摘要：The quality of the animal-human relationship and, consequently, the welfare of animals
can be improved by gentle interactions such as stroking and talking. The perception
of different stimuli during these interactions likely plays a key role in their emotional
experience, but studies are scarce. During experiments, the standardization of verbal
stimuli could be increased by using a recording. However, the use of a playback might
influence the perception differently than “live” talking, which is closer to on-farm practice.
Thus, we compared heifers’ (n = 28) reactions to stroking while an experimenter was
talking soothingly (“live”) or while a recording of the experimenter talking soothingly was
played (“playback”). Each animal was tested three times per condition and each trial
comprised three phases: pre-stimulus, stimulus (stroking and talking) and post-stimulus.
In both conditions, similar phrases with positive content were spoken calmly, using
long low-pitched vowels. All tests were video recorded and analyzed for behaviors
associated with different affective states. Effects on the heifers’ cardiac parameters were
assessed using analysis of heart rate variability. Independently of the auditory stimuli,
longer durations of neck stretching occurred during stroking, supporting our hypothesis
of a positive perception of stroking. Observation of ear positions revealed longer durations
of the “back up” position and less ear flicking and changes of ear positions during
stroking. The predicted decrease in HR during stroking was not confirmed; instead we
found a slightly increased mean HR during stroking with a subsequent decrease in HR,
which was stronger after stroking with live talking. In combination with differences in HRV
parameters, our findings suggest that live talking might have been more pleasurable to
the animals and had a stronger relaxing effect than “playback.” The results regarding the
effects of the degree of standardization of the stimulus on the variability of the data were
inconclusive. We thus conclude that the use of recorded auditory stimuli to promote
positive affective states during human-animal interactions in experimental settings is
possible, but not necessarily preferable.
