People who are exposed to a high level of stress or pain tend to blink more. In fact, the same is true for horses. Research from Canada shows that there is a correlation between how much the horse blinks and its level of stress. The Canadian researchers have found that horses exposed to pain or something dangerous tend to blink more.
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The most recognized method of measuring a horse's level of stress has long been the amount of the stress hormone cortisol. But the horse's facial expressions also reveal a lot about its state of mind. If it is exposed to dangers - you may recognize that it snorts and closes its eyes as much as possible, tightening its jaw and mouth. This is how most horses react to something dangerous.
Normal level of stress reactions:
To assess whether a horse has a high level of stress, the above is used to give points at either 0.1 or 2, of which 2 is the highest.
The Canadian researchers measured the blink rate in 23 horses to test the level of stress. They put them through three situations with different level of stress - separation from the herd, deprivation of food, and exposure to a dangerous object. In relation to the separation, they separated the horse from the herd so that it could not see the other horses. When it came to the food situation, the other horses were given food except the 'test horse'. As far as the exposure with a dangerous object, they threw a large ball in front of the horse. The researchers measured the horse's blink rate on video and compared it to the blink rate in the box when it was relaxed.
How much you blink is already a well-known way of examining stress in humans. But also in cattle (for example in connection with slaughter). It is not yet a phenomenon that is widespread as an indicator of stress in horses. But researchers believe that it may be in the future when we continue to study the wellbeing of horses.