Applied research note: comparison of the locomotor activity and circadian rhythm in 3 strains of laying hens as measured by tri-axial accelerometers

The objective of this study was to use tri-axial accelerometers to quantify circadian changes in the locomotor activity of three strains of laying hens. Animals were from either the White, Brown or Black strain of a farm that breeds free-range laying hens. Hens were fitted with commercially available sensors that record high resolution raw acceleration data, which were attached to the back of the hen by nylon harnesses and remained in place for 7 d. Separately, animals from each of the strains were allocated to an indoor hen house (density = 0.5 m2/hen), which had an artificial photoperiod (16L:8D,), and an adjacent outdoor pen (4 m2). Minute-by-minute activity data values (Vector Magnitude, VM) were calculated from the activity counts of each of the three axes. Mean (± S.E.) activity (counts/min) of the White strain (was significantly (P<0.001) higher than that of the other two strains. Hens were quiet in the dark period of the day, and were significantly (P<0.001) more active in the light period. Locomotor activity differed significantly (P<0.001) among strains in both the dark and the light periods. All hens exhibited a 24-h circadian rhythm in activity, and significantly different MESOR and acrophases (P<0.001). In conclusion, the tri-axial accelerometers tested in this study were useful for measuring locomotor activity in laying hens, and the animals adapted quickly to wearing the devices attached to harnesses. Hens from the three strains exhibited the same pattern in locomotor activity throughout the day, although they differed in the intensity of their activity