As a multidisciplinary field, laboratory animal science promotes or accelerates the emergence of innovative ideas and products. As research has increased, so has the demand for laboratory animals with reliable, standardized characteristics. Thus, the breeding, reproduction, and welfare of laboratory animals are now animals reliable and more. The aim of this study to investigate whether different litter sizes of mothers and different husbandry methods affect the physical and mental development of pups. 30 adults female Wistar Hanover albino rats weighing 200–250 g were used for the study. The weight of the pups was measured once a week from birth until the end of the study, and their physical development was observed. After the pups were weaned, they were randomly divided into cages by sex. The 45 male and 45 female pups were housed in groups of three, five, and seven per cage. When the pups were 12 weeks old, open field test, elevated plus-maze test and Morris water maze behavioral tests were performed every other day, and then plasma corticosterone levels were measured. When the male and female pups in the groups were 14 weeks old, six females were taken from each housing group and mated, and the conception rates and maternal behavior of the pups were observed. During lactation, physical developmental parameters and the body weight of the rats were affected by litter size. Among the post-weaning housing groups, cage density was found to affect weight gain and body weight between groups. It was found that only the sex factor caused significant differences in the behavior of the animals. Females housed with seven rats per cage had higher corticosteroid levels than other females. As a result, it was observed that cages with seven female rats were more physically and psychologically affected than those with three and five rats.