Auswirkungen von "Gentling"-Programmen auf das Verhalten von Laborratten (Wistar)

The goal of this study was to investigate whether there is a
“critical period” in the fourth and fifth week of life of
laboratory rats, where an effect comparable to a socialisation to
people can be achieved. Preliminary tests on 6 female wistar-rats
at the age of six weeks have been carried out to test different
methods of non-invasive stress assessment in rats, and to develop a
test procedure for the main experiments. Not all investigated
methods of stress assessment were applicable for the performed
study. For example it could be shown that the determination of
corticosterone metabolites in the faeces pointed out a distinct
circadian rhythm, but no stress-related peak after performing the
planned test procedure. The determination of IgA in the faeces has
not been adequate to show stress-induced changes either. The
developed test procedure consisted of different behaviour tests: a
modified home cage emergence test, a modified open field test, and
a handtest. Additionally, a neck grip and a body-surface
thermometry have been carried out, and catching has been evaluated.
In main experiment I, the animals have been allocated to different
cages, splitting into experimental and control groups in a
genetically balanced way. The rats have been housed in groups of
three under standard conditions in type-IV Makrolon cages. 24
female wistar rats of age 21 days have been used for main
experiment I (“early gentling”). The animals of the experimental
group have been gentled for 10 minutes each day in the fourth and
fifth week of life. All animals underwent tests to assess their
behaviour towards people at the beginning of the sixth, eighth,
tenth and fourteenth week of life, as well as at the age of six,
six and a half and nine months. Following the tests at the
beginning of the fourteenth week of life and at the age of six
months the same test procedure has been carried out by a person
unfamiliar to the rats (test with unfamiliar person). 12 female
wistar rats, which were sisters of the animals in main experiment I
and had been purchased together with them at the age of 21 days,
have been used for main experiment II (“late gentling”). All
animals were tested for the first time at the age of 6 months. In
this test, as in the subsequent test with the unfamiliar person,
they served as the zero check for the animals of main experiment I.
Following these tests, the animals were allocated into experimental
and control groups. The six animals of the experimental group were
gentled for 10 minutes each day for two weeks. After the two weeks
of gentling, at the age of six and a half months, and at the age of
nine months, the rats of both groups have been tested to assess
their behaviour towards people. For the main experiment III (early
“intensified gentling”) 24 female wistar rats of the age of 21 days
have been used. The animals of the experimental group were gentled
in the fourth and fifth week of life for 10 minutes twice each day.
Furthermore, the animals were talked to during the gentling and
recieved a food reward. The tests have been performed analogously
to the tests of main experiment I. All different parts of the test
procedure have been analysed separately. Furthermore five principal
target figures (PTF), summarising some results, have been defined.
PTF 1 summarised the audible vocalisation and the freezing
behaviour during the catching tests, PTF 2 the audible vocalisation
and biting during the manipulations and the neck grip as well as
the abortion of the neck grip, PTF 3 the behaviour during the
handtest, PTF 4 the behaviour towards the stressor in the open
field and PTF 5 summarised catching from the open field, without
vocalisation. High values have been rated as “tameness”. The “early
gentling” of main experiment I had a distinct effect on the
behaviour towards people. The animals of the experimental group
showed a significantly (p