Inbreeding in Chefs-de-Race,
Their Sires and Their Dams
Jones and Bogart, in "Genetics of the Horse" (Edwards Brothers,
Inc., Ann Arbor, Michigan, 1971), define inbreeding as the mating of two
individuals more closely related than the average of the breed. They
highly recommend that serious breeders know the amount of inbreeding in their
stock in order to appreciate the rate at which homozygosity is developing,
homozygosity being the condition where genes inherited from the sire and the dam
are alike. The amount of inbreeding estimates the percentage of genes put
in a homozygous condition. This estimate is always less than the the
actual because records will not allow for every relationship that exists.
Horses that are highly homozygous tend to stamp their own characteristics on
their offspring, a phenomenon often called "prepotency".
Prepotency also may be considered a regular or predictable transmission of
particular traits.
The amount of inbreeding can be calculated using a formula proposed by
Wright in 1923 (Mendelian Analysis of the Pure Breeds of Livestock, J. Hered.
14:339-348). Wright's formula generates a fraction (the coefficient of
inbreeding) which, when multiplied by 100, affords the amount of inbreeding as a
percentage.
The information presented below includes the amount of inbreeding for
202 chefs-de-race (not including Buckaroo, Chief's Crown or Pleasant Colony at this time), as well as for their sires and their dams. The raw data
are preceded by some general statistics.
Observations:
The general trend of inbreeding
percentage among chefs-de-race declined steadily
throughout the 20th century. The relationship between the percentage
of inbreeding and time is expressed by the following formula:
% Inbreeding = -0.0109 * Year + 22.262
Therefore, the overall rate at which inbreeding has declined
since 1900
is 0.0109 percent per year, although dramatic changes occurred until about 1940,
followed by a relatively steady percentage since then. Whether this pattern among chefs-de-race
represents the patterns found among all Thoroughbreds is not known at this
time. In any case, chefs-de-race foaled in successive ten-year time frames
display a diminishing amount of inbreeding.
The amount of inbreeding found among chefs-de-race covers the range from
over 13% for Ultimus down to 0% for Speak John, with some of the most
influential stallions being found at both ends of the spectrum. For
example, Havresac II (a key link to Ribot) and Bayardo (a key link to Hyperion)
are among the most highly inbred, while Native Dancer (the close up ancestor of
Raise a Native and Mr. Prospector) and Ribot himself are among the least inbred.
Arguably the best runners among the chefs-de-race - Secretariat (0.1953%),
Man o' War (0.8350%), Ribot (0.1465%), Nearco (0.9839%) and Sea-Bird (0.3906%) -
were all inbred below the average percentage of inbreeding for the time frame in
which they were foaled.
There is no significant pattern covering the relationship between
inbreeding in the chefs-de-race and inbreeding in their parents. Most (73,
36.1%) are less inbred than either parent, followed by 66 (32.7%) that are inbred
more than one parent but less than the other, and 58 (28.7%) that are inbred more
than either parent. The remaining 5 (2.5%) are inbred the same as one parent.
For 55.9% of the
chefs-de-race (113), their sire is more highly inbred than
their dam. For 43.1% of the chefs-de-race (87), the reverse is true.
There are two examples (1.0%) where the sire and dam of the chef-de-race exhibit
the same level of inbreeding.
There are observable differences in inbreeding among chefs-de-race sorted
by aptitudinal contribution; however, these differences are not statistically
significant.
One may conclude from the data that the amount of inbreeding in a
chef-de-race or his parents is unrelated to his ability to transmit consistent
aptitudinal type to his progeny. Prepotence for aptitudinal type
apparently has a different origin.
General Statistics:
Avg. % inbreeding of all chefs-de-race:
1.1181
Avg. % inbreeding of the sires of all chefs-de-race: 1.1558
Avg. % inbreeding of the dams of all chefs-de-race: 1.1884
% Inbreeding over Time
Avg. % inbreeding of chefs-de-race born before 1910: 1.8091
Avg. % inbreeding of chefs-de-race born 1910-1919: 1.5773
Avg. % inbreeding of chefs-de-race born 1920-1929: 1.3128
Avg. % inbreeding of chefs-de-race born 1930-1939: 1.0025
Avg. % inbreeding of chefs-de-race born 1940-1949: 0.9687
Avg. % inbreeding of chefs-de-race born 1950-1959: 0.9521
Avg. % inbreeding of chefs-de-race born 1960-1969: 0.9114
Avg. % inbreeding of chefs-de-race born after 1969: 0.9409
| Chefs-de-Race with Highest % Inbreeding |
Chefs-de-Race with Lowest % Inbreeding |
Ultimus: 13.2935
Havresac II: 6.5796
Bayardo: 4.2163
Gallant Man: 4.0015
Turn-to: 3.8940
Broad Brush: 3.4644
In Reality: 3.2764
Spy Song: 3.2495
Sunny Boy: 3.2227
Colorado: 2.8198
Vatout: 2.6855 |
Speak John: 0.0000
Native Dancer: 0.0488
Reliance II: 0.0488
Relko: 0.0488
Stage Door Johnny: 0.0977
Bold Bidder: 0.0977
Djebel: 0.0977
King's Bishop: 0.0977
Ribot: 0.1465
Promised Land: 0.1465
Secretariat: 0.1953 |
Inbreeding in Chefs-de-Race Relative to Their Sire and
Dam
Chefs-de-race with % inbreeding < % inbreeding in either sire or
dam: 73 (36.1%)
Chefs-de-race with % inbreeding > % inbreeding in either sire or dam: 58 (28.7%)
Chefs-de-race with % inbreeding > % inbreeding in sire and < % inbreeding
in dam: 27 (13.4%)
Chefs-de-race with % inbreeding < % inbreeding in sire and > % inbreeding
in dam: 39 (19.3%)
Chefs-de-race with % inbreeding = % inbreeding in either sire or dam: 5 (2.5%)
% Inbreeding in Chefs-de-Race by Aptitudinal Group Representation
Avg. % inbreeding for chefs-de-race in Brilliant: 1.3653
Avg. % inbreeding for chefs-de-race in Intermediate: 1.1377
Avg. % inbreeding for chefs-de-race in Classic: 0.9255
Avg. % inbreeding for chefs-de-race in Solid: 0.8945
Avg. % inbreeding for chefs-de-race in Professional: 1.0043
| |
Chef-de-Race |
Yr |
%IB
|
|
|
|
Sire |
Sire's
%IB |
|
|
|
Dam |
Dam's
%IB |
|
| |
Abernant
(B) |
1946 |
0.3906 |
|
|
|
Owen Tudor |
2.0410 |
|
|
|
Rustom Mahal |
0.1465 |
|
| |
Ack
Ack (I/C) |
1966 |
0.7910 |
|
|
|
Battle Joined |
1.6113 |
|
|
|
Fast Turn |
1.0620 |
|
| |
Admiral
Drake (P) |
1931 |
1.2061 |
|
|
|
Craig An Eran |
0.5859 |
|
|
|
Plucky Liege |
0.8423 |
|
| |
Alcantara
II (P) |
1908 |
0.8057 |
|
|
|
Perth |
1.0156 |
|
|
|
Toison d'Or |
1.0474 |
|
| |
Alibhai
(C) |
1938 |
0.7813 |
|
|
|
Hyperion |
2.1484 |
|
|
|
Teresina |
0.6348 |
|
| |
Alizier
(P) |
1947 |
0.3418 |
|
|
|
Teleferique |
0.8789 |
|
|
|
Alizarine |
0.2441 |
|
| |
Alycidon
(P) |
1945 |
1.7725 |
|
|
|
Donatello II |
0.7471 |
|
|
|
Aurora |
1.8799 |
|
| |
Alydar
(C) |
1975 |
0.3418 |
|
|
|
Raise a Native |
0.8423 |
|
|
|
Sweet Tooth |
4.1357 |
|
| |
Apalachee
(B) |
1971 |
0.7324 |
|
|
|
Round Table |
0.8350 |
|
|
|
Moccasin |
0.8789 |
|
| |
Asterus
(S) |
1923 |
1.2891 |
|
|
|
Teddy |
1.2891 |
|
|
|
Astrella |
1.0620 |
|
| |
Aureole
(C) |
1950 |
0.8789 |
|
|
|
Hyperion |
2.1284 |
|
|
|
Angelola |
0.9521 |
|
| |
Bachelor's
Double (S) |
1906 |
1.9067 |
|
|
|
Tredennis |
2.0410 |
|
|
|
Lady Bawn |
1.5845 |
|
| |
Bahram
(C) |
1932 |
0.8423 |
|
|
|
Blandford |
1.5576 |
|
|
|
Friar's Daughter |
1.6919 |
|
| |
Baldski
(B/I) |
1974 |
1.2061 |
|
|
|
Nijinsky II |
0.6348 |
|
|
|
Too Bald |
7.2241 |
|
| |
Ballymoss
(S) |
1954 |
1.7993 |
|
|
|
Mossborough |
1.7456 |
|
|
|
Indian Call |
1.0620 |
|
| |
Bayardo
(P) |
1906 |
4.2163 |
|
|
|
Bay Ronald |
0.9155 |
|
|
|
Galicia |
0.5859 |
|
| |
Ben
Brush (I) |
1893 |
1.2695 |
|
|
|
Bramble |
0.4883 |
|
|
|
Roseville |
0.7910 |
|
| |
Best
Turn (C) |
1966 |
0.7690 |
|
|
|
Turn-to |
3.8940 |
|
|
|
Sweet Clementine |
0.6836 |
|
| |
Big
Game (I) |
1939 |
1.8530 |
|
|
|
Bahram |
0.8423 |
|
|
|
Myrobella |
0.5859 |
|
| |
Black
Toney (B/I) |
1911 |
0.4883 |
|
|
|
Peter Pan |
0.2930 |
|
|
|
Belgravia |
1.6382 |
|
| |
Blandford
(C) |
1919 |
1.5576 |
|
|
|
Swynford |
0.8057 |
|
|
|
Blanche |
2.3633 |
|
| |
Blenheim
II (C/S) |
1927 |
1.3770 |
|
|
|
Blandford |
1.5576 |
|
|
|
Malva |
1.2061 |
|
| |
Blue
Larkspur (C) |
1926 |
1.8262 |
|
|
|
Black Servant |
0.3906 |
|
|
|
Blossom Time |
0.5859 |
|
| |
Blushing
Groom (B/C) |
1974 |
0.9521 |
|
|
|
Red God |
1.4355 |
|
|
|
Runaway Bride |
1.5308 |
|
| |
Bois
Roussel (S) |
1935 |
1.5039 |
|
|
|
Vatout |
2.6855 |
|
|
|
Plucky Liege |
0.8423 |
|
| |
Bold
Bidder (I/C) |
1962 |
0.0977 |
|
|
|
Bold Ruler |
0.5859 |
|
|
|
High Bid |
1.2695 |
|
| |
Bold
Ruler (B/I) |
1954 |
0.5859 |
|
|
|
Nasrullah |
0.5859 |
|
|
|
Miss Disco |
0.1953 |
|
| |
Brantome
(C) |
1931 |
0.4883 |
|
|
|
Blandford |
1.5576 |
|
|
|
Vitamine |
1.3184 |
|
| |
British
Empire (B) |
1937 |
0.6348 |
|
|
|
Colombo |
1.7993 |
|
|
|
Rose of England |
0.8789 |
|
| |
Broomstick
(I) |
1901 |
0.2930 |
|
|
|
Ben Brush |
1.2695 |
|
|
|
Elf |
0.7813 |
|
| |
Broad
Brush (I/C) |
1983 |
3.4644 |
|
|
|
Ack Ack |
0.7910 |
|
|
|
Hay Patcher |
0.2441 |
|
| |
Bruleur
(P) |
1910 |
0.8789 |
|
|
|
Chouberski |
0.4395 |
|
|
|
Basse Terre |
1.2061 |
|
| |
Buckpasser
(C) |
1963 |
1.1108 |
|
|
|
Tom Fool |
0.6348 |
|
|
|
Busanda |
0.4883 |
|
| |
Bull
Dog (B) |
1927 |
1.0620 |
|
|
|
Teddy |
1.2891 |
|
|
|
Plucky Liege |
0.8423 |
|
| |
Bull
Lea (C) |
1935 |
0.6836 |
|
|
|
Bull Dog |
1.0620 |
|
|
|
Rose Leaves |
0.9839 |
|
| |
Busted
(S) |
1963 |
0.7324 |
|
|
|
Crepello |
0.2441 |
|
|
|
Sans Le Sou |
0.1465 |
|
| |
Caro
(I/C) |
1967 |
0.4395 |
|
|
|
Fortino II |
1.0254 |
|
|
|
Chambord |
1.3965 |
|
| |
Chateau
Bouscaut (P) |
1927 |
0.3906 |
|
|
|
Kircubbin |
0.5371 |
|
|
|
Ramondie |
1.6919 |
|
| |
Chaucer
(S) |
1900 |
0.8789 |
|
|
|
St. Simon |
0.3906 |
|
|
|
Canterbury Pilgrim |
1.2061 |
|
| |
Cicero
(B) |
1902 |
0.8789 |
|
|
|
Cyllene |
1.4062 |
|
|
|
Gas |
1.0474 |
|
| |
Clarissimus
(C) |
1913 |
1.4062 |
|
|
|
Radium |
1.0254 |
|
|
|
Quintessence |
0.7471 |
|
| |
Colorado
(I) |
1923 |
2.8198 |
|
|
|
Phalaris |
0.7910 |
|
|
|
Canyon |
1.9336 |
|
| |
Congreve
(I) |
1924 |
1.2012 |
|
|
|
Copyright |
2.2559 |
|
|
|
Per Noi |
1.9873 |
|
| |
Count
Fleet (C) |
1940 |
0.2930 |
|
|
|
Reigh Count |
3.3032 |
|
|
|
Quickly |
0.5371 |
|
| |
Court
Martial (B) |
1942 |
1.4648 |
|
|
|
Fair Trial |
0.8057 |
|
|
|
Instantaneous |
0.0488 |
|
| |
Creme
dela Creme (C/S) |
1963 |
0.6836 |
|
|
|
Olympia |
0.7690 |
|
|
|
Judy Rullah |
0.8057 |
|
| |
Crepello
(P) |
1954 |
0.2441 |
|
|
|
Donatello II |
0.7471 |
|
|
|
Crepuscule |
0.8350 |
|
| |
Damascus
(I/C) |
1964 |
1.2012 |
|
|
|
Sword Dancer |
0.7471 |
|
|
|
Kerala |
1.0986 |
|
| |
Danzig
(I/C) |
1977 |
0.5371 |
|
|
|
Northern Dancer |
0.9521 |
|
|
|
Pas de Nom |
0.2930 |
|
| |
Dark
Ronald (P) |
1905 |
1.0474 |
|
|
|
Bay Ronald |
0.9155 |
|
|
|
Darkie |
1.4062 |
|
| |
Discovery
(S) |
1931 |
0.7690 |
|
|
|
Display |
1.1108 |
|
|
|
Ariadne |
1.5845 |
|
| |
Djebel
(I) |
1937 |
0.0977 |
|
|
|
Tourbillon |
0.4395 |
|
|
|
Loika |
2.2559 |
|
| |