How the Different Noise Types May Influence the Open-field Behavior of Rats?

The acoustic environment, included noises, is an utmost important component of the animals’ welfare. Environmental noises are harmful to the laboratory animals, therefore author tested the effect of different noise types. Before starting the noise exposures, a week preliminary period was inserted to socialize the animals. After that 12 young rats were exposed to musical stimuli (MAGY. ÁO. LAPJA, 2013. 135. 246-253.), thereafter a particular noise type only once, every second day, in the afternoon. Each rat spent approximately 7 minutes inside the open-field (OF) box and with simultaneous manual and video registration of behaviour was carried out by two independent observers. The following activities were evaluated: eating, moving by the walls, crossing the centre, sitting, grooming, watching and sniffing, freezing, stereotypical movement, urination and defecation rate. First the basic OF-behaviour, without any sound effect was registered and then the noise stimuli were presented in the following order: noise music (Takehisa Kosugi’s Violin Improvisation: 1989) in original and in two-times accelerated rhythm and two octaves higher in pitch (“rodentized”version”), selection of natural and technical noises. Predominantly the basic ethogram consisted of watching and sniffing (47.7%), moving by the wall (13.5%) (exploratory behaviour), sitting in the corner (19.2%), animals crossed the centre (13.9% of the time (showing the lack of fear) and no freezing or sleeping occurred. Noise music, especially the “rodentized” noise music, as well as the natural noises drastically decreased time, spent with moving, watching and sniffing, the duration of sitting in the corner and the nervous grooming increased. Freezing and stereotypical behaviour (moving the head from one side to another in sitting position) appeared, too. The noise music, especially the higher and accelerated noise music, as well as the natural noises drastically decreased the time of ambulation, watching and sniffing. In turn, the duration of sitting in the corner and the nervous grooming increased. Freezing, and stereotypical behaviour (moving the head from one side to another) appeared, too. Listening the natural noises (containing also cat and dog voices) basically had similar effect on the OF-behaviour as the “rodentized” noise music and rats crossed the centre the few times (sign of anxiety). The technical noises had less influence on the OF-behaviour: the freezing time reduced by 50%. The time for eating, the urination and defecation rate were reduced by all the four noise stimuli. From the point of view of animal welfare, the background music (e.g. radio) of the animal facilities should carefully be chosen to avoid the possible negative side-effects