Objective—To determine whether race history, including
the number of races and total race distance, was
associated with risk of superficial digital flexor tendon
(SDFT) injury in Thoroughbred racehorses in Japan.
Design—Matched case-control study.
Animals—515 Thoroughbred racehorses (case horses)
that sustained an SDFT injury during training or racing
in Japan during 2002 and 951 horses (control horses)
without SDFT injury that were matched with case horses
on the basis of age and month of the latest race.
Procedure—Variables related to race history were
compared between case and control horses by
means of conditional logistic regression.
Results—The odds of SDFT injury increased as mean
race distance and mean body weight at race time
increased. Compared with females that had never competed
in steeplechase races, males regardless of
steeplechase race history and females that had competed
in steeplechase races had higher odds of SDFT injury.
Conclusions and Clinical Relevance—Results suggest
that longer mean distance per race, heavier mean body
weight at race time, steeplechase experience, and sex
(male) increased the risk of SDFT injury in Thoroughbred
racehorses. (J Am Vet Med Assoc 2004;225:90–93)
Objective—To determine the growth-related changes
in metabolic and anatomic properties in equine muscle
fiber type, including hybrid fibers identified with
Animals—24 2-, 6-, 12-, and 24-month-old female
Procedure—Samples were obtained from the gluteus
medius muscle of all horses. Expression of
myosin heavy chain (MHC) isoforms MHC-I, -IIa, -IIb,
and -IIx in each muscle fiber was detected by use of
4 primary monoclonal antibodies: BA-D5, SC-71, BFF3,
and BF-35, respectively. Five muscle fiber types
(types I, I/IIA, IIA, IIA/IIX, and IIX) were immunohistochemically
identified. The area and activity of succinic
dehydrogenase (SDH) in each fiber type were determined
by use of quantitative histochemical staining
and image analysis.
Results—Although the proportion of type I and IIX
fibers did not change with age, the proportion of type
IIA and IIA/IIX fibers significantly increased and
decreased, respectively, from 2 months to 24 months
of age. The increase in proportion of type IIA fibers
with growth may have been attributable to muscle
fiber-type transition from type IIA/IIX fibers but not
from type IIX fibers. Values for SDH activity and fiber
area in hybrid fiber types were intermediate to those
for their respective pure phenotypes.
Conclusions and Clinical Relevance—Hybrid fibers
have an important role for determining the proportion
of muscle fiber type in horses < 24 months old, and
the metabolic and anatomic properties of the hybrid
fibers are well coordinated, as in mature horses.
(Am J Vet Res 2005;66:401–405)
To investigate the pharmacokinetics and antihistaminic effects (pharmacodynamics) of olopatadine in a small population of healthy horses after administration via nasogastric tube.
4 healthy adult Thoroughbreds.
Olopatadine (0.1 mg/kg, once) was administered via nasogastric tube. Blood samples were collected at predetermined time points for pharmacokinetic analyses of the drug in plasma. Olopatadine effects were investigated by measurement of cutaneous wheals induced by ID histamine injection (0.1 mL [10 μg]/injection) at predetermined time points. Inhibition effect ratios were calculated on the basis of measured wheal size (area) after versus before olopatadine administration.
Mean ± SD maximum plasma olopatadine concentration was 48.8 ± 11.0 ng/mL approximately 1.5 hours after administration. Median terminal half-life was 6.11 hours. Mean ± SD maximal effect was 88.2 ± 4.9% inhibition approximately 3.5 hours after drug delivery, and the inhibition effect remained > 80% for 12.5 hours after treatment. No signs of adverse clinical effects were observed.
CONCLUSIONS AND CLINICAL RELEVANCE
Results suggested olopatadine may have a strong, long-term inhibitory effect against histamine-induced wheals in the skin of horses. Clinical research with a larger number of horses is warranted.