title: The circadian rhythm of cortisol in the saliva of young pigs.
abstract: 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.
authors.affiliation: Department of Herd Health and Reproduction, Faculty of Veterinary Medicine, Utrecht University, The Netherlands. e.d.ekkel@id.dlo.nl
authors.forename: E D
authors.initials: ED
authors.lastname: Ekkel
authors.forename: S J
authors.initials: SJ
authors.lastname: Dieleman
authors.forename: W G
authors.initials: WG
authors.lastname: Schouten
authors.forename: A
authors.initials: A
authors.lastname: Portela
authors.forename: G
authors.initials: G
authors.lastname: Cornélissen
authors.forename: M J
authors.initials: MJ
authors.lastname: Tielen
authors.forename: F
authors.initials: F
authors.lastname: Halberg
mesh_terms: D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D006854:Hydrocortisone / Q000378:metabolism*; D008954:Models, Biological; D012463:Saliva / Q000378:metabolism*; D013552:Swine
chemical_list: D006854:Hydrocortisone