Thomas C. Krohn

The impact of cage ventilation on rats housed in IVC systems

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 animals 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.

The impact of low levels of carbon dioxide on rats

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.

Carbon dioxide concentrations in unventilated IVC cages

The use of individually ventilated cage (IVC) systems has become more common worldwide. The various systems are becoming more and more sealed in order to protect the animals against infections and the staff against allergens; which, however, may lead to problematic CO2 concentrations, if the cages are left unventilated. In this study it is shown that, depending on how tight the cage is and the number of animals housed in each cage, CO2 inside the cage within 2 h will increase to levels of between 2 and 8% .

Alcohol Facilitates CD1d Loading, Subsequent Activation of NKT Cells, and Reduces the Incidence of Diabetes in NOD Mice

Background Ethanol (‘alcohol’) is a partly hydrophobic detergent that may affect the accessibility of glycolipids thereby influencing immunological effects of these molecules. Methods The study included cellular in vitro tests using α-galactosylceramide (αGalCer), and in vivo NOD mice experiments detecting diabetes incidence and performing behavioural and bacterial analyses. Results Alcohol in concentrations from 0.6% to 2.5% increased IL-2 production from NKT cells stimulated with αGalCer by 60% (p<0.05). CD1d expressed on HeLa cells contained significantly increasing amounts of αGalCer with increasing concentrations of alcohol, suggesting that alcohol facilitated the passive loading of αGalCer to CD1d. NOD mice were found to tolerate 5% ethanol in their drinking water without signs of impairment in liver function. Giving this treatment, the diabetes incidence declined significantly. Higher numbers of CD3+CD49b+ NKT cells were found in spleen and liver of the alcohol treated compared to the control mice (p<0.05), whereas the amount of CD4+Foxp3+ regulator T cells did not differ. Increased concentrations of IFN-γ were detected in 24-hour blood samples of alcohol treated mice. Behavioural studies showed no change in attitude of the ethanol-consuming mice, and bacterial composition of caecum samples was not affected by alcohol, disqualifying these as protective mechanisms. Conclusion Alcohol facilitates the uptake of glycolipids and the stimulation of NKT cells, which are known to counteract Type 1 diabetes development. We propose that this is the acting mechanism by which treatment with alcohol reduces the incidence of diabetes in NOD mice. This is corroborated by epidemiology showing beneficial effect of alcohol to reduce the severity of atherosclerosis and related diseases.

How do rats respond to playing radio in the animal facility

In the animal facility, a range of different sounds are present. On the one hand, rats and humans will regard sound and noise differently even within the audible range, but on the other hand mice and rats being very adaptable to the environment may adapt to living in a noisy facility with e.g. a radio playing. It was the aim of the present study to investigate whether two different strains of rats had different preferences for different kinds of sound patterns, including radio, and to get an indication of whether they are able to distinguish between different sound patterns. The present preference study revealed that rats were able to distinguish between different sound patterns. They showed a clear preference for silence to anything else, which may be taken as an indication that they feel disturbed by the sound from the speaker.

Mice prefer draught-free housing.

An increasing number of rodents are housed in individually ventilated cage (IVC) systems, as these seem to be very effective for the protection of animals against infections, as well as protecting the staff against allergens. For the IVC systems to be properly ventilated, a huge amount of air has to be blown into the cage, which may cause a draught at animal level inside the cage. The aim of the present study was to evaluate the preferences of mice for differing levels of air speeds and air changes inside the cage. It has been concluded that mice do react to draughts, whereas they do not seem to be affected by a high number of air changes delivered without draught, which underlines the importance of applying draught-free IVC systems for mice.

Preferences for limited versus no contact in SD rats.

In biomedical research, single housing of rats is used in different test paradigms and the rats are traditionally group-housed prior to testing. Intuitively this separation may have a negative impact on animal welfare. The objective of this study was to assess the importance of non-tactile contact with a social partner. The hypothesis was that rats, previously housed in pairs, prefer non-tactile contact with a partner to single housing. Moreover, it was hypothesized that females show a higher preference for non-tactile contact than males. Animals were housed for 48 h in two-compartment cages, where the animal could choose either to spend time in the compartment, where only a perforated plexiglas wall separated it from its social partner, or to spend time in the compartment with no rat behind the plexiglas barrier. The proportion of time spent in the two compartments was evaluated. We found a significant effect on gender (P = 0.0368) with females spending significantly more time close to the companion animal. During their inactive period, females spent approximately half their time close to their partner, whereas males preferred to stay in the cage next to the empty compartment. Female rats also demonstrated more activity compared with males (P < 0.0001).