Postural Movements of Rabbits in Variable Height Caging

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Problem statement: The 8th edition of the Guide for the Care and Use of Laboratory Animalsrecommends that the minimum space for rabbit caging as 16in (40.5cm) in height. This recommendation is increased from the 14in height recommendation in the 1996 Guide publication and the same height requirement of the Animal Welfare Act.  Currently, we have several cages that are 15.125 inches for rabbit housing.

Description of research: The 8th edition of the Guide for the Care and Use of Laboratory Animalsrecommends that the minimum space for rabbit caging as 16in (40.5cm) in height. This recommendation is increased from the 14in height recommendation in the 1996 Guidepublication and the same height requirement of the Animal Welfare Act.  This change appears to be intended to allow less restricted vertical space for the rabbits.  It is unclear, however, if this less restricted vertical space actually makes a change in rabbits postural movements depending on this small change. In addition, the scientific basis for this recommendation is unclear. Our hypothesis was that rabbits housed in cages less than 16in would not have different postural movements then those housed in cages greater than 16in. The study examined two caging types: stainless steel rabbit cages with 15.125in cage height and stainless steel rabbit cages with 17in cage height. While the rack dimensions did differ between the two caging types, the individual cages on the rack were identical except for the interior height.  The postural movements of both New Zealand White (NZW) and Dutch belted (DB) rabbits sitting with ears up, sitting with ears down, reclining, rearing/sitting vertical, and those rabbits whose ears were touching the top of the cage were examined. 

Outcomes: There was a significant relationship between the proportion of NZW rabbits that sat with their ears up in the 15.125in cages (χ2 (1, N = 1,661) = 4.797, p = 0.029), and a significant relationship between the proportion of NZW rabbits that  sat with their ears down in the 17in cages (χ2 (1, N = 1,661) = 7.339, p = 0.007) . When examining the DB breed, there was a significant relationship between the proportion of rabbits that sat with their ears up in the 17in cages (χ2 (1, N = 355) = 5.822, p = 0.016).  There were no DB rabbits reported as having the ears touching the top of the cage in either cage type.  Like the NZW rabbits, there were no significant differences in the relationship between cage type and the proportion of rabbits reclining or rearing.  In addition, there was no difference in the relationship between cage type and the proportion of rabbits sitting with ears down.