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Type: Journal article
Title: Assessment of housing density, space allocation and social hierarchy of laboratory rats on behavioural measures of welfare
Author: Barker, T.
George, R.
Howarth, G.
Whittaker, A.
Citation: PLoS ONE, 2017; 12(9):1-22
Publisher: Public Library of Science
Issue Date: 2017
ISSN: 1932-6203
Statement of
Timothy Hugh Barker, Rebecca Peta George, Gordon Stanley Howarth, Alexandra Louise Whittaker
Abstract: Minimum space allowances for laboratory rats are legislated based on weight and stocking rates, with the understanding that increased housing density encourages crowding stress. However, there is little evidence for these recommendations, especially when considering positive welfare outcomes. This study consisted of two experiments which investigated the effects of housing density (rats per cage), space allocation (surface area per rat) and social rank (dominance hierarchy) on the ability to perform simple behavioural tests. Male Sprague Dawley (SD) rats (n = 64) were allocated to either high-density (n = 8) or low-density (n = 8) cages. The second experiment investigated the effects of surface area. SD rats (n = 40) were housed in dyads in either the large (n = 10) or small (n = 10) cage. In both experiments, animals were tested on a judgment bias paradigm, with their responses to an ambiguous stimulus being ascribed as optimistic or pessimistic. Animals were also tested on open-field, novel-object recognition and social-interaction tests. Recordings were taken from 1700-2100h daily for rat observation and social rank establishment. Dominant animals responded with significantly more optimistic decisions compared to subordinates for both the housing density (p<0.001) and space allocation (p = 0.0015) experiment. Dominant animals responded with increased social affiliative behaviours in the social-interaction test, and spent more time in the centre of the open-field test for both experiments. No significance was detected between housing density or space allocation treatments. These findings suggest that social rank is a significantly greater modifier of affective state than either housing density or space allocation. This finding has not yet been reported and suggests that future drafts of housing guidelines should consider animal social status in addition to floor space requirements.
Keywords: Rats; social stratification; animal sociality; animal behavior; psychological stress; behavior; animal cognition; motivation
Rights: © 2017 Barker et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
RMID: 0030076131
DOI: 10.1371/journal.pone.0185135
Appears in Collections:Public Health publications

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