Santos, R. A., Fontes, R. S., Ong, F. M. et al. 2010. Effects of environmental enrichment and housing system on weight gain of C57BL/6 mice. American Association for Laboratory Animal Science [AALAS] Meeting Official Program, 712-713 (Abstract #P100).

Our goal was to evaluate the effect of treatment represented by enrichment with cotton balls, and the housing system, by comparing the conventional (open cage) and the ventilated cage (IVC) systems on the weight gain of C57BL/6 inbred mice, as well as the multifactorial interactions. We used 149 weight records, 74 males and 75 females, over a 5-mo period, and employed analysis of variance and factor analysis to assess the results, with rejection level of 5%. Among males, housing in enriched open cage showed an average weight gain significantly higher (P < 0.05) than in the other groups, at all time periods, except day 28th. Among females, difference also was significantly higher in average weight gain, considering housing in the enriched open cage, on the 42nd, 49th, 56th, and 63rd d. Multifactorial analysis of interactions regarding weight gain showed that: 1) it was influenced by treatment on the 21st, 28th, 35th, 42nd, 49th, 56th, and 63rd d after weaning; 2) by sex on the 28th, 35th, 42nd, 49th, 56th, and 63rd d after weaning; 3) by the housing system on the 42nd, 49th, 56th, and 63rd d after weaning; 4) by the interaction of housing system with the treatment on the 21st, 28th, 35th, 42nd, 49th, and 56th d after weaning; and 5) by the interaction sex and treatment on the 56th and 63rd d after weaning. In addition, in enriched open cages the average weight gain was higher than in the average nonenriched open cages on the 21st, 28th, 35th, 42nd, 49th, and 56th d after weaning. Comparing housing systems, the open cages on the 21st, 28th, 35th, and 42nd d and enriched open cages on the 49th and 56th d after weaning showed better performance. On the 63rd d after weaning males performed better than females in enriched open cage. Therefore, prevailing interactions on weight gain were between the open cage housing system × treatment with enrichment.