The Dosage Index is a mathematical figure used by breeders of Thoroughbred racehorses as an attempt to quantify a horse's ability, or inability, to compete at various distances based upon the location of certain outstanding sires in its family.

Analysis of pedigrees and the ability to transmit raw speed or stamina date back to Lt. Col. J. J. Vullier, a French researcher who published a study on called Dosage. This was modified by Dr. Franco Varola, an Italian breeding expert, in two books entitled Typology Of The Race Horse and The Functional Development Of The Thoroughbred.

Little interest was shown at first but in 1981 Daily Racing Form breeding columnist Leon Rasmussen authored a new version of Dosage developed by American scientist and horse owner Steven A. Roman, Ph.D.

The new approach was written in a way that was much more accessible to owners, breeders and handicappers and was also backed up by solid statistical data.

The details of Dosage methodology are available in Dr. Roman's book "Dosage: Pedigree & Performance" published in 2002.

Steven A. Roman Dosage Pedigree and Performance Publisher: The Russell Meerdink Company Ltd. (16 Nov. 2011) Language: English |

Important stallions have been recognized as Chefs-de-Race (this translates to Masters of the Breed). The list includes stallions such as Northern Dancer, Rainbow Quest, Sadler’s Well, etc. whilst more recent additions to the list include Galileo and Cape Cross.

The list contains the Chefs "who through the performance characteristics of their descendants on the track and the success of their sons and daughters at stud ensure an enduring influence through successive generations." (Dr. Steven Roman)

Depending on the generation in which he appears, the stallion contributes a certain number of points to the subject horse. Galileo in the second generation, for instance, contributes more points than Galileo in the third generation.

Chef-de-Race stallions contribute points based upon the generation in which they appear in a horse’s pedigree:

Generation | Points |

1st | 16 |

2nd | 8 |

3rd | 4 |

4th | 2 |

The lower points in more distant generations is because the influence becomes less evident with each passing generation. A sire must be listed on the Chef-de-Race list in order to contribute Dosage points to the foal.

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

Brilliant | Intermediate | Classic | Solid | Professional |

Speed | <------------------------> | Stamina |

A ‘brilliant’ chef is a stallion who tends to produce runners who specialise in running at sprint distances. A Brilliant chef is in the pedigree will improve the runner's B score. A Professional chef tends to produce runners who win at long distances. Classic chefs tend to produce good runners over classic distances.

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

The list was last revised in 2019. The newest additions to the chefs-de-race roster are Darshaan (Solid), Dubawi (Intermediate/ Solid), Fasliyev (Brilliant), Linamix (Classic/Solid), Shamardal (Intermediate/Classic), and Unbridled's Song (Intermediate).

We now show an analysis of two of our racehorses. We have 1977 Ayr Gold Cup winner Jon George who was very fast and won over sprint distances and multiple jumps winner Minster Glory.

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

In the profile of Jon George the largest number (16) appears in the Brilliant category. He gets 4 Brilliant points from grandsire Tom Fool (2nd gen), 4 from Nasrullah (3rd gen), 2 from Bulldog (4th gen) and one point each from Roman and Nearco (4th gen). He also gets 4 Intermediate points from his Tom Fool as Tom Fool is split between the Brilliant and Intermediate categories. Eight Brilliant points come from him damsire who is Grey Sovereign (Brilliant). The profile is skewed towards the speed end of the distribution.

This is the profile of a sprinter.

Now compare the profile of Minster Glory.

This profile slants to the right, indicating stamina rather than speed. The largest of the figures (11) appear in the Classic and Professional categories.

Minster Glory's pedigree shows Ninisky (C/P) in second generation. Nijinsky II (C/S), Crepello (P), Habitat (B), Sharpen Up (B/C) are all in in third generation. Northern Dancer (B/C), Tom Rolfe (C/P), Donatello II (P), Sir Gaylord (I/C) all contribute to the fourth generation.

This gives 7 points for Brilliant (Habitat gives 4, Sharpen Up gives 2 and Northern Dancer 1). Intermediate is just one (from Sir Gaylord). Eleven points for Classic are deived from Ninisky (4), Nijinsky and Sharpen Up (2 each) and a point from each of Northern Dancer, Tom Rolfe and Sir Gaylord. Nijinsky contributes the two Solid points. The eleven Professional points come from Ninisky (4), Crepello (4), Donatello (2) and Tom Rolfe (1).

This gives the profile of 7 1 11 2 11.

The dosage index (DI) is the ratio of a horse’s speed points to stamina points. Points gained to the left of middle are for speed. Points to the right of middle are for stamina. The Classic category (middle) is divided equally between speed and stamina.

For Jon George, 16 + 5 + 2.5 are his speed points. That makes 23.5 speed points. On the right side we have 2.5 + 0 + 0, for a total of 2.5 stamina points. Divide speed by stamina. 23.5 divided by 2.5 equals 9.4. This means the horse has 9.4 times as much speed as stamina.

For Minster Glory we have a DI of (7 + 1 + 6.5) speed points divided by (6.5 + 2 + 11) stamina points. The DI is therefore 0.74.

B | I | C | S | P | DI | CD | |

Jon George | 16 | 5 | 5 | 0 | 0 | 9.40 | 1.42 |

Minster Glory | 7 | 1 | 11 | 2 | 11 | 0.74 | -0.2812 |

The Center of Distribution (CD) marks the balancing point of all the numbers in the profile. It is like a see-saw with weights which correspond to the score in the B I C S P categories distributed along its length. Where does the point of balance need to be placed to level the see-saw?

This is the Center of Distribution and the formula is as follows:

CD | = | [(B x 2) + I] | - | [S + (P x 2)] |

total points | ||||

Where: B = Brilliant points I = Intermediate points S = Solid points P = Professional 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 gauge for viewing the Center of Distribution.

B | I | C | S | P |

+2 | +1 | 0 | -1 | -2 |

For Jon George, the CD = 1.42. This is given by inserting the profile numbers into the formula, which will give 37 divided by 26 which is +1.42.

This means the point of balance must be moved to the left to the +1.42 mark on this scale. That marks the perfect balancing point for Jon George’s dosage profile.

The Center Of Distribution points to that approximate distance for which a horse is bred to race. The Center of Distribution can help indicate the ideal distance for a horse based on an approximate scale.

Dist(f) | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18+ |

CD | +2 | +1 | 0 | -1 | -2 | ||||||||||

B | I | C | S | P |

We have applied dosage statistics to our horses and you can see the tables by following the link here.