SAEVA Congress 2018 Proceedings | 12-15 February 2018 | ATKV Goudini Spa
made and evaluated do exist between laboratories. It is, thus, highly advisable that
the practitioner endeavor to use the same laboratory for all hematological analyses,
especially if it is anticipated that such testing will become routine. In the same vein,
it is important to establish a range of normal values for the particular facility doing the
work, rather than relying on previously published values. An example of how
hematocrit can vary is shown in Table 1.
Table 1. Hematocrits in Thoroughbreds (TB) and Standardbreds (SB) following
racing or maximal exercise.
Breed and Sampling Condition
n
PCV %
TB; 10 mins after racing 800-1400 m 86 67 ± 1.8
TB; 1 hr after racing 800-1400 m 86 49 ± 2.0
TB; within 10 mins racing 1201-2401 m 46 60 ± 4.0
TB; within 10 mins racing 1000-2200 m 45 64 ± 2.0
SB; 1 yr old 28 37-49
SB; 2 yrs, untrained 37 40-52
SB; 2 yrs, trained 55 46-57
SB; 3 yrs old 84 48-61
SB; 4 yrs old, females & geldings 65 50-61
SB; 4 yrs old, male 81 53-65
Although wide ranges of normal values for different parameters exist, variations in
results obtained from individual horses are much narrower. In other words, the
normal range for a population reflects differences between the individuals comprising
the group, rather than day-to-day variation of each animal. Consequently, if a
horse's normal parameters are well established, deviations from normal may be
noted quickly and reliably. In order to determine the normal range for an individual, it
would appear that at least 6 sets of results are necessary, with no more than 2
weeks elapsing between consecutive samplings. Even then, considerable variability
may be present. Determination of Hb concentration on 7 consecutive days in a small
number of horses revealed that results can vary by as much as 4.2 gm/100 ml, or
nearly 20% from the mean value for a given individual.
The age and breed of the horse being examined may have an effect on the results of
hematology, and may warrant consideration when interpreting the data.
Thoroughbreds tend to have higher RBC numbers, PCV, and Hb concentrations than
other breeds, when the same equipment and techniques are being used. Yearlings
and 2-year-olds (particularly if untrained or just beginning training) usually have
lower values than their older counterparts. Mean corpuscular volume also tends to
increase with age.
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