Technical note: use of accelerometers to describe gait patterns in dairy calves

Developments in accelerometer technology offer new opportunities for automatic monitoring of animal behavior. Until now, commercially available accelerometers have been used to measure walking in adult cows but have failed to identify walking in calves. We described the pattern of acceleration associated with various gaits in calves and tested whether measures of acceleration could be used to count steps and distinguish among gait types. A triaxial accelerometer (sampling at 33 readings/s with maximum measurement at +/-3.2 g) was attached to 1 hind leg of 7 dairy calves, and each calf was walked to a familiar large arena (29.1 x 4.8m) and encouraged to walk and run for 8 to 10 min while being video recorded. The video recordings were watched in slow motion and a total of 54 recordings of 3 to 6s duration of either galloping (n=21), trotting (n=13), or walking (n=21) were identified and the number of steps were counted. Accelerometer data was then analyzed for each gait. Steps could be clearly identified by changes in the acceleration in the forward and vertical axes and vector sum, but less clearly in the lateral axis. The number of steps counted using the forward axis was highly correlated with the number observed from the video recordings. Galloping, trotting, and walking differed significantly in the median interpeak intervals in acceleration in the forward axis and in the vector sum of the acceleration in the 2 axes. Interpeak intervals could be used to discriminate among the 3 gaits, although walking was most clearly distinguished from galloping. Automated measures of acceleration of the leg in the forward and vertical dimensions can be used to count steps and classify gaits of calves.