Evaluation of Potential Low-stress Handling Methods in Crl:CDSD Rats (Rattus norvegicus)

Low-stress handling methods have been studied in detail in mice, but relatively little research exists concerning preferred handling methods in rats. Most recommendations for low-stress handling of rats have been extrapolated from the mouse literature, despite known differences in handler interaction between the 2 species. The goal of the current study was to evaluate common methods of handling in rats, including application of recognized, low-stress handling methods from other species to rats, in order to determine relative stress levels associated with the handling methods. Seventy male and 70 female, 8-wk-old, Crl:CDSD rats, were housed either individually or in pairs, and were handled weekly or daily using one of the following methods: encircling of the torso (standard thoracic hold), handled using a tunnel, handled using a protective bite glove, handled using a soft paper towel, or tickled prior to being handled by the torso ( n = 10 per sex per treatment group). Body weight and clinical observations were scored at each handling session, abbreviated functional observation batteries were performed every other week, and an interaction test and hematology were conducted prior to study and on the day of study termination. Rats that were socially housed and handled weekly using the standard thoracic hold showed the least evidence of stress, while those that were singly housed and handled weekly using a protective bite glove or tunnel showed the highest level of stress. These effects were predominantly seen in males. This study suggests that standard low-stress handling methods used for other species may not be optimal for rats, and that additional research is needed to identify alternative methods to the standard thoracic hold that would further reduce stress during handling in rats.