Affiliation:
1. Department of Livestock Sciences, Faculty of Higher Studies, Cuautitlan National Autonomous University of Mexico (UNAM) Mexico City Mexico
2. Doctorate in Animal Production and Health Sciences National Autonomous University of Mexico (UNAM) Mexico City Mexico
3. Department of Medicine and Epidemiology, School of Veterinary Medicine University of California Davis Davis California USA
Abstract
AbstractBackgroundParasympathetic tone activity (PTA) in response to nociceptive stimulus in conscious non‐sedated horses is unknown.ObjectivesStudy PTA, heart rate (HR), and horse grimace scale (HGS) at rest and during mechanical nociceptive stimulation.AnimalsNinety healthy young adult horses (females, males): 30 each of Friesians, Quarter Horses, and Warmbloods.MethodsProspective control study. The study consisted of habituation to equipment (Day 1), baseline recordings (Days 2 and 3), and nociceptive testing applying mild pressure to the metacarpus (Day 4). Parasympathetic tone, HR, and HGS were recorded simultaneously on Days 2 to 4. Each study lasted 30 minutes and was done in triplicate at 3 different time points per day.ResultsBaseline PTA was not different among breeds. It decreased in Warmbloods and Quarter Horses during placement of the stimulus device without stimulation (P < .01). A significant decrease in PTA (P < .001) occurred during nociceptive stimulus (marked in Quarter Horses, intermediate in Warmbloods, and mild in Friesians). Heart rate and HGS increased significantly (P < .001) during the stimulus in all breeds but returned to baseline poststimulation. Friesians required higher pressure (P < .05) to elicit an aversive response to the stimulus.ConclusionsHorses' PTA, HR, and HGS change in response to a mild mechanical nociceptive stimulus with Friesians showing less variation. Stress induced a decrease in PTA in Quarter Horses and Warmbloods but not in Friesians. Friesians appeared to be more tolerant to pain based on PTA, HR, and HGS findings compared with other breeds.