Abstract
The widespread use of individually ventilated cage (IVC) systems today has made the impact of CO2 on rodents a highly important matter. Leaving cages from these systems without ventilation increases CO2 concentrations inside the cages, as CO2 generated from the animals is no longer removed actively. In modern IVC systems the CO2 levels may reach 3-5% within a very short time, as the cages are very tightly sealed. The aim of the present study was to investigate the effects of 1%, 3%, and 5% CO2 by studying the preferences of the animals as well as changes in the heart rate and systolic blood pressure as measured by telemetry. The rats avoided the cages, which contained 3% CO2. In the telemetric study an anaesthetic effect on the rats were seen at 3% as a drop in the heart rate, and at 5% CO2 a drop in the systolic blood pressure was also seen. The results from the present study could indicate that CO2 levels of up to 3% do not affect the animals, or at least only to a minor extent, but that if the animals are exposed to CO2 levels of higher than 3% they are affected directly as seen by changes in physiological parameters and preferences.