New research by French behavior scientists and geneticists reveals that chronic stress can actually affect horses at a genetic level—specifically, in the process of gene activation.

According to Aline Foury, MSc, researcher at the National Institute for Agricultural Research (INRA) in Bordeaux, long-term stressful situations can cause alterations in the activation of genes that would “express”—or create and release—certain molecules through a genetic process known as transcription. At the 2013 French Equine Research Day, held earlier this year in Paris, Foury said different genes express specific molecules known as “messenger RNA,” and each particular combination creates what is called a “regulatory pathway.”

Stress-induced alterations of the gene activation in these regulatory pathways appear to, in turn, affect biological processes such as inflammatory responses and cell survival. And when these are affected, the horse’s general health is affected, as well.

In a recent study on the topic, Foury and colleagues monitored 19 Welsh pony foals starting when at 10 months of age. The team separated the ponies into two experimental groups: impoverished conditions and enriched conditions. The team housed the impoverished ponies in small, individual stalls and granted them one hour of individual pasture time three days a week. They fed these ponies three times a day and mostly left the animals alone