Objective—To determine the mechanism that enables horses to partially counteract the shift of the center of pressure under the hoof induced by changes in hoof morphology attributable to growth and wear during a shoeing interval.
Animals—18 clinically sound Warmblood horses.
Procedures—Horses were evaluated 2 days and 8 weeks after shoeing during trotting on a track containing pressure-force measuring plates and by use of a synchronous infrared gait analysis system set at a frequency of 240 Hz. All feet were trimmed toward straight alignment of the proximal, middle, and distal phalanges and shod with standard flat shoes.
Results—Temporal characteristics such as stance time and the time between heel lift and toe off (ie, breakover duration) did not change significantly as a result of shoeing interval. Protraction and retraction angles of the limbs did not change. Compensation was achieved through an increase in the dorsal angle of the metacarpohalangeal or metarsophalangeal (fetlock) joint and a concomitant decrease of the dorsal angle of the hoof wall and fetlock. There was an additional compensatory mechanism in the hind limbs during the landing phase.
Conclusions and Clinical Relevance—Horses compensate for changes in hoof morphology that develop during an 8-week shoeing interval such that they are able to maintain their neuromuscular pattern of movement. The compensation consists of slight alterations in the angles between the distal segments of the limb. Insight into natural compensation mechanisms for hoof imbalance will aid in the understanding and treatment of pathologic conditions in horses.
Objective—To determine the effect of differences in structural and mechanical tendon properties on functionality of the passive stay apparatus in horses.
Sample—5 forelimbs each from nondwarf Friesians, dwarf Friesians, and ponies.
Procedures—Harvested forelimbs were loaded to test the passive stay apparatus. Tendons that stabilize the distal portion of the limb (superficial digital flexor tendon, deep digital flexor tendon, and tendo interosseus [suspensory ligament]) were isolated, and force-elongation data were obtained. Bone lengths, initial tendon lengths, and initial tendon cross-sectional areas were measured, and Young moduli were calculated. A model was used to determine whether joint angles could be explained by these 4 factors only.
Results—Dwarf limbs were unable to stand passively under loading because tendons that prevent overextension of the distal limb joints were too long and compliant to prevent over-extension. Tendon properties of limbs of nondwarf Friesians appeared to be intermediate between those of ponies and dwarf Friesians.
Conclusions and Clinical Relevance—Dysfunction of the passive stay apparatus in dwarf Friesians could be related to differences in structural and material properties of the tendons that result in hyperextension of the joints under loading. Nondwarf Friesians had intermediate tendon properties, which might be a breed-specific variation. Results indicated that certain tendon properties were associated with load failure of the stay apparatus and provided additional information about the functionality and requirements of the passive stay apparatus.
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 evaluate the effect of various head and neck positions on intrathoracic pressure and arterial oxygenation during exercise in horses.
Animals—7 healthy Dutch Warmblood riding horses.
Procedures—The horses were evaluated with the head and neck in the following predefined positions: position 1, free and unrestrained; position 2, neck raised with the bridge of the nose aligned vertically; position 4, neck lowered and extremely flexed with the nose pointing toward the pectoral muscles; position 5, neck raised and extended with the bridge of the nose in front of a vertical line perpendicular to the ground surface; and position 7, neck lowered and flexed with the nose pointing towards the carpus. The standard exercise protocol consisted of trotting for 10 minutes, cantering for 4 minutes, trotting again for 5 minutes, and walking for 5 minutes. An esophageal balloon catheter was used to indirectly measure intrathoracic pressure. Arterial blood samples were obtained for measurement of Pao2, Paco2, and arterial oxygen saturation.
Results—Compared with when horses were in the unrestrained position, inspiratory intrathoracic pressure became more negative during the first trot (all positions), canter and second trot (position 4), and walk (positions 4 and 5). Compared with when horses were in position 1, intrathoracic pressure difference increased in positions 4, 2, 7, and 5; Pao2 increased in position 5; and arterial oxygen saturation increased in positions 4 and 7.
Conclusions and Clinical Relevance—Position 4 was particularly influential on intrathoracic pressure during exercise in horses. The effects detected may have been caused by a dynamic upper airway obstruction and may be more profound in horses with upper airway disease.
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)