Foaling mares are totally relaxed, stress free, study finds

Cardiac and circulatory demands remain at a low level

Surprisingly, during labor the heart rate of mares does not increase. On the contrary, the mares even miss some individual heart beats due to delayed stimulus conduction in the heart. In humans, such second-degree atriventricular (AV) blocks often require medical treatment but many healthy horses show AV blocks at rest. On physical activity, e.g. when the horse is ridden, the heart beat becomes regular and the beat frequency increases. The finding of AV blocks during foal­ing 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.

No stress during foaling

The level of stress hormones remains low in foaling mares and the researchers did not find an adrenaline rush at any point. Foaling clearly does not evoke a stress response. 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.

Horses thus experience giving birth very differently from human mothers. They need a safe environment to give birth: all the foals in the study were born at night, when the stable was quiet. As the Head of the Research Group, Christine Aurich, explains, "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."