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Fear-Related Behaviour in Two Mouse Strains Differing in Litter Size

Published online by Cambridge University Press:  11 January 2023

A M Janczak*
Affiliation:
Agricultural University of Norway, Department of Animal Science, PO Box 5025, N-1432 Ås, Norway
B O Braastad
Affiliation:
Agricultural University of Norway, Department of Animal Science, PO Box 5025, N-1432 Ås, Norway
M Bakken
Affiliation:
Agricultural University of Norway, Department of Animal Science, PO Box 5025, N-1432 Ås, Norway
*
† Contact for correspondence and requests for reprints

Abstract

The present experiment compared the fear-related behaviour of a mouse strain selected over 101 generations for high litter size with that of a randomly selected strain. The H-strain, selected for large litter size, has a mean (± SD) litter size at birth of 21.5 ± 3.5 pups. The randomly bred C-strain has a mean (± SD) litter size of 9.6 ± 2.2 pups. The elevated plus-maze, the light:dark test and a resident:intruder test were used to measure how the mice responded to novelty. In the elevated plus-maze, a well-validated model of animal anxiety, the H-strain was significantly more anxious (having a lower percentage of entries into open arms) than the C-strain at 9 weeks of age. In the light: dark test, in which the light levels were similar to those in the home environment, the H-strain did not differ significantly from the C-strain in its avoidance of the brightest area. In the resident: intruder test, where aggression-trained, older H-strain males were the residents, 11-week-old intruding mice of the C-strain spent a higher percentage of their time in flight and immobility than intruders of the H-strain. There were clear anxiety- and fear-related differences between the strains, which may be related to their selection history. The results illustrate a need for further studies on the consequences of selection for increased production for the ability of animals to adapt to their home environment and cope with environmental changes.

Information

Type
Research Article
Copyright
© 2000 Universities Federation for Animal Welfare

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