Sampriti Roy, University of Calcutta
The 21st century has seen the rise of many novel methods of diagnosis and surgery. Non-invasive/ minimally invasive procedures are one of them. Without breaking the skin of an individual, non-invasive procedures reduce the risks and discomfort that an individual would face in invasive methods and when it comes to animals, these procedures can reduce the use of a lot of special equipment. Measuring stress in animals is important in assessing animal emotional state and some of the conventional methods to do so are measuring heart rate variability or cortisol levels. However, there is now a possibility that these methods could be replaced by one demonstrated by Richard et al. The recently published study has established that assessing the Spontaneous Blink Rate (SBR) is a valid and fast alternative to measure stress and attention in horses.
In the study that observed 33 horses, 16 were categorised as reactive to a stressor (sight and sound of hair clippers) and the other 17 were found to have a relatively low reactivity to the same. The SBR was observed alongside the conventional saliva cortisol and heart rate variability in order to test its effectiveness. In earlier research (Merkies et al), the SBR was said to decrease during stressful situations. But in this study, after an initial fall was observed for just a moment (lesser time in the more reactive horses and greater time in the poorly reactive horses), the SBR rate began to increase rapidly. The initial fall was explained to be due to an initial increase in concentration/vigilance response to the stressor, which makes the initial fall observation important to be considered while using SBR as a measure of stress. It was also observed that the animals who reacted to stress more definitively, were prone to making quicker decisions about the threats in their environments.
One of the primary aims of this study was to validate Spontaneous Blink Rate (SBR) as a measure of stress through correlation against conventional measures of stress centred on activation of the HPA (hypothalamic-pituitary-adrenal) and SAM (sympathetic adrenal medullary) axes. The activation of the SAM axis is mainly seen during times of physical stress whereas the HPA axis is activated during times of psychological stress. In the study, the stress response was seen in both the SAM and HPA axes, representing shared axes response to a psychological stressor (hair clipper sight and sound). It was found that there was a significant correlation between SBR and the conventional measures of stress associated with HPA and SAM axes.
Through this study, the researchers have aimed to put forward an alternative way to measure the effects of stimuli on animals. It is hoped that through future research, the application of SBR response on both horses and other animal species will be better understood and that novel methods such as SBR will prove to be beneficial both in terms of efficiency and convenience of diagnosis of stress.
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