Individual housing of female mice: influence on post- surgical behaviour and recovery Short title: Individual housing of mice after surgery

Individual housing of laboratory mice may increase vulnerability to surgical stress, and interfere with postsurgical recovery. To analyse the effect of housing conditions on recovery, pairand single-housed female C57BL/6J mice underwent a minor laparotomy +/analgesia, anaesthesia only or no treatment. Animals were monitored using non-invasive methods during the immediate postsurgical period to assess pain and general impairment. While no appearance or posture abnormalities were observed postexperiment, home cage behaviours were affected distinctly. Discriminant analysis identified self-grooming, locomotion, climbing and resting as mainly responsible for experimental group separation. Behavioural rhythmicity was disrupted, and behaviours related to wellbeing, such as nest building, climbing and burrowing, decreased. Behavioural pain signs (e.g. press) increased. Most behavioural alterations showed a gradation between treatments, e.g. burrowing latency ranged from an intermediate level following anaesthesia only and surgery with analgesia, to pronounced prolongation after surgery without analgesia. Significantly lower burrowing performance after surgery without analgesia in individuallyhoused animals indicates better recovery in pairs. Social interaction in pairs–an important component of normal behaviour (64%) and a potential indicator for direct social support–was nearly absent (0.3-0.5%). While anaesthesia and surgery resulted in clear changes in behaviour, differences between housing conditions were minor. Hence, despite a tendency towards better recovery in pairs, we found no distinct negative effect of individual housing. In conclusion, both housing conditions are acceptable during the period immediately following minor surgery, though social housing is always preferable in female mice. DOI: https://doi.org/10.1258/la.2012.012027 Posted at the Zurich Open Repository and Archive, University of Zurich ZORA URL: https://doi.org/10.5167/uzh-69188 Originally published at: Jirkof, Paulin; Cesarovic, Nikola; Rettich, Andreas; Fleischmann, Thea; Arras, Margarete (2012). Individual housing of female mice: influence on postsurgical behaviour and recovery. Laboratory Animals, 46(4):325-334. DOI: https://doi.org/10.1258/la.2012.012027