Horse Genetics for Speed Paul R Earl Facultad de Ciencias Biolgicas Universidad Autnoma de Nuevo Len

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Horse Genetics for Speed Paul R Earl Facultad
de Ciencias BiológicasUniversidad Autónoma de
Nuevo LeónSan Nicolás, NL 66451, Mexico
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PrologueHorse
genetics including systematics and phylogeny, the
genetics of morphologic traits, color variation
and the inherited diseases, molecular genetics,
immunogenetics, genetic aspects of diseases,
cytogenetics and gene maps, linkage and modern
breeding technologies, behavioral and
developmental genetics, genetic conservation, the
genetics of performance traits, conformation,
locomotion and physiological traits, genetic
improvement and standardized genetic nomenclature
for the horse are all touched on in The Genetics
of the Horse by Ann T. Bowling A. Ruvinsky,
Editors, CAB Inter-national, Wallingford, UK,
2000.
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Horse evidence supports Darwin-Wallace evolution
by an infinite number of small changes through
millions of years. Welcome macroevolution, even
though it is absent in horses! Sports by
breeders fit macroevolutiongiant steps! Equine
paleontology strongly supports classic microstep
evolution as put forth by Ronald Fisher (1930),
thousands of other biologists and the educated
public. .In paleontology, the horse is by far the
best documented mammal. Regardless, Hollywood
puts the Roman army on horses when they only had
ponies!
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The horse sequence from early Hyracotherium
(4 toes on each front foot, 3 on hind
feet) to living Equus traces the loss of toes,
skull changes and size increases that
characterize horse evolution. Vestiges of the
first second toes still exist as splint bones
on the cannon bones. The evolution of modern
horses is linked to the spread of grasslands in
the late Tertiary epoch. Equus arrives 4 million
years ago, the genus of all modern equines. The
evolutionary aspects were first worked out in the
late 1800's and involved people like Thomas
Huxley. The evolutionary sequences provides the
most classic example of dramatic longterm
evolutionary change within a lineage with the
rise and fall of branching species, one replaced
by another..
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When paleontologic horses started to become
runners, there was a simultaneous increase in
body size, leg length and length of the face.
The bones of the legs became fused together. The
leg bones and muscles became specialized for
efficient to-and-fro strides, without flexible
leg rotation. Horses stood on tiptoe thus adapted
for speed. Their weight was supported by elastic
ligaments that ran under the fetlock to the big
central toe (coffin bone).
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Speed depends mostly on the integrety of the
legs. In the illustration of Bull Lea you see
that his front tendons are a little bowed.
Overexcercise must lead to inflammation such as
inflammation of the suspensory tendons. A bowed
horse had muscles SO STRONG that they uprooted
the ligaments from the bone. Of course, these
suspensory tendons will reset, yet not as good as
new.
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Order Perissodactyla, Family Equidae, Genus
EquusThe taxonomy of horses, donkeys and zebras
is a start for genetics as the study of the
earliest equids is another and anatomy
another.Equus burchelli, the Plains zebra of
Africa Equus zebra, the Mountain zebra of South
AfricaEquus grevyi, Grevy's zebra, the most
horse-like zebra. Equus caballus, the true
horse, which once had several subspecies. Equus
hemionus, the desert-adapted onagers of Asia
the Mideast, including the kiangEquus asinus,
donkeys of northern Africa.
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The real environmentFixed races,
scandal, insurance fraud, high finance in the
millions of dollars and murders like the Woodward
accident mark the horse industry and the
millionaire horsey set. Certainly, a few progeny
have replaced siresperhaps the teaser. Horse
games are a form of entertainment, chisling and
bribery in which the servants, stealing what they
can, perform for royalty possibly in the present
form of moviestars who have replaced many of the
millionaire families of a century ago. This much
is clear.
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Genetics starts hereEven sires like
Native Dancer, pulled in the Kentucky derby!, are
inbred. The antique suggestion is Breed the best
with the best, yet good performers arise at
randomoften. The reason that there is no real
trend in most sires is that they are rather close
to being copies of each other. Talk of
compatability, doses, nicks, line breeding and so
on is only part of a mystique.
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Bull Lea, the sire of Citation. His uncle was
Sir Gallahad III.
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When the rank of the horse is compared to
the year, no correlation is derived.
This means that the breed has not improved in
100 years, despite Secretariat being rather
remarkable. One can add that Hancock, Woodward
Senior and others paying 125,000 to
import the sire Sir Gallahad III in the 1920s
reinforced inbreeding through breeding the best
with the best..Thisat randomis a rather strong
statement, disturbing for the little old ladies
who are pouring over horse pedigrees as if they
were founding a new religion. Do you expect the
greatest performer Secretariat also to have been
the greatest sire or grandsire or specialist
broodmare sire? Things dont work that way, do
they ?
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Plucky Liege was one of the most important
broodmares of the 20th Century. Two of her sons,
Sir Gallahad III and Bull Dog were leading sires
in America, and 2 others, Bois Roussel and
Admiral Drake were sires of classic winners in
England, Ireland and France. Plucky Liege
produced 12 foals in all, 11 of which were
winners, and 6 of which won stakes, including 2
classic winners. Five foals were sired by
Teddy.As so common, a leading broodmare sire Mr
Prospector 1970, Raise a Native out of Gold
Digger by Nashua has Teddy on the male and female
lines of his pedigree.
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ACE, the angiotensin converting enzymeThis
enzyme has the hilarious speed gene that never
will prove out.. Nonetheless, ACE is much better
than nothing, though quite out-of-place since it
is studied as relating to hypertension and
myoinfarctions in humans. Sports medicine is not
yet extended to racehorses. This gene is
involved in human arteriosclerosis and
hypertension. Someone of bottomless
ignorance has confused blood pressure with
the functionality of the legs as
limiting for SPEED in racehorses.
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From quite a different view, all variables of all
kinds are testable very easily in every race,
fixed or unfixed. Run the horse races in analysis
of variance (ANOVA). The problem here is
different finding insertion/deletion
polymorphisms in ACE genes in horses that do
indeed have distinct athletic abilities. Can
genetic and environmental risks be told apart in
relation to cardiac difficulties such as the
mitral valve problems in certain few horses?
Well wait and see.
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Nasrullah, sire of Bold Ruler the sire of
Secretariat.
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The impression is that the enormous nucleotide
sequencing power of todays genetics is going to
be used to rip off the breeders that are foolish
enough now to pay 150,000 stud fees for
carboncopy stallions. The Sittingbourne Research
Centre in Kent, UK offers DNA screening tests
that identify specific characteristics relating
to trainability, performance and soundness, even
identifying optimum track distances for
individual horses. Isnt that nice?
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What is Bull Lea telling us? Legs not lungs.He
was bowed in BOTH legs. Speed causes some loss of
function, yet of course not his best sire
genetics. ACE came over from human sports
medicine. Do those people need hypertension ? ? ?
At this point please note that emboli floating
about are likely to be filtered out BY THE LEGS.
The danger for horses seems to be the ignorant
and fraudulent nature of the ACE promoters.The
forelegs are like puppets on strings pulled from
the shoulders. That pull is so very great, it can
pull the ligaments off the bones.
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Blood volume expansion together with muscle
movements and increased intrathoracic pressure,
supplements venous return and increases atrial
and myocardial fiber stretching and pressure.
Exercise increases the plasma levels of many
hormones like endorphin, arginine vasopressin,
cortisol, catecholamines and the hormones of the
renin-angiotensin-aldosterone system, especially
ACE. These are hormones involved in the control
of cardiovascular function and fluid balance as
well as with stress and relief from pain. See
The ACE gene and muscle performance, Nature,
vol. 403, p. 614, 10 February 2000.
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To understand how variations in the ACE gene
might influence how you run, you need to know
what ACE does. Angiotensin is present in the
blood. Under certain conditions, the kidneys
secrete the hormone renin into the blood which
cleaves a 10-aminoacid protein from
angiotensinogen to form the compound angiotensin
I. ACE can knock 2 aminoacids off angiotensin I
to form angiotensin II. Angiotensin II has
several functions. It
directly increases blood pressure by constricting
arteries. It indirectly raises blood pressure and
blood volume by stimulating the thirst centers in
the brain and directing the kidneys to conserve
more minerals and water.
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Altering vascular tone considerably influences
blood pressure.ACE inhibitors relate to lowering
hypertension and reducing heart failures. Their
beneficial effects can be attributed to blocking
the production of angiotensin II from angiotensin
I.There are alternative enzymes capable of
converting angiotensin I into angiotensin II like
chymase. Many OTHER FACTORS like bradykinin as a
vasodilator are involved in controlling the
circulation like pulse rate and air flow
respiration. Certainly, more than one gene calls
for investigation !
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What else do we need to know? The pulse and the
arterial saturation percent of OXYGEN. These
variables (never reported! ?) by oxymeter are
common to human and NOT to veterinary medicine.
Incidentally, red blood cells can be both
nutritionally and hormonely increased. That is
packed cell volume can be most easily tested.
AGAIN, deworming helps. Many variables are easy
to obtain continuously. Treadmills and various
other devices, variables and tests are used
little.
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The inhibition of ACE reduces hypertension.What
the speed gene people are saying is that if the
heart works even harder, more races will be won.
Will the ligaments fly off the bones before the
heart attacks ? What is human and what is equine
and what is normal and what is pathologic are
being confused by people who just dont know.
More much information is missing. Is ACE an
undetected racing dope ? Or better Would it
work? You can bet its been tried unsuccessfully
in horses. When will ACE reports on humans from
the Athens Olympics be available ?