NOTE: The following was oringially published online in 1997, so you may note that the examples seem a bit old. While the data included here is still valid, I will eventually update the examples with more recent material.


by K.M. Jones

What Is Dosage?

Dosage is a mathematical analysis of the strengths in a thoroughbred pedigree based upon the location of certain outstanding sires in its family.

Who Are The Important Sires?

There are too many to list here; about 190 at this time have been recognized as Chefs-de-Race (Masters of the Breed). In general, they are the stallions which have had a remarkable influence on the breed over the last century; the names which remain like Round Table, Princequillo, Danzig, etc. when other stallions of short-lived popularity have disappeared.

Dr Roman's current Chef-de-Race list

Depending on the generation in which it appears, the stallion contributes a certain number of points to the subject horse. Round Table in the 2nd generation, for instance, contributes more points than Round Table in the 3rd generation.

Specifically - Chef-de-Race stallions contribute the following points, based upon the generation in which they appear:
  • 1st generation .... 16 points
  • 2nd generation .... 8 points
  • 3rd generation .... 4 points
  • 4th generation .... 2 points

This follows the assumption that the influence becomes less and less evident with each passing generation. Remember - the sire MUST be listed on the Chef-de-Race list in order to contribute Dosage points to the foal.

What Type of Influence?

Chef-de-Race stallions have been assigned to one or more of these categories:

Brilliant - Intermediate - Classic - Solid - Professional

These five categories represent the spectrum of speed (Brilliant) to stamina (Professional). Just as a prism separates light into definite visible bands, dosage separates a horse's inherited aptitudes into definite visible categories.

A Brilliant chef is one who has been identified as one who tends to produce runners who excel at extremely short distances. His appearance in the pedigree will improve the runner's Brilliant score.

A Professional chef tends to produce runners who excel at extremely long distances. Classic chefs tend to produce good "classic" distance runners and so on.

Some stallions have been named a Chef in more than one category, like Mr. Prospector who is a "Brilliant/Classic" Chef. If he appears in the foal's pedigree, his allowable points will be split between those two categories. For instance, if he appears in the 2nd generation in the pedigree, he is worth 8 points to the profile. 4 points are added to the profile's Brilliant score, and 4 points are added to the Classic score.

  B - I - C - S - P DI CD
Demaloot Demashoot 15 - 10 - 7 - 0 - 0 8.141.25
Spring Marathon 7 - 2 - 9 - 5 - 11 0.66 -0.32

What Is The Dosage Profile?

The dosage profile is a series of 5 numbers which show the reader exactly how many points this horse has inherited from sires in each category.

For instance, look at Demaloot Demashoot's profile above. See how the largest number (15) appears in the Brilliant category? Note also how the entire profile slants toward the speed end of the spectrum. This is the profile of a sprinter. The horse's race record bears that out. All of his victories came at 6 furlongs or less, including triumphs in the Clarinet King Stakes and the Count Fleet Sprint [G3] in which he scorched the six panels in 1:08 1/5!

Now compare the profile of Spring Marathon. Quite different, isn't it? This profile slants to the right, indicating a propensity for stamina. Note how the largest of the figures appears in the Professional category. You have probably not heard of this horse as he has raced only in England. Do you care to guess what type of event he has been excelling at? If you guessed "something really, really long" you're right. On the flat he placed at 11 1/2 furlongs and 14 furlongs, then graduated to even longer tests. Recently he won a 3 mile hurdle. The dosage profile clearly points to distance capabilities for this horse.

How Is the Profile Calculated?

Some of you have asked via email for a step-by-step crash-course in profile calculation. I've already hinted that the profile points come from the sires and their location in the pedigree - but for the specifics, please go to the profile calculation page.

Profile Calculation page

What Is The Dosage Index?

The dosage index (DI) is simply the ratio of speed points to stamina points. Everything to the left of middle is speed. Everything to the right of middle is stamina. The Classic category (in the middle) is divided equally between speed and stamina.

For Demaloot Demashoot, 15 + 10 + 3 are his speed points. That makes 28 speed points. On the right side we have 3 + 0 + 0, for a total of 3 stamina points. Divide speed by stamina. 28 divided by 3 equals 8.14. This means the horse has over 8 times as much speed as stamina.

For Spring Marathon, the index is 0.66, indicating that he has only two-thirds as much speed as stamina. Just for your information - more stamina than speed often flags a good turf performer.

Dosage & The Derby

You may have heard that any horse whose DI is greater than 4.00 cannot win the Kentucky Derby. This figure was selected arbitrarily, but by history because up until 1991, no horse with a higher DI had ever won the race. (Strike the Gold won with a DI of 9.0 only because Alydar was yet to be named to the Chef-de-Race list in the Classic category. After that designation, the DI for Strike the Gold fell to the more realistic figure of 2.6 which more accurately reflected his abilities and those of most offspring of Alydar.) Real Quiet won in 1998 with a DI over the 4.0 limit, and subsequent Chef-de-Race additions have actually raised his DI even further. Such is the nature of statistics - it won't be accurate 100% of the time. The 4.0 barrier is still a good historical yardstick for a classic distance race, but is bound to be broken again someday - only because horses don't race against distances, they race against other horses.

What Is The Center Of Distribution?

The Center of Distribution (CD) marks the balancing point of all the numbers in the profile. Picture a see-saw with weights of various sizes randomly distributed along its length. Where does the fulcrum need to be placed to balance the see-saw? That's what the CD is. It comes from a slightly more complex formula. If you are interested, here it is:

[(Bril x 2) + Int] - [Solid + (Prof x 2)] / total points

The result of this formula will always be a number between +2 and -2. If you were to assign the value +2 to the Brilliant category, +1 to Intermediate, and so on as shown here, you will have created a gage for viewing the Center of Distribution.


For Demaloot Demashoot, the CD = 1.25. This means the imaginary fulcrum must be moved to the left, all the way to the +1.25 mark on this scale. That marks the perfect balancing point for Demaloot Demashoot's unique dosage profile. For Spring Marathon, whose CD is -0.32, the fulcrum must be moved to the right, into the negative numbers, into the realm of stayers.

What Advantage Is There In Knowing The Center Of Distribution?

All thoroughbreds were bred for a specific distance. The CD points to that approximate distance. Below is a scale, which although not absolute, may show how the Center of Distribution can help indicate the ideal distance for the horse:

furlongs = 4...5...6...7...8...9..10...11...12...13..14..15...16...17...18+
CD Scale = +2+10-1-2

The European sprint champion LOCHSONG was phenomenally fast, and posted most of her victories at the 5 furlong distance. Look at her figures:

LOCHSONG - profile = 6-0-0-0-0 ... DI= Infinity ... CD= 2.00

When the word "infinity" is used for a Dosage Index, it simply means that no stamina is present with which to make the calculation. A whole number cannot be divided by zero (Ask your math teacher). Some people prefer to show this as the numerical result of "0". Either way it is a clear flag that the runner has earned no stamina points through dosage.

Now, if a 2 mile race were about to begin, and the entrants were Lochsong, Demaloot Demashoot, and Spring Marathon, which do you think has the best inherited advantages? Which has the lowest CD? That's the advantage in knowing the Center of Distribution.


How some people might use dosage to

Some Related Sites of Interest

Blue Hen Mares - Equine Info's list of influential broodmares.
Bloodstock Research Information Services - The world's greatest FREE daily thoroughbred newsletter (Bloodstock Journal) can be found here. Also, look up the dosage figures of almost any thoroughbred in the world (for a small fee).
Pedigree Query Database - Look up pedigrees and Dosage figures FREE but be aware that anyone can add data here and the Dosage figures will be correct only if the pedigree is correct.

Questions or Comments?

Has this page helped you at all? We'd like to hear about it. Feel free to email the author.