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Aurich, J., Wulf, M., Ille, N., Erber, R., von Lewinski, M., Palme, R., et al. (2015). Effects of season, age, sex and housing on salivary cortisol concentrations in horses. Domest. Anim. Endocrinol., .
Abstract: Abstract Analysis of salivary cortisol is increasingly used to assess stress responses in horses. Since spontaneous or experimentally induced increases in cortisol concentrations are often relatively small for stress studies proper controls are needed. This requires an understanding of factors affecting salivary cortisol over longer times. In this study, we have analysed salivary cortisol concentration over 6 mo in horses (n = 94) differing in age, sex, reproductive state and housing. Salivary cortisol followed a diurnal rhythm with 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 non-pregnant mares with and without a corpus luteum existed. In stallions, mean daily salivary cortisol and plasma testosterone concentration 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.
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Krueger, K., Marr, I., Dobler, A., & Palme, R. (2019). Preservation of fecal glucocorticoid metabolites and immunoglobulin A through silica gel drying for field studies in horses. conphys, 7(1).
Abstract: Non-invasive methods enable stress evaluation through measuring fecal glucocorticoid metabolites (FGMs), and immunoglobulin A (IgA) in the feces avoiding stressful blood drawing or stressful restraining of animals in the field. However, FGMs and IgA are mostly analysed in freshly frozen samples, which is difficult when fresh samples cannot be frozen immediately or frozen samples cannot be stored or transported. Good results were also derived from air-dried fecal samples, which are hampered by unstable air humidity in the field. These difficulties may be overcome, when drying of samples could be induced with colorless silica gel (SiO2) granules in a secure set-up, such as an air tight tube. We determined the speed of drying 1.5 g of a fresh fecal sample from six horses on air and on silica gel. Furthermore, FGMs and IgA were analysed in differently stored subsamples from 12 horses: in frozen fecal samples, in air- or silica gel-dried samples stored for 1 day and for 7 days, and in wet fecal samples kept in a tube at room temperature for 7 days. FGM levels remained stable in feces dried on air or on silica gel for 7 days, whereas IgA quantities showed a significant loss. Under field conditions, when freezing or transporting the frozen samples is not possible and humidity hampers air drying, drying samples on silica gel in air tight tubes appears to be very helpful and reliable for analysing FGMs.
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