2003

Telemetry as a method for measuring the impact of housing conditions on rats' welfare
Krohn, T.C., Hansen, A.K., Dragsted, N.
Animal Welfare, 12, pp. 53-62, 2003
Abstract:
Various tools have been developed over previous years to study the welfare of laboratory animals. These include preference tests, which are commonly used to evaluate housing environments. Preference tests, however, have some pitfalls: they supply information only on the animals' present preferences, and they allow the animal the choice only between the options offered. Other methods based upon the collection of clinico-chemical data require handling of the animals, which can be stressful in itself. An alternative may be to use telemetry to measure the changes in physiological parameters caused by different environmental conditions. The aim of this study was to use telemetry to evaluate the short-term impact of housing conditions on rodents. We monitored heart rate, blood pressure and body temperature in rats kept on three different types of flooring - bedding, grid floors and plastic floors. The study revealed significant differences in systolic and diastolic blood pressure, heart rate and body temperature between rats housed in the three conditions, indicating that both grid floors and plastic floors are more stressful for the animals than bedding. The observed differences did not diminish over the two-week observation period. The grid floor housing induced elevations in blood pressure and heart rate. Blood pressure remained elevated even when the animals were returned to standard bedding, whereas the heart rate declined back to its original value immediately in response to this shift. This study shows that telemetry is a very effective tool but that it needs integrating with other methods; in addition, a greater understanding of the biological significance of the changes in cardiovascular parameters is required before the hypothesis that these changes represent an indication of distress can be accepted.

 

The impact of low levels of carbon dioxide on rats
Krohn, T.C., Hansen, A.K., Dragsted, N.
Laboratory Animals, 37, pp. 94-99, 2003
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 scaled. 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.

 

The impact of cage ventilation on rats housed in IVC systems
Krohn, T.C., Hansen, A.K., Dragsted, N.
Laboratory Animals, 37, pp. 85-93, 2003
Abstract:
Today the use of individually ventilated cage systems (IVC systems) is common, especially for housing transgenic rodents. Typically, in each cage a ventilation rate of 40 to 50 air changes per hour is applied, but in some systems even up to 120 air changes per hour is applied. To reach this rate, the air is blown into the cage at a relatively high speed. However, at the animal's level most systems ventilate with an air speed of approximately 0.2 m/s. In the present paper, two studies were conducted, one analysing whether an air speed below 0.2 m/s or just above 0.5 m/s affects the rats, and another study analysing whether air changes of 50, 80 and 120 times per hour affect the rats. In both studies, monitoring of preferences as well as physiological parameters such as heart rate and blood pressure, was used to show the ability of the animals to register the different parameters and to avoid them if possible. Air speeds inside the cage of as high as 0.5 m/s could not be shown to affect the rats, while the number of air changes in each cage should be kept below 80 times per hour to avoid impacts on physiology (heart rate and systolic blood pressure). Also the rats prefer cages with air changes below 80 times per hour if they have the opportunity of choosing, as shown in the preference test.