Reducing Stress When Hauling Horses

Even though horses may seem content in a trailer, many experience stress during transport. According to a recent study on equine behavior during transport*, several behaviors can be used to assess stress. Examples include pulling back, licking the trailer, turning their head, flank-watching, and pawing.

“Identifying which horses are particularly stressed during transport based on their behavior can help detect animals that might develop respiratory disease or other transport-related medical issues following trailering,” noted Kathleen Crandell, Ph.D., a Kentucky Equine Research nutritionist.

Horses should be able to lower their heads while trailering, especially over long distances, to promote drainage of mucus and infectious agents from the respiratory tract. If a horse’s head remains elevated for prolonged periods of time, mucus and microorganisms can invade the lower respiratory tract and potentially cause infection.

To explore the link between stress, head position, and respiratory disease following transport, researchers analyzed the behavior of a group of horses kept in stalls prior to transport and again during an eight-hour trailer ride. They subsequently compared those behaviors with various physiological stress responses such as heart rate and blood cortisol levels, known also as the “stress hormone.” The researchers noted the following:

• Heart rate and serum cortisol concentrations were higher at unloading than directly before loading. Both values returned to normal within 12 hours of the journey.
• A higher occurrence of stress-associated behaviors was noted in horses with higher serum cortisol concentrations measured at the time of unloading.
• The proportion of neutrophils (a type of white blood cell often increased in cases of infection) in the tracheal wash, the amount of tracheal mucus, and bacterial concentration in the tracheal wash were increased after transport.
• Horses that frequently exhibited stress-associated behaviors spent more time with their heads in an elevated position during transport. These horses accumulated more mucus and bacteria in their lower respiratory tract, putting them at higher risk for developing respiratory disease following transport.
• The highest frequency of stress-related behaviors occurred during the first hour of transport, suggesting this to be the most stressful part of a journey.

These data suggest that horses showing stress-induced behaviors during transport could be more likely to develop respiratory disease following transport and may need extra attention before departure and upon arrival.

“Administering antioxidants and omega-3 fatty acids may be indicated for horses that experience stress during transport,” advised Crandell. “Antioxidants such as the vitamins E and C stop the production of and damage caused by reactive oxygen species and other free radicals produced in the body under stressful conditions such as transport and exercise.”

Kentucky Equine Research offers two different antioxidant supplements: Nano•E, a water-soluble, natural-source of vitamin E, and Preserve PS (Preserve in Australia), a source of natural vitamin E, vitamin C, and other antioxidants.

In addition, omega-3 fatty acids have natural anti-inflammatory properties and are widely used to support the health of the respiratory tract. EO•3 is a marine-derived source of both DHA and EPA, omega-3 fatty acids that confer the most health benefits to horses.

*Padalino, B., S.L. Raidal, P. Knight, et al. 2018. Behaviour during transportation predicts stress response and lower airway contamination in horses. PLoS One 13(3):e0194272.