Study: Foaling Mares Not Stressed

Study: Foaling Mares Not Stressed

The need to care for the newly born foal was also not perceived as stressful: Contact between the mare and the foal was associated with a further state of relief and relaxation, the team said.

Photo: Vetmeduni Vienna

It is often assumed that giving birth is both stressful and painful for the mother. This might be the case for humans, but does it also apply to horses or are we transferring human experiences to the animals?

Scientists at the Vetmeduni Vienna have investigated the stress associated with birth in horses and other domestic animals, and the findings show that, contrary to expectations, mares appear to be completely relaxed when foaling.

Foaling in horses is extremely fast. Labor and the active part of foaling (those that result in the foal's delivery), take 10 to 20 minutes and are considerably shorter than giving birth in humans or in cows. Is this brief period stressful for the mares or are horses more relaxed than humans when giving birth? Researchers recently set out to find out.

Christina Nagel, MSc, PhD, and colleagues, closely observed 17 foalings at the Brandenburg State Stud in Neustadt, Germany, and recorded electrocardiograms before, during, and after foaling. The researchers also took samples of saliva and blood and analyzed the levels of stress hormones such as cortisol and epinephrine.

“Normal foaling appears to cause just the opposite of a stress response,” Nagal said.

The team found that mares' heart rates did not increase during labor. The mares even missed some individual heart beats due to delayed stimulus conduction in the heart, the team said. In humans, such second-degree atriventricular (AV) blocks often require medical treatment, but many healthy horses show AV blocks at rest. The fact that foaling mares exhibited AV blocks suggests that mares are strongly influenced by the parasympathetic nervous system, which usually causes a state of rest and relaxation. Its antagonist, the sympathetic nervous system, would prepare the organism for a stress response but does not seem to be active while the animals are giving birth, the team concluded.

Additionally, the team found that stress hormone levels remains low in foaling mares, and the researchers did not observe adrenaline rushes at any point. The need to care for the newly born foal was also not perceived as stressful: Contact between the mare and the foal was associated with a further state of relief and relaxation, the team said.

Christine Aurich, DVM, PhD, head of the research group, explained, “Parturition in horses requires a state of relaxation in the mare. This is an advantage in wild horses because mares can postpone labor until they perceive the environment as calm and safe. Once this is the case, foaling proceeds within a very short time.”

The study, “Parturition in horses is dominated by parasympathetic activity of the autonomous nervous system,” was published in Theriogenology

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