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Domest Anim Endocrinol. 2015 Jul;52:11-6. doi: 10.1016/j.domaniend.2015.01.003. Epub 2015 Jan 21.

Effects of season, age, sex, and housing on salivary cortisol concentrations in horses.

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Division for Obstetrics and Reproduction, University of Veterinary Sciences, Vienna 1210, Austria. Electronic address:
Graf Lehndorff Institute for Equine Science, Neustadt (Dosse) 16845, Germany.
Centre for Artificial Insemination and Embryo Transfer, University of Veterinary Sciences, Vienna 1210, Austria.
Institute for Physiology, Pathophysiology and Experimental Endocrinology, University of Veterinary Sciences, Vienna 1210, Austria.


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.


Cortisol; Diurnal rhythm; Horse; Housing; Reproduction

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