Effects of sounds of different quality on the behaviour and heart beat parameters of goats

Abstract

In alpine regions, bells are used to relocate free-ranging grazers like cows and goats. Considering that goats have a well-developed hearing capacity, sounds (e.g. a chime of a bell) may act as stressors depending on their characteristics. The aim of this study was to test whether a non-uniform sound (chime of a bell) varying in amplitude and frequency and a uniform sound (sinusoidal tone) with continuously increasing amplitude and constant frequency lead to stress responses in terms of behaviour and heartbeat. Twenty-nine goats were tested individually in a test arena in two sessions, each lasting five consecutive days with one trial per day. A day before the first trial, reference values were collected without playback. During the following five trials, playbacks were conducted. Differences in behaviour and heartbeat parameters between test and reference values were analysed by using generalised linear mixed-effects models. During the first trial, the relative feeding duration was decreased and the relative alertness duration was increased during both stimuli, but more when goats were exposed to the non-uniform than the uniform sound. For both stimuli, the relative feeding duration increased (trial×stimulus: P=0.05) and the relative alertness duration decreased (trial×stimulus: P=0.004) from the first to the fifth trial but returned to the levels of the reference values sooner when goats were exposed to the uniform than the non-uniform sound. Cardiac activity was not affected by the stimuli. Altogether, the chime of a bell led to higher behavioural arousal than the uniform sinusoidal tone, indicating a potential of the chime to being more aversive to goats than a uniform sound. With repeated exposure to the stimuli, goats habituated to both stimuli, but habituation was faster to the sinusoidal sound than to the chime of a bell. Free-ranging goats in alpine regions usually are equipped with bells 24h a day during the summer season. Thus, the question arises whether the long-term exposure to the chime of a bell might have negative effects on animal welfare.