Cage position preferences of rats

Abstract

Polycarbonate and stainless steel are commonly used cage body materials for laboratory rodents. The aim of this study was to assess preference of rats for the cage material. Altogether 64 male rats were used, 32 in two different facilities. The study cages were made of either stainless steel with a polycarbonate false inner half (Kuopio) or polycarbonate with a steel false inner half (Oulu). There were four different options for alignment of false cage halves and food hopper, and likewise
two options for which end of the cage faced the wall. A video camera with time lapse recording of one second each minute was used. Weekly recording started at 16.00 and ended at 01.30, and each cage was recorded when the rats were aged
four, five, six. seven and eight weeks, The results were processed separately for both facilities and for day and night. Statistical analysis was done with ANOVA using alignment of food hopper to false inner cage half and direction to the wall as
the main effects during the daytime the location of the rats in nontransparent steel body cages is largely governed by the light intensity created by cage walls and hopper, but stainless steel was clearly preferred in three of four possible
combinations. During the night the element of tight direction became less important, but again hopper and steel combination was more attractive than the hopper and polycarbonate combination. In polyearbonate cages with false steel inner half cages: the light intensity difference had a less prominent role. However, during the day, placing the feed hopper with steel was preferred. During the night, the even distribution was indicative of a slight preference to the familiar wall material,
polycarbonate. In conclusion, in both study sites stainless steel was favored in 3 out 4 possible combinations during the day, During the dark, when transparency of the material was less critical, animals accustomed to a stainless steel cages
preferred steel over polycarbonate, but for animals raised in polycarbonate cages neither steel nor polycarbonate was favored.