Qiviut cortisol reflects hypothalamic–pituitary–adrenal axis activity in muskoxen (Ovibos moschatus)

• Published in: General and comparative endocrinology Vol. 306; p. 113737
• Main Authors: Di Francesco, J., Mastromonaco, G.F., Checkley, S.L., Blake, J., Rowell, J.E., Kutz, S.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 15.05.2021
• Subjects: ACTH; Adrenocorticotropic Hormone - metabolism; Animals; Arctic; Hair - metabolism; Hair cortisol; Hydrocortisone; Hypothalamo-Hypophyseal System - metabolism; Muskox; Pituitary-Adrenal System - metabolism; Qiviut; Ruminants; Wildlife; ACTH; Muskox; Arctic; Wildlife; Qiviut; Hair cortisol
• ISSN: 0016-6480; 1095-6840
• DOI: 10.1016/j.ygcen.2021.113737

•Qiviut cortisol can be used as a biomarker of long-term HPA axis activity in muskoxen.•ACTH injections are not reflected in qiviut cortisol in the absence of hair growth.•Body region affects qiviut cortisol levels.•The cortisol concentration in a specific segment of qiviut changes over time.•The cortisol concentration in shed qiviut differs from fully grown shaved qiviut. Muskoxen (Ovibos moschatus) are increasingly exposed to a broad diversity of stressors in their rapidly changing Arctic environment. There is an urgent need to develop validated tools to monitor the impact of these stressors on the hypothalamic–pituitary–adrenal (HPA) axis activity of muskoxen to help inform conservation actions. Here, we evaluated whether muskox qiviut (dense wooly undercoat) cortisol accurately reflects changes in HPA axis activity. Two repeated pharmacological challenges, involving weekly administrations of saline (control group) or adrenocorticotropic hormone (ACTH) during five consecutive weeks, were done on captive muskoxen, in winter (no hair growth) and summer (maximum hair growth). Pre-challenge qiviut cortisol levels were significantly higher in the shoulder than in the neck, but neither differed from rump concentrations. Qiviut cortisol levels significantly increased (p < 0.001) in response to the administration of ACTH during the hair growth phase, but not in the absence of growth (p = 0.84). Cortisol levels in the qiviut segment grown during the summer challenge increased significantly over a six-month period in the ACTH-injected muskoxen with a similar trend occurring in the control animals. Finally, cortisol levels in shed qiviut were significantly higher and not correlated to those of fully grown qiviut shaved three months earlier. Our results show that cortisol is deposited in qiviut during its growth and that qiviut cortisol can thus be used as an integrated measure of HPA axis activity over the period of the hair’s growth. Differences in qiviut cortisol across body regions, significant differences in qiviut segments over time, and differences between shed qiviut versus unshed qiviut, highlight the importance of consistent design and methodology for sample collection and analyses in order to account for sources of variation when using qiviut cortisol as a biomarker of HPA axis activity in muskoxen.