Monitoring lab animal feeding by using subcutaneous microchip transponders: Validation of use with group-housed rats

Groups of three rats were fitted with subcutaneous microchip transponders typically used for animal identification. Each group was housed in a custom-designed plastic cage, which contained a pellet feeder tunnel instrumented with a ring-type sensor. The animals were continuously videorecorded for 24 h by using illumination invisible to them during the dark cycle. We performed four experiments in which video confirmation of feeding (i.e., pellet dispensing) was compared to identification of a specific animal by the automated microchip scanning system. When the system was optimized in two experiments, the accuracy of feeding with detection was 96% and 99%. These figures represent 420 pellets dispensed per 24 It in one study and 252 pellets dispensed per 24 It in the other. The use of subcutaneous microchip transponders is an effective method to monitor the individual feeding behaviors of rats housed in groups.