Cortisol levels in saliva have long been used as an indicator of stress in horses, but a new study has identified other markers that may be more accurate to determine the stress a horse experiences.
Dr. María Contreras-Aguilar, Séverine Henry, Caroline Coste, Fernando Tecles, Damián Escribano, Jose Cerón and Martine Hausberger found that the level of the enzyme butyrylcholinesterase in saliva rose with acute stress. The biggest increases in the enzyme were seen in horses that also exhibited behavioral sings of stress. They determined that butyrylcholinesterase is the most reliable predictor of behavior responses from stress in horses.
To test horse's responses to stress, the researchers created a study that used nine horses between the ages of 5 and 22. They used a gauze-filled plastic tube to collect saliva; this tube was clipped to the halter and worn like a bit for one minute. Samples were taken when the horse was standing in his stall, when the horse was lead to an arena, when an umbrella was opened in the arena, and 30 and 40 minutes after the umbrella had been opened.
The scientists tested each saliva sample for alpha-amylase, lipase, total esterase, butyrylcholinesterase, adenosine deaminase and cortisol. They also recorded each horse's behavior for one minute after the umbrella was opened. The behaviors were assessed, and an index of emotions was used to determine the level of stress each horse exhibited
There were significant changes in the majority of the biomarkers after the umbrella was opened. They determined that butyrylcholinesterase was the most reliable predictor of behavioral responses to stress in horses.
Read the full study here.
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