Physiological changes in laboratory rats caused by different housing.

Males rats of the Wistar strain (Institute of Physiology, CSAV ) were divided into six groups from the 30th to the 200th day of age. Rats (n = 54) were put into cages in various numbers (1, 2, 3, 4, 6 and 8 animals in a cage) and were weighed regularly and the consumption of water and food was measured. At the end of the experiment the animals were killed and the weight of some organs and haematological values were determined. During the experiment the highest weight was attained in animals with 3 or 4 members in one cage. The differences in weight were significant from the 80th day of age. The consumption of diets and water was not influenced significantly by the number of animals in a cage. On the 200th day, the differences between the groups were found in the weight of some organs, and in some haematological values.