Technical note : validation and comparison of 2 commercially available activity loggers

To validate the accuracy of 2 commercially available activity loggers in determining lying, standing, walking, and number of steps in dairy cows, 30 cows were fitted with the CowScout Leg (GEA Farm Technologies, Bönen, Germany) system and the IceTag (IceRobotics Ltd., Edinburgh, Scotland) system. The CowScout Leg logger reports standing and lying in 15-min periods, whereas the IceTag logger reports standing and lying every second. To make data comparable, the IceTag data were therefore also summarized over 15-min periods corresponding to the paired CowScout Leg sensor. These data from the 2 systems were then analyzed (more than 1,000 cow days in total). Video recordings of a total of 29.5 h were used for labeling the behaviors of the selected cows (n = 10) and these labels were used as a gold standard to determine the accuracy with which these 2 loggers can record behavioral states lying, standing, walking, and the behavioral event number of steps. A concordance correlation coefficient analysis showed that both the standing and lying durations obtained with the 2 systems were almost perfectly correlated with the video labeling (IceTag: ρc = 0.999 and 0.999, respectively; CowScout Leg: ρc = 0.995 and 0.996, respectively). However, both loggers performed poorly regarding number of steps (classified as an event; IceTag: ρc = 0.629; CowScout Leg: ρc = 0.678) and CowScout Leg did not detect walking (classified as a state) very accurately (ρc = 0.860). The IceTag system does not measure walking behavior. When comparing the 2 loggers, the correlation between them for standing and lying was substantial (ρc = 0.953 and ρc = 0.953, respectively). The number of steps poorly correlated between the 2 loggers (ρc = 0.593), which might be due to the CowScout Leg logger being attached to the front leg and the IceTag logger being attached to the hind leg. We conclude that both the IceTag and the CowScout Leg logger are able to record standing and lying almost perfectly, but the step counting by both loggers and the walking recording by the CowScout Leg logger are not very accurate.