title: Effects of season, age, sex, and housing on salivary cortisol concentrations in horses.
abstract: Analysis of salivary cortisol is increasingly used to assess stress responses in horses. Because spontaneous or experimentally induced increases in cortisol concentrations are often relatively small for stress studies, proper controls are needed. This requires an understanding of the factors affecting salivary cortisol over longer times. In this study, we have analyzed salivary cortisol concentration for 6 mo in horses (n = 94) differing in age, sex, reproductive state, and housing. Salivary cortisol followed a diurnal rhythm with the highest concentrations in the morning and a decrease throughout the day (P < 0.001). This rhythm was disrupted in individual groups on individual days; however, alterations remained within the range of diurnal changes. Comparison between months showed highest cortisol concentrations in December (P < 0.001). Cortisol concentrations increased in breeding stallions during the breeding season (P < 0.001). No differences in salivary cortisol concentrations between nonpregnant mares with and without a corpus luteum existed. In stallions, mean daily salivary cortisol and plasma testosterone concentrations were weakly correlated (r = 0.251, P < 0.01). No differences in salivary cortisol between female and male young horses and no consistent differences between horses of different age existed. Group housing and individual stabling did not affect salivary cortisol. In conclusion, salivary cortisol concentrations in horses follow a diurnal rhythm and are increased in active breeding sires. Time of the day and reproductive state of the horses are thus important for experiments that include analysis of cortisol in saliva.
authors.affiliation: Division for Obstetrics and Reproduction, University of Veterinary Sciences, Vienna 1210, Austria. Electronic address: joerg.aurich@vetmeduni.ac.at.
authors.forename: J
authors.initials: J
authors.lastname: Aurich
authors.affiliation: Graf Lehndorff Institute for Equine Science, Neustadt (Dosse) 16845, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Wulf
authors.affiliation: Centre for Artificial Insemination and Embryo Transfer, University of Veterinary Sciences, Vienna 1210, Austria.
authors.forename: N
authors.initials: N
authors.lastname: Ille
authors.affiliation: Centre for Artificial Insemination and Embryo Transfer, University of Veterinary Sciences, Vienna 1210, Austria.
authors.forename: R
authors.initials: R
authors.lastname: Erber
authors.affiliation: Graf Lehndorff Institute for Equine Science, Neustadt (Dosse) 16845, Germany.
authors.forename: M
authors.initials: M
authors.lastname: von Lewinski
authors.affiliation: Institute for Physiology, Pathophysiology and Experimental Endocrinology, University of Veterinary Sciences, Vienna 1210, Austria.
authors.forename: R
authors.initials: R
authors.lastname: Palme
authors.affiliation: Centre for Artificial Insemination and Embryo Transfer, University of Veterinary Sciences, Vienna 1210, Austria.
authors.forename: C
authors.initials: C
authors.lastname: Aurich
mesh_terms: D000367:Age Factors; D000818:Animals; D001947:Breeding; D002940:Circadian Rhythm; D005260:Female; D006736:Horses / Q000502:physiology*; D006799:Housing, Animal; D006854:Hydrocortisone / Q000032:analysis*; D008297:Male; D011247:Pregnancy; D012098:Reproduction / Q000502:physiology; D012463:Saliva / Q000737:chemistry*; D012621:Seasons; D012737:Sex Factors; D013739:Testosterone / Q000097:blood
chemical_list: D013739:Testosterone; D006854:Hydrocortisone
keywords: Cortisol; Diurnal rhythm; Horse; Housing; Reproduction