Bruce Lowe, who placed such an importance on the female family that he developed a system for monitoring the descendants of foundation families. Equally extreme in his thinking as Estes, Lowe attributed the fortunes of most English classic winners and leading English sires to attributes found in their female family: “My own impression is that even these three great progenitors (referring to the 3 foundation sires) owe their survival and fame mostly to the female lines they were mated with. The Figure system is based mainly upon identifying and tracing the origin of these female lines.


In recent years, research has emerged aimed at quantifying the significance of the female family relative to the importance of the race record, but only in broodmare prospects. Research has focused on isolating each variable (mares with strong race records and noticeably poor female families versus unplaced mares with blatantly strong female families), then fast forwarding through time to see which control group performed best.

Early returns clearly favor racing class as the best predictor of long term success in broodmare prospects. Some studies indicate a closer margin of difference, but others have shown a nearly two to one ratio in terms of stakes production, graded stakes production, and average earnings per starter. While these studies have been praised for isolating each variable, there have been criticisms that the researchers failed to take into account the quality of stallions each control group.


In an effort to study these same variables in stallion prospects, we searched stallion registers from the late 1990’s in an attempt to find stallions entering stud with one of the two attributes, but not both. Like the broodmare studies, the goal was to find two control groups, one with relatively weaker race records but strong female families, and the other with solid race records and nondescript female families.

The obvious shortcoming in this research model, as it applies to stallion prospects, is that it’s nearly impossible to find a large enough group of unplaced stallion prospects with poor female families. Female equivalents are plentiful, but few stallion farms will invest in a stallion directory page for a stallion with such credentials. For this reason, our control group of stallions with strong female families included stallions who failed to win at the graded level, but clearly weren’t as inept as the strong female family study groups in the broodmare studies.

Our first group included 42 stallions entering stud between 1996 and 2000 with relatively weak racing credentials, but obviously strong female families. Assigning objective criteria for identifying strong female families was virtually impossible considering the large discrepancies in percentages and raw numbers amongst females in different families. The lone objective criteria was that we used only credentials in the first two dams. Determinations were based strictly on the credentials the family had at the time he entered stud. Obviously, some of these stallions saw improvements in their families in future years, but breeders would have had no knowledge of this as they made their breeding decisions. Subject stallions for this group are included in Table 1.

Table 1 – Stallions with Strong Female Families, Lesser Race Records

  • Ago
  • Anziyan
  • Ataka
  • Bustopher Jones
  • Classy Prospector
  • Crimson Classic
  • Crimson Guard
  • Crown Ambassador
  • Cyberspace
  • Danjur
  • Danzatame
  • Diamond
  • Exetera
  • Fashion Find
  • Fort Wayne
  • Gold Regent
  • In Case
  • JP Hammer
  • King of the Hunt
  • Laabity
  • Lacotte
  • Leestown
  • Malibu Moon
  • Newton’s Law
  • New Way
  • Open Forum
  • Outflanker
  • Pin Stripe
  • Pioneering
  • Ponche
  • Private Interview
  • Proud and True
  • Red River George
  • Sasha’s Prospect
  • Sea Salute
  • Shuailaan
  • Squadron Leader
  • Stormy Atlantic
  • Tahoe City
  • Tough Call
  • Wayne County
  • Wheaton

For our comparison group, we compiled 30 stallions (also entering stud from 1996 to 2000) who won graded stakes in spite of weak female families. We also included stallions who were grade one-placed. Stallions with stronger race records are listed in Table 2.

Table 2 – Stallions with Strong Race Records, Lesser Female Families

  • Anet
  • Archer’s Bay
  • Boone’s Mill
  • Captain Bodgit
  • Catienus
  • Cobra King
  • Comeonmom
  • Confide
  • Evansville Slew
  • Formal Gold
  • Free House
  • Friendly Lover
  • Intidab
  • Judge TC
  • King of the Heap
  • Langfuhr
  • Lil’s Lad
  • Lite the Fuse
  • Lord Carson
  • Maria’s Mon
  • Patton
  • Rizzi
  • Robannier
  • Silver Charm
  • Smoke Glacken
  • Talkin Man
  • The Vid
  • Wagon Limit
  • Yankee Victor
  • Zeeruler

The resulting study groups sired 2,704 foals in their first crop (1128 by the stallions with stronger female families and 1576 by stallions with stronger race records), and 17,059 foals lifetime through April 8th of this year.

Before revisiting the issues surrounding opportunities and the CI, we’ll first take a look at the raw data by category for both groups relative to the overall breed average in Table 3 below:

Table 3 – Comparative Sire Statistics and Breed Average when applicable

Stallions w/Strong Race Records Stallions w/Strong Fem. Families Breed Average
Avg. Introductory fee $7,931 $2,953
Median Introductory fee $5,000 $2,500
CI for 1st book of mares 1.45 1.11 1.00
AEI for 1st crop of foals 1.39 1.13 1.00
Overall CI 1.36 1.16 1.00
Overall AEI 1.30 1.07 1.00
% winners from starters 71.7 65.9 67.8
% SW’s from starters 5.7 4.8 5.2
% stakes horses from starters 11.1 9.3 8.1
% graded SW’s from starters 1.3 .9 1.2
Avg. earnings per starter $52,719 $41,241 $41,475

As one might have expected, stallions with higher-end racing credentials commanded significantly loftier stud fees during their first breeding season. Whether you’re looking at average or median figures, stallions with stronger race records stood for at least twice the amount of their more blue-blooded counterparts. While it ultimately has little to do with actual quality and is a poor predictor of future success, the discrepancy in stud fees does give us some insight into what the marketplace (mare owners) is willing to pay for in first year sires. It also reflects the higher visibility of stallions who bring strong race records to the breeding shed.

A quick glance at both groups immediately raises the issue of mare quality. The second group with strong race records are much more likely to get higher quality initial books of mares, and subsequently, a better chance at long term success. In order to avoid the criticisms aimed at the mare studies of not quantifying opportunities, we examined the Comparable Index (or CI, a commonly used index used to determine relative mare quality in a stallion’s book; the average earnings for foals out of the same mares, but sired by different stallions with 1.00 representing the breed average) for each stallion’s first book of mares.

After compiling the CI for each stallion’s initial crop and weighing each CI relative to the sire’s crop size, we found the average CI for the group with strong female families to be 1.11. The corresponding index for stallions with strong race records was 1.45, indicating that mares being sent to stallions with strong race record group typically produce foals with a 30% higher earning capacity. These figures will allow us to make references about how each group outperforms (or perhaps underperforms) compared to their opportunities.

The strong female family group actually outperformed their CI (as measured by the Average Earnings Index (or AEI, the average earnings for a sire’s progeny during a calendar year, with 1.00 being the average for the breed), albeit by a statistically insignificant margin (.02). Stallions with stronger race records slightly underperformed, posting a AEI that was .06 lower than their CI. In examining their lifetime statistics (as of April 8, 2008), both groups lagged behind their CI, though the group lacking strong racing credentials fell at a slightly quicker pace.

More significant separation occurred when comparing percentage of winners from starters as well as overall stakes production (both graded and non-graded). Sires with strong racing credentials get winners from starters at 71.7% while sires with strong female families checked in with 65.9%, a figure that fails to even reach the breed average of 67.8%.

In terms of stakes production, sires with strong race records outperformed their counterparts as well as the breed average in all categories, particularly when it comes to graded stakes winners, where their progeny win graded events at a rate 44% faster than sires with strong female families. It should be noted here that sires with strong female families actually failed to hit the breed average, falling short by over 30%. Sires with strong female families also failed to hit the breed average benchmark when it came to average earnings per starter. Sires with strong race records outperformed both groups by approximately 27%.

While these results don’t tip the scales of perspective quite so heavily in favor of racing credentials as recent mare studies, it’s important to remember the difficulties of isolating racing and family variables mentioned above. As a result, the gap formed between racing credentials in the female family group narrows, as does the resulting data. Unlike the mare studies, where mares with strong female families typically failed to break their maidens, the comparative group in stallion studies is littered with horses talented enough to break their maidens and go on to even place in graded stakes.

Clearly, it would be foolish to disregard either variable altogether, but for those whose budget does not allow for a stallion prospect with strong racing and family credentials, the quiet accumulation of research out there suggests the proper racing credentials should be pursued first.

Posted in Articles by developer January 16, 2023

Author: developer

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