DEVELOPMENT AND APPLICATION OF A PREFERENCE TEST SYSTEM TO EVALUATE HOUSING CONDITIONS FOR LABORATORY RATS

Improved knowledge of the ethological needs of laboratory animals can be used not only to verify current guidelines on laboratory animal housing, but also to refine these guidelines if desirable, Carefully chosen experiments can provide valid information about preferences or aversions towards specific housing conditions. The results of preference tests should be interpreted carefully and considered with results from direct measures of animal welfare. This paper gives the details of a preference test system for laboratory rats which is based on the principles described previously in relation to a preference test system for laboratory mice. With the present test system the preferences for various heights and light intensities in the cage were studied. Preferences are expressed as relative dwelling times (RDT) per cage, Female rats (n = 9) tended to prefer lower cages (height 80 mm, RDT 29.9%; height 160 mm, RDT 30.3%) when compared with higher cages (height 240 mm, RDT 18.3%; height 320 mm, RDT 19.2%). Male rats (n = 9) tended to prefer the lowest cage (RDT 38.6%), but also spent quite some time in the highest cage (RDT 25.3%). Possibly, motivation for rearing did not exceed motivation to be in a more sheltered area under the test conditions, Both albino (n = 11) and pigmented (n = 11) rats significantly preferred cages with a low light intensity (< 100 1x) over those with higher light intensities (100-380 1x); this effect was more pronounced in the albino (RDT 77.9%) than in the pigmented (RDT 51.1%) rats, The results suggest that light intensities > 100 1x are aversive to rats, and may be experienced as unpleasant by these animals. The methodology described may be adaptable to studies of other housing conditions, and possibly also to studies of preference in other species.