![]() In mice, ABR recordings showed that a single exposure to noise of 100 dB for 2 h induced temporary hearing loss ( 4), and an exposure to noise of 110 dB for 60 min even induced permanent hearing loss ( 5). Kenneled dogs that were constantly exposed to noise between 100 and 108 dB for 6 months developed hearing loss as indicated by measurements of the auditory brainstem response (ABR) ( 3). So far, little research has been conducted investigating the effect of noise on the hearing capacities of animals. With repeated exposure, goats habituated to both stimuli ( 2). Goats have been found to show higher behavioral arousal when being exposed to the playback of a bell compared to the playback of a uniform sinusoidal sound, indicating that the bell sound might be more aversive to goats than the uniform sound. The chime of these cowbells is characterized by high and varying amplitudes from 90 to 113 dB at a distance of 20 cm, the approximated distance between the bell and the cows’ ears ( 1). In alpine regions, cows are often equipped with a bell throughout the summer season to ensure that farmers can locate their animals on the wide alpine pastures, many areas that are obstructed from view. This may reflect an altered acoustic perception of the playback stimulus in dairy cows that are routinely exposed to bells. The 85-dB stimulus increased arousal and avoidance compared with the 65-dB stimulus, with bell experience and earplugs leading to a general decrease in avoidance of the stimulus. In general, behavioral and cardiac indicators did not indicate severe hearing impairment due to routine bell exposure. Heart rate and heart rate variability indicated increased sympathetic activation during the exposure to 85 dB compared with 65 dB. Exposure without earplugs to 85 dB but not to 65 dB increased heart rate. The proportion of cows leaving the feeding rack after onset of the playback was reduced by bell experience and earplugs and was increased when exposed to 85 dB compared with 65 dB. Cows reacted faster without earplugs and when they were exposed to 85 dB compared with 65 dB. The effects of bell experience, amplitude, and earplugs on the latency to the first behavioral and cardiac response to a 5-s playback were analyzed using linear mixed-effects models, considering dependencies within the data set. On 24 farms, half of them routinely using cowbells, 96 Brown Swiss cows were tested in a 2 × 2 factorial cross-over design (65 or 85 dB, without or with earplugs) in a balanced order. In addition, we tested whether wearing earplugs, mimicking hearing impairment, reduced the cows’ reactivity toward the playback. ![]() Cows that were either used to wearing a bell or not were exposed to a playback of low and high amplitude (=varying loudness). ![]() For the assessment, behavioral and cardiac indicators were used as indirect measures of hearing capacity. ![]() The aim of this study is to test whether routine bell exposure affects the reactivity to a noise stimulus and might be associated with hearing impairment in cows. Constant exposure to the chime of a bell may affect cows’ acoustic perception in general. In alpine regions, cows are often equipped with bells during pasture season to ensure that farmers can locate them. ![]()
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