Dairy calves social preferences and the significance of a companion animal during separation from the group

The present study investigated social preferences and separation stress in dairy calves. Twelve calves were subjected to two different experimental tests: (1) a social preference test were the calves could choose between a familiar and an unfamiliar calf in a Y-maze, and (2) a separation test were the test calf were taken out from their home pen and placed in a unfamiliar pen, once together with a familiar calf, once together with an unfamiliar calf and once alone. In the social preference test, the calves spent significantly more time in the area where the familiar calf was placed (P < 0.05). In the separation test, the calves vocalized more (P < 0.05), showed less locomotor activity (P < 0.001), were more immobile (P < 0.001) and explored the pen less (P < 0.001) when separated alone compared to separation with a companion calf. The calves vocalized more when separated with an unfamiliar calf (P < 0.05) compared to when separated with a familiar calf. The calves that spent most time with the familiar calf in the social preference test were more immobile when separated with an unfamiliar calf (rs = 0.60, P < 0.05). In conclusion, calves seem to prefer a familiar calf to an unfamiliar calf, and the presence and familiarity of a companion calf affects the calves’ reaction to separation.