The Rasmussen Factor is one of the many tools in the pedigree planner’s strategy box.

Named after one of the latter day icons of pedigree analysis, the late Leon Rasmussen, it refers to inbreeding to superior females through different individuals. The U.S. based analyst observed that matings which brought together a duplication of these matriarchs through two different progeny within five generations, had a noteworthy strike rate in Graded stakes races.

While inbreeding (the reinforcement of ancestors within four generations) and line breeding (reinforcement five generations and further) of both males and females has been practiced since the inception of the Thoroughbred, the Rasmussen Factor honed in on this one type of duplication.

Leon Rasmussen and co-author Rommy Faversham published a book in 1999 entitled “Inbreeding to Superior Females”, which outlined this theory and its application.

Probably one of the most obvious examples of this pattern is Danehill, who is inbred to NATALMA via two different progeny, namely Northern Dancer and Spring Adieu.

Eleven years on from the initial highlighting of this phenomenon and on the other side of the globe, it’s interesting to see how the Rasmussen Factor (or ‘RF’) is faring in Australia.

What better way to get to the heart of the matter than by analysing the pedigrees of Group 1 winners?

The pedigrees of victors of Australian racing’s top echelon over the consecutive racing years 07/08, 08/09 and 09/10 were scrutinised. Over these three years there were several horses that won multiple Group 1 races and some over more than one season. In total, there were 132 individual winners under the magnifying glass.

In order to compare the Group 1 winners’ pedigrees with those of the general Thoroughbred population, they were compared with the same number of horses (132), whose pedigrees were sourced from three different yearling catalogues. Close to hand were the first 44 lots from each of the 2011 catalogues for the Gold Coast Magic Millions, Inglis Classic and Perth Magic Millions. As we know, the lots are catalogued alphabetically based on their dams’ name, so it’s about as random as we can achieve.


The Group 1 Winners

Of the 132 Group 1 winners analysed, the matings of 13 of them (10%) created a Rasmussen Factor pattern.



Group 1 Winner


Female Inbreeding -Through Her Progeny

DARIANA Redoute’s Choice – Beldarian BEST IN SHOW 5f x 5f  Show Lady / Sex Appeal 
HEAVENLY GLOW Spinning World – Starsphere BEST IN SHOW 5f x 5f  Minnie Hawk / Sex Appeal 
DEALER PRINCIPAL Flying Spur – Volte FLOWER BOWL 5m x 5 f  His Majesty / Bowl of Flowers 
TYPHOON ZED Zeditave – Royal Diploma GAY HOSTESS 4m x 5m  Crowned Prince / Queen’s Colours 
LINKY DINK (NZ)  Keeper – Gimmick SOMETHINGROYAL 5 m x 5 m  Secretariat / Sir Gaylord 
ORANGE COUNTY (NZ)  Volksraad – Saffy SOMETHINGROYAL 4m x 5f  Secretariat / Loyal Land 
MARKUS MAXIMUS (NZ)  Pentire – Shafty Lady MILAN MILL 4m x 4m, 5f  Millicent 
ZARITA (NZ) Pentire – Gin Player MILAN MILL 4m x 5f  Mill Reef / Millicent 
SHOCKING Street Cry – Maria de Castiglia NATALMA 5f x 5m, 5f  Raise The Standard / Northern Dancer / Spring Adieu 
WHOBEGOTYOU Street Cry – Temple of Peace NATALMA 5 f x 5m  Raise The Standard / Northern Dancer 
SHOOT OUT High Chaparral – Pentamerous HARDIEMMA 5m x 5f  Shirley Heights / Bempton 
ORTENSIA Testa Rossa – Aerate’s Pick LALUN 5m x 5m  Bold Reason / Never Bend 
IRISH LIGHT Fastnet Rock – Aspen Falls CRIMSON SAINT 4m x 5f  Royal Academy / Terlingua 


Superior Females BEST IN SHOW, SOMETHINGROYAL, MILAN MILL and NATALMA were all represented by two Group 1 winners each.

FLOWER BOWL and GAY HOSTESS were each represented by one Group 1 winner, but are both granddaughters of BOUDOIR II, demonstrating that this particular family is also predominant.

HARDIEMMA, CRIMSON SAINT and LALUN all have a single Group 1 winner in this table.

The Yearlings

Of the 132 yearlings scrutinised, the matings of 8 of them (6.1%) created a Rasmussen Factor pattern to Superior Females.


Yearling Lot / Sale


Female Inbreeding – Through Her Progeny

Lot 44 Inglis Classic Domesday – Law Demee BEST IN SHOW 5f x 5f Monroe / Show Lady
Lot 37 GC Magic Millions Nadeem – Burleigh Sky Shantha’s Choice / Hurricane Sky
Lot 4 GC Magic Millions Street Sense – Barents Sea FLOWER BOWL 5m x 5m His Majesty / Graustark
Lot 20 GC Magic Millions Holy Roman Emperor – Best Percentage FLOWER BOWL 5m x 5m His Majesty / Graustark
Lot 17 Perth Magic Millions Good Journey – La Parure LITTLE HUT 5m x 5m Northfields / Habitat
Lot 30 Inglis Classic Casino Prince – La Jez ROLLS 3m x 4f Flying Spur / Shoal Creek
Lot 28 GC Magic Millions Any Given Saturday – Blind Panic LASSIE DEAR 5f x 4f Weekend Surprise / Lassie’s Lady
Lot 33 Perth Magic Millions Saxon – Light Control FAIRY BRIDGE 4m x 4m Sadler’s Wells / Fairy KingThe Superior Females which emerged in these untried and randomly selected pedigrees were a similar group to those present in the Group 1 winners.

FLOWER BOWL had two representatives, while BEST IN SHOW and DANCING SHOW (Best in Show’s granddaughter) each had one yearling inbred to them.

With one representative each were Superior Females ROLLS, LASSIE DEAR and FAIRY BRIDGE.

In Summary

With 10% of the Group 1 winners bred on the Rasmussen Factor and 6.1% of the random yearling sample bred on this pattern, it is clear that utilisation of this pedigree theory is beneficial.

In effect, there are 40% more RF horses in the Group 1 winning sample than in the random yearling sample.

How to Use the Rasmussen Factor

Now that we have shown that it is worthwhile applying this theory to your breeding plans, what are the best ways to access the Superior Females shown to have the best strike rate? Using the 13 Group 1 winners in our 3 season survey, we can get an overview of this technique.


This mare is the ancestress of several sires and broodmare sires at Australia’s finger tips.

Dariana is by Best In Show’s direct descendant REDOUTE’S CHOICE. Her dam sire Last Tycoon is by TRY MY BEST, another descendant of Best In Show.

Heavenly Glow is by SPINNING WORLD, another descendant of Best In Show. She is out of a mare by Celestial Bounty, another son of TRY MY BEST.


As an aside, young sire DOMESDAY is emerging as a stallion responding very well to RF pattern matings to Best In Show. Stakes Placed Domesky carries a RF to Best In Show’s daughter Monroe, via Domesky’s damsire MASTERCLASS. While Domesday’s current best runner Pressday does not carry an RF to Best In Show, he is actually line bred to Best In Show’s taproot mare, TORPENHOW. Nijinsky II, sire of Pressday’s second damsire Upper Nile, is a member of this family.


In our Group 1 winners analysis, Dealer Principal carried a RF to this Superior Female. Flower Bowl’s son HIS MAJESTY is present in the pedigree of Danehill, so mares from the Danehill line are ripe for an RF mating. Dealer Principal carries HIS MAJESTY through his grandsire Danehill, while his dam’s damsire WHISKEY ROAD is another descendant.

HIS MAJESTY (also sire of PLEASANT COLONY) is brother to GRAUSTARK (sire of JIM FRENCH, AVATAR and KEY TO THE MINT), so combinations of these ancestors can create a RF pattern.

Typhoon Zed, while not a RF breeding to Flower Bowl, is RF bred to Gay Hostess, who is out of a three quarter sister to Flower Bowl. Their common ancestress is the Blue Hen mare, BOUDOIR II. In Typhoon Zed’s pedigree, his sire ZEDITAVE carries Gay Hostess’s son CROWNED PRINCE, while his dam carries another of her sons, MAJESTIC PRINCE.


This Superior Mare creates the Rasmussen Factor in two of the Group1 winners in our 3 season survey.

Linky Dink carries the half brothers SECRETARIAT and SIR GAYLORD, sons of Somethingroyal. Secretariat appears as second damsire of Linky Dink’s sire Keeper, while Sir Gaylord appears on his dam’s sire line.

Orange County carries SECRETARIAT as damsire of VOLKSRAAD, while his dam’s broodmare sire is SUPER GRAY, whose dam Loyal Land (dam of Super Gray) is a daughter of Somethingroyal.

Both Linky Dink and Orange County are New Zealand breds. The New Zealanders learnt nearly 20 years ago that creating a RF pattern to Somethingroyal can create spectacular results. Champion racehorse Veandercross was bred on a Somethingroyal RF involving her progeny Sir Gaylord on his tail male line and Loyal Land (dam of Super Gray) through his dam.


The New Zealanders strike again with a pair of Pentire Group 1 winners with a Milan Mill duplication through different individuals.

Pentire carries Milan Mill’s revered son MILL REEF and in the pedigree of Markus Maximus’s dam, we not only have another line to Mill Reef, but also the presence of his half sister Millicent, dam of WESTERN SYMPHONY.

Zarita is also by Pentire out of a mare carrying Western Symphony. In both Zarita and Markus Maximus, Western Symphony is the second damsire.

Other Milan Mill descendants to use for creating a RF mating include MOSCOW BALLET, PETERHOF, FUJI KISEKI, YASEY and TAOISEACH.


DANEHILL is already bred on a RF pattern to this Superior Female, however including him in a mating carrying other Natalma family members will create a ‘fresh’ RF pattern pedigree.

The two Group 1 winners with a RF to Natalma in our list are both by Street Cry. His sire MACHIAVELLIAN is a direct descendant. Melbourne Cup winner Shocking is out of a DANEHILL mare, so therefore Shocking carries three lines to Natalma through 3 different progeny, namely Raise the Standard (granddam of Machiavellian), Northern Dancer and Spring Adieu (granddam of Danehill).

WHOBEGOTYOU, also by Street Cry, combines Raise the Standard and Northern Dancer, grandsire of his damsire Carnegie.

Other family members to be utilised to create Natalma RF matings include EL MOXIE, YOUTHFUL EGS, ARCTIC TERN, SHEDAD, ORPEN, EXIT TO NOWHERE, WAY OF LIGHT, EAGLE EYED, DIATRIBE and AL SAMER.

It might be a little difficult nowadays to squeeze a RF to Natalma’s dam ALMAHMOUD into a 5 generation pedigree. If it were possible, we could include HALO (a grandson of Almahmoud) in this group.


Best known as the dam of SHIRLEY HEIGHTS, Hardiemma has few other well known descendants with which to create a RF pattern.

Hardiemma’s other descendant of note, through her daughter Bempton, is PENTIRE. Shoot Out was conceived in New Zealand on a mating of High Chaparral with Pentire mare, Pentamerous. High Chaparral carries the far more frequently found SHIRLEY HEIGHTS.

Other sources of Shirley Heights include DARSHAAN, OAK RIDGE and SLIP ANCHOR.


Talk about brotherly love. This is not the first time a top horse has carried a combination of Lalun’s sons Never Bend and his half brother Bold Reason. Racehorses such as High Chaparral, Racing To Win, Carnegie , In the Wings and Roman Emperor are amongst a very long list carrying this RF pattern.

Added to that list is Ortensia, whose sire Testa Rossa carries Bold Reason (as damsire of PERUGINO), while her dam contributes Never Bend as sire of her damsire, LOOSEN UP.

Bold Reason is easily accessed through SADLER’S WELLS’ many sons and daughters, as well as his full relations FAIRY KING and TATE GALLERY, who all have him as their damsire. FAIRY KING is of course, the sire of ENCOSTA DE LAGO.

Never Bend is also relatively common, with sires and broodmare sires such as MILL REEF, RIVERMAN, GREEN DESERT, STRAIGHT STRIKE, ESPERANTO, BENDING AWAY, TWINING, HULA CHIEF, HULA TOWN, J.O. TOBIN, SWITCH IN TIME, NAMNAN and DON’T SAY HALO as examples.


Like Hardiemma, Crimson Saint does not have a lot of key descendants, however two of them are very significant!

I refer to STORM CAT and ROYAL ACADEMY. The dam of Royal Academy and granddam of Storm Cat through daughter Terlingua, the combination of these two has produced to Group 1 winning filly, Irish Lights. She is by FASTNET ROCK (damsire Royal Academy) out of a HENNESSY (by Storm Cat) mare.

Handy sire DANE SUPREME and New Zealand based success POSTPONED are other tail female descendants of Crimson Saint.

Storm Cat has several prolific sire sons and grandson in Australia, including TALE OF THE CAT, HENNESSY, STATUE OF LIBERTY, GIANT’S CAUSEWAY and his son SHAMARDAL.

Royal Academy has not only been a long term icon in Australia himself, but has produced several sire sons, such as BEL ESPRIT, VAL ROYAL, ALI-ROYAL, RAHEEB and WANTED.

The list of Superior Females detailed above from our Group 1 winners survey is by no means definitive, however most of them are certainly regular contributors to a RF list of top class racehorses. LASSIE DEAR, THONG / SPECIAL and LITTLE HUT also have a great strike rate.

A similar survey of US Grade 1 winners carrying the Rasmussen Factor was conducted in 2000 and also came up with a 10% (10.1% to be exact) strike rate. Rather than comparing this statistic with the general population however, the study compared them with US Graded Stakes Winners in general (not just Grade 1) and found that 7.8% carried the Rasmussen Factor.

Provided other aspects of the pedigree are conducive to positive inheritance in combination with physical compatibility, the Rasmussen Factor is proving a valuable tool for the production of top class racehorses. If a piece of gear or a method of training were to improve the chances of producing a Group 1 winner by a significant percentage, everyone would be employing them. As any trainer will lament, it’s hard enough to win a race, let alone a Group One!