Seasonal variation in daily body temperature fluctuations in grazing sheep in the Aso region, Japan

Abstract

The purpose of this study was to analyze the body temperature fluctuations of pastured sheep between summer and winter using a small data logger. Experiments were conducted for 21 days in both summer and winter using 10 non-pregnant, mature Suffolk sheep (average parity 2.6 ± 1.3). In summer, sheep were pastured from 08:00 to 16:00 and remained in the sheepfold at other times. Sheep were fed hay cube and concentrated feed (at 16:00). In winter, sheep were pastured all day and fed Bermuda grass hay and concentrated feed twice a day (08:00 and 16:30). Body (vaginal) temperature was recorded using a data-logger attached to a modified progesterone-free body implant device for sheep every 30 minutes. In summer, body temperature increased sharply at the start of pasturing and increased slowly towards the end of pasturing and at feeding time. In winter, body temperature sharply increased at feeding time (08:00 and 16:00), then exhibited a diphasic increase at 09:00 and 17:30. Daily body temperature fluctuations were very different between the seasons, with those in summer being significantly higher. The present study revealed that the start of pasturing and feeding contributed to an increase in body temperature.