Anne Peters



Anne Peters
P.O. Box 3926
Midway, KY 40347
(859) 846 - 9794




Pedigree Theories and Selection Techniques

Why Inbreeding?
Noted examples of closely inbred horses (listed chronologically)

Anyone who reads the literature about Thoroughbred breeding has got to wonder why all this fuss about inbreeding? Many of the articles here on the Pedigree Post site draw attention to inbreeding and linebreeding with a flourish. Can that be all there is to pedigree study?

Well, clearly not. There are many factors, genetic and environmental, that come into play when breeding livestock, especially race horses. But the reason why many pedigree students concentrate on inbreeding is because of the very definition of what it is and what it does on a genetic level. To put it simply, inbreeding is a long-term breeding strategy that is not for everyone, certainly not for the impatient breeder wanting immediate results.

By definition, "inbreeding" is the mating of two closely related individuals. The degree of relationship varies. "Closebreeding" refers to the mating of very close relatives such as sibling to sibling or parent to offspring matings. In the Thoroughbred, it is generally accepted that repeating any ancestor within four generations falls under their outer limits of "inbreeding," while any duplications beyond that four generation limit are described as "linebreeding."

Geneticists and livestock breeders use the term "linebreeding" to refer to any mating program (even closer than four generations) that repeats lines to a specific, presumably superior, ancestor. This is done in the hopes of increasing the chances of that ancestor's superior genes coming down to the resulting offspring. This is the purpose of linebreeding, to increase the potential for inheriting superior gene combinations. These same experts know that using this breeding method with closely related individuals (i.e., inbreeding and closebreeding) is a very risky business because while it may increase the possibility of inheriting superior genes, it also increases the possibility of inheriting any hidden, possibly negative recessive characteristics that may go along with this ancestor's genotype.

Let's use a prominent example. One of the best older horses in training this year is Juddmonte Farm's Skimming, who is inbred 2x3 to Northern Dancer, since his sire is Nureyev (by Northern Dancer) and his dam is a daughter of Lyphard (by Northern Dancer). Anyone who looks at Skimming can see that this was a highly successful experiment. Not only is he a truly superior runner, a multiple grade one winner, he is also exactly what one would expect from an inbreeding experiment to the genetic dynamo Northern Dancer. Northern Dancer was a small, muscle bound, fiery bay stallion with great speed and determination. Skimming is very much the image of his inbred ancestor, from size and body type to color, temperament, and running style.

Skimming is one successful example, in fact is one of the most dramatic examples of inbreeding to Northern Dancer, a trend that is very popular right now (and very successful, we should also add), but there are far more failed examples than we'd like to list here. Many horses that are the result of such close inbreeding to Northern Dancer have been nothing at all like Skimming. Not even close. Inbreeding can produce marvels, but it can also produce the worst of the worst. Ugly. Unsound. Slow. Bad tempered. Unhealthy. Infertile.

So why do many pedigree enthusiasts pursue inbreeding patterns in their matings? Because, as livestock breeders and scientists have known for hundreds of years, one of the quickest ways to "fix" desired characteristics into a bloodline of any species is through the use of inbreeding to individuals carrying those characteristics. If you want a strain of animals that breeds true to a certain rare color, you use only individuals with that color and ones that are known to breed true to that color. If you want to breed a strain of mice prone to produce tumors (for laboratory study), you inbreed using individuals from that strain.

By the same token, if you want to improve any bloodline of any species, one of the quickest ways is to inbreed to the most superior individuals. If you want to breed super cows, you inbreed to cows that were superior milkers, or to bulls known to produce superior milkers. If you want to breed super horses, you inbreed to superior horses.

If that's the case, then why aren't super horses all extremely closely inbred, because they most certainly aren't. Studies indicate that inbreeding 4x4 or closer appears in only about 25 percent of stakes winners, leaving 75 percent without this inbreeding factor.

The reasons for this also lie in the study of genetics. Closebreeding (of siblings or parent to offspring) is one of the surest way to reveal recessive traits, and these come out in close matings as often as the desirable traits. So at least half the time, usually more (depending on the quality of the parents) closebred matings result in animals that are effectively culls. The only way to eliminate the undesirable recessive traits entirely is by no longer using breeding animals known to carry those recessive or undesirable traits.

Continued, unrelenting inbreeding over a series of generations also has a negative impact that is quite real and is referred to as "inbreeding depression." The lines may become dominant for certain characteristics, but they also tend to become weaker, less vigorous individuals than animals that are not as inbred. They are also often physically smaller and "runty." Even if you inbreed for large size, extremely inbred animals from these lines may be large, but they will also tend to be less healthy, higher maintenance animals with more physical problems.

But the upside of this situation is that these animals will tend to breed true, because they can do little else but pass on the characteristics programmed into their genetics. When crossed with harmonious outside lines that need their strengths, or add strengths where there are weaknesses, miracles can, and do happen. These outcrosses, with one or both parents being inbred (but to different strains) often result in a condition known as "heterosis" or hybrid vigor. Heterosis is just the opposite of inbreeding depression, since it tends to produce an individual that is bigger and stronger than either parent. This is often the formula for producing superior performance horses.

So we've moved from close inbreeding and it's dangers, to outcrossing and hybrid vigor. What about the in-between?

Inbreeding within the fourth and sixth generations of the offspring avoids many of the problems of closebreeding, but also pushes the desired ancestor(s) influence further back. Since with each generation, a horse's genetic impact is theoretically reduced by half (Galton's Law of Ancestral Contribution), something has to be done to compensate. This is accomplished by using prepotent horses as targets of the inbreeding, that is, individuals known to pass on their characteristics in a highly predictable manner. So one's chances of doubling up on a dominant, positive characteristic are increased via linebreeding to a prepotent ancestor. And especially effective via "typical" individuals of that prepotent ancestors, as in the case of Skimming, who has the "typical Northern Dancer sons" Nureyev and Lyphard in his pedigree.

In fact, in many cases, inbreeding to a super runner may not be as effective as inbreeding to a superior breeding stallion because the great runner may not be "prepotent" or dominant in its genetics, while a top stallion almost always is. Many "super horses" (like the outcrossed Secretariat) are believed to be the highly vigorous result of crossing unrelated strains and getting the ultra-hybrid result. This is also why many of these super horses severely disappoint at stud, because being hybrids with heterozygous gene combinations (versus homozygous dominant combinations found in prepotent horses), they are can not, by definition, be prepotent.

So, let's put things in perspective. Inbreeding focuses specific genes. Inbred animals are likely conduits for certain specific characteristics coming from their inbred ancestor. Too much inbreeding is not good and rarely produces the superior runner. But inbred animals frequently make outstanding breeding stock because when outcrossed, superior hybrid individuals often result.

In other words, inbreeding, done intelligently, and pursued using good judgement, good horsemanship, and good animals, has the potential to create superior breeding stock. This breeding stock has the potential, with clever outcrossed matings that invoke some linebreeding to propotent ancestors, to create some outstanding runners based on the concept of hybrid vigor.

Inbreeding is not for everyone and not for every mating. There is a difference between breeding to get a top runner and breeding to get a future broodmare or stallion. More importantly, a mating is not good just because it has inbreeding to any given ancestor. First, the ancestor needs to be a superior, prepotent one. Second, there should be a pattern and a building toward a goal. This is what you see in the matings of the best horses by the best breeders.

This article originally appeared on the website Pedigree Post, September 16, 2001. Copyright by Anne Peters 2001.

Dam of Leedes (by Spanker) 16xx - 2x1 Old Morocco Mare
Betty Leedes 17xx - 2x3 Spanker (*her dam's pedigree is disputed)
Sister to Old Country Wench (17xx) - 3x2 Hautboy
Snap 1750 - 4x3 Bay Peg
Miss Elliott 1756 (dam of Gimcrack) - 2x2 Partner
Rachel 1763 (dam of Highflyer) - 2x3 Godolphin Arabian
Eclipse 1764 - 3x4 Sister to Old Country Wench
Prunella 1778 - 3x3 Blank
Goode's Twigg 1778 - 1x2x3x4 Janus
Buzzard 1787 - 3x4 Cade
Beningborough 1791 - 4x3 Tartar
Bedford 1792 - 3x3 Herod
Robin Redbreast 1796 - 2x2 Papillon; 3x3 Herod
Sorceror 1796 - 3x3 Matchem
Penelope 1798 - 4x3 Snap
Orville 1799 - 3x3 Herod
Financier 1800 - 2x2 Messenger
Castrel 1801 - 3x4 Herod
Selim 1802 - 3x4 Herod
Bob Booty 1804 - 3x3 Herod
Sir Archy 1805 - 3x4 Herod
Whalebone 1807 - 3x4 Herod
Web 1808 - 3x4 Herod
Young Empress 18xx (dam of Ariel, below) - 3x3x3 Messenger

Harpalice 1814 - 2x3 Mercury

Filagree 1815 - 3x3 Trumpator
Henry 1819 - 2x2 Diomed
Emilius 1820 - 3x4 Highflyer
Cobweb 1821 - 3x4 Young Giantess
Ariel 1822 - 3x4x4x4 Messenger
Humphrey Clinker 1822 - 3x3 Sir Peter Teazle
Guiccioli 1823 (dam of Birdcatcher, Faugh-A-Ballagh) - 3x3 Bagot
Black Maria 1826 - 3x3 Diomed
Bonnets O' Blue 1827 (racemare; dam of Fashion) - 2x2 Sir Archy
Maria West 1827 (dam of Wagner, below) - 3x2 Citizen
Flirtilla Jr. 1828 - 1x2 Sir Archy
Trifle 1828 - 2x3 Sir Archy
Marpessa 1830 (dam of Pocahontas) - 3x3 Whiskey
Muley Moloch 1830 - 3x3 Beningborough
Post Boy 1831 - 3x3x3 Diomed
Rosalie Somers 1831 (dam of Revenue, Commodore) - 2x3 Sir Archy
Boston 1833 - 3x3 Diomed
Maria Black 1834 (broodmare) - 3x3 Sir Peter Teazle
Wagner 1834 - 2x3 Sir Archy; 3x4x3 Citizen
Grey Eagle 1835 - 3x3 Sir Archy
Sovereign 1836 - 3x3 Stamford
Alice Hawthorn 1838 - 3x4 Dick Andrews; 4x4x4 Beningbrough; 4x4 Evelina
Diversion 1838 - 3x3 Little Folly; 3x4 Penelope; 3x4 Waxy
Chloe Anderson 1839 (broodmare) - 3x3 Sir Archy; 3x3 Transport
Gaze 1842 (broodmare) - 3x3 Phantom; 3x3 Filagree
Windhound 1847 - 3x4 Peruvian
Lexington 1850 - 3x4 Sir Archy
Strathconan 1863 - 2x4 Touchstone
Wellingtonia 1869 - 3x2 Pocahontas
Galopin 1872 - 3x3 Voltaire
Petrarch 1873 - 3x3 Touchstone
Barcaldine 1878 - 2x3 mare known as Darling's dam
Hanover 1884 - 3x3 Vandal
Le Sancy 1884 - 3x4 Windhound; 3x4 Alice Hawthorne
Carbine 1885 - 3x4 Brown Bess
Amphion 1886 - 3x3 Newminster
Sainfoin 1887 - 3x3 Stockwell
Orvieto 1888 - 3x3 Thormanby
Sierra 1889 (dam of Sundridge) - 3x3 Stockwell
Americus 1892 - 3x3 Lexington; 3x3 Novice
Le Sagittaire 1892 - 3x3 Strathconan
Flying Fox 1896 - 3x2 Galopin
Vahren 1897 (dam of The Tetrarch, below)- 3x4 Macaroni
Marcovil 1903 - 3x3 Hermit
Bromus 1905 (dam of Phalaris) - 2x3 Springfield
Bayardo 1906 - 4x2 Galopin
Ultimus 1906 - 2x2 Domino
Marchetta 1907 - 3x3 Hermit
The Tetrarch 1911 - 4x4 Doncaster; 4x4 Speculum; 4x4 Rouge Rose
Pommern 1912 - 3x3 Hampton; 4x3 Distant Shore
Gay Crusader 1914 - 3x3 Galopin
Gainsborough 1915 - 3x4 Galopin
Havresac II 1915 - 2x3 St. Simon
Noontide 1915 (broodmare) - 3x2 Domino; 3x3 Springfield
High Time 1916 - 3x3x2 Domino
Golden Myth 1918 - 3x3 Bend Or
Ksar 1918 - 3x2 Omnium II
Selene 1919 (dam of Hyperion, Sickle, Pharamond II) - 3x4 Pilgrimage
Filibert de Savoie 1920 - 3x3 Le Sancy
Pharos 1920 - 4x3 St. Simon
Sansovino 1921 - 3x3 Pilgrimage
Friar's Carse 1923 (champion, dam of War Relic, below) - 3x4 Bend Or
Reigh Count 1925 - 3x3 St. Frusquin
Blue Larkspur 1926 - 3x4 Padua
Vatout 1926 - 3x4 Gallinule
Firdaussi 1929 - 3x3 Chaucer
Gold Bridge 1929 - 3x3 Orby
Hyperion 1930 - 4x3 St. Simon; 6x4x5x4x6 Galopin
Museum 1932 - 3x3 Bayardo
Stop Watch 1933 (dam of Stymie, below) - 2x4 Colin
Bois Roussel 1935 - 4x3 St. Simon
Equestrian 1936 (sire of Stymie, below) - 3x3 Broomstick
Heliopolis 1936 - 4x3 Canterbury Pilgrim
War Relic 1938 - 3x3 Fairy Gold; 3x3 Rock Sand
Tourzima 1939 - 3x3 Durbar II; 3x3 Banshee
Nafah 1940 (dam of Miss France, below) - 2x3 Zariba
Stymie 1941 - 3x3 Man O'War
Swoon 1942 (broodmare) - 2x4 Sweep
General Don 1943 - 2x3 Lee O. Cotner
Avenger II 1944 - 3x3 Swynford
Sunny Boy 1944 - 3x3 Gainsborough
Djeddah 1945 - 4x3 Teddy; 4x3 Durbar II; 4x3 Banshee
Coronation V 1946 - 2x2 Tourbillon
Miss France 19426 (dam of Talgo) - 2x3 Asterus
Battlefield 1948 - 3x3 Fair Play
Crafty Admiral 1948 - 3x4 Teddy; 3x4 Plucky Liege
Flagette 1951 (dam of Herbager) - 2x2 Firdaussi
Turn-to 1951 - 3x3 Pharos
Hugh Lupus 1952 - 2x3 Tourbillon; 4x5x3 Bruleur
Apollonia 1953 - 2x3 Tourbillon
Gallant Man 1954 - 3x3 Mumtaz Mahal
Orisini II 1954 - 2x3 Athanasius
Tim Tam 1955 - 3x3 Bull Dog
Dan Cupid 1956 - 4x2 Sickle
Daring Duchess 1958 (broodmare) - 3x4x3 Lee O. Cotner
Spicy Living 1960 - 4x3 Blenheim II; 5x5x3 Mumtaz Mahal
Won't Tell You 1962 (dam of Affirmed) - 3x5x4 Sir Gallahad III
Dr. Fager 1964 - 3x4 Bull Dog
In Reality 1964 - 3x3 War Relic
Sweet Tooth 1965 (dam of Alydar, Our Mims) - 3x3 Bull Lea
Spectacular Bid 1976 - 3x3 To Market
Weekend Surprise 1980 (dam of A.P. Indy) - 2x4 Somethingroyal
Wild Again 1980 - 4x3 Hyperion; 3x4 Nearco
Precisionist 1981 - 3x4 Olympia
Broad Brush 1983 - 3x3 Turn-to
Danehill 1986 - 3x3 Natalma
Quiet American 1986 - 3x2 Dr. Fager; 4x3 Cequillo
A.P. Indy 1989 - 4x3 Bold Ruler
Mutakddim 1991 - 3x4 Buckpasser
Lammtarra 1992 - 2x4 Northern Dancer
Petionville 1992 - 3x4 Buckpasser
Silken Cat 1993 - 3x4 Bold Ruler
Spinning World 1993 - 2x4 Northern Dancer
Desert King 1994 - 3x3 Northern Dancer
Touch Gold 1994 - 3x3 Northern Dancer
Skimming 1996 - 2x3 Northern Dancer
Speightstown 1998 - 3x4 Secretariat; 4x5x4 Bold Ruler
Rock of Gibraltar 1999 - 3x3 Northern Dancer
Cosmonaut 2002 - 3x3 Seattle Slew
Stevie Wonderboy 2003 - 3x3 Weekend Surprise
Ingrid the Gambler 2004 - 3x3 Storm Cat
Big Brown, 2005 - 3x3 Northern Dancer; 3x4 Damascus