title: Impact of climate on thermal rhythm in pastoral sheep.
abstract: The effects of environmental conditions on temperature rhythms were investigated in ewe lambs at pasture. Two groups of 20 lambs had heart rate (HR), vaginal temperature (T(v)), ear-canal temperature (T(c)) and ear-pinna temperature (T(p)) monitored continuously for 3 days. Climatic conditions were recorded at the same time and Temperature Humidity Index (THI) calculated. One group experienced fine clear weather for the 3 days, the other group experienced 2 days of heavy rain. During periods of fine weather, the daily rhythm for T(v) and T(c) was monophasic. However, heavy rain and a constant THI reduced the amplitude of the recorded temperature rhythms. Daily T(v) and T(c) patterns correlated strongly with THI, with a phase lag of 2 h. Peak T(v) and T(c) were at approximately 17:00 h each day. Mean maximum daily amplitudes were approximately 1.3 degrees C for T(v) and T(c). Mean T(v) was 39.3+/-0.1 and 39.6+/-0.1 for weeks 1 and 2, respectively, while mean T(c) was 38.9+/-0.1 and 39.2+/-0.1. Changes in T(v) and T(c) were closely correlated. We conclude that climate has a major effect on body temperature rhythms.
authors.affiliation: Bioengineering Technologies, Technology Development Group, HortResearch, Private Bag 3123, Hamilton, New Zealand. tlowe@hortresearch.co.nz
authors.forename: T E
authors.initials: TE
authors.lastname: Lowe
authors.forename: C J
authors.initials: CJ
authors.lastname: Cook
authors.forename: J R
authors.initials: JR
authors.lastname: Ingram
authors.forename: P J
authors.initials: PJ
authors.lastname: Harris
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000818:Animals; D001143:Arousal / Q000502:physiology; D001833:Body Temperature Regulation / Q000502:physiology*; D002980:Climate; D005260:Female; D006339:Heart Rate / Q000502:physiology; D011603:Psychophysiology; D012756:Sheep / Q000502:physiology*; D012881:Skin Temperature / Q000502:physiology