Evaluation of Stress Response under a Standard Euthanasia Protocol in Horses Using Analysis of Heart Rate Variability.

The research article evaluates how standard procedures for euthanizing horses can influence heart rate variability (HRV), a marker for stress. Results indicated that certain parts of the process increased sympathetic activity in horses, although the presence of owners or the type of illness leading to euthanasia did not affect stress levels. However, horses suffering from colic showed abnormal breathing patterns during euthanasia.

Overview of the Research Process

• The study was a prospective clinical analysis of standard protocols for euthanizing horses and their impacts on HRV. HRV is generally considered an indicator of stress response, which this study aims to quantify during different stages of euthanasia.
• The study was conducted on 40 different horses who were being euthanized for various reasons at different locations, with or without the presence of their owners.
• The euthanasia process included sedating the horses with either xylazine or a mixture of xylazine and butorphanol, inducing general anesthesia using diazepam and ketamine, and ultimately euthanizing the horses using pentobarbital.

Data Collection and Analysis

• The researchers collected ECG data from the horses at three different points during the euthanasia process: during sedation, during anesthesia, and from anesthesia until death. The data were gathered using a telemetric ECG.
• The HRV was then analyzed, with the researchers focusing on the low frequency (LF) and high frequency (HF) components of the HRV, as well as the sympathovagal balance, represented by the LF/HF ratio.
• The results revealed significant differences in the LF, HF and LF/HF ratio at the three stages of euthanasia. There was a dominant sympathetic activity during the preparation phase of euthanasia and at the time of pentobarbital injection.

Results and Conclusion

• The study found that neither the location of euthanasia nor the presence of the horse’s owner had any impact on stress parameters.
• The horses’ reactions during euthanasia, such as excitation or groaning, did not show significant differences in the HRV measurement.
• Interestingly, horses which were suffering from colic were found to exhibit recurring breathing during euthanasia, indicating a different stress response.
• The conclusion of the study suggests that HRV provides a sensitive and non-invasive way to measure sympathovagal stimulations experienced by a horse during euthanasia. Furthermore, the researchers believe more studies should be conducted on euthanasia protocols for horses with colic, as the stress response in these cases appears different.