Using subcutaneous bio-loggers to monitor circadian rhythmicity of temperature, heart rate and activity in sheep under intensive housing conditions

Abstract

ABSTRACT Subcutaneous bio-loggers were used to monitor temperature (T), heart rate (HR), and activity (ACT) of eight ewes managed under intensive housing conditions (permanent stabling and fed once per day). Animals were fed barley straw ad libitum and 0.45 kg concentrate per ewe per day at 08:00 h. Ewes received a surgically implanted bio-logger programmed to record data every 30 min for 12 d. Mean (±SE) T was lower (P < 0.001) in the day (37.88 ± 0.01°C) than at night (38.14 ± 0.01°C), and maximum T occurred at 23:00 h (38.31°C) and minimum T at 08:00 h (37.36°C), immediately after food distribution; however, mean HR (74.41 ± 0.49 bpm) and ACT (15.10 ± 0.30 mg) were higher (P < 0.001) in the day than at night (66.42 ± 0.38 bpm and 6.56 ± 0.22 mg, respectively); maximum HR (87.71 bpm) occurred at 09:30 h, and maximum ACT at 10:00 h (28.47 mg). The cosinor curves for T, HR, and ACT of the eight ewes fit a 24-h rhythm (P < 0.0001). In conclusion, ewes permanently housed presented a clear T, HR and ACT 24-h circadian rhythmicity, whose peaks were coincident with feeding time of the grain-based concentrate.