Wyse C A, Zhang X, McLaughlin M, Biello S M, Hough D, Bellingham M, Curtis A M, Robinson J E, Evans N P
Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow G61 1QH, United Kingdom; Department of Molecular and Cellular Therapeutics, Royal College of Surgeons in, Ireland, 123, St Stephens Green, Dublin.
Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow G61 1QH, United Kingdom.
Physiol Behav. 2018 Oct 1;194:362-370. doi: 10.1016/j.physbeh.2018.06.001. Epub 2018 Jun 15.
Entrainment of circadian rhythms (CR) to the light dark cycle has been well described under controlled, experimental conditions. However, studies in rodents have reported that rhythms in the laboratory are not always reproduced under field conditions. The aim of this study was to characterise the CR of sheep maintained under conditions of standard UK farm animal husbandry and to investigate the effects of environmental challenges presented by season, weaning and changes in housing on CR. Male sheep (n = 9) were kept at pasture, or group housed in barns, under natural photoperiod for one year. CR in locomotor activity were monitored using accelerometry, and 24 h patterns in plasma cortisol and melatonin were measured every 4 h by ELISA. CR was measured before and after weaning, in summer and winter, and at pasture and by barn housing. Cosinor analysis revealed high amplitude, diurnal rhythms in locomotor activity that were disrupted by weaning and by barn housing. Rhythms in winter showed an interrupted night time activity pattern, but only when the sheep were kept at pasture. Cortisol and melatonin secretion followed typical circadian patterns in winter and summer. The CR of the sheep under the field conditions of this study were strikingly robust under basal conditions, but easily disrupted by environmental challenges. Interrupted patterns of activity during the long nights of wintertime, not previously reported for sheep kept in experimental conditions were recorded. Based on these findings, we propose that animals require exposure to more complex environments than the laboratory in order to exhibit their true circadian phenotype.
在受控的实验条件下，昼夜节律（CR）与明暗周期的同步已得到充分描述。然而，对啮齿动物的研究报告称，实验室中的节律在野外条件下并不总是能重现。本研究的目的是描述在英国标准农场动物饲养条件下饲养的绵羊的CR，并研究季节、断奶和饲养环境变化所带来的环境挑战对CR的影响。9只雄性绵羊在自然光照周期下，在牧场放牧或圈养在 barns 中一年。使用加速度计监测运动活动中的CR，并通过酶联免疫吸附测定法每4小时测量一次血浆皮质醇和褪黑素的24小时模式。在断奶前后、夏季和冬季、在牧场和圈养时测量CR。余弦分析显示，运动活动中存在高振幅的昼夜节律，断奶和圈养会使其受到干扰。冬季的节律显示夜间活动模式被打断，但仅当绵羊在牧场放牧时如此。皮质醇和褪黑素的分泌在冬季和夏季遵循典型的昼夜模式。在本研究的野外条件下，绵羊的CR在基础条件下非常稳健，但容易受到环境挑战的干扰。记录到了冬季长夜期间此前未在实验条件下饲养的绵羊身上出现的活动中断模式。基于这些发现，我们提出，动物需要接触比实验室更复杂的环境才能展现其真正的昼夜表型。
