Influence of the Number of Animals per Cage on the Anxiety Levels in Mice

Abstract

original RESUMO Este estudo teve como objetivo avaliar o efeito do número de animais por gaiola sobre o comportamento de ansiedade em camundongos expostos ao labirinto em cruz elevado. Trinta camundongos foram divididos em dois grupos: grupo 1 (G1) e 2 (G2) com 10 e 20 animais, respectivamente, em cada gaiola. Ao atingir 90 dias de idade, cada animal foi submetido ao labirinto em cruz elevado, apenas uma vez no período de 5 minutos. Os parâmetros avaliados em ambos os grupos foram: porcentagem do número de entradas nos braços abertos (% NBA) e a porcentagem de tempo gasto nos braços abertos (% TBA). A análise estatística não detectou diferenças significativas entre os dois grupos na % NBA (p = 0,87), nem com relação à % TBA (p = 0,98). O trabalho concluiu que a manutenção de 10 ou 20 animais por gaiola não causou nenhuma alteração significativa nos níveis de ansiedade dos mesmos, o que sugere ser indiferente manter 10 ou 20 camundongos por gaiola. ABSTRACTThis study aimed to evaluate the effect of the number of animals per cage behaviour of anxiety in mice exposed to elevated plus-maze. Thirty Swiss mice were divided into 2 groups: group 1 (G1) and group 2 (G2) with 10 and 20 animals respectively in each cage. Upon reaching 90 days of age, each animal was submitted to the elevated plus-maze, only once in the period of 5 minutes. The parameters evaluated in both groups were: percentage of the number of entries in open arm (% nBA) and percentage of time spent in open arms (% tBA). The statistical analyis did not yield significant difference between the two groups in regarding %nBA (p = 0.87) nor with respect to tBA% (p = 0.98). Our work concluded that the maintenance of 10 or 20 mice per cage did not cause any significant alteration in the anxiety levels of the animals, thus it suggests being indifferent to maintain 10 or 20 mice per cage.

Detrimental Effects of Restricted Cage Size on Reproductive Performance, Exploration Ability, and Anxiety but Not Working Memory of Kunming Mice

“…Considering the higher anxiety levels observed in mice from the restricted cage ( Figure 2C ), it is also possible that poor reproductive performance is, at least partially, caused by unwell emotional states such as anxiety. Although breeding density varies proportionally with cage size for a certain group size, previous reports (Loo et al, 2001 ; Bellei et al, 2011 ; Buijs et al, 2011 ) did not find significant differences in reproductive performance between two groups of mice with different breeding densities (10 and 20 mice per cage, respectively) in the same cage with the size of (34 × 49 × 16 cm 3 ). The anxiety levels also showed no significant difference between the two groups.…”

“…Nowadays, much attention is being paid to the welfare of laboratory animals (Reeb-Whitaker et al, 2001;Gonder and Laber, 2007), and the conditions of keeping laboratory animals have been the focus of several studies, as environmental factors such as cage size may interfere with the results of behavioral tests (Loo et al, 2001;Mcglone et al, 2001;Wolfer et al, 2004;Julia et al, 2008). For example, previous studies have shown significant effects of cage size on reproductive performance (Julia et al, 2008;Whitaker et al, 2009), aggressiveness level (Loo et al, 2001), anxiety level (Bellei et al, 2011), and exploration and cognitive abilities (Forsyth and Young, 2007;Julia et al, 2008;Line et al, 2010). Therefore, animal welfare, including cage size, is critical to the reliability of research using laboratory animals.…”