The effect of age at separation from the dam and presence of social companions on play behavior and weight gain in dairy calves.

Play behavior positively affects welfare of farm animals, yet impoverished social environment during early ontogeny may limit the opportunity or motivation to play. This study investigated the independent and the combined effects of the presence of the dam during the colostrum feeding period and subsequent group housing on play behavior and growth in dairy calves. Forty female calves were allocated to 1 of 4 treatments according to a 2×2 factorial design. The treatments were with or without mother during the 4d after birth and companion housing (single pens or grouped housing in pens of 4 calves between 1 and 8wk of age). After 8wk of age all calves were housed in groups of 4 calves. Play behavior of the calves was observed at 2, 5, and 12wk of age in the following situations: 6 h of spontaneous behavior in the home pen, a 15-min open-field test, and a 15-min social test with an unfamiliar calf. Additionally, play behavior after grouping or relocation at 8wk of age was recorded during two 2-h sessions. There were no significant effects of the mother by companion interaction either on the amount of play behavior in any of the tests or on the body weights of the calves. Presence of the mother after birth did not increase later playfulness, with the exception of higher spontaneous play at 12wk of age. When calves were housed in groups of 4, they played more in the home pen on wk 2 and 5 than individually housed calves of the same age. In contrast, individually housed calves were more playful during open-field tests and social tests on wk 2 and 5. At 8wk, single calves that were placed in a new pen with 3 unfamiliar calves played more than twice as much as grouped calves that were just moved to a new pen with familiar companions. These results show that single-housed calves are deprived of natural levels of play, as demonstrated by both their lower spontaneous play behavior and the higher rebound effect when they are exposed to larger spaces or larger spaces plus companions. Calves that stayed with their mothers for 4d postpartum grew much better until the end of the second week. After that, grouped calves grew better until wk 10 and they tended to be heavier for at least 2wk after relocation or mixing at wk 8. The study shows that brief maternal rearing and group housing independently improve different aspects of performance and welfare of dairy calves.