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Updated: Aug 4, 2026

Instrumentation of Near-term Fetal Sheep for Multivariate Chronic Non-anesthetized Recordings
Published on: October 25, 2015
Impact of climate on thermal rhythm in pastoral sheep
T E Lowe1, C J Cook, J R Ingram
1Bioengineering Technologies, Technology Development Group, HortResearch, Private Bag 3123, Hamilton, New Zealand. tlowe@hortresearch.co.nz
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.
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