Updated on 09/17/2011 2:30PM

Dosage: Explaining the system

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The theory of Dosage was popularized in this country in the early 1980's by Leon Rasmussen and Steve Roman. They contended that a horse's potential at various distances could be mathematically determined by the presence in his pedigree of certain influential stallions, dubbed chefs-de-race.

Those stallions, such as Northern Dancer, Mr. Prospector, and Stage Door Johnny, have been classified into categories based on the performance of their offspring. Roman periodically adds new sires to the list and reclassifies others.

A horse's Dosage profile is calculated by assigning points in five categories based on the chefs-de-race in his pedigree. The categories, from left to right in the Dosage profile, are called brilliant, intermediate, classic, solid, and professional.

These numbers are then used to calculate two more figures - the Dosage index and center of distribution. In both cases, the lower the number, the longer the distance that should suit the horse.

Dosage has mainly been associated with the Kentucky Derby. Adherents believe that only horses with a Dosage index of 4.00 or under are genetically predisposed to win the Derby.

Since the theory was put forward in 1981, 20 of the 23 Derby winners have qualified on Dosage. This figure is perhaps not as impressive as it sounds: In most years, a large majority of Derby runners qualify on Dosage.

Another method some Dosage believers use to narrow the Derby field is called the dual qualifier system. To be considered a Derby contender under this system, the horse must qualify on Dosage and also be either a foreign champion or weighted within 10 pounds of the highweight on the Experimental Handicap, a ranking of 2-year-olds made each year by a committee.

The dual qualifiers in this year's Derby field are Action This Day, Birdstone, Lion Heart, Read the Footnotes, and The Cliff's Edge.

This system has not been very successful in recent years. None of the last six winners - Real Quiet, Charismatic, Fusaichi Pegasus, Monarchos, War Emblem, and Funny Cide - was a dual qualifier, and Real Quiet and Charismatic were among the few horses in their fields that did not even qualify on Dosage.

The Dosage and dual qualifier systems still have some passionate adherents. But the systems' failures in recent years have left few serious handicappers among the believers.