TRANSPORT STRESS LINKED TO PREMATURITY

New research from Austria suggests that the stress of transport late in a mare’s pregnancy can cause her to deliver her foal prematurely.

Foaling is normally triggered when the maturation of a healthy fetus causes levels of the hormone cortisol to rise. But cortisol is also associated with stress, and researchers hypothesized that increased production of the hormone in response to other stimuli, such as shipping, might influence the timing of foaling.

To determine the influence of transportation-associated stress on foaling, researchers at the University of Veterinary Medicines in Vienna shipped a group of 12 pregnant mares for three hours. Another group of three pregnant mares re-mained in the barn to serve as a control group. At the start of the study, researchers determined that all mares were close to foaling based on pH measurements of mammary secretions (colostrum).

Bloodwork on all mares revealed that the transported group had higher levels of cortisol compared to the non-transported controls. Four mares in the “stressed” group foaled within 12 hours of transport and eight foaled within 51 hours. The mares who were not shipped did not foal for at least 88 to 144 hours (three to six days) after the start of the study.

The researchers note that almost half of the foals from the transported group had incomplete ossification of the bones of their knees and hocks, an indicator of prematurity. They advise that transporting late-stage gestation mares be done only under veterinary guidance.

Reference: “Road transport of late pregnant mares advances the onset of foaling,” Journal of Equine Veterinary Science, July 2018