Transrectal examinations might just be part of the routine in the breeding industry. But is that routine really acceptable for animal welfare?

A group of German and Swiss researchers have recently looked into the stress levels that pregnant and lactating mares experience during transrectal ultrasound exams and found that nonlactating Thoroughbred mares perceived the exams as modest temporary stressors.

“In the interest of equine welfare, our study confirms that wherever abdominal ultrasounds can replace rectal ultrasounds—generally speaking, after 90 days of gestation—the abdominal ultrasound should be performed,” said study author Hanno Schönbom, DrMedVet, an assistant at the Unit for Reproductive Medicine in the University of Veterinary Medicine, in Hannover, Germany.

In their study of 25 Thoroughbred broodmares, Schönbom and his fellow researchers noted significant increases in stress parameters when transrectal ultrasounds were performed on pregnant, nonlactating mares. The procedure caused notable increases in salivary cortisol concentrations and in heart rate variability, indicative of acute stress, Schönbom said. Transabdominal ultrasounds, effective without clipping and with application of isopropyl alcohol, resulted in no such increases in cortisol level, he added