Automated measurement of synchronisation in pair-housed dairy calves: preliminary results

Behavioural synchronisation has been proposed as indicator of positive welfare and social cohesion in cattle, although few data are available in calves. However, its assessment relies on time-consuming methods, like direct observation or video recording. This study aimed to examine the presence of synchronism in pair-housed dairy calves by analysing accelerometer data. Eight Italian Friesian female calves were pair-housed (2.59 m2/animal) since birth (maximum age difference of 24 hours) and enrolled in the study from 2 to 18 days of age. Each calf was equipped with an accelerometer positioned on the right hind leg. Calves were managed in compliance with Council Directive 2008/119/EC and milk replacer was administered twice daily. Calf starter and hay were provided since 2 and 7 days of age, respectively. Accelerometer data, collected with a sampling interval of 60 seconds, were analysed to measure lying and activity expressed as minutes per hour. To identify possible synchronism within the couple, days 3, 6, 12 and 18 of age were selected and overlapped. The correlation coefficient between the time series of the animals of the same pair was calculated for each day. Data analysis outlined an increased lying synchronisation along the experimental period. Moreover, a simultaneous reduction of lying behaviour during milk feeding is evident for all the animals, implying a synchronism in activity pattern feeding-related. This study provides preliminary evidence of synchronisation in pair-housed calves, reflecting the development of social cohesion since early age. The automated measurement of synchronisation through accelerometer data might represent a promising tool for the evaluation of positive welfare in calves.