Investigation of Food Marking and Contamination Behaviors Informs Feeding Practice in Research Colonies of Laboratory...

The laboratory opossum, Monodelphis domestica, serves as a critical marsupial model in biomedical research. Proper feeding approaches are essential for promoting animal growth and wellbeing. In this study, we systematically evaluated food scattering and potential food contamination from feces across 4 feeding methods: direct placement of food pellets on bedding and using 3 different types of containers. We conducted timed daily observations of food scattering and marking behaviors in 22 animals, capturing images by photograph at specific intervals over the course of a week. Body weight was measured before and after the trial. Our findings revealed that the containers did not prevent food scattering behaviors, as evidenced by comparable survival curves for food scattering across all methods (P > 0.05, log-rank test). Although the paper tray and ceramic dish delayed the occurrence of food marking by feces, indicated by a significant extension in the time to marking events (P = 0.009 and P < 0.001, respectively), these containers introduced new animal welfare concerns. The paper tray increased bleeding incidents in digits and paw pads nearly 8-fold (P = 0.0002), presumably due to sharp edges. The ceramic dish was associated with urine marking, and small but statistically significant weight loss (0.7%, P < 0.05). By 144 h, all cages showed food contamination regardless of the feeding method. The results suggest that containers provide minimal benefit in preventing food contamination, and some types of containers may pose health risks. Therefore, we propose that placing food pellets directly on the bedding, a practice used for 45 y of laboratory opossum maintenance, is acceptable for promoting optimal health and operational efficiency for this species. Our results fill a significant gap in care practices and offer insights into optimal colony management for this important research model.