Download Ergogenic Aids to Performance in the Race Horse: Nutrients or Drugs1

nutrition and Performance
Ergogenic Aids to Performance in the Race Horse:
Nutrients or Drugs1
DAVID H. SNOW2
EquiSci International, Wahroonga, New South Wales, Australia
INDEXING
KEY WORDS:
•ergogenic •horse •performance
•nutrients
•drugs
Horses compete in a variety of athletic disciplines
controlled by regulations that govern the presence of
drugs at the time of competition. These regulations
try to ensure a "level playing field" as well as protect
the welfare of the horse and rider. In addition, where
betting is involved they also try to prevent the use of
compounds to manipulate performance. Prevention of
manipulation is vital if owner and punter support, and
thus the financial stability of racing, is to be main
tained.
Racing jurisdictions have developed regulations
from the extremely strict operation in most thorough
bred racing countries that prohibit the presence of all
compounds that can influence the systems of the body.
0022-3166/94
If fully enforced, these would lead to the absurdity of
banning all nutrients! In most states in the United
States there is more latitude, as both prerace medica
tion (furosemide and phenylbutazone) and compounds
such as anabolic steroids are allowed. Although few
would argue against the banning of stimulants and de
pressants, debate continues in many jurisdictions as
to whether any, some or all therapeutic drugs should
be permitted and what constitutes legitimate nutri
tional supplements.
Attempts to decide which substances should be
prohibited at the time of racing are made difficult be
cause of the problems in demonstrating experimentally
whether a compound can influence performance. Due
to the large number of variables, a 1% change in per
formance, which can have a dramatic effect on the
outcome of a race, is virtually impossible to demon
strate using either treadmill exercise tests or race track
performance. This difficulty has also enabled claims
for performance enhancement to be made for a variety
of compounds. Support for these claims is often only
based on anecdotal evidence or even just hope. This
difficulty is also used as a justification for having blan
ket rules prohibiting the presence of all compounds
that may be considered to affect the body. Difficulties
in proving effects on performance may also explain
why most regulations in horse racing are virtually all
encompassing compared with the defined substances
in the International Olympic Committee's rules on
prohibited substances.
Ergogenic aids (ergogenic, meaning "tending to in
crease work or work producing") can be used to im
prove performance in the following ways (Williams
1983): 1) improve physiological capacity directly, 2)
remove psychological restraints to physiological ca1 Presented as part of the Waltham Symposium on the Nutrition
of Companion Animals in association with the 15th International
Congress of Nutrition, at Adelaide, SA, Australia, on September
23-25, 1993. Guest editors for this symposium were Kay Earle,
John Mercer and D'Ann Finley.
1 To whom correspondence should be addressed: EquiSci Inter
national, 45 Campbell Drive, Wahroonga, NSW, 2076, Australia
S3.00 ©1994 American Institute of Nutrition.
2730S
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ABSTRACT Since the domestication of the horse and
its use in various types of athletic competition, its diet
has developed from that associated with grazing to
feeding of additional energy in the form of grains up to
the present situation when numerous supplements are
fed in hopes of enhancing performance. Many if not all
of these may be considered as ergogenic aids, and under
the rules of racing in many countries should be con
sidered as a prohibited substance. Until recently, a blind
eye has been turned to whether the rules should be
enforced against many nutritional supplements, for ex
ample, vitamins and amino acids, especially when given
in amounts vastly in excess of normal requirements.
However, although arguably a nutrient, large doses of
sodium bicarbonate and possibly other compounds with
the potential of improving buffering capacity have been
used extensively, and rules and detection methods have
been introduced to curtail this. This paper reviews the
nutritional supplements currently in use and discusses
whether the singling out of alkalinizing agents as an
enforceable prohibited substance is justified, whereas
other substances such as fats can be supplemented in
high amounts. J. Nutr. 124: 2730S-2735S, 1994.
ERGOGENIC
AIDS TO PERFORMANCE
2731S
ergogenic aid; would it also be considered the first
doping agent, if some of today's regulators were
present?
Since those early days of domestication, when feed
ing grain in addition to hay or grass commenced, there
was virtually no change in the feeding of horses until
the last 30 years. However, our general increase in
knowledge about the nutritional demands of exercise
has led to changes in feeding patterns and to what is
fed. This has contributed to what could be considered
as part of the fine tuning of the horse's body and im
proved performance. However, I believe we are now
at a stage where there are uncertainties as to what is
an allowable nutritional supplement to have a horse
fit for the racecourse and what may be considered to
enhance performance, thereby breaching racing's reg
ulations. In attempting to consider where we presently
stand, the usage of nutritional supplements is briefly
considered. Although it may be debatable which sup
plements should be considered as potential ergogenic
agents, all are discussed in the recent texts on ergogenics (Lamb and Williams 1991;, Williams 1983).
Further details on many of the compounds discussed
are provided in these proceedings by Hintz (1994) and
Kronfeld et al. (1994).
Carbohydrate and glycogen
The successful training and racing of a horse re
quires sufficient energy intake to maintain an ideal
body weight and glycogen stores. To do this, the pro
portion of grain in the diet is increased, levels being
controlled to prevent an animal becoming overweight,
developing laminitis or exertional rhabdomyolysis. For
whatever reason the horse has the ability to store large
quantities of glycogen within muscle; Concentrations
in the well-trained and well-fed horse are 600-700
mmol glucosyl units/kg dry matter (DM) (Snow
1993b). Despite this high content, some workers in
the field have investigated glycogen supercompensa
tion programs. Although there have been some claims
that this can be achieved (Snow 1993b), overall the
results are equivocal. Studies showing some benefit
have controls with relatively low muscle glycogen
content. In addition to attempts to supercompensate,
attempts have also been made to see if glycogen re
pletion rates can be increased. The use of intravenous
(IV) glucose, oral glucose and glucose polymers has
been investigated (Snow 1993b). These were of no
benefit, and this work has been supported by the recent
studies of Davies et al. (1994).
Fat
It has been well documented that horses can tolerate
fat in concentrations considerably higher than would
be found in their normal diet [National Research
Council (NRC) 1989, Potter et al. 1992]. In addition
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pacity and 3) provide a mechanical advantage specific
to the sport.
Over the last 30 years, great advances have been
made in all three categories, leading to marked im
provements in human athletic performance. Lesser
improvements have been seen in equine sports. The
possibilities of motivational enhancement led to the
employment of sports psychologists. In the horse
world, changing behavioral attitude, often influenced
by sex hormones, can have a marked influence on per
formance. The terms losing heart or becoming sour
are words only too commonly used to describe a dis
appointing performance. The ability to prevent or
overcome this often is the hallmark of a good trainer.
In the third category, improvements in equipment
and track design following detailed biomechanical in
vestigations have led to marked improvements. This
has also occurred within horse racing, resulting from
such things as improved horseshoes, sulky (cart) and
track design.
Of relevance to this paper are the ergogenic aids
that may lead to improvement through physiological
pathways. These may be obvious drugs such as am
phetamines, caffeine, narcotics and anabolic steroids
or compounds that are in the grey area between nu
trients and when in excess drugs. Physiologically, per
formance can be enhanced by either increasing max
imum work output per unit time, that is, increased
strength, delaying the onset of fatigue at a particular
level of performance or improving neuromuscular co
ordination. All of these are influenced by training and
conventional nutritional programs. However, our in
creased knowledge of the causes of fatigue, for ex
ample, acidosis and the decline in muscle ATP, glycogen depletion, hypovolemia and hyperthermia, also
allow possible improvement through nutritional sup
plementation as well as by drugs. The use of stimulants
such as amphetamine to change central perception of
fatigue are universally condemned, whereas the al
lowable use of anabolic steroids for possible strength
enhancement varies between countries (see review by
Snow 1993a).
Where a diversity of views exists is the use of com
pounds that can delay the onset of fatigue due to their
peripheral effects. Most of these compounds may be
considered normal nutrients, but when given in ab
normal quantities the question whether their use
should be permitted is raised.
In the wild, a horse spends most of its time grazing,
with occasional bursts of activity when playing or es
caping from predators. All its nutritional requirements
are met by eating native grasses. Domestication of the
horse and its employment in tasks requiring increased
energy utilization led to dietary modifications. In the
notes to Xenophon The Art of Horsemanship, there is
reference to, in Greek times, the feeding of barley
(Morgan 1984). Therefore, the feeding of grain to pro
vide additional energy could be considered the first
IN THE HORSE
2732S
SUPPLEMENT
Cernitine
Carnitine, a low-molecular-weight water-soluble
quaternary amine, is associated with numerous aspects
of fat and carbohydrate metabolism. Because of this,
it has been claimed that carnitine could be a useful
ergogenic aid. In humans and laboratory animals, re
sults on the use of this compound have been equivocal.
Studies in horses have found that carnitine is poorly
absorbed after oral administration to horses (Foster
and Harris 1989, Foster et al. 1988). After high dose
IV administration, there appeared to be no change in
muscle carnitine concentration (Foster 1989). There
fore, despite the availability in Australia of a carnitine
preparation for IV administration, there appears to be
no rational reason for its use.
Protein
From the early 1970s to mid-1980s, the feeding of
high protein diets was in vogue. Diets often contained
up to 16% protein. These diets probably followed the
fashion of human athletes consuming diets with high
amounts of protein. It is now generally accepted that
it is not necessary to exceed ~10% of protein in the
diet. Furthermore, it is the quality of the protein as
well as the amount of key amino acids that is of im
portance rather than the quantity. Following mainly
anecdotal reports on the improvement of performance
in humans seen with tryptophan and branched chain
amino acids (Grunewald and Bailey 1993), these com
pounds have also been sold for horses. The beneficial
effects of tryptophan in humans have been recently
discounted in a study by Stensrud et al. (1992).
Vitamins
Many vitamins, especially those belonging to the
B-complex, are vital in metabolic regulation. It has,
therefore, been suggested that their requirements in
crease during periods of intense activity. However,
these increased requirements are usually met by in
creased feed intake, especially if complete rations are
used. However, just as in the human athlete, there is
a belief among many trainers that megadoses of vita
mins enhance performance. One extremely successful
horse race trainer has been reported to feed 20 g ascor
bic acid and 10 g vitamin E daily to his race horses
(Snow and Frigg 1987).
Just as in many other areas examining the effects of
nutrition on performance, equivocal results have been
reported in humans when supplementation with var
ious vitamins has been examined (Williams 1983). In
horses, studies have been extremely limited. A study
of biotin supplementation showed no effect on the de
velopment of the lactate threshold (Lindner et al.
1992). The effects of the relationship between lipid
peroxidation, which may contribute to fatigue and vi
tamin E status, have been recently investigated with
respect to endurance performance (McMeniman and
Hintz 1992, Petersson et al. 1991).
Electrolytes
and water
It is well accepted that adequate amounts of elec
trolytes and water are required for optimum perfor
mance as well as the avoidance of risks to the health
of the animal. The major thermoregulatory mechanism
in the horse is sweating. As sweat in the horse is hypertonic, depletion of electrolytes as well as water are
major causes of fatigue in endurance events. To pre
vent problems arising from electrolyte and water de
pletion, adequate supplementation of electrolytes and
water before and during competition is undertaken.
In addition to water, of major concern is adequate
intake of sodium because normal diets are very low
in this electrolyte. The necessity for supplementation
with trace elements is unknown. In race horses, it has
been common practice to give electrolyte solutions in
travenously (jugging) or orally (drenching) before
competition. The rationale for this and its usefulness
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to the obvious use of fat as an energy-dense compound
to increase energy intake in horses with a poor appetite
or with very high energy demands (e.g., horses com
peting in endurance competitions), it has also been
claimed that increased fat intake will enhance perfor
mance (Potter et al. 1992) in both endurance and
sprinting events. It has also been claimed (Potter et al.
1992, Snow 1993b) that feeding increased fat will in
crease muscle glycogen concentrations. Again, in
creased muscle glycogen has been seen in those studies
where it would appear that controls had initially low
muscle glycogen content. One study has shown that
by using isoenergetic diets, both high protein and high
fat diets resulted in lower muscle glycogen than the
normal diet (Pagan et al. 1987). On the other hand,
Harkins et al. (1992) using isoenergetic diets found
increased glycogen content when a higher proportion
of fat was fed.
A recent study at the University of Sydney found
that 3 wk of feeding fat had no influence on muscle
glycogen content (Eaton et al. 1994). Harkins et al.
(1992) found decreased sprinting time in horses fed a
high fat diet. However, this study can be criticized
because a cross-over design was not used. Some studies
have found increased blood or plasma lactate concen
trations associated with maximal exercise, whereas
others have found decreased concentrations (Snow
1993a). On metabolic grounds, it is difficult to under
stand how feeding increased fat can improve perfor
mance requiring supramaximal effort. In endurance
activities, feeding fat will be beneficial in ensuring ad
equate energy intake and may also lead to a glycogensparing effect due to enhanced free fatty acid utiliza
tion (NRC 1989).
ERGOGENIC
AIDS TO PERFORMANCE
is questionable. It may be of some benefit after a long
trip to the racecourse during which the horse may have
lost considerable amounts of fluid and electrolytes
through sweating.
Buffering compounds
2733S
owners and regulators is should all of these nutritional
attempts be considered legal and advances in optimal
feeding or should some differentiation be made? In
human athletics it would appear that presently there
are no constraints on the use of any nutritional agents.
Enhancement of muscle glycogen stores, megadoses
of vitamins and the use of electrolytes, including so
dium bicarbonate, are all permitted at any time before
competition. In endurance events in both human and
equine competitions, the use of energy substrates,
electrolytes and water are not only permitted but also
encouraged because of welfare concerns despite al
lowing improved performance. However, in horse
racing the situation is different with, as discussed pre
viously, regulations in many countries banning all nu
trients because all, in one way or another, affect the
various systems of the body. However, for obvious
reasons these rules are not enforceable, although it
could be argued that certain dietary alterations, for
example, feeding fat, could lead to enhanced and ma
nipulated performances. There also appears to be no
monitoring of the use of amino acid and vitamin sup
plements.
Prohibition of buffering compounds
In contrast to the freedom to use most nutrients,
many racing jurisdictions have recently introduced
regulations against the use of compounds that will
improve buffering capacity. Presently, this rule is only
enforced in some countries, notably in Australia, by
the measuring of prerace blood or plasma bicarbonate
or total CO2 concentrations. Because of endogenous
concentrations, threshold levels have been established
(Auer et al. 1993). The levels have been set to prevent
the administration of bicarbonate before racing rather
than daily supplementation with low doses. The latter
have not been found to alter normal resting values (D.
Lloyd and R. J. Rose, personal communication). The
established threshold levels may vary, for example, in
New South Wales the threshold is presently 35 and
37 mmol/1 of total carbon dioxide within plasma for
standardbreds and thoroughbreds, respectively. In the
United States where the diuretic furosemide may be
permitted, the establishment of threshold values will
be even more difficult because this drug could influ
ence bicarbonate excretion (Roelofson 1993).
The strongest argument against the use of buffering
agents is the possibility of manipulation of races by
having horses running on or off bicarbonate. When
sodium bicarbonate was being freely used in standardbred racing in Sydney, there was apparently a
strong relationship between betting and horses ad
ministered bicarbonate (D. Lloyd, personal commu
nication). On the other hand, it could be argued that
the attainment of high blood bicarbonate concentra
tions with minimal health risk should be just as permissable as using supplements to ensure high muscle
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With high intensity exercise, fatigue is thought to
be related to increasing acidity of muscle and a de
crease in muscle ATP. It has been suggested that im
provement in either intra- or extracellular buffering
could improve performance. In humans, it has been
demonstrated that in certain situations, oral admin
istration of sodium bicarbonate several hours before
competition is beneficial. In horses, a number of stud
ies have been carried out examining whether sodium
bicarbonate administration can influence supramaxi
mal performance (Harkins and Kammerling 1992,
Lloyd et al. 1993a, Snow 1993c). Overall, these studies
have been unable to show any improved race track
performance. However, metabolic studies found that
sodium bicarbonate administration resulted in an in
creased blood lactate concentration and reduction in
decline in muscle ATP (Greenhaff et al. 1991). This
would theoretically lead to prolonged onset of fatigue
and allow faster racing times. Despite the lack of ben
eficial effects seen experimentally, anecdotal evidence
from the extremely widespread use of sodium bicar
bonate (often termed by horsemen a milkshake when
incorporated with other ingredients) on the race track
(until its prohibition), especially in standardbreds,
suggests a beneficial effect. On the race track, amounts
up to 1 g/kg of sodium bicarbonate, resulting in venous
blood total carbon dioxide concentrations in excess of
40 mmol/1 (Lloyd et al. 1993b), have been reported.
In contrast to humans where doses in excess of ~0.3
g/kg are often associated with gastrointestinal side ef
fects, these extremely high doses would appear to be
generally well tolerated by horses.
More recently, the oral administration in humans
of very high doses (20-30 g/d for up to 5 d) of creatine
has been shown to increase muscle total creatine pool
in some individuals (Harris et al. 1992). It has been
reported that this can enhance sprinting performance
(Harris et al. 1993). It has been suggested that this is
brought about by increasing the creatine/phosphocreatine pool, enhancing dynamic buffering within mus
cle. It is thought to be of most benefit in muscle with
relatively low creatine phosphate content. The effects
of creatine administration on race horse performance
are being currently investigated. In a number of coun
tries including Australia it is being fed to race horses
with anecdotal reports of beneficial effects.
The overview presented here indicates that com
pounds belonging to different nutritional categories
have and are still being used in an attempt to improve
performance. The difficult question for feed and sup
plement manufacturers, nutritional advisors, trainers,
IN THE HORSE
2734S
SUPPLEMENT
lators are justifiably concerned about manipulation of
performance, it is surprising that one of the easiest
ways to influence performance, that is, racing outside
the horses ideal weight, is not monitored by the very
easy weighing of horses before a race. This option has
been used for many years in greyhound racing and in
Japan for thoroughbred racing. The questions raised
are extremely difficult to answer, especially in racing,
whose future is dependent on a betting public de
manding the minimum of underhanded tactics. How
ever, it is time that these questions are openly dis
cussed.
LITERATURE CITED
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of bicarbonate administration
(milkshake) in Standardbred
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Davies, A. J., Evans, D. L., Hodgson, D. R. & Rose, R. J. (1994)
Effects of an oral glucose polymer on muscle glycogen resynthesis
in standard bred horses. }. Nutr. 124: 2740S-2741S.
Eaton, M. D., Hodgson, D. R., Evans, D. L., Bryden, W. L. &. Rose,
R. J. (1994) Effect of diet containing supplementary fat on the
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Foster, C. V. L. a Harris, R. C. (1989) Plasma carnitine concen
trations in the horse following oral supplementation using a triple
dose regime. Equine Vet. J. 21: 376-377.
Foster, C. V. L., Harris, R. C. & Snow, D. H. (1988) The effect
of oral L-carnitine supplementation
on the muscle and plasma
concentrations in the Thoroughbred Horse. Comp. Biochem.
Physiol. A Comp. Physiol. 91: 827-835.
Greenhaff, P. L., Harris, R. C., Snow, D. H., Sewell, D. A. &.Dunnett,
M. (1991 ) The influence of metabolic alkalosis upon exercise
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129-134.
Grunewald, K. K. & Bailey, R. S. (1993) Commercially marketed
supplements for bodybuilding athletes. Sports Med. 15: 90-103.
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alkalosis on performance in Thoroughbreds during a 1,600m race.
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creatine in resting and exercised muscle of normal subjects by
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glycogen. Because bicarbonate administration can alter
postrace urine pH and also cause diuresis, it might
interfere in the excretion of other drugs. It therefore
has the potential as a masking agent. A study has in
dicated that it will make the detection of the narcotic
etorphine more difficult to detect (D. Lloyd, personal
communication). Other arguments against its legiti
mate use include the following: I) it is not given as a
normal nutrient in the feed but in very vast quantities
in an unnatural manner (nasogastric tubing) and 2) al
terations in blood bicarbonate concentrations result
in nonphysiological levels, therefore resulting in a
pharmacological effect.
The relative ease in monitoring bicarbonate admin
istration allows abuse to be readily detected, although
the significance of concentrations just in excess of
threshold values can lead to controversy. However,
what is going to be the situation if creatine supple
mentation is shown to be successful? The alteration
of intracellular buffering will not be easily determined
and detection will probably have to rely on measure
ment of plasma or urinary creatine concentrations. If
as in humans creatine administration only increases
muscle creatine to concentrations still within normal
physiological ranges, it could be argued that this
should be permissible as a relative deficiency is being
corrected by supplementation. This is despite the
compound not being present in the normal diet and
being administered in megadoses. Interestingly, al
though creatine under the present rules is illegal in
Australia, in Sweden it was recently decided that it is
a legitimate compound to feed (S. Persson, personal
communication). On the other hand, the administra
tion of bicarbonate before racing is illegal in Sweden.
Apparently the different rulings are based on the fact
that nasogastric tubing before racing is illegal, the
normal way of bicarbonate administration and not on
whether it may influence performance. What would
be the situation if a delayed release preparation of bi
carbonate could be developed?
If these buffering compounds are prohibited, why
should fat administration be allowed if anecdotal and
some scientific evidence indicates it enhances perfor
mance? Is there not just as much scope for manipu
lation of form? Should not fat administration be con
sidered in a similar manner to creatine, that is, the
feeding of a nutrient in amounts not found in the nor
mal diet? As our knowledge of the relationship of cer
tain of the body's compounds to performance increases
and may allow us to adopt feeding strategies to im
prove performance, which are we going to accept or
are we going to remain in a time warp? Are we going
to prevent the use of substances that may im
prove performance and even reduce postcompetition
stresses? Are scientifically based nutritional improve
ments to be considered as providing optimal sports
nutrition, or because they could be used to manipulate
performance will they be prohibited? Although regu
ERGOGENIC
AIDS TO PERFORMANCE
2735S
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IN THE HORSE