The circadian rhythm of cortisol in the saliva of young pigs

E.D. Ekkel, S.J. Dieleman, W.G.P. Schouten, A. Portela, G. Cornelissen, M.J.M. Tielen, F. Hallberg

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41 Citations (Scopus)


Single and population-mean cosinor analyses document a circadian rhythm in salivary cortisol of pigs (p < 0.001). The midline estimated statistic of rhythm, the MESOR (M), is 1.50 +/- 0.07 ng/ml. For the group of 14 pigs studied there was a predictable variation of 64% around this mean in salivary cortisol within a day: the double circadian amplitude, 2A, was 0.96 ng/ml, with a 95% confidence interval ranging from 0.60 to 1.32 ng/ml. A measure of timing, the acrophase, phi, was 10 h 52 min from the phase reference (0030, the middle of the daily dark span of the 24-h light-dark cycle in which the pigs were kept). The 95% confidence interval of phi extended from 9 h 48 min to 12 h 12 min from the reference time. The chronobiologic approach provides indispensable quantitive characteristics as reference standards for future basic or applied work.
Original languageEnglish
Pages (from-to)985-989
JournalPhysiology and Behavior
Issue number3
Publication statusPublished - 1996


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