2005

An ethological approach to housing requirements of golden hamsters, Mongolian gerbils and fat sand rats in the laboratory—A review
Sørensen, D.B., Krohn, T.C., Hansen, H.N., Ottesen, J.L., Hansen, A.K.
Applied Animal Behaviour Science, 94 (3-4), pp. 181-195, 2005
Abstract:
When housing hamsters and gerbils little has been done to identify the preferences of these species. The solitary nature of fat sand rats and hamsters is often discordant with housing practices in animal laboratories. This article provides a comparison of the behaviour of wild-living animals with that of laboratory housed conspecifics, focusing on possible problems related to social structure and enrichment. More studies are needed to reveal the impact of group-housing on hamsters and fat sand rats, just as preference studies on possible enriching resources needs to be undertaken in order to optimise the housing conditions of laboratory hamsters, gerbils and fat sand rats.

 

The welfare impact of gavaging laboratory rats

Bonnichsen, M., Dragsted, N., Hansen, A.K.

Animal Welfare, 14, pp. 223-227, 2005

Abstract:

Gavaging (oral dosing) has previously been shown to have only a short-term effect on behavioural parameters in the laboratory rat. The aim of this study was to determine if the gavaging of laboratory rats influenced their heart rate, blood pressure and body temperature, and if so, whether the duration of this impact correlated with the volume gavaged. The three stress parameters were measured using telemetric transponders placed in the abdomen of eight female Sprague-Dawley (Mol:SPRD) rats. Using a Latin Square cross-over design, the rats were gavaged with three different doses of barium sulphate (4, 10 and 40 ml kg–1); in addition, there was a control of no dose, only insertion of the tube. The heart rate, blood pressure and body temperature of the rats were monitored continuously for 4 h after dosing and again for 1 h, 24 h after dosing. The gavaging of laboratory rats was shown to induce an acute reaction: after 30 min, blood pressure and heart rate were significantly higher than before gavaging, and body temperature was significantly higher 60 min after gavaging — indicators of stress levels comparable to those of other basic experimental procedures. A significant correlation between heart rate and dosage was observed until 10 min after gavaging. This indicates that the dosage gavaged is of only minor importance in causing stress, and only important for the most acute reaction. However, because of the resistance and discomfort observed when administering a 40 ml kg–1 dose, this dose should be administered only with caution.

 

Fluctuating asymmetry in relation to stress and social status in inbred male Lewis rats
Sorensen, D.B., Stub, C., Jegstrup, I.M., Ritskes-Hoitinga, M., Hansen, A.K.
Scandinavian Journal of Laboratory Animal Science, 32 (2), pp. 117-123, 2005
Abstract:
Environmental or intrinsic stressors acting on growing animals and humans may be expressed as small, random deviations from symmetry in otherwise bilaterally symmetrical characters - a phenomenon known as fluctuating asymmetry (FA), the mechanism behind which is not yet clear. In this study, we investigated the effects of two known stressors (grid floor and single housing) on the development of FA in young male Lewis rats compared to housing under normal conditions (bedding) or an enriched environment. It was found that such environmental factors have an impact on FA in rats. Initially, FA was found to be high in all rats. In bedding and in enrichment groups, FA decreased throughout the study (P<0.05 in bedding group and P<0.001 in enrichment group from five to eleven weeks of age). FA in singly housed rats and in rats on a grid floor did not change significantly throughout the study. FA in these rats was considerably higher than in rats housed on bedding with or without environmental enrichment (P<0.001). Moreover, the influence of social status on FA was evaluated. Dominant rats housed in the enriched environment were found to have a higher FA of combined traits than subordinate rats at eight weeks of age (P<0.01), but except for this result, no relationship between FA and dominance was found. Singly housed rats showed significantly higher FA than dominant as well as subordinate rats (P<0.001). In conclusion, FA of selected traits may hold a potential for measuring stress influences in laboratory animals, which can be of some importance in welfare research.

 

PNMT transgenic mice have an aggressive phenotype
Sorensen, D.B., Johnsen, P.F., Bibby, B.M., Bottner, A., Bornstein, S.R., Eisenhofer, G., Pacak, K., Hansen, A.K.
Hormone and Metabolic Research, 37 (3), pp. 159-163, 2005
Abstract:
PNMT (phenylethanolamine-N-methyl-transferase) is the enzyme that catalyzes the formation of epinephrine from norepinephrine. In transgenic mice over-expressing PNMT, observations revealed a very high level of aggression compared to their background strain, C57BL/6J. To evaluate the influence of PNMT on aggression and emotionality in this transgenic line, single-sex male and female groups were independently established that consisted of either four wild-type mice or four transgenic mice overexpressing PNMT. The members of each group were littermates. Mixed single-sex groups consisting of two transgenic mice and two wild-type mice were also established. Almost no fights were observed within the female groups. in males, the transgenic line showed a significantly higher level of fighting than controls (p = 0.007) and mixed male groups (p = 0.02). Housing mice from the transgenic line in mixed groups with wild-type mice seems to decrease the level of aggression in the transgenic line. In conclusion, this is the first study to demonstrate a clear, significant increase in aggression arising from PNMT overexpression. This suggests an important role for central epinephrine levels in aggressive behavior.