Neves, S. 2011. Effects of environmental enrichment on the production of C57BL/6 mice kept in different housing systems. American Association for Laboratory Animal Science [AALAS] Meeting Official Program, 788 (Abstract #P201).

The goal of this study was to evaluate the effects of environmental enrichment on the performance of C57BL/6 mice kept in conventional animal facilities (open cage; OC) and individually ventilated caging system (IVC). We analyzed the interactions between treatments (enrichment compared with no enrichment) and housing systems (OC compared with IVC) for 5 mo evaluating: fertility rate, parturition interval, prolificity, number and percentage of weaned pups, percentage of preweaning mortality, and weight gain of weaned pups. We used 32 breeding pairs, divided into 4 groups (group A: nonenriched open cage; group B: enriched open cage; group C: nonenriched IVC; group D: enriched IVC) with 8 breeding pairs per group. We obtained the following significant results: 1) significant difference among groups A and B (A, n = 170; B, n = 189, P < 0.05 ), and groups A and D (A, n = 170; B, n = 168, P < 0.05), where there was higher mortality in group A; 2) interaction among a significant average of weaned × treatment (A, m = 6.57; B, m = 6.69; C, m = 5.89; D, m = 6.26; F = 6.83; P = 0.014); 3) interaction among a significant percentage of preweaning mortality × treatment (A = 58%; B = 21%; C = 31%; D = 17%; F =6.83; P = 0.014), where enrichment had a positive effect. In terms of average weight gain, males and females kept in enriched open cage showed significantly higher weight gain. Therefore, in the multifactorial analysis, there was a widespread relationship between the percentage of pups weaned and the treatment, with the enrichment treatment providing the best results. The prevailing interactions on weight gain were between the open cage housing system × treatment with enrichment.