The study has not undergone the rigors of peer-review, although Dr. Bertone said he plans to submit it for publication in the Journal of the American Veterinary Medical Association.
Benefits and limitations of cortisol measurement in equines.
In equines and other species, cortisol levels fluctuate over the course of a day, with peak secretion in the morning. Measurement of free cortisol levels has diagnostic value in detecting relative adrenal insufficiency (RAI) or critical illness-related corticosteroid insufficiency (CIRCI), both transient conditions that can accompany acute illness.
Despite decades of study of how corticosteroid measurement correlates to a variety of equine physiologic processes, there is no association between cortisol and any meaningful measure of horse "contentment."
In a study by Rietmann and colleagues of horses with pain from laminitis, for example, cortisol levels were found to be poorly correlated with other physiologic and behavioral measures of stress responses.
Nedim C. Buyukmihci, VMD, an Emeritus Professor of Veterinary Medicine at the University of California, Davis, took issue with the premise of evaluating cortisol as a key measure of horse welfare.