The use of aspen blocks and tubes to enrich the cage environment of laboratory rats
Female and male outbred Wistar rats (n=48) were allocated into three groups at weaning; control, tube and block groups (n = 8 males and 8 females in each) Animals were conventionally housed for five weeks in groups of four per cage with either an aspen tube (20x12x12 cm) or an aspen block (6x6x6 cm) in addition to the aspen bedding. The control animals had no enrichment items in their cages. The use of tube and block was assessed by measuring both the volume gnawed and via video recordings, which were done by the instantaneous sampling method at 1 min intervals. The growth of the animals was followed by weighing the animals three times during the study. Rats with the tubes in their cage spent over, 80 % of their time during light period inside the tube and over 20 % during dark period. Furthermore, when the lights were turned off, rats increased other contacts (on and beside) with the tube from 5 % to about 40 %. Animals with blocks spent about 3 % of their time during the light period on top of the block or in its vicinity and about 11 % during the dark period. The amount gnawed was essentially the same with both items and increased slightly with time. The enrichment items did not have any effects on the growth of the animals. In conclusion, the enrichment items have the advantage of not introducing any extra or new compounds into the cage environment, since they are made from the same raw material as the bedding. The rats used the items not only for gnawing but also for other activities. The inside of the tube was mainly used as shelter from the light The aspen tube seemed to have more enrichment value for rats than the aspen block‘ since it allowed a wider range of behaviour patterns to be expressed. These items were reusable, economical and species-appropriate for en riching the cage environment of laboratory rats.
Keywords: environmental enrichment, gnawing, rat.