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.


Leave a Comment:


Just to clarify - hip# 4233 is a filly?  It said colt in the introductory paragraph.

Fascinating stuff I must say. It would be great to follow this yearling and see if it's more successful than it's non RF sibs.

  • Scot's reply:  Oops, I had a "she" where I meant "he."  It's been fixed, thanks for pointing out the error!
19 Aug 2009 3:32 PM
steve from st louis

I glad my wife won't let me fund a small stable because my pedigree fetish would just get me in trouble. I remember what D. Wayne always said, "Fall in love with the individual before you see the pedigree page." Like picking stocks, picking yearlings is an art not a science. And I'm a terrible artist.

19 Aug 2009 3:36 PM

What is the meaning of " inbred 3 x 3"

  • Scot's reply:  The quick answer is "the inbred influence is in the third generation of the sire's and dam's pedigrees."  The better answer is "read this!"
19 Aug 2009 3:47 PM

I read about the RF several years ago and after believing the results, decided to use it in my breeding decision.

I went one step further to find that inbreeding to BOTH parents of a superior horse really worked well.  Charismatic is a prime example of inbreeding to both parents of Secretariat.

My entry in the sale (Hip 4841) is inbred twice using the RF.  She has Somethingroyal 4x6 (with Bold Ruler 4x5) and Victoriana 5x5 (with Northern Dancer 4x5).

The other interesting fact is that Somethingroyal/Bold Ruler produced Secretariat.  Neither the mare nor the stallion are chestnut, but the foal is chestnut.  That leads me to believe the foal got the X factor.

The Victoriana/Northern Dancer line produced Vice Recent & Deputy Minister.

19 Aug 2009 4:30 PM

It would be interesting to go back one generation and look at Rasmussen factor crosses for Lassie Dear.  I suspect there are a lot of them.  I know in particular that Lanes End has really liked breeding their Indy mares to Lemon Drop Kid.

  • Scot's reply:  I can confirm that even looking at just the female progeny of Weekend Surprise I found several cases of Lassie Dear inbreeding.  You mentioned Lemon Drop Kid ... add in Deerhound and Black Mambo and Uncle Abbie and My Friend Max (discussed here!) and it's obvious that Lassie Dear's influence will abound in future generations!
19 Aug 2009 4:48 PM

So with RF the idea is to duplicate sirelines and female lines that have been successful in the past and hope for a colt?

If the mating produces a filly then the superior genotype of the inbred mare is concentrated in an attempt to replicate the inbred mare?

When inbred to the grandsire's dam and result is a filly. What is RF about that?

Mr AP what is your opinion on the integrity of the Y chromosome? (Does the Y change through successive generations or not?)

19 Aug 2009 5:53 PM

Interesting article, Scot.

For now, I'll offer but one observation-

Re-the "studies" that either prove, or disprove the value of Rasmussen Factor(s)- be mindful that the very acceptance of a theory (thus practiced) may tend to distort the findings of its relative success. As example-if one believes a theory's validity and puts it to practice then, all else equal, all other considerations will receive somewhat less weight-tending to "dilute" its potential positive impact (if indeed it had that potential + effect in reality). So, it would seem the best data to evaluate for a study on R.F. were those R.F. horses created before Rasmussen's observations were publicized. Similar could be said for "known" nicks. Would be curious to know if Alan factors this into his assessments/ponderings?    

19 Aug 2009 6:37 PM


Would Hip 1328 fit this same description with the strong mare Crimson Saint?  Terlingua on top and Alydariel on the bottom?  I believe this would give a 4x4 to Crimson Saint.  

Although the first dam has not been particularly impressive, they are changing the line in which she has been bred going away from El Corredor and switching to Bernstein.  How much attention should this cross get?

  • Scot's reply:  Yes, another great RF example.  I've actually been looking for Terlingua inbreeding through daughters... she is about the same age as Weekend Surprise (1976 vs. 1980) so examples should become more numerous as time passes.  ... The mare in this case, Weekend Dancer, produced a Mexican grade II winner with El Corredor, who is a Raise a Native/Northern Dancer cross with Secretariat as damsire of his grandsire.  Bernstein is a Northern Dancer/Raise a Native cross with Secretariat as his sire's damsire.  I suspect that this is a situation where the resulting foal's considerable inbreeding will give the bloodlines a chance to shine. I'm a proponent of close inbreeding when the bloodlines are solid but the individuals are themselves weak.
20 Aug 2009 12:17 AM

A filly that has a double RF to interesting mares is hip 4681.

While the first two dams are blank (first dam has never been bred to anything of quality until this filly and 2nd dam has been on an international journey of sorts), it's an extremely strong Canadian family that's anchored in this filly by a formula 1 RF to Ciboulette.

To further enforce the class of the pedigree, you also have an RF to the good producer Bebop, who's daughters produced Stop the Music, Hatchet Man, Buckaroo, etc.

The rest of the pedigree is sex balanced with Tom Fool coming thru Buckpasser and Bebopper.

This filly, if the physical is decent, could be quite the bargain. Her sire is a bit cold at the moment and the lack of produce immediately under her is going to deter a lot of buyers.

But she's worth a gamble at a small price in my opinion.

20 Aug 2009 1:03 PM
Kerby Chua

Just a point of clarification... When do you say its INBREEDING and when do you say its LINEBREEDING?

I am a believer of Rasmussen Factor breeding. The key there is really the linebreeding or inbreeding to a Blue Hen/Dominant mare...

  • Scot's reply:  Thanks, Kerby.  Thoroughbreds are considered inbred if the duplication occurs within five generations, line-bred if in earlier generations.  We discussed Thoroughbred inbreeding notation a while back... it's worth a read!
21 Aug 2009 2:02 AM
Kathy Hall

I am fasinated with all these theories and didn't know about the RF and True Nicks when I made a breeding decision for a mare that I found in the English Show Circuit. She had a tatoe and so I did the Tatoo ID and found her to be a Dr. Blum mare. So I got excited and went through the stud books to locate a stallion that also had Dr. Fager in the pedigree that wasn't too expensive as this mare was already 12 and had never had any foals. This being said I bred her to Cashel Castle who is double Mr. Prospector through Silver Ghost and goes to Dr. Fager through Quick Nurse Dam of Unreal Zeal by Mr. Prospector. My mare is Chestnut and Cashel Castle most of the time has produced Gr/R fillys but I got a drk bay colt. He is in the OBS yearling sale Hip # 690...Let me know how I did with this choice...Thanks Kathy

21 Aug 2009 8:46 AM
jeff v

I've seen (SRO) in horses names in sales results.Please ,what does that mean?

22 Aug 2009 11:32 AM
Pedigree Shelly

         I find the Rasmussen Factor very interesting ! I've always been facinated with studying female families . I've always liked Weekend Surprise.What a broodmare! My filly is out of a Summer Squall mare plus she is inbred 4x5 to My Dear Girl ! I'm looking for a AP Indy line stallion to breed her to .                           That would give the resulting foal Weekend Surprise on the top and bottom. I was looking at the stallion Flatter ,by AP Indy out of a Mr. P mare . My filly is by Honour and Glory .  I was also curious on how foal sharing agreements are arranged ? Sorry to go off the subject :) What do you think ??

22 Aug 2009 5:38 PM

One of my favorite RF illustrations occurs in the pedigree of Ellen's Best, 7th dam of Rachel Alexandra.

  • Scot's reply:  Great example!  Following that line a bit further, we see her daughter Ro Dear with an RF to Selene ... Ro Dear's great-granddaugher Early Decision whose sire has an RF to Lavendula ... Early Decision's daughter Kim's Blues with an RF to Imperatrice ... Kim's Blues' daughter Lotta Kim with an RF to Pocohontas ... and of course Lotta Kim is the dam of phenom Rachel Alexandra.
25 Aug 2009 12:09 AM
The Five-Cross Files

The superfilly's pedigree shows that 30% of ancestors in her first four generation are Rasmussen Factor matings.

26 Aug 2009 10:54 AM
JR - Adam Man

Did this horse get bought back?  I don't see her sold....  thanks

  • Scot's reply:  She was listed as an "out" at the sale.  But ... her dam is going through the ring at the Keeneland November sale as hip 3870.  Amber Myth will sell in foal to Master Command, meaning the carried foal has a 3 x 3 cross to Weekend Surprise!
06 Oct 2009 3:29 PM
JR - Adam Man

Thanks Scot!

07 Oct 2009 1:04 PM
jose y. quiros

it would be interesting to find out how successful RF's are if found on the x-factor line.

14 Oct 2010 11:31 PM

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