Abstract: Summary The aim of this study was to study the physiological, especially thermoregulatory, responses during intense exercise in the clipped horse compared to the horse with winter coat. Six Standardbred trotters were studied before and after clipping. They performed an inclined incremental high intensity treadmill exercise test and were monitored during recovery. The clipped horse differed significantly (ANOVA) during exercise as compare to coated: less increase in central venous blood temperature, higher skin surface temperature, greater difference skin to ambient temperature and higher rate of nonevaporative heat loss. The clipped horse had significantly lower total cutaneous evaporative heat loss from walk to end of peak exercise and a shorter time for recovery for the respiratory rate using a paired t test. The clipped horse showed a tendency (P = 0.059) to decreased oxygen uptake during the stepwise increase in workload. We concluded that the clipped horse experienced less strain on the thermoregulatory system due to an enhanced heat loss. Some clipped horses in the study showed a more efficient power output; future studies with emphasis on respiration and oxygen demand are needed to explain this.

Abstract: Reasons for performing study: Assessing back movement is an important part of clinical examination in the horse and objective assessment tools allow for evaluating success of treatment. Objectives: Accuracy and consistency of inertial sensor measurements for quantification of back movement and movement symmetry during over ground locomotion were assessed; sensor measurements were compared to optical motion capture (mocap) and consistency of measurements focusing on movement symmetry was measured. Methods: Six nonlame horses were trotted in hand with synchronised mocap and inertial sensor data collection (landmarks: T6, T10, T13, L1 and S3). Inertial sensor data were processed using published methods and symmetry of dorsoventral displacement was assessed based on energy ratio, a Fourier based symmetry measure. Limits of agreement were calculated and visualised to compare mocap and sensor data. Consistency of sensor measurements was assessed using Pearson correlation coefficients and linear regression to investigate the effect of speed on movement symmetry. Results: Dorsoventral and mediolateral sensor displacement was observed to lie within ± 4–5 mm (± 2 s.d., 9–28% of movement amplitude) and energy ratio to lie within ± 0.03 of mocap data. High levels of correlation were found between strides and trials (0.86–1.0) for each horse and each sensor and variability of symmetry was lowest for T13 followed by T10, T6, L1 and S3 with no significant effect of speed at T6, T10 and T13. Conclusions: Inertial sensor displacement and symmetry data showed acceptable accuracy and good levels of consistency for back movement. The small mediolateral movement amplitude means that changes of <25% in mediolateral amplitude (also unlikely to be detected by visual assessment) may go undetected. New sensor generations with improved sensor sensitivity and ease of use of equipment indicate good potential for use in a field situation.

Abstract: Reasons for performing study: The exact relationship between the saddle pressure pattern during one stride cycle and the movements of horse and rider at the walk are poorly understood and have never been investigated in detail. Hypothesis: The movements of rider and horse account for the force distribution pattern under the saddle. Method: Vertical ground reaction forces (GRF), kinematics of horse and rider as well as saddle forces (FS) were measured synchronously in 7 high level dressage horses while being ridden on an instrumented treadmill at walk. Discrete values of the total saddle forces (FStot) were determined for each stride and related to kinematics and GRF. The pressure sensitive mat was divided into halves and sixths to assess the force distribution over the horse's back in more detail. Differences were tested using a one sample t test (P<0.05). Results: FStot of all the horses showed 3 peaks (P1-P3) and 3 minima (M1-M3) in each half-cycle, which were systematically related to the footfall sequence of the walk. Looking at the halves of the mat, force curves were 50% phase-shifted. The analysis of the FS of the 6 sections showed a clear association to the rider's and horse's movements. Conclusion: The saddle force distribution during an entire stride cycle has a distinct pattern although the force fluctuations of the FStot are small. The forces in the front thirds were clearly related to the movement of the front limbs, those in the mid part to the lateral flexion of the horse's spine and the loading of the hind part was mainly influenced by the axial rotation and lateral bending of the back. Potential relevance: These data can be used as a reference for comparing different types of saddle fit.

Abstract: Reasons for performing study: Studies on the prevalence and predisposing factors of bite and kick injuries in horses have not been reported in a population-based data sample. Objectives: To investigate the prevalence of bite and kick injuries in horses and associated risk factors in a representative sample of horses in Switzerland. Methods: A questionnaire on the incidence of disease and injury, which included the frequency of bite and kick injuries and their association with breed, housing, use and feeding regime, was sent to 2559 horse owners randomly selected throughout Switzerland. Results: The data of 2912 horses with 897 disorders diagnosed by a veterinarian were analysed. There were 231 injuries, 50 (21.6%) caused by a bite or kick from another horse; this number corresponded to 5.6% of all diseases and injuries and concerned only 1.7% of all the horses evaluated. Warmblood, Thoroughbred and Arabian horses had a 4.3 times higher risk of bite or kick injuries than horses of other breeds. Eighteen per cent of injuries were associated with a change in housing management and occurred regardless of whether horses were kept in groups permanently or sporadically. Conclusions and potential relevance: A stable group hierarchy and a housing system that provides adequate space and is adapted to horse-specific behaviour are important factors in prevention and kick and bite injuries.

Abstract: Reasons for performing study: Identifying the underlying problem of equine back pain and diseases of the spine are significant problems in veterinary orthopaedics. A study to validate a preliminary biomechanical model of the equine back based on CT images including longissimus dorsi (LD) muscle is therefore important. Objectives: Validation of the back model by comparing the shortening of LD muscles in the model with integrated EMG (IEMG) at stance during induced lateral flexion of the spine. Methods:Longissimus dorsi muscle activity at stance has been used for validation. EMG electrodes were placed laterally at the level of T12, T16 and L3. Reflective markers have been attached on top of the spinous processes T5, T12, T16, L1 and the sacral bone (OS1, OS2) for motion tracking analysis. A virtual model of the equine's back (T1–S5) was built with inclusion of a simplified LD muscle by 2 separate contours left and right of the spine, starting at tuber coxae laterally and attaching to the spinous process T5 medially. Shortening of LD during induced lateral flexion caused by the kinematic data (input) was compared to the 3 EMG signals (T12, T16 and L3) on the active side via correlation. Results: Pearson correlation coefficient between IEMG and shortening length of LD in the model was (mean ± s.d.) 0.95 ± 0.07 for the left side and 0.91 ± 0.07 for the right side of LD. Conclusions: Activity of the LD muscles is mainly responsible for stabilisation of the vertebral column with isometric muscle contraction against dynamic forces in walk and trot. This validation requires muscle shortening in the back, like induced lateral flexion at stance. The length of the shortening muscle model and the IEMG show a linear relationship. These findings will help to model the LD for forward simulations, e.g. from force to motion.