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Dosage explained

A century-old idea: read a racehorse's type from the stallions behind it.

Dosage estimates whether a pedigree leans towards speed or stamina by scoring the most influential stallions in the first four generations.

Early 1900s Colonel Vuillier A French cavalry officer notices the same great stallions recurring in champions' pedigrees, and devises the first "dosage".
1960s–70s Franco Varola Names the chefs-de-race — influential sires — and sorts them by the type of horse they pass on, from pure speed to pure stamina.
1981 Dr Steven Roman Turns the idea into numbers: the Dosage Profile, Dosage Index and Centre of Distribution used today.
2026 Still evolving The chef-de-race list continues to be updated, with 23 new chefs added in April 2026.

Five aptitude groups

BBrilliantSprinting, 5–6f
IIntermediateMilers, 7–9f
CClassicDerby trip, 10–12f
SSolid13–15f
PProfessionalTwo miles and beyond

Nearer stallions count more

Sire · 16 8 8 4444 2222 2222

Only stallions on the chef-de-race list score. Their points go to their group, and add up to the Dosage Profile — for example, Frankel's is 5-2-23-15-1.

Dosage Index (DI)

(B + I + ½C) ÷ (½C + S + P)

Speed points against stamina points. Around 1 is balanced; higher leans to speed.

Centre of Distribution (CD)

(2B + I − S − 2P) ÷ total

A balance point from +2 (all speed) to −2 (all stamina).

Useful — but flawed

Dosage has real blind spots, and taken alone it can badly misread a pedigree. Here's what goes wrong, and how to allow for it.

See the six problems →
What's wrong with dosage

Six blind spots, and how to allow for them.

Tried across a full 470-lot yearling sale, classic dosage called a Gr.1 middle-distance family a sprinter, rated sprinter-stayer crosses as "balanced", and put most European pedigrees in the stayers' column. Here's why, and what to look at instead.

The problem with dosage How to allow for it
1
The dam counts for nothingOnly stallions score. The mare — and everything her family has actually won — is ignored.
Read the dam's family tooThree generations of the female line: what the dam's foals have won, at what level, and her family number.
2
Today's sires score nothingFew current stallions are chefs-de-race, so the most important name in the pedigree — worth 16 of the 64 points — usually adds zero.
Let real results decideThe distances a family has actually won over are better evidence than a sire's group on a list. Use dosage when the family has little to go on.
3
The CD averages away the truthA sprinter crossed with a stayer and a pure middle-distance pedigree can both score a CD of exactly zero.
Look at speed and stamina separatelyCheck the Brilliant and Intermediate points against the Solid and Professional points. A pedigree with plenty of both is not the same as a balanced one.
4
Thin pedigrees swing wildlyA pedigree with only a few dosage points can hit an extreme on one stallion, and the Dosage Index can shoot to infinity.
Treat thin pedigrees with careWhen a pedigree has only a few dosage points, one stallion can swing the figures. Don't lean on them.
5
Built on American racingIts benchmarks come from US dirt racing. European pedigrees, full of stamina influences, get pushed into the stayers' column.
Compare like with likeCompare a pedigree with others in the same sale or the same racing country, not with American benchmarks.
6
A number with no reasonsA DI of 1.67 doesn't tell you why — or whether to believe it.
Ask for the reasonsLook at which stallions make up the figure, and at the races the family actually won, before believing a single number.
Next: Why the dam

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