MICE AT DRAUGHT?! A RESEARCH ON WELL BEING OF MICE IN INDIVIDUALLY VENTILATED CAGES 

by M.J. VONCK, Utrecht University

The study was presented at the 2000 AALAS meeting in San Diego by Dr. Vera Baumanns.

The number of air changes per hour to be used in Individually Ventilated Cages is still a matter of discussion between users of these relatively new and sophisticated equipment. The suspect or feeling(?) that high number of air changes can cause draught and therefore negatively affect the wellbeing of rodents, is a matter of concern between rodents’ behaviour experts.

It is well known that draught sensation in humans occur when the speed of the air is above 0,2 m/sec but no objective data are actually available for mice.

Another key point is in relation with the position of the air inlet/outlet in the cage; it was demonstrated before in earlier type of IVC systems with air inlets/outlets located in the side wall of the cage, cause a massive avoidance behaviour by females Balb/c mice because the air was directly blown in on animal eight height. In this study a new generation of IVC with the air blown in from the back side of the top cover was used. The authors found a less uncomfortable condition for mice probably due to the fact that air entering  the cage is not blown in directly onto the animals.

The wellbeing of Balb/c mice housed in Individually Ventilated Cages was evaluated in this study using  indirect indicators : preference and avoidance tests. A complex protocol was set up by the authors in order to evaluate as many situations as possible in terms of air changes, available nesting material, static condition (no ventilation, possible in this study thanks to the special circular PAL filter, 0,2 micron, capable to avoid the accumulation of CO2 when ventilation is off).

Results seems to suggest that 60 air changes per hour do not show any significant avoidance and that nesting material improve wellbeing of mice. More studies should identify  the ventilation rate at which avoidance of the IVC become significant.