Dosage: Pedigree & Performance
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Dosage, a technique for classifying Thoroughbred pedigrees by type, originated in the early part of the 20th century from the research of the Frenchman Lt. Col. J. J. Vuillier. In his classic study of the extended pedigrees of the best runners in England and France, Vuillier (in LES CROISEMENTS RATIONNELS DANS LA RACE PURE) observed that very few stallions appeared with any great frequency. He called these stallions chefs-de-race. He also noted that the degree of inheritance attributed to these chefs-de-race was essentially constant in all pedigrees, the absolute value (or Dosage figure) varying from sire to sire. Furthermore, he demonstrated that in successive 15 to 20 year time frames, new series of chefs-de-race emerged which eventually established their own fixed degree of influence. This process, in which new series of chefs-de-race periodically become dominant, provides a rational model for the evolution of the Thoroughbred race horse. Vuillier believed that the objective in breeding should be to attain Dosage figures in the foal as close as possible to the established Dosage figures for the breed. For some time he practiced his theories successfully in the employ of H. H. The Aga Khan, breeder of such notables as Bahram, Majideh, Mahmoud, and Nasrullah, among many others.

Some years later, the Italian Dr. Franco Varola (in TYPOLOGY OF THE RACE HORSE and THE FUNCTIONAL DEVELOPMENT OF THE THOROUGHBRED) developed a modified version of Dosage that retained the principle that Thoroughbred evolution proceeds through the influence of a very small number of the stallions at stud in any era. Varola did, however, shift the emphasis from quantity (i.e., the degree of inheritance associated with individual sires) to quality (i.e., the pattern of aptitudinal traits inherited from key ancestors). Discounting the generation in which his expanded list of chefs-de-race appeared, he arrived at a distribution of aptitudinal traits in a given pedigree that described the "type" of the horse being analyzed. The most significant point made by Varola was that the characteristics transmitted by his chefs-de-race were not necessarily those they possessed as runners. The focus, instead, was entirely on the qualities passed on as breeding animals. Thus, in contrast to conventional pedigree analysis based on an historical perspective of ancestral performance, Dosage relies on the dynamics of inheritance. As an alternative and complementary method of pedigree interpretation, it may help avoid potential problems associated with the traditional concept of "breeding the best to the best".

Our approach, which first appeared publicly as a series of articles in Leon Rasmussen's Bloodlines column in Daily Racing Form just prior to the 1981 Kentucky Derby, has been to fuse the basic ideas of Vuillier and Varola, incorporating both quantitative and qualitative components in the hope of providing additional insights. In order to establish greater utility, we chose to use more accessible four-generation pedigrees instead of the extended pedigrees used previously. We also re-introduced Vuillier's approximation of a genetic effect by halving the influence of any chef-de-race in each successive earlier generation. Finally, we established a statistical method for evaluating the results of our analysis. In this framework, Dosage in its latest configuration was developed.

Each chef-de-race is assigned to one or two of five aptitudinal groups (Brilliant, Intermediate, Classic, Solid, and Professional) covering the spectrum (from left to right) of speed to endurance. The assignments are made to best reflect the traits that these stallions predictably and consistently transmit to their offspring. For bookkeeping purposes we assign a total potential value of 16 points to each generation. Since there are, progressively, one, two, four, and eight sires in the first four generations, chefs-de-race that appear among these sires will contribute 16, 8, 4, and 2 points each as we work back. The points for all chefs-de-race present are then tallied in the appropriate aptitude columns. Chefs-de-race that confer two aptitudinal characteristics have their points split between the two aptitudes. In the end, the total points in each column produce the Dosage Profile (DP), a series of five numbers that reflect the relative proportions of each of the five aptitudes and is expressed in the order:


For example, the DP of the leading classic sire Halo, dk.b. or br. c., 1969 (Hail to Reason-Cosmah, by Cosmic Bomb), himself a chef-de-race, is calculated as follows:

  DP: 11 6   26 1 2

The ratio of points in the speed wing (Brilliant points + Intermediate points + one-half the Classic points) to points in the stamina wing (one-half the Classic points + Solid points + Professional points) is the Dosage Index (DI). This number is directly proportional to the inherited prepotent speed in a pedigree and inversely proportional to the stamina. A DI of 1.00 indicates a balance of the two. The DI of Halo is 1.88 ((11 + 6 + 13) divided by (13 + 1 + 2)).

If we consider the five aptitude groups as points spaced equally along a linear scale where Brilliant is assigned a value of +2.00, Intermediate is +1.00, Classic is 0.00, Solid is -1.00, and Professional is -2.00, the DP allows for the calculation of the Center of Distribution (CD), that point along the scale corresponding to the total combined influences of all chefs-de-race in the pedigree. In that sense, it is a balance point (analogous to a center of gravity) of all weighted aptitudes supplied by chefs-de-race in the four generations. Calculation of the CD is done by taking the sum of twice the Brilliant points plus Intermediate points minus Solid points minus twice the Professional points and dividing that number by the total points in the DP. An exact balance of speed and stamina yields a CD of 0.00. The CD for Halo is 0.50 (((2 x 11) + 6 - 1 - (2 x 2)) divided by (11 + 6 + 26 + 1 + 2)), which places the combined effect of all chefs-de-race in his four generation pedigree equidistant between the Classic and Intermediate aptitudes.

For reference, a current list of chefs-de-race is located at this site. The chefs-de-race are shown in alphabetical order along with their aptitudinal assignments where B=Brilliant, I=Intermediate, C=Classic, S=Solid, and P=Professional.

Research using the described methodology as a tool for pedigree classification has resulted in many revealing observations including the following:

1. There is a direct correlation between the DI or CD and performance at varying distances as determined from separate populations of stakes winning sprinters, middle distance runners, and routers. As expected, the sprinters have the highest values (reflecting the importance of speed in short races), the routers have the lowest (confirming the need for endurance in long races), and the middle distance runners fall in between. In general, the Dosage figures correlate with the average distance of the races in each category. The precision of the technique is highlighted in the table below where average Dosage figures are displayed for specific distances between 5 1/2 and 12 furlongs for open stakes between 1983 and 2015. The correlation is virtually linear, confirming the direct relationship between distance and the speed/stamina characteristics of pedigrees as expressed by Dosage figures.

5 1/2 f   3.93   0.81
6 f   4.14   0.86
6 1/2 f   3.59   0.80
7 f   3.65   0.81
8 f   2.92   0.68
8f & 70 yds   3.21   0.72
8 1/2 f   3.01   0.69
9 f   2.83   0.65
9 1/2 f   2.52   0.58
10 f   2.49   0.57
11 f   2.11   0.48
12 f   2.01   0.43

2. Elite Thoroughbreds as a group (e.g., champions, classic winners, leading sires) have significantly lower DIs and CDs than the general population of stakes winners, suggesting that outstanding performance on the track or at stud benefits from a large component of inherited stamina. There is no evidence, however, of an inherent superiority associated with lower Dosage figures. In other words, a lower DI is not better than a higher DI. Rather, the lower Dosage figures merely reflect the fact that our most prestigious races are run at longer distances and that successful competitors are aptitudinally suited to those races. Elite Thoroughbreds also have a higher point total in their DP than do typical stakes winners, acknowledging the fact that they tend to be somewhat better bred, at least to the extent that more chefs-de-race in a pedigree correlate with superior breeding stock.

3. Six winners of the Kentucky Derby since 1940 (Strike the Gold, Real Quiet, Charismatic, Giacomo, Mine That Bird and American Pharoah), and six winners of the Belmont Stakes over the same time frame (Damascus, Conquistador Cielo, Creme Fraiche, Commendable, Sarava and American Pharoah) have had a DI above 4.00. This is in direct contrast to dirt stakes winners in general, of which almost one-fourth have a DI greater than 4.00 and for which the average DI is about 3.5. The combination of Dosage and our observation that 26 winners of the Kentucky Derby since 1972 were ranked as a juvenile within 10 pounds of the high weight on the Experimental Free Handicap or were named juvenile champion in another country has become an especially powerful tool in isolating the true classic contenders. In the 21 Derbies where a "dual qualifier" (i.e., DI and two-year-old form) failed to win, 16 finished second, and in 10 of those races, a qualifier subsequently won either the Preakness or Belmont Stakes. The implications of this result are that a pedigree suited to distance, along with a demonstration of high-class, early maturity are more important for classic performance than other factors such as form in the pre-Derby preps at distances less than ten furlongs. Over the past four-plus decades, an average of only about three and a half starters per Derby have met both criteria, including longshot winners Genuine Risk, Gato del Sol, Ferdinand, Alysheba, Unbridled, Sea Hero, Go for Gin, and Thunder Gulch. In addition, the "dual qualifiers" have accounted for 9 exactas and 5 trifectas. Twenty-six percent of all "dual qualifiers" won at least one classic race.

4. The average DI of juvenile stakes winners steadily decreases throughout the season, indicating a larger speed component in the pedigree of winners early in the year relative to winners later on. This phenomenon parallels the need for greater stamina as the distances of races for two-year-olds increase through the year.

5. The DI of many steeplechase champions since 1972 exceeds the classic guideline figure of 4.00 despite the long distances associated with steeplechase racing. This result suggests that the pace of these races is well within the ability of speed-bred runners and that their quickness over the jumps can be a more important factor for success. The remainder of steeplechase champions have had a DI close to 1.00 or less, more typical of expectations for competitors at very long distances. Surprisingly, there are few steeplechase champions with a DI in the range of middle distance flat racers.

6. The average DI of stakes winners at tracks favoring speed is higher than the average DI of stakes winners at tracks where speed is less favored. This result is consistent with the observation that brilliantly bred runners often carry their speed further on the speed-oriented surface.

7. Turf stakes winners have, on average, a lower DI than stakes winners on dirt. Furthermore, the turf runners have a significantly greater representation of Solid and Professional chefs-de-race in their pedigree. This result is consistent with the observation that turf races are run at a longer average distance than are races on dirt.

The studies described here are based on large populations that reflect statistically significant trends. The Dosage user must recognize, however, that within these populations there is great variation. Accordingly, Dosage figures for an individual may not conform to those of the whole population. Greater accuracy and increased predictability depends in large part on a continual modification and refinement of the chef-de-race list, guided by the principle of a better description of reality.