Objective—To determine whether serum concentrations
of biomarkers of skeletal metabolism can,
in conjunction with radiographic evaluation, indicate
severity of osteochondrosis in developing
Animals—43 Dutch Warmblood foals with varying
severity of osteochondrosis.
Procedure—24 foals were monitored for 5 months
and 19 foals were monitored for 11 months. Monthly
radiographs of femoropatellar-femorotibial and tibiotarsal
joints were graded for osteochondral abnormalities.
Serial blood samples were assayed for 8 cartilage
and bone biomarkers. At the end of the monitoring
period, foals were examined for macroscopic
Results—Temporal relationships were evident
between certain serum biomarkers and osteochondrosis
severity in foals during their first year.
Biomarkers of collagen degradation (collagenasegenerated
neoepitopes of type-II collagen fragments,
type-I and -II collagen fragments [COL2-3/4Cshort],
and cross-linked telopeptide fragments
of type-I collagen) and bone mineralization (osteocalcin)
were positive indicators of osteochondrosis
severity at 5 months of age. In foals with lesions at
11 months of age, osteochondrosis severity correlated
negatively with COL2-3/4Cshort and osteocalcin
and positively with C-propeptide of type-II procollagen
(CPII), a collagen synthesis marker.
Radiographic grading of osteochondrosis lesions
significantly correlated with macroscopic osteochondrosis
severity score at both ages and was
strongest when combined with osteocalcin at 5
months and CPII at 11 months.
Conclusions and Clinical Relevance—The ability of
serum biomarkers to indicate osteochondrosis severity
appears to depend on stage of disease and is
strengthened with radiography. In older foals with
more permanent lesions, osteochondrosis severity is
significantly related to biomarker concentrations of
decreased bone formation and increased cartilage synthesis.
(Am J Vet Res 2004;65:143–150)
Objective—To investigate the effects of moderate
short-term training on K+ regulation in plasma and erythrocytes
during exercise and on skeletal muscle
Na+,K+-ATPase concentration in young adult and
Animals—Four 4- to 6-year-old and four 10- to 16-yearold
Dutch Warmblood horses.
Procedure—The horses underwent a 6-minute exercise
trial before and after 12 days of training. Skeletal
muscle Na+,K+-ATPase concentration was analyzed in
gluteus medius and semitendinosus muscle specimens
before and after the 12-day training period.
Blood samples were collected before and immediately
after the trials and at 3, 5, 7, and 10 minutes after
cessation of exercise for assessment of several
hematologic variables and analysis of plasma and
whole-blood K+ concentrations.
Results—After training, Na+,K+-ATPase concentration
in the gluteus medius, but not semitendinosus, muscle
of middle-aged horses increased (32%), compared
with pretraining values; this did not affect the
degree of hyperkalemia that developed during exercise.
The development of hyperkalemia during exercise
in young adult horses was blunted (albeit not significantly)
without any change in the concentration of
Na+,K+-ATPase in either of the muscles. After training,
the erythrocyte K+ concentration increased (7% to
10%) significantly in both groups of horses but did not
change during the exercise trials.
Conclusions and Clinical Relevance—In horses, the
activation of skeletal muscle Na+,K+-ATPase during
exercise is likely to decrease with age. Training
appears to result in an increase in Na+,K+-ATPase
activity in skeletal muscle with subsequent upregulation
of Na+,K+-ATPase concentration if the existing
Na+,K+-ATPase capacity cannot meet requirements.
(Am J Vet Res 2005;66:1252–1258)
Objective—To quantify and compare biochemical
characteristics of the extracellular matrix (ECM) of
specimens harvested from tensional and compressive
regions of the superficial digital flexor tendon
(SDFT) of horses in age classes that include neonates
to mature horses.
Sample Population—Tendon specimens were collected
on postmortem examination from 40 juvenile
horses (0, 5, 12, and 36 months old) without macroscopically
visible signs of tendonitis.
Procedure—Central core specimens of the SDFT
were obtained with a 4-mm-diameter biopsy punch
from 2 loaded sites, the central part of the midmetacarpal
region and the central part of the midsesamoid
region. Biochemical characteristics of the
collagenous ECM content (ie, collagen, hydroxylysylpyridinoline
crosslink, and pentosidine crosslink
concentrations and percentage of degraded collagen)
and noncollagenous ECM content (percentage of
water and glycosaminoglycans, DNA, and hyaluronic
acid concentrations) were measured.
Results—The biochemical composition of equine
SDFT was not homogeneous at birth with respect to
DNA, glycosaminoglycans, and pentosidine concentrations.
For most biochemical variables, the amounts
present at birth were dissimilar to those found in
mature horses. Fast and substantial changes in all
components of the matrix occurred in the period of
growth and development after birth.
Conclusions and Clinical Relevance—Unlike cartilage,
tendon tissue is not biochemically blank (ie, homogeneous)
at birth. However, a process of functional adaptation
occurs during maturation that changes the composition
of equine SDFT from birth to maturity.
Understanding of the maturation process of the juvenile
equine SDFT may be useful in developing exercise programs
that minimize tendon injuries later in life that
result from overuse. (Am J Vet Res 2005;66:1623–1629)
Objective—To investigate the effects of early training
for jumping by comparing the jumping technique of
horses that had received early training with that of
horses raised conventionally.
Animals—40 Dutch Warmblood horses.
Procedure—The horses were analyzed kinematically
during free jumping at 6 months of age.
Subsequently, they were allocated into a control
group that was raised conventionally and an experimental
group that received 30 months of early training
starting at 6 months of age. At 4 years of age,
after a period of rest in pasture and a short period of
training with a rider, both groups were analyzed kinematically
during free jumping. Subsequently, both
groups started a 1-year intensive training for jumping,
and at 5 years of age, they were again analyzed kinematically
during free jumping. In addition, the horses
competed in a puissance competition to test maximal
Results—Whereas there were no differences in
jumping technique between experimental and control
horses at 6 months of age, at 4 years, the experimental
horses jumped in a more effective manner
than the control horses; they raised their center of
gravity less yet cleared more fences successfully than
the control horses. However, at 5 years of age, these
differences were not detected. Furthermore, the
experimental horses did not perform better than the
control horses in the puissance competition.
Conclusions and Clinical Relevance—Specific training
for jumping of horses at an early age is unnecessary
because the effects on jumping technique and
jumping capacity are not permanent. (Am J Vet Res 2005;66:418–424)
Objective—To quantify variation in the jumping technique
within and among young horses with little
jumping experience, establish relationships between
kinetic and kinematic variables, and identify a limited
set of variables characteristic for detecting differences
in jumping performance among horses.
Procedure—The horses were raised under standardized
conditions and trained in accordance with a fixed
protocol for a short period. Subsequently, horses
were analyzed kinematically during free jumping over
a fence with a height of 1.05 m.
Results—Within-horse variation in all variables that
quantified jumping technique was smaller than variation
among horses. However, some horses had less
variation than others. Height of the center of gravity
(CG) at the apex of the jump ranged from 1.80 to 2.01
m among horses; this variation could be explained by
the variation in vertical velocity of the CG at takeoff ( r,
0.78). Horses that had higher vertical velocity at takeoff
left the ground and landed again farther from the
fence, had shorter push-off phases for the forelimbs
and hind limbs, and generated greater vertical acceleration
of the CG primarily during the hind limb pushoff.
However, all horses cleared the fence successfully,
independent of jumping technique.
Conclusions and Clinical Relevance—Each horse
had its own jumping technique. Differences among
techniques were characterized by variations in the
vertical velocity of the CG at takeoff. It must be determined
whether jumping performance later in life can
be predicted from observing free jumps of young
horses. ( Am J Vet Res 2004;65:938–944)
Objective—To determine whether differences in
jumping technique among horses are consistent at
Animals—12 Dutch Warmblood horses.
Procedure—Kinematics were recorded during free
jumps of horses when they were 6 months old (ie, no
jumping experience) and 4 years old (ie, the horses
had started their training period to become show
jumpers). Mean ± SD height of the horses was 1.40 ±
0.04 m at 6 months of age and 1.70 ± 0.05 m at 4
years of age.
Results—Strong correlations were found between
values from 6-month-old foals and 4-year-old horses
for variables such as peak vertical acceleration generated
by the hind limbs ( r, 0.91), peak rate of change of
effective energy generated by the hind limbs ( r, 0.71),
vertical velocity at takeoff ( r, 0.65), vertical displacement
of the center of gravity during the airborne
phase ( r, 0.81), and duration of the airborne phase ( r,
Conclusions and Clinical Relevance—Although
there are substantial anatomic and behavioral
changes during the growing period, certain characteristics
of jumping technique observed in naïve 4-year-olds
are already detectable when those horses are
foals. ( Am J Vet Res 2004;65:945–950)
Objective—To evaluate quantitative ultrasonography for objective monitoring of the healing process and prognostication of repair quality in equine superficial digital flexor (SDF) tendons.
Animals—6 horses with standardized surgical lesions in SDF tendons of both forelimbs.
Procedures—Healing was monitored for 20 weeks after surgery by use of computerized ultrasonography. Pixels were categorized as C (intact fasciculi), B (incomplete fasciculi), E (accumulations of cells and fibrils), or N (homogenous fluid or cells). Four scars with the best quality of repair (repair group) and 4 scars with the lowest quality (inferior repair group) were identified histologically. Ratios for C, B, E, and N in both groups were compared.
Results—During 4 weeks after surgery, lesions increased 2- to 4-fold in length and 10-fold in volume. Until week 3 or 4, structure-related C and B ratios decreased sharply, whereas E and N ratios increased. After week 4, C and B ratios increased with gradually decreasing E and N ratios. At week 12, C and B ratios were equivalent. After week 12, C ratio increased slowly, but B ratio more rapidly. At week 20, C ratio remained constant, B ratio was substantially increased, and E and N ratios decreased. Values for the inferior repair group were most aberrant from normal. Ratios for C differed significantly between repair and inferior repair groups at weeks 16 and 18 and for B beginning at 14 weeks.
Conclusions and Clinical Relevance—Computerized ultrasonography provided an excellent tool for objective monitoring of healing tendons in horses and reliable prognostication of repair quality.
Objective—To determine the speed of sound (SOS)
in equine articular cartilage and investigate the influence
of age, site in the joint, and cartilage degeneration
on the SOS.
Sample Population—Cartilage samples from 38
metacarpophalangeal joints of 38 horses (age range,
5 months to 22 years).
Procedure—Osteochondral plugs were collected
from 2 articular sites of the proximal phalanx after the
degenerative state was characterized by use of the
cartilage degeneration index (CDI) technique. The
SOS was calculated (ratio of needle-probe cartilage
thickness to time of flight of the ultrasound pulse),
and relationships between SOS value and age, site,
and cartilage degeneration were evaluated. An analytical
model of cartilage indentation was used to evaluate
the effect of variation in true SOS on the determination
of cartilage thickness and dynamic modulus
with the ultrasound indentation technique.
Results—The mean SOS for all samples was 1,696
± 126 m/s. Age, site, and cartilage degeneration had
no significant influence on the SOS in cartilage. The
analytical model revealed that use of the mean SOS
of 1,696 m/s was associated with maximum errors of
17.5% on cartilage thickness and 7.0% on dynamic
modulus in an SOS range that covered 95% of the
Conclusions and Clinical Relevance—In equine
articular cartilage, use of mean SOS of 1,696 m/s in
ultrasound indentation measurements introduces
some inaccuracy on cartilage thickness determinations,
but the dynamic modulus of cartilage can be
estimated with acceptable accuracy in horses regardless
of age, site in the joint, or stage of cartilage
degeneration. (Am J Vet Res 2005;66:1175–1180)