A fear of flying can lead to such extreme stress that many people find themselves unable to board an airplane. While horses aren’t likely to show a true "fear of flying," they are undoubtedly stressed by air travel, according to a recently completed study of in-flight horses.

In addition to revealing stress levels of horses during air and road transport, the study led by Hajime Ohmura, DVM, PhD, of the Japan Racing Association’s Equine Research Institute, also provided the researchers an opportunity to better evaluate the usefulness of heart rate variability (HRV) in analyzing equine stress.

Using an electrocardiogram, Ohmura et al. measured heart rate and heart rate variability of six healthy Warmblood horses during:

• A 24-hour pre-transportation quarantine;
• A 4 ½-hour trailer ride;
• A 5-hour waiting period after the trailer ride; and
• An 11-hour flight.

The team found that both air travel and road travel both caused major spikes in the heart rate of study horses compared to rest in quarantine. They also learned that the HRV (variations between heart rates) could be an even more "sensitive" indicator of the kind of stress that horses experience during transport, Ohmura said. HRV determines how much the beat-to-beat interval (the heart rate) changes in a given amount of time