16 female Holstein calves were removed from their pen, which allowed limited visual and tactile contact with other calves, and placed in an arena which allowed no visual contact with other calves for a period of 15 min (open-field test). The heart rate responses to the open-field test were measured at 5 and 15 weeks of age, at 7 and 14 weeks of age after a period of exercise, and at 8 weeks of age in the presence of a familiar or unfamiliar person. Calves were scored on the amount of time they spent running and jumping, walking, vocalizing and defaecating, and sniffing and licking. Scores for run/jump increased and those for walk/vocal/defaecate decreased with age. Prior exploration of the open-field decreased scores for sniff/lick and walk/vocal/defaecate, but did not affect those for run/jump. When the test was repeated over 2 consecutive days, scores for run/jump were higher on day 1 than on day 2, but were not reduced by a preceding period of exercise on either day. Heart rate increased during the open-field test and the rise was correlated with the run/jump score. Basal heart rates decreased with age, but the heart rate response to the open-field test was unaffected by age, prior exploration or exercise. Calves with high walk/vocal/defaecate scores made more contact with familiar and unfamiliar people than calves with low scores.
|Publication Title||Applied Animal Behaviour Science|
|Author Address||Research Centre, Agriculture and Agri-Food Canada, P.O. Box 90, Lennoxville, Quebec J1M 1Z3, Canada.|
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