Investigation of the effects of litter size and caging on physical and mental development in rats

Objective: In this study, we aimed to evaluate if different litter size of the mothers and different cage density affect the physical and mental development of the their pups. Materials and Methods: In the study 30 adult female Wistar Hannover albino rats weighing 200-250 g were used. Starting from the birth, the weights of the pups were measured weekly. The physical development parameters were observed. After the pups were weaned, they were randomly divided into cages, according to sex. Rats were housed in groups of three, five and seven per cage. When the pups were 12 weeks old, they were subjected to the behavioral tests(open field, elevated plus maze and Morris water maze) and then plasma corticosterone level was measured. Random selected females of each group were mated for observing maternal behavior. Results: During lactation, the litter size influenced the physical development parameters and body weight of rats. It was determined that the cage density affected the weight gain and the body weight between groups. It was observed that only gender factor caused significant differences in animal behavior. Females which are housed seven rats per cage, have higher corticosteroid levels than other females. All statistical comparisons were considered statistically significant at p value <0.05. Conclusion: As a result, it was found that caging groups of three and five, did not affect the physical and mental status of rats; however, rats housed in seven per cage were affected. Key words: rat, caging, litter size, animal welfare