Effects of Cage Crowding on Body Weight and Feeding Behavior in Male Balb/c Mice: A Preliminary Study

The laboratory mouse (Subfamily Murinae) is widely used in research due to its genetic accessibility, small size, and rapid reproduction. Since the 17th century, mice have played a key role in biomedical studies, particularly in oncology and genetics. Our current project investigates stress in mice and the potential effects of three pharmacological compounds. Hematological and biochemical parameters will be assessed before and after stress exposure and treatment. As a preliminary step, we tested whether cage overcrowding could serve as a suitable method for inducing stress in mice, given its simplicity and short application period. We aimed to observe potential effects on body weight and behavior. Twenty BALB/c laboratory mice were randomly assigned to two groups. The control group was housed in three cages (4, 3, and 3 mice), while the experimental group (10 mice) was kept in a single cage to induce overcrowding. The experiment lasted two weeks. Food and water were provided ad libitum, and food consumption was recorded weekly. Body weight was measured daily, and behavioral changes were observed through direct observation. All mice gained weight by the end of the experiment, including those in the overcrowded cage. Mild aggression was observed during the first 2–3 days in the experimental group, but behavior normalized afterward, with no additional signs of stress. These findings suggest that overcrowding triggered only short-term adaptation rather than sustained stress. Under the conditions applied, cage overcrowding did not reliably induce measurable stress and will not be included in the main study. Future trials will explore more robust stress-inducing methods such as intermittent light, white noise, or immobilization.