A new method to measure behavioural activity levels in dairy cows

Abstract

Changes in the behavioural activity of farm animals are widely used as an indicator for the assessment of animal welfare. In this study on dairy cattle we validated a new method for automatic 24 h recording of behavioural activity, the Actiwatch ® activity monitoring system (AMS). The AMS is a very compact ( 27 mm×26 mm×9 mm, 16 g) accelerometer developed for long-term activity monitoring (e.g. 45 days at 1 min interval; 64 KB memory). The AMS devices were attached to the hind leg of 12 dairy cows, and recordings of activity were taken at 1 min interval for 10 consecutive days. AMS recordings were compared with video recordings taken on five simultaneous days in order to investigate first, whether specific behavioural activities could be distinguished by the AMS, and second, which behavioural activities could be differentiated. The consistency between devices was examined by comparing the recordings of two AMS devices attached to the same leg. The effect of positional application was tested by attaching a device to both the left and right hind leg. In order to distinguish statistically between the different levels of activity obtained from the AMS recordings dynamic thresholds were determined. High and low activity counts were then calculated using these thresholds. The activity counts were highly correlated with the behavioural patterns derived from video recordings (high activity: r s=0.75, P<0.001; low activity: r s=0.65, P<0.001). The mean number of low activity bouts (NB LA) calculated from the AMS recordings and the mean number of lying bouts (NB LY) derived from the video recordings agreed completely (mean NB LA and mean NB LY both equal to 7.8). This result and the mean duration of NB LA (upper AMS: 57.4 min, lower AMS: 59.0 min) correspond strongly with the findings of other studies of the resting behaviour of dairy cows. The recordings from two AMS devices (upper AMS; lower AMS) attached to the same leg ( r s from 0.70 to 0.99, all P<0.001) showed higher correlation coefficients compared to the recordings from two AMS devices attached to different legs ( r s from 0.60 to 0.87, all P<0.001). In conclusion, the results suggest that the AMS can be used to reliably measure objectively different levels of behavioural activity in dairy cows, and also the temporal organisation of the different activity levels without any restriction of the animal’s freedom of movement.