Stress and The Equine Immune System

By: MSU Extension/Karen Waite

During the winter, ice, snow, sleet, power outages and significant temperature fluctuations sometimes happen all in the same day. The winter months have provided a great deal of stress, not only in people, but also in horses and other animals. What is stress in horses, and is it really something that horse owners need to be concerned about?

According to Carey Williams, Extension equine specialist at Rutgers University, stress may be defined as “…the body’s response to anything it considers threatening. For a horse, this could be a number of factors, including trailering and traveling, showing, poor nutrition, feeding at irregular times, changes in other routines, environmental toxins, interactions within their social environment, variations in climate and illness.” Each of these potential stressors can cause unique issues in the horse. Long-term stress may result in a depressed immune system and subsequently, a greater risk of illness in the animal.

The immune system of the horse is a fascinating and complex, yet typically effective physiological means of fighting off disease causing agents such as bacteria, viruses and other pathogens. The three main factors that influence immune system function in the horse include: stress, nutrition and age. If a horse is young or very old, when they are not receiving an appropriate level of nutrition, or when they are otherwise stressed, their immune system may fail to protect them effectively, therefore increasing the risk of disease. At this time of year, cold stress combined with age, low body condition, or some combination of the three may create a situation where horses are more susceptible to illness.

When considering the many factors of stress causing agents, maintaining proper immune system function is a primary concern. When horses are transported to events where large numbers of unfamiliar horses congregate, such as a horse show, rodeo or organized trail ride, there is the potential for them to be exposed to pathogens. It is imperative to realize that their immune system may be compromised by the stress of travel or a change in routine.

Michigan State University Extension recommends the following practices to reduce the risk of disease to horses, regardless of the time of year:

• Maintaining a body condition score of 5
• Keeping horses on a regular vaccination, deworming and dental schedule
• Maintaining a similar feeding routine when at home or on the road
• Making sure horses are physically prepared for the work they are asked to do.
• Implementing good biosecurity procedures when traveling and returning home

While there are no guarantees that horses will always stay healthy, practicing these methods will assist in the prevention of illness and disease.

This article was published by Michigan State University Extension. For more information, visit http://www.msue.msu.edu. To contact an expert in your area, visit http://expert.msue.msu.edu, or call 888-MSUE4MI (888-678-3464).