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 hou sing, but also to refine these guidelines if desirable, Carefully chos en experiments can provide valid information about preferences or aver sions towards specific housing conditions. The results of preference t ests should be interpreted carefully and considered with results from direct measures of animal welfare. This paper gives the details of a p reference test system for laboratory rats which is based on the princi ples described previously in relation to a preference test system for laboratory mice. With the present test system the preferences for vari ous heights and light intensities in the cage were studied. Preference s 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, RD T 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 hi ghest cage (RDT 25.3%). Possibly, motivation for rearing did not excee d motivation to be in a more sheltered area under the test conditions, Both albino (n = 11) and pigmented (n = 11) rats significantly prefer red cages with a low light intensity (< 100 1x) over those with higher light intensities (100-380 1x); this effect was more pronounced in th e albino (RDT 77.9%) than in the pigmented (RDT 51.1%) rats, The resul ts suggest that light intensities > 100 1x are aversive to rats, and m ay be experienced as unpleasant by these animals. The methodology desc ribed may be adaptable to studies of other housing conditions, and pos sibly also to studies of preference in other species.