DOSAGE – A Layman’s Guide

The Dosage System dates back to the early 20th century and a study of the pedigrees of the best horses in England and France undertaken by Lt. Col. J.J.Vuillier. He noted that within the pedigrees of these “best horses” that only a small number of stallions repeatedly appeared. He also noted that their influence in terms of inherited ability was broadly constant in all pedigrees. He also noted the emergence of new influential sires (he called them “chefs-de-race”) over time.

Vuillier’s theories have subsequently been added to by Dr Franco Varola, who concluded that the characteristics transmitted by the chefs-de-race were not necessarily those that they possessed themselves during their racing careers.

In more recent times, the theories were expressed in numerical form by Dr Steven Roman who used four generations of pedigree and assigned points for each chef-de-race that appears. The influence of each successive generation is halved to approximate genetic effect.

All chefs-de-race are assigned to one of 5 categories based upon the stamina they appear to impart. The 5 categories are Brilliant-Intermediate-Classic-Solid-Professional. They are in order from extreme speed through to extreme stamina. These are the 5 numbers you will see quoted, such as 4-2-22-12-0 (this is the 5 generation dosage of recent Royal Ascot winner, Japan). This is known as the dosage profile.

The dosage index number is calculated by adding the points in the Brilliant + Intermediate + 50% of Classic (in this instance 4+2+11=17) and dividing by the sum of the points in 50% of Classic + Solid+ Professional  (in this instance 11+12+0=23). 17/23 = 0.74.

The centre of distribution is a similar calculation and reflects the balance of speed and stamina. The calculation is 2x Brilliant + Intermediate (in this instance 8+2=10) minus Solid + 2x Professional (in this instance 12+0=12).  10-12 = -2. This is then divided by the total points (in this instance 40). -2/40 = -0.05.
So the raw figures for Japan are 4-2-22-12-0…..Dosage Index 0.74…Centre of Distribution -0.05. As a guide the average Derby winner has an index around 1.00 and a centre of distribution around 0.

Once you have these raw figures and an understanding of what they represent in terms of potential stamina, you have a powerful predictive tool. Even with just the basic dosage numbers, you are a statistical leap ahead of any traditional pedigree analysis.

To take dosage analysis a step further still, you have to understand the over simplistic parlance used regarding a horse’s stamina. “Stays a mile” or “doesn’t stay a mile” are terms used by even the most respected individuals and organisations. They almost imply that a horse stops running at a certain distance. In the real world, horses have an optimum stamina range. I would define this as a distance(s) at which a horse produces it’s best performance rating and this can vary according to age, going, course configuration, pace of the race and the way in which it is trained. These are obvious factors that impact upon a horse’s stamina.

As horses mature they become more able to produce their distance attributes (sprinters can sprint faster and stayers can stay further). If the ground is soft, there is more emphasis on stamina. If the course is uphill/downhill there is more emphasis on stamina. If the pace is strong, there is more emphasis on stamina. Trainers can adapt regimes to utilise either speed or stamina. I attempt to account for all of these, in past races as well as upcoming races, when assessing if a horse’s dosage numbers imply progression/regression at any given distance.

I also use dosage as a predictor of class in lightly raced horses. This is a more nuanced approach, but briefly, a low number of dosage points does not necessarily mean a lower class horse, but, a high number of dosage points is a likely indicator of a horse with potential class. Rather like a slow race time does not indicate a poor horse (the race may just have been slowly run) but a fast time is a definite indicator of a good horse.