ALLELIC DI­VER­SITY

EQUUS - - Stock & Trade -

The charts pre­sented here con­tain data of in­ter­est to all Thor­ough­bred breed­ers. They com­pare all Triple Crown win­ners plus other great Amer­i­can race­horses se­lected to give a fairly even rep­re­sen­ta­tion through time. Pop­u­lar sire lines are marked. Note the pat­tern of dots at the bot­tom, which rep­re­sent sire-line or dam­sire-line an­ces­tors that ap­pear only once in a given pedi­gree (“non-re­peats”), an ex­cel­lent mea­sure of the in­di­vid­ual an­i­mal’s het­erozy­gos­ity and allelic di­ver­sity.

SIRE LINES: In ear­lier years, the St. Si­mon–Vedette blood­line (black) was the most pop­u­lar, with Nashua hav­ing seven re­peats in his pedi­gree. Old Eclipse blood­lines, es­pe­cially Bon­nie Scot­land (green) were also heav­ily pa­tron­ized. The Phalaris era (pink line) be­gins with Na­tive Dancer in 1953, ac­cel­er­ates with North­ern Dancer (1964), and then comes into ab­so­lute dom­i­nance af­ter Sec­re­tariat (1973). In round num­bers, the av­er­age num­ber of non-re­peated sire-line an­ces­tors for the whole time pe­riod is four. It is five be­fore 1975 but falls to three for the pe­riod 1975 to 2018. Horses with the high­est sire-line di­ver­sity are War Ad­mi­ral, Ci­ta­tion and Carry Back with seven and, out­stand­ingly, Sec­re­tariat with nine. In stark con­trast, 13 of Jus­tify’s 16 sire-line an­ces­tors trace to Phalaris, with three non-re­peats.

DAM­SIRE LINES: The trend in dam­sire lines lags be­hind that of sire lines, but Phalaris creep is none­the­less ev­i­dent: Early Vedette and Bon­nie Scot­land (green) lines drop off as the pink Phalaris line rises. The pat­tern of non-re­peats is a lit­tle dif­fer­ent than for sire lines: The over­all av­er­age is three, but for early years it’s only 2.5. Af­ter 1975, it rises to 3.5, in­di­cat­ing that as di­ver­sity in sire lines fell, Thor­ough­bred breed­ers have in fact sought brood­mares with a broader ge­netic base.

Ten of Jus­tify’s 16 dam­sire-line an­ces­tors trace to Phalaris; in to­tal 23 of 32 an­ces­tors rep­re­sented in Jus­tify’s five-gen­er­a­tion pedi­gree trace to this one an­i­mal, yield­ing an inbreeding co­ef­fi­cient of over 70 per­cent, far higher than the Thor­ough­bred av­er­age of 12.5 per­cent. He has four non-re­peated dam­sire-line an­ces­tors. In con­trast, horses with the high­est dam­sire-line di­ver­sity are Pleas­ant Colony with six and As­sault, Mid­dle­ground, Tim Tam, Kauai King and Hansel each with five. If pur­sued, a strat­egy of seek­ing brood­mares with more diverse pedi­grees will shore up the long-term vi­a­bil­ity of the breed.

Sec­re­tariat’s pedi­gree. Cunningham and col­leagues frankly state, “The Thor­ough­bred horse breed­ing in­dus­try has changed dra­mat­i­cally in the last 40 years with the cur­rent em­pha­sis [on] pro­duc­tion of year­lings to fetch as much money as pos­si­ble at auc­tion, rather than the pre­vi­ous goal of pro­duc­ing su­pe­rior race­horses.” They go on to say, “This com­mer­cial pres­sure has re­sulted in a de­crease in the num­ber of stal­lions in the breed­ing pop­u­la­tion and a large in­crease in the num­ber of foals sired by pop­u­lar stal­lions. Forty years ago most stal­lions cov­ered a max­i­mum of 40 mares per sea­son, com­pared with [some] cur­rent stal­lions that cover close to 200 mares. The ‘big book’ era [re­ally takes off] with the foal crop of 1996. These changes lower the ef­fec­tive pop­u­la­tion size of the breed” ---and the in­evitable re­sult is a steep in­crease in inbreeding.

HIS­TOR­I­CAL TEN­DENCY TO INBREEDING

The found­ing of a breed, which by def­i­ni­tion in­volves the in­clu­sion of some in­di­vid­u­als while ex­clud­ing oth­ers, is it­self a “ge­netic bot­tle­neck” that re­duces the di­ver­sity of al­le­les. Al­le­les are clus­ters of mol­e­cules as­so­ci­ated with dif­fer­ent func­tional zones (loci), along the DNA strand. Vari­ant al­le­les govern the same as­pects of the in­di­vid­ual’s growth and phys­i­ol­ogy but ac­com­plish the task in slightly dif­fer­ent ways---for ex­am­ple, by fa­vor­ing some meta­bolic path­ways over oth­ers or by in­creas­ing (or in­hibit­ing) the pro­duc­tion of cer­tain pro­teins, en­zymes, amino acids or cell types. These ba­sic chem­i­cal and phys­i­o­log­i­cal func­tions un­der­pin ev­ery as­pect of life, in­clud­ing growth, de­vel­op­ment, re­pro­duc­tive suc­cess, im­mu­nity to dis­ease, the abil­ity to heal from in­juries, over­all

sound­ness and ath­letic per­for­mance. Allelic di­ver­sity within an in­di­vid­ual’s genome is a mea­sure of its de­gree of het­erozy­gos­ity0. Cunningham and col­leagues found that Thor­ough­breds pos­sess 37 per­cent fewer al­le­les than other horse breeds stud­ied.

A small num­ber of founder in­di­vid­u­als, ge­netic drift (the sta­tis­ti­cal ten­dency for ho­mozy­gos­ity0 to in­crease in iso­lated pop­u­la­tions) and the dis­pro­por­tion­ate use of pop­u­lar sires are im­por­tant fac­tors act­ing to in­crease inbreeding in do­mes­tic mam­mals. His­tor­i­cally, old breeds with closed stud­books also tend to have high rates of ho­mozy­gos­ity and low allelic di­ver­sity. To un­der­stand re­cent breed­ing trends in the Thor­ough­bred, it’s im­por­tant to re­al­ize that for all of the above rea­sons, the breed was al­ready at high risk for allelic loss even be­fore the cur­rent fad for Phalaris.

The Thor­ough­bred was cre­ated in the 17th cen­tury with a rel­a­tively small

pop­u­la­tion of less than 400 in­di­vid­u­als, and the stud­book was ef­fec­tively closed by 1791. Af­ter its found­ing, the breed went through sev­eral ad­di­tional bot­tle­necks. While other stal­lions were re­spon­si­ble for pa­ter­nal lin­eages early in its his­tory, by the mid-1800s only three re­mained: the By­er­ley Turkmene, the Dar­ley Arabo-Turkmene and the Godolphin (called an “Ara­bian” but ac­tu­ally an al­most even mix of Turkmene, Hobby and Barb; see “A Brief His­tory of the Thor­ough­bred,” EQUUS 448). Fur­ther, each of these three foun­da­tion sires is linked to the liv­ing pop­u­la­tion through only one male-line de­scen­dant: Herod (By­er­ley Turkmene), Eclipse (Dar­ley) and Matchem (Godolphin) (see “Foun­da­tion Sires and Dams,” EQUUS 449).

The per­cent­age of pa­ter­nal lin­eages at­trib­ut­able to the Dar­ley has been in­creas­ing for more than 175 years and is now re­spon­si­ble for 95 per­cent of pa­ter­nal lin­eages in the modern pop­u­la­tion

(see “Eclipse on Top,” EQUUS 451). In­deed, Cunningham’s sur­vey found that just 10 foun­da­tional Thor­ough­breds were re­spon­si­ble for 45 per­cent of the ge­netic makeup of the sam­ple of liv­ing horses stud­ied. The top 20 con­trib­uted 65 per­cent and the top 30, 72 per­cent. The con­tri­bu­tion of all 158 iden­ti­fied founders equals 81 per­cent, with the re­main­ing 19 per­cent due to un­known fac­tors, in­clud­ing novel mu­ta­tions and un­recorded or un­doc­u­mented an­ces­tors.

The most im­por­tant Thor­ough­bred an­ces­tor is the Godolphin, re­spon­si­ble for 13.8 per­cent of al­le­les in the liv­ing pop­u­la­tion. He is fol­lowed by the Dar­ley with 6.5 per­cent, the Cur­wen Bay Barb at 4.2 per­cent, the Ruby mare at 4.2 per­cent and the By­er­ley Turk at 3.3 per­cent. The distaff side of the pedi­gree is im­por­tant be­cause mam­mals in­herit all so­matic cel­lu­lar func­tions (which are gov­erned by the “ex­tra-nu­clear” or “mi­to­chon­drial” DNA) from their moth­ers. Ac­cord­ing to Cunningham’s study, just 10 foun­da­tional brood­mares ac­count for 72 per­cent of ma­ter­nal lin­eages. The top 20 are re­spon­si­ble for 89.9 per­cent of the ma­ter­nal lin­eages in liv­ing Thor­ough­breds, while the top 30 ac­count for 94 per­cent. These find­ings are in ac­cord with stud­ies of wild mam­mal pop­u­la­tions, which have shown that the ef­fec­tive num­ber of founders be­comes con­stant af­ter only a few gen­er­a­tions; in other words, some an­i­mals leave dis­pro­por­tion­ately large num­bers of off­spring while, over time, the con­tri­bu­tions of oth­ers sim­ply wash out. The ge­netic con­tri­bu­tion of fa­vored foun­da­tional in­di­vid­u­als then tends to wield con­stant in­flu­ence through all fu­ture gen­er­a­tions.

Mar­ket-based se­lec­tive breed­ing, which for the modern Amer­i­can Thor­ough­bred means seek­ing to pro­duce year­lings that will sell at auc­tion for the high­est prices, in­creases po­ten­tial for the dis­pro­por­tion­ate rep­re­sen­ta­tion of pop­u­lar sires. When a pop­u­la­tion goes through a bot­tle­neck, rare al­le­les tend to be lost as allelic di­ver­sity is re­duced, but Cristina Luis, PhD, E. Gus Cothran, PhD, and Maria do Mar Oom, PhD, writ­ing in the Jour­nal of Hered­ity in 2007, make the sig­nif­i­cant point that the het­erozy­gos­ity (inbreeding co­ef­fi­cient) calculated for the whole pop­u­la­tion is not re­duced pro­por­tion­ally, be­cause rare al­le­les con­trib­ute lit­tle to het­erozy­gos­ity. Rare al­le­les lie at the root of su­pe­rior phys­i­ol­ogy, and any­one who hopes to pro­duce a great race­horse should be in quest of them, for rare al­le­les and rare com­bi­na­tions of al­le­les are the ge­netic key to the out­stand­ing ath­leti­cism shown by Man o’ War and Sec­re­tariat.

The chance of putting rare al­le­les into play in­creases as the num­ber of dif­fer­ent an­ces­tors in­creases. Com­pare the high di­ver­sity of an­ces­tors rep­re­sented in the pedi­grees of cham­pi­ons such as War Ad­mi­ral, Ci­ta­tion, Tim Tam, Carry Back, Kauai King and es­pe­cially Sec­re­tariat versus the muchtouted and heav­ily Phalaris-bred North­ern Dancer, Seat­tle Slew, Swale, Sun­day Si­lence, Hansel, War Em­blem, Smarty Jones, I’ll Have An­other, Amer­i­can Pharoah and Jus­tify!

DELE­TE­RI­OUS EF­FECTS OF INBREEDING

Com­mon wis­dom among an­i­mal breed­ers en­cour­ages “breed­ing the best to the best to get the best.” Breed­ing win­ners to win­ners is sup­posed to be the best guar­an­tee of pro­duc­ing a win­ner---but in terms of ge­net­ics, this pro­to­col pro­motes an in­crease in the de­gree of ho­mozy­gos­ity, which means a de­crease in the di­ver­sity of al­le­les within the in­di­vid­ual’s genome. When dif­fer­ent al­le­les in­ter­act with each other, as well as with al­le­les at other nearby loci, the ef­fect is called pleiotropi­sm. Pleiotropi­sms are of­ten ad­van­ta­geous, and they con­fer what is termed “hy­brid vigor.” In phys­i­o­log­i­cal terms this may mean greater size and strength, in­creased re­sis­tance to dis­ease, in­creased meta­bolic ef­fi­ciency, in­creased sound­ness, or in­creased fer­til­ity through greater se­men qual­ity and higher con­cep­tion and foal­ing rates. It can cer­tainly also mean greater po­ten­tial for speed, and that’s the bot­tom line in breed­ing race­horses. Un­for­tu­nately, while ho­mozy­gos­ity may in­crease a race­horse’s speed and thus his chances of win­ning, the same ho­mozy­gos­ity at other loci acts to in­hibit other---and of­ten more sub­tle---ad­van­tages con­ferred by hy­brid vigor.

Most vari­ant al­le­les have neu­tral to pos­i­tive ef­fects, but some are dele­te­ri­ous or even lethal. Most dele­te­ri­ous ef­fects are not strong, cre­at­ing only slight de­pres­sions in phys­i­o­log­i­cal func­tions, sound­ness or fe­cun­dity (con­cep­tion and foal­ing rates), but oth­ers cause or con­trib­ute to what is broadly termed “ge­netic dis­ease” or in­her­i­ta­ble dis­ease. Heterozy­gous in­di­vid­u­als with greater allelic di­ver­sity have markedly lower lev­els of ge­netic dis­ease, whereas the chance of ge­netic dis­ease and the po­ten­tial to pass ge­netic dis­eases to off­spring in­crease with ho­mozy­gos­ity.

Inbreeding is de­fined as the prob­a­bil­ity that any given pair of al­le­les in a foal are iden­ti­cal---one in­her­ited from its sire and an iden­ti­cal one from its dam. The inbreeding co­ef­fi­cient is calculated by trac­ing the pedi­gree of an in­di­vid­ual back to com­mon an­ces­tors. This leads us to an un­der­stand­ing of why inbreeding is of such con­cern: Hun­dreds of stud­ies con­ducted over the past cen­tury on many dif­fer­ent species of mam­mals demon­strate “inbreeding de­pres­sion”---re­duc­tion in fit­ness, the abil­ity to adapt, sur­vive and thrive---in wild pop­u­la­tions with high de­grees of inbreeding. Like­wise, Cunningham’s

team notes that “while some stud­ies have not found sig­nif­i­cant ef­fects of inbreeding on re­pro­duc­tive fit­ness in horses … there is con­tin­u­ing con­cern that the nar­rowed ge­netic base of the Thor­ough­bred may be lim­it­ing progress in per­for­mance and con­tribut­ing to an in­creased fre­quency of her­i­ta­ble dis­eases.” Cer­tainly, Phalar­is­in­tense pedi­grees have not worked to in­crease rac­ing speed---race times in Triple Crown con­tests are not even close to records set by Sec­re­tariat more than 40 years ago---even con­sid­er­ing Jus­tify’s stand­out per­for­mance in this year’s Preak­ness Stakes.

De­crease in fe­cun­dity is thought to re­sult from an in­creas­ing pro­por­tion of em­bryos that are ho­mozy­gous for lethal re­ces­sive al­le­les. Such foals typ­i­cally die in utero and are ei­ther silently re­sorbed or else recorded as aborted preg­nan­cies. Modern prac­tices, such as the use of hor­mones to in­duce es­trus and ovu­la­tion and to im­prove re­pro­duc­tive rates, can mask neg­a­tive ef­fects of inbreeding, but dele­te­ri­ous ef­fects of ho­mozy­gos­ity can still be de­tected.

For ex­am­ple, in stud­ies in­volv­ing more than 2,000 English and Ir­ish mares L.H. Mor­ris, W.R. Allen and col­leagues writ­ing in the Equine Vet­eri­nary Jour­nal re­port high lev­els of em­bryo loss: While 94.8 per­cent of Thor­ough­bred mares were re­ported preg­nant at some point in the breed­ing sea­son, the foal­ing rate was only 82.7 per­cent. In par­al­lel fash­ion, a re­port in the Jour­nal of An­i­mal Sci­ence by M. Sevinga and col­leagues in the Nether­lands found that a high in­ci­dence of re­tained pla­centa in Friesian horses is sig­nif­i­cantly cor­re­lated with de­gree of inbreeding. The inbreeding co­ef­fi­cient in the modern Friesian is even higher than in the Thor­ough­bred, rang­ing from about 15 per­cent to 19 per­cent.

Dele­te­ri­ous ef­fects on con­for­ma­tion and sound­ness at­trib­ut­able to high de­grees of inbreeding have also been re­ported for a dozen horse breeds, so it should not be sur­pris­ing that these ef­fects, in­clud­ing re­duc­tion in height, heart­girth, cannon bone cir­cum­fer­ence, hoof size and horn qual­ity would show up in the Thor­ough­bred as well, even though it is dif­fi­cult to es­tab­lish a di­rect causative link be­tween inbreeding and such cat­a­strophic struc­tural break­downs as those suf­fered by Eight Belles, who sus­tained mul­ti­ple frac­tures af­ter fin­ish­ing sec­ond in the 2008 Ken­tucky Derby, and Bar­baro, who won the 2006 Ken­tucky Derby but broke his leg two weeks later in the Preak­ness Stakes.

While these dis­as­ters raised pub­lic con­cern be­cause they oc­curred dur­ing Triple Crown races and were broad­cast on TV, they are but the tip of the ice­berg. A good in­di­ca­tion of di­min­ished sound­ness in the Thor­ough­bred horse was re­ported by E. Mitchell in 2008, who showed that the av­er­age num­ber of ca­reer starts in modern flat-track racers is much less than it was 40 years ago, sug­gest­ing that the ma­jor­ity of

horses bred for the track might not be able to endure more than the half­dozen starts that is the av­er­age to­day. Forty years ago, the av­er­age was more than 50 ca­reer starts for elite-class horses, with some in­di­vid­u­als log­ging 150 starts be­fore re­tir­ing to stud (see “The Thor­ough­bred Gene Pool,” EQUUS 452).

CON­FOR­MA­TION AND GROWTH

The modern trend to­ward in­tense Phalaris breed­ing presents a unique op­por­tu­nity for re­searchers to ex­am­ine large num­bers of horses who are more closely re­lated than half-sib­lings. Of ex­treme value to breed­ers would be con­for­ma­tion anal­y­sis of a “sta­tis­ti­cal” sam­ple of Phalaris-breds (i.e., 50 or more in­di­vid­u­als). Re­sults are more cer­tain and trends more valid as the num­ber of horses stud­ied grows. Lack of space here re­stricts me to merely show­ing breed­ers how to set up such a study.

Since I can fea­ture only a few in­di­vid­u­als, I have cho­sen to be­gin with those most closely re­lated, i.e., horses trac­ing in ei­ther sire line or dam­sire line to Phalaris through the pop­u­lar stal­lion Mr. Prospec­tor. The first ques­tion of in­ter­est is whether there is a fam­ily re­sem­blance; I ad­dress this both by di­rect com­par­i­son of the re­lated horses and by con­trast­ing them with horses of dif­fer­ent breed­ing. Anal­y­sis re­veals that Phalaris-breds do in fact look sim­i­lar, with gen­er­ally small dif­fer­ences in body pro­por­tions. At the same time they look dif­fer­ent from cham­pion-qual­ity Thor­ough­breds of other breed­ing.

Horses bred from Mr. Prospec­tor go back through Phalaris to Bend Or, and thence through Bird­catcher and Pot8- O’s to Eclipse. Eclipse-bred horses

all have a ten­dency for lower withers, thicker muscling, a more “down­hill” build, and a more “rounded” look to the neck and haunches com­pared to Thor­ough­breds who de­scend from ei­ther Matchem or Herod. Their get are by con­trast gen­er­ally taller, with

higher withers, more level over­all body bal­ance, a long “slash­ing” shoul­der, and flat, lathy mus­cu­la­ture. Al­most all Matchem-line horses in our day de­scend from West Aus­tralian, and many of those (es­pe­cially in Amer­ica) come from his de­scen­dant Man o’ War. They tend to be longer-bod­ied than Eclipse-breds, with mas­sive bone. The Phalaris-breds fea­tured in this ar­ti­cle con­sis­tently present the rounded Eclipse body style, with the most di­ver­gent in­di­vid­ual be­ing Bravazo, the only sire line Phalaris horse in this study whose dam­sire line goes to Matchem (through Man o’ War) rather than Eclipse.

Many avail­able pho­to­graphs make it pos­si­ble to look at Phalaris-breds at dif­fer­ent times in their lives. An­other study that would give im­por­tant re­sults use­ful to Thor­ough­bred breed­ers and train­ers would track the pat­tern of growth and mat­u­ra­tion among these closely re­lated horses and con­trast that with elite-class race­horses of other blood­lines. I have not at­tempted that here be­cause the fo­cus of this ar­ti­cle is to look at Jus­tify’s con­for­ma­tion and per­for­mance as a 3 year old. How­ever, even though my sam­ple is not big enough to con­sti­tute sta­tis­ti­cal sig­nif­i­cance, it is of in­ter­est to see how Jus­tify’s ap­pear­ance and struc­tural frame change from the time when his race train­ing be­gan at the age of about 2 years to his 3-year-old photo taken just be­fore the 2018 Belmont Stakes. Like­wise, pho­tos of Amer­i­can Pharoah are now avail­able at ages 2, 3 and 6.

INBREEDING AND CON­FOR­MA­TION

Does inbreeding cre­ate horses that are con­for­ma­tion­ally in­fe­rior or struc­turally weak? Af­ter the Eight Belles and Bar­baro dis­as­ters this pos­si­bil­ity came into wide dis­cus­sion. For horse breeds, as with dog breeds, this ques­tion must be answered in terms of num­bers and time. Num­bers, be­cause un­less the foal dies in utero, with modern vet­eri­nary care and or­di­nary good luck, it will prob­a­bly live to adult­hood. All

Phalaris-bred foals are not of stakesclas­s qual­ity any more than are all foals of any other breed­ing; and his­tor­i­cally in the Thor­ough­bred there has al­ways been an enor­mous amount of prun­ing ---or wastage. Only a small per­cent­age of su­pe­rior in­di­vid­u­als make the grade as race­horses, while those who don’t will be eu­tha­na­tized or gelded and sold to horse-show com­peti­tors or back­yard own­ers. The ma­jor­ity of them are per­fectly vi­able in­di­vid­u­als who get along just fine un­der less in­tense ath­letic de­mand.

It is im­por­tant to keep this in per­spec­tive be­cause ev­ery horse pre­sented in this ar­ti­cle is of cham­pi­onship qual­ity. Even top-class Phalaris-breds, how­ever, show con­for­ma­tional dif­fer­ences both on the plus and on the mi­nus side when com­pared to horses of other breed­ing. On the plus side, they tend to have near-level over­all body bal­ance, just “down­hill” enough to pre­vent “fly­ing up” and wind re­sis­tance with ac­cel­er­a­tion. They also have long fore­limbs, which helps them reach for­ward to in­crease the length of stride. An im­por­tant but more in­tan­gi­ble fac­tor is that they tend to be good-minded and easy to train. On the mi­nus side, two func­tion­ally sig­nif­i­cant prob­lems plague them: first, di­min­ish­ing “bone”---limb cir­cum­fer­ence di­min­ish­ing from the knee down­ward to the hoof, par­tic­u­larly with a ten­dency to­ward small, round an­kles backed by small sesamoids. The sec­ond prob­lem has been shelly, thin hoof horn and/or thin soles and dig­i­tal cush­ions. Like the Quar­ter Horses they re­sem­ble, Phalaris-breds are mas­sively mus­cu­lar but tend to have less than the ideal amount of “bone” to sup­port the weight of the body above and, par­tic­u­larly, to with­stand with­out break­down the thrust, torque and im­pact forces that their pow­er­ful mus­cu­la­ture

gen­er­ates (see “A Sense of Pro­por­tion,” EQUUS 388).

Again as in the Quar­ter Horse, Phalaris-breds are dis­ad­van­taged by the fact that they ap­pear to ma­ture early. I say “ap­pear” be­cause there are no early ma­tur­ing horses in terms of skele­tal de­vel­op­ment; all horses’ bones ma­ture at the same rate, and no horse on Earth is skele­tally or den­tally ma­ture un­til he is 6 years old. Races for 3-year-olds such as the Ken­tucky Derby, Preak­ness Stakes and Belmont Stakes are open only to horses who have not

yet achieved skele­tal ma­tu­rity. Horses who ap­pear more ma­ture on the out­side than their skele­tons within can “fool” a trainer into push­ing them too hard. This is an area where I think Bob Baf­fert has shown both knowl­edge and wis­dom, be­cause all his colts ap­pear to love to run ---im­ply­ing that they have been “ex­posed but not over-ex­posed,” in other words, they have been prop­erly con­di­tioned but have not ex­pe­ri­enced sig­nif­i­cant pain from ex­ces­sive ath­letic de­mand. Jus­tify, how­ever, also stands out over all his closely re­lated

com­peti­tors in pos­sess­ing very cor­rect, sub­stan­tial limbs, pow­er­ful hindquar­ters and har­mo­nious build. Of all the horses re­viewed here, Jus­tify’s con­for­ma­tion is the most sim­i­lar to Sec­re­tariat’s (and so is his run­ning

style, which we will dis­cuss later).

Above, I also men­tioned the fac­tor of time. How long---how many gen­er­a­tions---of inbreeding can a pop­u­la­tion of horses stand be­fore the per­cent­age of vi­able ath­letes drops be­low a level that is eco­nom­i­cally or func­tion­ally sus­tain­able? At what point does ge­netic “load”---the bur­den of dele­te­ri­ous al­le­les packed into the geno­type0 by inbreeding ---be­come so great that few if any foals grow up to ac­tu­ally race? Some wild pop­u­la­tions of other species, such as the chee­tah and snow leop­ard---which his­tor­i­cally have suf­fered from se­vere pop­u­la­tion loss and bot­tle­neck­ing and thus have inbreeding co­ef­fi­cients far above those of Thor­ough­breds---con­tinue to pro­duce vi­able off­spring al­beit with alarm­ingly low con­cep­tion and birth rates. Ge­netic dis­eases as­so­ci­ated with inbreeding that would ob­vi­ate a rac­ing ca­reer in­clude hy­dro­cephalus, con­gen­i­tal blind­ness and wob­bler syn­drome, which are present and in­creas­ing in the Thor­ough­bred.

In a sig­nif­i­cant 2009 study, Robert C. Ty­ron and col­leagues tested 1,031 Amer­i­can Quar­ter Horses and Amer­i­can Paints for five dele­te­ri­ous al­le­les: HYPP (hy­per­kalaemic pe­ri­odic paral­y­sis), LWFS (lethal white foal syn­drome), GBED (glyco­gen branch­ing en­zyme de­fi­ciency), HERDA (hered­i­tary equine re­gional der­mal as­the­nia), and PSSM (type 1 polysac­cha­ride stor­age my­opa­thy). All horses tested were per­for­mance cham­pi­ons in an ar­ray of dis­ci­plines in­clud­ing bar­rel rac­ing, cut­ting, rein­ing, Western plea­sure, hal­ter, work­ing cow and rac­ing. Hal­ter horses had sig­nif­i­cantly greater fre­quen­cies for HYPP and PSSM (more than 200 times higher) than other groups---prob­a­bly be­cause the hy­per­mus­cu­lar phe­no­type0 that wins Quar­ter Horse and Paint Horse hal­ter cham­pi­onships is en­hanced by HYPP and/or PSSM. By con­trast, race­horses had the low­est fre­quen­cies. “It is un­clear why the rac­ing sub­groups had a lower fre­quency of dis­ease al­le­les,” the re­searchers noted, “par­tic­u­larly be­cause heterozy­gous car­ri­ers of au­to­so­mal

re­ces­sive con­di­tions do not pre­sum­ably have a phe­no­type as­so­ci­ated with them. Less in­ten­sive inbreeding … cou­pled with the use of var­i­ous sire lines … may have lim­ited the am­pli­fi­ca­tion of [dele­te­ri­ous] al­lele fre­quen­cies in rac­ing blood­lines. Thor­ough­breds con­tinue to be bred into the Amer­i­can Quar­ter Horse lin­eage through the use of ap­pen­dix Quar­ter Horses.”

How do eco­nom­ics play into in­creas­ing inbreeding? A horse race is won by the fastest horse that shows up on race day, not nec­es­sar­ily by an ex­cep­tion­ally fast horse. Is bet­ting on a race be­tween snails or tur­tles just as en­ter­tain­ing as bet­ting on a race be­tween horses? Since the re­port by Cunningham and col­leagues in 1991, 10-year av­er­ages for win­ning times, even for races of one mile or less, no longer ap­pear to be drop­ping, and race times for Triple Crown win­ners are cer­tainly slower than the records set in 1973 by Sec­re­tariat. As long as the rules for Thor­ough­bred rac­ing man­date no min­i­mum qual­i­fy­ing speed---ex­pressed in sec­onds per mile or miles per hour (as in har­ness rac­ing)--the po­ten­tial for short-term prof­itabil­ity will al­most cer­tainly pre­vail over any con­cern for the long-term sound­ness or over­all vi­a­bil­ity of the Thor­ough­bred.

The modern trend in Thor­ough­bred breed­ing for pro­duc­ing mar­ketable year­lings rather than cre­at­ing great race­horses is surely both silly and un­sus­tain­able in an ath­letic dis­ci­pline where both speed and sound­ness are re­quired. Jus­tify will cer­tainly re­tire to stud, and as­sum­ing he proves to be fer­tile, he will pass on his in­tense Phalaris her­itage to ev­ery foal he sires. Ev­ery time he is bred to a Phalaris mare, the de­gree of inbreeding dou­bles again. Is it no longer pos­si­ble to bring mares of other blood­lines to a cham­pion like Jus­tify? Are such mares no longer avail­able? I would love to see Jus­tify cover a book of mares heavy on Dark Ron­ald (Touch­stone–Sir Peter Tea­zle/Herod), Prince­qui­llo (St. Si­mon–Bird­catcher), Hype­r­ion (Bay Ron­ald/Touch­stone–St. Si­mon/Vedette), Te­trarch, Man o’ War or West Aus­tralian breed­ing. Such mares are still com­monly used to pro­duce cham­pion even­ters, tim­ber racers, steeplecha­sers and jumpers who are not only sound but fast. Fast race­horses have not come ex­clu­sively from Phalaris breed­ing, ei­ther re­cently or in the past.

GAL­LOP­ING STYLE

On this ba­sis, we ob­vi­ously also want to know whether there is a Phalar­is­bred gal­lop­ing style that is faster than that of other blood­lines. The re­view above makes it clear that it doesn’t mat­ter whether the win­ning horse is fast, as long as he can out­pace oth­ers against which he is raced. When high-stakes rac­ing is essen­tially a clone war with ev­ery horse closely re­lated to his com­peti­tors, gal­lop­ing ef­fi­ciency may make the dif­fer­ence be­tween cham­pi­onship and ob­scu­rity.

I have pre­vi­ously re­viewed gal­lop biome­chan­ics of fast horses and of other mam­mals such as chee­tahs that are also fast run­ners versus slower species such as gi­raffes or ele­phants. I am amused, and per­haps not too sur­prised, to see my il­lus­tra­tions and text re­pro­duced (with­out at­tri­bu­tion or credit) in sev­eral on­line Thor­ough­bred blogs. What my re­views have ap­par­ently ac­com­plished---es­pe­cially “Se­crets of Sec­re­tariat’s Speed” (EQUUS 434)---is

to make Thor­ough­bred fanciers aware that there is such a thing as a dou­ble­sus­pen­sion trans­verse gal­lop---and that horses ca­pa­ble of it are in­evitably win­ners. A few cham­pi­ons across blood­lines, in­clud­ing Man o’ War, Phar Lap, Se­abis­cuit, Prince­qui­llo, John Henry and Sec­re­tariat, con­sis­tently showed this gal­lop­ing style, and Jus­tify also ap­pears to be­long to this elite cadre. A horse’s abil­ity to pro­duce this type of gal­lop de­pends upon neu­ro­mus­cu­lar co­or­di­na­tion and the elas­tic­ity of his back as much as upon su­pe­rior power. No

study of the preva­lence of the dou­ble­sus­pen­sion trans­verse gal­lop has been per­formed to date upon a sta­tis­ti­cal sam­ple of Thor­ough­breds, but it would be rel­a­tively easy to do and would yield enor­mous prac­ti­cal ben­e­fit to flat-track train­ers as well as to in­vestors who select which colts to pur­chase for train­ing.

A telling com­par­i­son I have not pre­sented be­fore an­a­lyzes gal­lop­ing style in terms of thrust and land­ing phase. The premise is sim­ple: If the cen­ter fielder in a base­ball game catches the ball and the play is at sec­ond, he will

throw the ball in a low arc di­rectly to the sec­ond base­man. If, how­ever, the play is at the home plate, in or­der to hit the catcher’s mitt the cen­ter fielder will have to throw the ball not only with more power, but with a much higher arc. In short, the po­ten­tial flight dis­tance is a func­tion of the height of the arc. This is a ma­jor in­sight when it comes to speed in race­horses be­cause the fastest horses are those who spend the most time fly­ing through the air dur­ing the gal­lop’s pe­riod(s) of sus­pen­sion. In this com­par­i­son, Sec­re­tariat

shows him­self to be essen­tially unbeatable. How­ever, Jus­tify’s tech­nique is very good, and I am es­pe­cially im­pressed by his elas­tic back and long fore­limbs, which al­low him to stretch far for­ward dur­ing the land­ing phase.

Yet an­other way to as­sess cham­pi­onship speed in race­horses is to look at the pelvic an­gle in the most col­lected versus the most ex­tended phase of the gal­lop. Rac­ing speed, as I have pointed out in many pre­vi­ous ar­ti­cles, is not pri­mar­ily cre­ated by the horse’s legs. Rather, it is the flex­i­bil­ity of the an­i­mal’s back, par­tic­u­larly the coil­ing and un­coil­ing of the loins, which is the biome­chan­i­cal heart of speed. Coil­ing of the loins is ef­fected by the horse’s ab­dom­i­nal and il­iop­soas mus­cu­la­ture, while un­coil­ing is ac­com­plished by the periver­te­bral mus­cles---pri­mar­ily the

longis­simus dorsi---which par­al­lel the spine and ex­tend from the base of the neck to the pelvis. To cre­ate for­ward thrust, the horse first coils his loins. Then he presses one or both hind limbs against the ground as ef­fort switches from the ab­dom­i­nals to the long

periver­te­brals. The body is thrust for­ward as the longis­simus dorsi con­tracts, un­coil­ing the loins. The more deeply the horse coils its loins dur­ing the col­lected phase of the gal­lop, the greater the range through which it will un­coil them dur­ing the

ex­tended phase, and this is what cre­ates su­pe­rior speed.

Jus­tify comes off the win­ner in this com­par­i­son---even over Sec­re­tariat! Jus­tify’s max­i­mum loin-coil­ing rolls the rear end of his pelvis down some 37.4 de­grees, more than Sec­re­tariat’s

max­i­mum at 34.8 de­grees. The best photo of Sec­re­tariat’s un­coiled pelvis re­veals an an­gle of 19.5 de­grees---this is the most his pelvis and topline “flat­ten out”---whereas the re­mark­able photo of Jus­tify that I an­a­lyze here catches him in the same phase of the gal­lop stride with pelvis un­coiled to 3.8 de­grees, cre­at­ing a dif­fer­ence of 33.6 de­grees be­tween coiled and un­coiled phases, much more than what avail­able pho­tos al­low me to doc­u­ment for Sec­re­tariat. Man o’ War shows a dif­fer­ence of 26.8 de­grees and Amer­i­can Pharoah shows 16.3 de­grees, both of which are also greater than Sec­re­tariat’s 15.3 de­grees.

Con­for­ma­tion­ally, Sec­re­tariat’s pelvic an­gle is not only longer but steeper than ei­ther of the Phalaris-breds or Man o’ War. A steeply-an­gled pelvis con­duces to power but not flex­i­bil­ity, as it is more dif­fi­cult for such a horse to “un­coil” the loins. None­the­less, Sec­re­tariat is the fastest of the four horses an­a­lyzed, and this tells us ex­actly what would be needed to cre­ate a cham­pion that could run faster than Sec­re­tariat: the same spinal elas­tic­ity shown by Man o’ War or Jus­tify, com­bined with a longer, some­what steeper pelvis pack­ing greater power.

Straight car­riage is an­other fac­tor cru­cially im­por­tant to rac­ing suc­cess. A train whose wheels are partly off the track, or a car that needs a front-end align­ment not only wastes fuel but

This is a ma­jor in­sight where it comes to speed in race­horses be­cause the fastest horses are those that spend the most time fly­ing through the air dur­ing the gal­lop’s pe­riod(s) of sus­pen­sion.

op­er­ates as if driven for­ward with the brakes on. A horse who runs crooked--with his body out of align­ment with his in­tended di­rec­tion---will not only be slower than he should be, but will pre­ma­turely wear his joints out.

Horses with crooked car­riage show a pat­tern of over­weight­ing ei­ther the left or the right pair of limbs, and they pound es­pe­cially heav­ily upon the fore hoof of the fa­vored side. My re­view of films of Amer­i­can Pharoah brought out the fact that he of­ten ran with his head an­gled off to the right, im­ply­ing that he over­weights the left pair of limbs and es­pe­cially the left fore­limb (see “Amer­i­can

Pharoah and the Triple Crown,” EQUUS 458). An­other story in the same is­sue, “Amer­i­can Pharoah’s Lucky Horse­shoe” de­scribes the spe­cial “Pharoah plate” that the colt needed to wear on his left fore hoof. I was of course sorry to see this con­fir­ma­tion of crooked car­riage in a cham­pion.

Amer­i­can Pharoah proved to be gen­er­ally a bit above av­er­age in terms of race times; how fast would he have been had he been taught to run straight rather than merely spe­cially shod in or­der to try to make up for the fact that he ran crookedly? The knowl­edge of how to help a horse dis­cover straight car­riage has not been com­mon at the flat track (or, in all fair­ness, in any other eques­trian dis­ci­pline), but the tech­niques have been known for more than 300 years. I have said in print that I be­lieve Sec­re­tariat, who showed re­mark­ably straight car­riage, taught this ef­fi­cient (and more com­fort­able) way of go­ing to him­self. Jus­tify like­wise runs straight and han­dles the turns flu­idly, in a man­ner com­pa­ra­ble to Sec­re­tariat.

I’ve pre­sented a lot of data in this re­view, with sug­ges­tions for needed re­search that could eas­ily be funded by the in­dus­try. The bot­tom line of this dis­cus­sion goes di­rectly against the short-term-gains phi­los­o­phy that says “win­ning is ev­ery­thing, and only win­ners count.” What I’m sug­gest­ing is that to cre­ate great race­horses, breed­ers must turn to “good” in­di­vid­u­als---fast, sound, cor­rectly con­formed and good­minded---who did not hap­pen to win. In short, to get great race­horses, and (more im­por­tant) to pre­serve the fu­ture vi­a­bil­ity of the Thor­ough­bred, it is vi­tally nec­es­sary to breed to losers! It will also be nec­es­sary for more train­ers to take cer­tain pages from other eques­trian

dis­ci­plines in terms of se­lect­ing ap­pro­pri­ate colts and fil­lies, con­di­tion­ing them and teach­ing them to un­der­stand and love the game they’re be­ing asked to play.

The Thor­ough­bred is the world’s great­est breed of horse, but its fu­ture is in jeop­ardy. With en­light­ened prac­tices in both breed­ing and train­ing, we can look for­ward to a con­tin­u­ing string of Triple Crown cham­pi­ons who are not just de­signer-bred one-note John­nies but who, like Jus­tify, ex­em­plify the su­pe­rior ath­leti­cism that is the Thor­ough­bred’s birthright.

DAM­SIRE LINES

SIRE LINES

This chart de­picts the win­ning race times for all Triple Crown win­ners since Sir Barton in 1919. Times prior to 1930 are not pre­sented for the Belmont or Preak­ness Stakes be­cause ear­lier race dis­tances were dif­fer­ent. Jus­tify’s time for the Preak­ness in­di­cates a stand­out ath­letic ac­com­plish­ment and hints that break­ing the “Sec­re­tariat ceil­ing” may yet be pos­si­ble.

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