Dosage Index and birthdates for 2024 Kentucky Derby contenders

May 2nd, 2024

Since the Dosage Index became a Kentucky Derby (G1) handicapping tool a few decades back, some interest remains in how the current contenders stack up.

I've never been a fan of Dosage as a metric for indicating whether young horses can negotiate 1 1/4 miles on a certain first Saturday in May, for reasons spelled out in detail in this space. For a quicker summary, see my comparable piece on the anomalies of the Dosage Index for the 2023 Derby. 

By popular demand, however, here is the 2024 Derby field with each entrant's Dosage Index as well as birthdate. Below the table I'll point out problems with the Dosage methodology, as evidenced by a few of these numbers. 

HorseDosage IndexBirthdate
#1 Dornoch2.50April 22
#2 Sierra Leone2.00March 31
#3 Mystik Dan3.00March 4
#4 Catching Freedom5.67March 8
#5 Catalytic 3.00March 21
#6 Just Steel4.00March 9
#7 Honor Marie3.24May 4
#8 Just a Touch3.57May 5
#9 Encino - SCR2.33March 14
#10 T O Password1.00May 20
#11 Forever Young3.00Feb. 24
#12 Track Phantom2.20Feb. 17
#13 West Saratoga3.00March 19
#14 Endlessly2.60March 25
#15 Domestic Product3.00Feb. 22
#16 Grand Mo the First1.22Feb. 6
#17 Fierceness5.00March 28
#18 Stronghold3.00Jan. 24
#19 Resilience3.50March 24
#20 Society Man3.80April 19
#21 Epic Ride1.40May 17
AE#22 Mugatu3.00April 17

According to the Dosage theory as applied to the Derby, an Index of 4.00 is supposed to be the threshold; anything higher connotes a stamina concern. 

The two who surpass this so-called limit are both premier contenders, Catching Freedom at 5.67 and Fierceness at 5.00. Yet the minute you look at their actual pedigrees, the numbers make no sense.

In fact, Catching Freedom has already won the 1 3/16-mile Louisiana Derby (G2) with a sustained rally. That's as close as you can get to demonstrative proof, in the laboratory of the racetrack, that another sixteenth wouldn't be an issue.

But to illustrate the foibles of Dosage as a prognosticator, note that Catching Freedom has a classic-oriented pedigree top and bottom. Sire Constitution is responsible for 2020 Travers (G1) star and Kentucky Derby runner-up Tiz the Law. (We won't count his Belmont [G1] win since it was shortened in the COVID year.) Constitution is himself by Tapit, responsible for a record-tying four Belmont winners at the 1 1/2-mile distance, out of a Distorted Humor mare. 

Catching Freedom is out of a mare by Pioneerof the Nile, sire of 2015 Triple Crown champion American Pharoah (whose Dosage Index was 4.33). Pioneerof the Nile is himself by Empire Maker, the 2003 Belmont hero, and arguably the chief stamina influence carrying American Pharoah.

So why on earth is Catching Freedom's Dosage Index so high? The calculation depends entirely upon whether certain designated stallions (chefs-de-race) appear within the first four generations. Leaving aside other quibbles about the formula, the list of stallions is outdated, and most of them are now passing beyond the fourth generation. Hence they literally don't count, and neither do the newer elite sires.

Catching Freedom's Dosage Index therefore ignores the significant contributions of Tapit, Distorted Humor, and Empire Maker. 

Moreover, his calculation is also adversely affected by how Unbridled is categorized: the Dosage system classifies him as a "Brilliant" and "Intermediate" sire, as though his influence were on the speedier side of the equation. Catching Freedom is inbred to Unbridled, so his double points are all weighted toward increasing his Index. Yet Unbridled factors in classic pedigrees, suggesting that his Dosage classification doesn't reflect the aptitude he is transmitting. 

Omissions are affecting the Dosage Index of Fierceness. Only one ancestor on his sire's side counts (Gone West in the tail-male line); the influential Deputy Minister doesn't. Nor does it reflect the stamina in Fierceness's dam, a granddaughter of Bernardini and Empire Maker. She is by Stay Thirsty, the 2011 Travers winner and Belmont runner-up. 

There are perfectly sensible reasons to wonder if a feast-or-famine type of favorite is worth the risk in the Derby, given his inability (so far) to deal with a troubled break or adversity. But if Fierceness does lose, race dynamics, not the distance in itself, would be a likelier culprit. 

The diminishing number of designated sires who contribute to the Dosage Index can cause other absurdities. Points are allocated according to first, second, third, or fourth generation, but when you only have a couple of distant sires to assign points, the whole picture is skewed by the small sample. 

For example, Mystik Dan's 3.00 Dosage Index is based on a grand total of two points. That's the number a great-great-grandsire is worth. In his case, it's Bold Ruckus, who belongs to both the "Intermediate" and "Classic" categories in the Dosage system. Alas, Mystik Dan's paternal grandsire, the celebrated Into Mischief, is not a chef-de-race, and thus cannot count. 

Domestic Product's identical 3.00 Index likewise relies entirely on one qualifying ancestor, Awesome Again. Because he's in the third generation, he contributes all four points that go into calculating the Index. Domestic Product's top half, including Into Mischief and Distorted Humor, is a blank as far as Dosage is concerned. 

Bold Ruckus also puts his two cents in West Saratoga, with a few other more logical ancestors, but not Curlin, Uncle Mo, and Candy Ride.

Nor does breed-shaping Sunday Silence contribute an iota to the Dosage calculations for Forever Young and T O Password.

The horse with the most chefs-de-race, and therefore the most points overall (36) in his Dosage profile, is Honor Marie. At least his 3.24 Index is calculated on a broad basis across his pedigree, but even here, Storm Cat doesn't count - yet another giant factor left out from the Dosage system.

As the case studies of Honor Marie, Domestic Product, and Mystik Dan illustrate, similar Indices can be generated from wildly varying numbers of points that leave a lot to be desired. 

To sum up, you're not getting the whole pedigree analyzed and quantified in a Dosage Index; you're getting whatever selected sires are still hanging around within four generations. And no mares, no female lines with all of their mitochondrial power, need apply. 

Finally, regarding birthdates: as with pedigrees, context is required, and it's inadvisable to be doctrinaire about it. A contender with a later foaling date might or might not be behind on the developmental curve. 

For example, Honor Marie and Just a Touch were born a day apart in May, but they have totally different profiles. Honor Marie has plenty of foundation from a successful juvenile campaign, while Just a Touch got started late but enters on a rapidly progressive upswing. 

Perhaps T O Password's very late birthday has contributed to his lack of experience with only two starts. But the question about seasoning, and racing savvy, is more salient than his physical age. 

Remember that the first two across the wire in the 2019 Derby, the disqualified Maximum Security and the promoted Country House, were both May foals who had not yet celebrated their actual third birthday.