Thoroughbred Pedigree Review of KEESEP Hip #4233 -- A Rasmussen Factor Case Study

The Rasmussen Factor 

Back a few months ago, we discussed inbreeding notations in Thoroughbred pedigrees. At the time, I indicated that we'd want to look at the Rasmussen Factor (RF) at some point in the future.

Since then, I've had several emails asking about the subject. There seems to be an air of mystery -- or perhaps just some misunderstanding -- about what the RF actually is.

Really, it's not hard. Developed by Leon Rasmussen and Rommy Faversham, the Rasmussen Factor specifically identifies female family inbreeding in a subject horse. The pattern of duplication is key:

  1. The duplicated mare must be an inbred influence
    • She must appear in the subject horse's sire and dam
    • The duplication must come through different progeny
  2. The mare must be considered a superior female.  In other words, any success that the pattern might have relies on using a proven mare.  You're not going to produce the next A.P. Indy (or Rahy or Serena's Song or Unbridled) using subpar stock.

Basically, the RF theory holds that horses with a superior mare duplicated in this distinct pattern are more likely than their non-RF counterparts to be successful as racers and breeding stock.

Discussing any breeding theory tends to excite a lot of people, both those who are devotees and others who are detractors.  With the Rasmussen Factor, the debate is especially passionate.  Some studies claim to prove the theory, while other research would indicate that female family inbreeding is actually a negative factor.  The arguments include such questions as what exactly makes a mare a superior mare; does the sample for any given study truly represent the overall population; and how important is the actual location of the duplicated mare in the subject horse's pedigree?

For the record, I tend to pay more attention to the female lines in a pedigree than I do the male lines, and I'm a proponent of close inbreeding to any superior pedigree influence when it's done in a reasonable and well-considered manner.  Put those two tendencies together and it's common for my own horses and my recommended matings to have RF patterns.  But like any breeding theory, this practice is one of many, many factors in a good mating, and it necessarily comes after a good physical match between the sire and dam, and after considerations of class and aptitude.

Hip 4233 at the Keeneland September Sale

What prompted my thoughts on the Rasmussen Factor today was a particular offering at the upcoming Keeneland September yearling sale.  The online catalog is now live and -- as I normally do -- I went through the hips to see if any foals were being offered out of my list of "favorite mares."  With 5,000+ hips in the sale, there are some years when I'll find a dozen or more foals offered from my list of 100 active mares.  This year, it's just five yearlings -- but hip 4233 in particular was of great interest. 

Hip 4233 is a Kentucky-bred dark bay or brown colt by the Vinery-Florida stallion Congrats (SRO), out of Amber Myth (by Holy Bull (SRO)).  Now, Congrats is a son of A.P. Indy (SRO), whose dam is the great Secretariat mare Weekend Surprise.  And as you can see on the catalog page pedigree, Amber Myth's dam is also a daughter of Weekend Surprise.  Hip 4233, therefore, is inbred 3 x 3 to this mare. (Additionally, the colt has a 4 x 4 cross to Northern Dancer.)

It occurred to me that while duplications of Weekend Surprise are becoming more numerous through her many stallion sons, this sale offering is the first instance I've seen where one of the duplications comes through one of her daughters.  (Weekend Surprise has appeared in many RF patterns through her stallion sons, seven of which -- Summer Squall (1987), Honor Grades (1988), A.P. Indy (1989), Saithor (1991), Devongate (1994), Tiger Ridge (1996), and Eavesdropper (2000) -- have sired black type progeny.)

So I decided to trace Weekend Surprise's 3-l female line forward and figure out whether or not this is the first instance of an RF through a female line. Here's what I came up with:

  • Weekend Surprise had six fillies, and all of them have become producers.
  • There are 27 fillies out there who are female-line granddaughters of Weekend Surprise.
  • 13 fillies -- including KEESEP hip #4233 -- have Weekend Surpise as a third dam.
  • 4 fillies claim Weekend Surprise as a fourth dam.

Of these 50 female-line descendents, four are RFs to the great mare (in addition to hip #4233):

  1. Bird Whisper is a 2007 filly by A.P. Indy's son Golden Missile (SRO) out of Storm Strip; she has Weekend Surprise 3 x 3 and she also complies with the breeding theory that promotes "sending to the sire the best blood of his dam."  Golden Missile's broodmare sire line traces back to Hail to Reason, as does Storm Strips sire line, giving Bird Whisper a 5 x 5 cross to the son of Turn-to.
  2. Unnamed 2008 filly is by the A.P. Indy son Malibu Moon (SRO) out of Weekend Sky (AUS). This is an especially interesting cross because the filly's granddam, Almond Essence (pedigree), is not only out of a half-sister to A.P. Indy, but is also by his sire Seattle Slew. This yields inbreeding of Seattle Slew 3 x 3 and Weekend Surprise 3 x 4.
  3. Unnamed 2009 colt is by Corinthian (SRO) out of Quiet Weekend.  This colt, like all the others mentioned, has A.P. Indy as his second source of Weekend Surprise. In his case, though, the Lane's End stallion is his great-grandsire. This colt has Weekend Surprise 4 x 3 and adds inbreeding to Mr. Prospector and Buckpasser.
  4. Unnamed 2009 filly is a full sister to the colt being sold at this year's Keeneland September sale.

It turns out that not only isn't this pattern rare, it's actually starting to be done with great regularity, somewhere close to six percent of the time. Breeders are apparently keen on the duplication and are willing to try it out fairly close up in their matings.

So, other than the Weekend Surprise influence, how does our sale colt look?  Well, he's a bit light on his immediate catalog page; his dam never ran and his granddam won just a maiden race. But plenty of black type jumps off the page a bit further down and it's clear that Amber Myth is well regarded even without a race record:  her last public sale (Keeneland November 2004) saw her pull in $190,000 in foal to Grand Slam (SRO).  Unfortunately, Amber Myth hasn't done much to improve her page as a producer -- of three foals of racing age, the 4-year-old ran once unplaced in Panama and the 3-year-old hasn't gone to post.  There is some reason to hope, however:  Amber Myth's 2-year-old filly has placed in all three of her juvenile starts this year (maiden special weights at Keeneland and Churchill Downs).

One final note:  multiple graded winner Weekend Surprise herself was bred on a Rasmussen pattern.  Her sire and her second damsire were half-brothers, both sons of Somethingroyal.  So when a foal is born with a double of Weekend Surprise, there's an automatic four crosses to the dam of Secretariat.

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