Behavioural reactivity affected by chronic stress: An experimental approach in calves submitted to environmental instability

Whereas physiological and behavioural responses to acute stressors are well documented chronic str ess remains difficult to assess in farm animals. Th e aim of the present paper is to investigate whether calves' behavioural re actions to acute events are modified during chronic intermittent stress. Th irty-two calves housed in pairs were wed. For half of the calves the partne r and the pen were changed once a week for 14 weeks (regrouped calves) whil e the others remained unchanged (controls). Four behavioural tests were per formed to assess calves' reactivity to novel or sudden events, to predator cues and to restraint. In the water spray rest, regrouped calves were start led more often. in the umbrella test, regrouped calves took a longer time t o feed in front of the closed umbrella but no differences between the two t reatments were observed on opening the umbrella. In the dog test regrouped calves moved more and looked at the dog more often. In the restraint test, regrouped calves were more agitated These differences disappeared wizen the tests were repeated In conclusion, repented changes in the social and phys ical environment of calves enhances their behavioural reactivity to novelty . This is likely to make them more adaptive to potential changes in their e nvironment.