PLENARY LECTURE
Use of blood biochemistry for positive
performance diagnosis of sport horses
in practice
A. LINDNER
Arbeitsgruppe Pferd, Laurahöhe 14, D-45289 Essen, Germany
SUMMARY
RÉSUMÉ
The measurement of many biochemical and other type of variables is
done for performance diagnosis of sport horses. However, the term performance diagnosis in practice has different meanings. The parameter of differentiation between the meanings is the regularity of measurements. When
variables are measured on a regular basis they provide formation for sports
performance diagnosis (= positive performance diagnosis). When variables
are measured sporadically they are used to give information for poor performance diagnosis of sport horses (=negative performance diagnosis).
Most persons involved in performance diagnosis do the latter even though
they believe they are doing the former. Variables shown to give some information about the likelihood of horses not competing successfully, thus providing information on negative sports performance (poor performance), do
not seem to provide useful information for positive performance diagnosis.
Also, variables allowing a distinction between untrained and trained horses
are of no use for positive performance diagnosis. Positive performance diagnosis has to provide a means to discriminate between similarly trained
horses at certain times during the training programme or the competitive
season. The only single informative biochemical blood variable of benefit
for positive performance diagnosis of sport horses in practice is lactate.
However, two conditions to use it successfully for positive performance diagnosis have to be fulfilled : it has to be measured regularly in the same horse
during standardized exercise, and a data base built with results of horses tested the same way is needed to compare the values and draw the conclusions
on the competititve level and optimization of training programmes.
Utilisation de la biochimie sanguine pour le diagnostic de performance positif des chevaux de sport en pratique. Par A. LINDNER.
KEY-WORDS : performance - diagnosis - biochemistry blood - lactate - horses.
MOTS-CLÉS : performance - diagnostic - biochimie sang - lactate - cheval.
Revue Méd. Vét., 2000, 151, 7, 611-618
La mesure de nombreuses variables, biochimiques et autres, est pratiquée
pour le diagnostic des performances chez les chevaux de sport. Cependant,
le diagnostic des performances a différentes significations en pratique. Le
paramètre de différenciation entre ces significations est la régularité des
mesures. Quand les variables sont mesurées régulièrement, elles fournissent
une information pour le diagnostic des performances sportives (= diagnostic de performance positif). Quand les variables sont mesurées de manière
irrégulière, elles sont utilisées pour donner une information concernant le
diagnostic des mauvaises performances des chevaux de sport (= diagnostic
de performance négatif). C'est ce dernier qui est effectué par la plupart des
personnes impliquées dans le diagnostic de performances, même si elles
pensent effectuer le premier. Les variables qui semblent donner une information sur la probabilité que des chevaux n'effectuent pas correctement une
compétition, donc fournissant une information négative (mauvais résultat),
ne semble pas fournir d'information utile pour le diagnostic positif. De
même, les variables permettant une distinction entre chevaux entraînés et
non entraînés sont sans intérêt pour le diagnostic de performance positif. Le
diagnostic de performance positif doit fournir un moyen de faire la différence entre des chevaux entraînés de la même manière à certaines périodes
au cours de leur programme d'entraînement ou de la saison de compétition.
La seule variable biochimique sanguine ayant une valeur informative pour
le diagnostic de performance positif chez le cheval en pratique est le lactate. Cependant, deux conditions doivent être remplies pour l'utiliser correctement : il doit être mesuré régulièrement chez le même cheval pendant un
exercice standardisé et une banque de données, construite avec les résultats
de chevaux testés dans les mêmes conditions, est nécessaire pour comparer
les valeurs et tirer des conclusions quant à l'aptitude à la compétition et à
l'optimisation des programmes d'entraînement.
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LINDNER (A.)
Introduction
For a long time, the measurement of many biochemical and
other types of variable has been suggested to allow for an
objective assessment of the competitive capability of sport
horses [39, 41, 45, 48]. Many different variables are indeed
supposedly measured for this purpose. This has been
demonstrated with the results of the evaluation of a questionnaire answered by veterinarians and trainers working with
sport horses in Germany, Austria, Italy and Switzerland
during a series of six two-day practical courses on equine
performance diagnosis in 1997-8. One of the questions
addressed was : Which variable/s do you use for performance
diagnosis of your horse/s at rest or during and after exercise ?
Out of a total of about 150 course participants 76 answered
the questions. The evaluation of the questionnaire showed
that many different variables were being measured (figure 1),
physiological variables more frequently than hematological
and blood biochemical ones. Although this result is most
likely biased because the practical courses were on performance diagnosis and training control with blood lactate measurements, only the measurement of lactate concentration in
blood or plasma was done as often as the physiological
variables. The reason for favouring the physiological
variables was that their measurement was practical and veterinarians and trainers believed that it supplied them valuable
additional information on health and performance of their
horses. Blood or plasma lactate concentration was measured
so often because it provided additional information on actual
performance of a horse, and sometimes on health status as
well.
Another interesting result of the evaluation was that the
large majority of the biochemical and hematological
variables were measured in the horse under resting conditions (figure 1). In most cases, heart and respiratory rate were
measured consecutively in horses at rest and after exercise,
and blood for lactate analysis was preferentially taken after
exercise, in most cases only once.
The key question on the use of any variable for performance diagnosis is whether it provides the expected benefit
(validity). Another questionnaire given to the participants of
the performance diagnosis courses addressed the question
"What do you mean with performance diagnosis ?". The evaluation showed that the meaning of performance diagnosis
was very ambiguous. This result fully reflects the situation in
practice. Discussions on the definition demonstrated that
most participants meant to objectively evaluate actual or
potential sports performance capacity. However, most of
them admitted that they were measuring the variables when
they felt that they needed information on the lack of expected
sports performance capacity of their horses. Although sometimes it may be difficult to differentiate between terms there
is one clear parameter of differentiation: regularity of measurement. When variables are measured on a regular basis in
horses they provide information for sports performance diagnosis (= positive performance diagnosis). When variables
FIGURE 1. — Variables measured for performance diagnosis (76 veterinarians and trainers).
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USE OF BLOOD BIOCHEMISTRY FOR POSITIVE PERFORMANCE DIAGNOSIS OF SPORT HORSES IN PRACTICE
are measured sporadically, in some cases even only once in
life, they are used to attempt to add information for poor performance diagnosis of sport horses (= negative performance
diagnosis). Some of the blood or plasma biochemical
variables which have been shown to inform about the likelihood of not competing successfully, thus providing information on negative sports performance, are : Bilirubin (when
increased [48]), Gamma-glutamyltranferase (when increased
[46]), Creatine-phosphokinase (when increased [1, 26, 43,
45]), Potassium (when above 4.0 mmol/l [50]), and
Phosphate (when increased [16]). But nobody has demonstrated that measuring these variables also may allow for positive performance diagnosis.
In literature an innumerable amount of references are
found in which authors describe or at least allude to the benefit of certain biochemical and other variables for discriminating between untrained and trained horses (table I). We have
to be aware that this is not what matters in positive performance diagnosis of sport horses. Positive performance diagnosis has to provide trainers, riders and veterinarians with a
means to discriminate between similarly trained horses at
certain times during the training programme or the competitive season. Through continuous application of positive performance diagnosis it is possible to help find an answer to the
question why a horse is better than others: Is it the genetic
make-up ? Or is the environment (training and health management) ?
Fine, but with which variable/s can positive performance
diagnosis be provided ? A search through literature for studies on the validity of biochemical variables for positive performance diagnosis demonstrates that there are not many.
This also holds for other types of variable. The vast majority
of variables reacts to exercise, but this does not ensure that
they are also suitable for positive performance diagnosis of
sport horses.
We have examined the potential of several biochemical
variables for positive performance diagnosis in sport horses.
For this purpose, on one occassion, 15 standardbred race
horses (six were two-year-olds and the others between 3 and
6 years old) were submitted to a standardized exercise test
(SET) on a racetrack. Conditions were kept as similar as possible for all horses during the testing day [31, 32]. The SET
consisted of four or more runs depending on when the blood
lactate concentration of a horse exceeded 4 mmol/l. Speed in
the first run was 6 m/s, and it was increased by 1 m/s for each
run. Blood samples were taken within 30 seconds after each
run from jugular vein and analyzed for Creatine-kinase (CK),
Aspartate-aminotranferase (AST), Lactate dehydrogenase
(LDH), Cortisol, Alanine, Free Fatty Acids and Thiobarbituric Acid-like reactive Substances (TBArS).
To determine whether a variable allowed a distinction between horses of different performance capability we first plotted running speed for each horse in each run against the measured value of a variable. Performance capability was defined in the horses older than 2 years by their actual racing
record. Horses of two years of age had not yet raced but were
in full training. Only blood lactate concentration allowed
clearly to discriminate between faster and slower horses, and
it was also possible to distinguish between most of the twoyear-old horses and the older ones (figure 2). All the other
variables measured did not allow for distinguishing discriminating between horses of differing racing records, and if at all
only partially between horses two-years old and older. The
graph for TBArS is presented as an example of this type of
variable (figure 3).
Further analysis of data among groups demonstrated that
the values of Lactate, Cortisol and TBArS, and to some
extent also CK, after the fourth run allowed to distinguish
between two-year-old horses and older ones. For this purpose
the median (for CK, AST and LDH) or mean value of each
group for each variable after the fourth run was compared
* = after exercise ; in all other references cited blood was taken from horses under resting conditions
TABLE I. — Studies in which the use of biochemical variables other than blood or plasma lactate was investigated for differentiation between
trained and untrained horses (only variables which were cited in at least two independent studies were considered).
Revue Méd. Vét., 2000, 151, 7, 611-618
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LINDNER (A.)
FIGURE 2. — Concentration of lactate in blood of two year old and older Standardbred racehorses during a standardized exercise test (15 horses).
FIGURE 3. — Concentration of TBArS in blood of two year old and older Standardbred racehorses during a standardized exercise test (15 horses).
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USE OF BLOOD BIOCHEMISTRY FOR POSITIVE PERFORMANCE DIAGNOSIS OF SPORT HORSES IN PRACTICE
statistically. The fourth run was selected because it was the
most intensive one run by all horses tested, and it was expected that at the highest comparable work stress distinguish between horse groups would be easiest (table II). The results
demonstrated very clearly that only blood lactate, as well as
plasma TBArS and plasma cortisol concentration, allowed to
significantly distinguish between the two age groups´ build.
The really important step of positive performance diagnosis is to inform accurately about the actual competitive level
of a horse. To examine the validity of the variables for this
purpose the relation of values of the variables measured after
a defined workload and the racing record of the horses tested
was examined with linear and exponential regression analysis. The racing record is defined internationally as time needed to run a kilometre (or a mile), and is used to objectively
compare performance of Standardbred horses. Again the
value chosen for the variables measured was the one after the
fourth run of SET. The results of the regression analysis
demonstrated that only the blood lactate concentration after
the fourth run gave a reasonable explanation for the racing
record (linear regression ; r2 = 0.89 ; p = 0.001 ; n = 7).
Another approach to examine the dependence of biochemical or other variables from competitive performance parameters like racing record is to derive parameters which describe
the development of the values of a variable with increasing
workload. Out of the measured biochemical variables only
the blood lactate concentration of each horse had a positive
exponential relation with the speed of exercise. The other
variables were not always related exponentially or linearly in
all horses with speed of exercise. Thus a parameter to describe the relation between these variables and speed was not
calculated. Only the blood lactate concentration measured
after each run was plotted against running speed to derive
mathematically v4 from the blood lactate-running speed relation (v4 = velocity run under defined conditions inducing
4 mmol/l blood lactate concentration). This parameter is used
widely to examine effects of conditioning and to diagnose
positive performance of sport horses [13, 20, 24, 37].
The result was that v4 was linearly correlated with the race
record of the Standardbred horses tested (figure 4). This
negative correlation is corroborated regularly in our tested
horses. Our conclusion is that v4 and therefore lactate measu-
Best racing time
(minutes : seconds for 1 km, only seconds shown)
TABLE II. — Validity of certain biochemical variables for differentiation of age groups in Standardbred
horses (6 two-year old horses and 9 older ones) comparing values after fourth run of a standardized
exercise test.
FIGURE 4. — Relation between best actual racing time and v4 of
Standardbred Trotters (n = 7 ; r = 0.77 ; p < 0.01).
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LINDNER (A.)
TABLE III. — The services of positive performance diagnosis of sport horses.
rement in blood or plasma (not interchangeable [30, 51]) is
actually the best parameter or variable to offer veterinarians
and trainers the service of positive performance diagnosis of
sport horses. This conclusion is supported by studies done by
several other authors where correlations between competitive
success and v4 or blood/plasma lactate concentration has
been described (for endurance riding DEMONCEAU [15],
ERICKSON et al [17] ; for three day eventing GALLOUX
[20] ; for Standardbred racehorses CASINI and GREPPI
[11], COUROUCÉ [13], KRZYWANEK [28], PONCHARD
[38] ; for Thoroughbred racing BAYLY et al [5], DAVIE
[14], EVANS et al [19], HARKINS et al [24], PONCHARD
[38] ; for Quarterhorse racing ERICKSON et al [18]). No
other variable has shown so frequent and so good a relation
with competitive performance.
Nowadays the practical application of positive performance diagnosis, once it has been recognized that this is the
service wanted, is not a matter of which variable should be
used but how we use the measurement of blood/plasma lactate concentration for this purpose. The participants of the
courses on performance diagnosis and training guidance
expressed their interest in this service. Of the above mentioned authors, COUROUCÉ [13], DAVIE [14] and we ourselves offer the service of positive performance diagnosis in
practice. The measurement of lactate in blood or plasma is a
routine inexpensive procedure, and the testing procedures are
no mystery either. Although each group uses different exercise test prescriptions, we seem to be providing useful service
to our clients.
The bottleneck in providing positive performance diagnosis is that it is necessary to have a data base. No reference
value can be formulated because v4 or lactate values depend
on the test prescription, and the test prescriptions are influenced by many factors. The most important ones are track
length and surface as well as horse type. For anybody wanting to offer the service it is necessary to realize that a data
base is necessary to compare results of horses. The more specific and larger the data base for each client´s horses is the
better the service that can be provided. As a matter in fact : it
is the only way to provide satisfactorily the service. Most
persons wanting to provide the service to a client do not
explain to them sufficiently that to build a data base takes
time, the longer
• the less horses the client has or wants to be tested regularly,
• the less different the competitive level of horses of a
client is.
The sports disciplines for which it is easiest to build up a
data base are Standardbred and Thoroughbred/Quarterhorse
racing. In many cases in these sports disciplines, one owner
owns several horses, or several trainers and owners of horses
in a race-track cooperate. But even for these sports disciplines it takes time before the service provides useful information (table III).
Of the services offered the ranking of horses according to
their actual competitive level is most quickly achievable. In
practice this is a very useful service of positive performance
diagnosis, especially in trot, pace and gallop racing where
horse fluctuation within barns is high, and time to race horses
short. The service supplies the trainer or veterinarian with
additional and objective information on the actual performance capability of a "new" horse, of a horse recovering
from injury, or of the development of a horse through training.
The dream of all sport horse owners is to be able to tell at
an early stage whether a horse will be fast or not. Potential
positive performance diagnosis may give further information
for this matter. For this purpose horses need to be regularly
tested at an early age. Very many factors play a role in the
outcome of elite athletes. The work published by BARREY
et al [4] is very promising. They found a positive genetical
relation between v4 and racing success in Standardbred
horses.
In conclusion, blood biochemistry for positive performance diagnosis of sport horses in practice relies on lactate
measurements. Other biochemical variables may supply
additional information but the only single informative bioRevue Méd. Vét., 2000, 151, 7, 611-618
USE OF BLOOD BIOCHEMISTRY FOR POSITIVE PERFORMANCE DIAGNOSIS OF SPORT HORSES IN PRACTICE
chemical blood variable for this service is lactate. Positive
performance diagnosis can only be provided if measuring of
blood or plasma lactate is done regularly in the same horse. If
measurement of lactate (or other variables) is not done regularly in a horse then the service of negative performance diagnosis is supplied. This service does not allow efficiently for
assessing the competititve level of horses and optimization of
training programmes.
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