title: Influence of transrectal and transabdominal ultrasound examination on salivary cortisol, heart rate, and heart rate variability in mares.
abstract: Pregnancy diagnostics in equine reproduction are routinely performed using transrectal ultrasonography, although it is also possible to visualize the fetus by transabdominal ultrasound examinations from the 90th day of gestation onward. We hypothesized that ultrasound examinations may stress the mare and that the gestational stage status and lactation may influence the mare's stress reaction. To investigate the stress reaction, 25 thoroughbred mares of different age, pregnancy and lactational status underwent a transrectal examination. In pregnant mares, an additional transabdominal examination was performed. Salivary cortisol concentration, mean heart rate, and heart rate variability of mares were assessed to evaluate the reactions of hypothalamic-pituitary-adrenal (HPA) axis and of the autonomic nervous system. Significant differences were observed between lactating and nonlactating mares; with a lower responsiveness to stress in lactating mares. The transrectal ultrasound examination in nonlactating mares induced a significant increase in salivary cortisol (P < 0.05), and in the heart rate variability parameter, ratio of low to high frequencies (P < 0.05). This reflects an activation of the HPA axis and a shift to more sympathetic dominance. In contrast, a transabdominally performed pregnancy check did not induce an activation of the HPA axis over basal level but increased the mean heart rate and low to high frequency ratio. The results of this study indicate that checks of advanced pregnancies can be easily performed by transabdominal ultrasonography. With regard to animal welfare, this technique should be preferred during midgestation in nonlactating mares.
authors.affiliation: Clinic for Horses-Unit for Reproductive Medicine, University of Veterinary Medicine Hannover, Hannover, Germany; National Stud Lower Saxony, Celle, Germany.
authors.forename: Hanno
authors.initials: H
authors.lastname: Schönbom
authors.affiliation: Clinic for Horses-Unit for Reproductive Medicine, University of Veterinary Medicine Hannover, Hannover, Germany.
authors.forename: Ana
authors.initials: A
authors.lastname: Kassens
authors.affiliation: Clinic for Horses-Unit for Reproductive Medicine, University of Veterinary Medicine Hannover, Hannover, Germany.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Hopster-Iversen
authors.affiliation: Clinic for Horses-Unit for Reproductive Medicine, University of Veterinary Medicine Hannover, Hannover, Germany.
authors.forename: Jutta
authors.initials: J
authors.lastname: Klewitz
authors.affiliation: Clinic for Cattle, University of Veterinary Medicine Hannover, Hannover, Germany.
authors.forename: Marion
authors.initials: M
authors.lastname: Piechotta
authors.affiliation: National Stud Lower Saxony, Celle, Germany.
authors.forename: Gunilla
authors.initials: G
authors.lastname: Martinsson
authors.affiliation: Thoroughbred Studfarm Harzburg, Bad Harzburg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Kißler
authors.affiliation: Swiss Institute of Equine Medicine, Agroscope and University of Berne, Avenches, Switzerland.
authors.forename: Dominik
authors.initials: D
authors.lastname: Burger
authors.affiliation: Clinic for Horses-Unit for Reproductive Medicine, University of Veterinary Medicine Hannover, Hannover, Germany. Electronic address: harald.sieme@tiho-hannover.de.
authors.forename: Harald
authors.initials: H
authors.lastname: Sieme
mesh_terms: D000818:Animals; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006736:Horses / Q000502:physiology*; D006854:Hydrocortisone / Q000737:chemistry / Q000378:metabolism*; D011247:Pregnancy; D012463:Saliva / Q000737:chemistry*; D014463:Ultrasonography / Q000379:methods / Q000662:veterinary*
chemical_list: D006854:Hydrocortisone
keywords: Cortisol; Mare; Stress; Transabdominal ultrasonography; Transrectal ultrasonography