Circadian rhythm of locomotor activity and body temperature in free-range laying hens as measured by triaxial accelerometers and subcutaneous biologgers

Biosensors are essential tools for monitoring temperature in poultry because they provide real-time data that can enhance animal welfare and productivity. The aim of this study was to evaluate the use of triaxial accelerometers and subcutaneous biologgers to monitor of locomotor activity (LA) and body temperature (BT) in free-range laying hens, to explore their potential for assessing circadian patterns relevant to welfare monitoring. Five hens were fitted with a harness that carried an accelerometer to record LA for 6 d. In addition, hens received a surgically implanted biologger to record BT every 15 min. Animals were housed indoors that had an artificial photoperiod (16L:8D) and an adjacent outdoor pen. Hen BT decreased between 1900 h and 2300 h, and was lowest 30 min before lights turned off at 2330 h. From that moment, BT increased throughout the night and until 0900 h in the morning; after which, it remained stable until the evening. Animals remained practically motionless during darkness, and began moving immediately after lights turned on. BT and LA exhibited a 24-h circadian rhythm. There was a significant correlation between BT and LA (P<0.01), but BT was not correlated with ambient T. LA was correlated with indoor and outdoor ambient T (P<0.01). In conclusion, free-range laying hens exhibited clear circadian rhythms in LA and BT, which were synchronized with the light-dark cycle. Ambient T influenced LA, which was correlated with BT. Those findings can contribute to the optimization of management practices that are intended to maximize welfare and productivity.