Consumption of SDS diet was measured daily to identify any effects of treatment on consumption of normal diet, and to determine when the rats had recovered from
treatment.
2.5. Post-treatment testing Post-treatment testing began when all rats had recovered from any ill-effects of
treatment and had resumed their normal consumption of SDS; G 7 days were allowed for this. Rats from all groups were food deprived overnight for 16 h and then presented
with 20 g of the same ‘novel’ food they received prior to treatment for 30 min. As on treatment day, this food was provided in each rat’s own bowl that had been wiped out
with a damp cloth. The time taken for each rat to investigate the bowl and the rat’s activity during the 30-min presentation were recorded. Consumption was measured on
removal of the bowl. Bowls were then emptied, washed and dried, and returned to the rats 1 half h later containing a measured amount of SDS. The time taken to investigate
the bowl was recorded. Post-treatment testing of all groups was repeated every 7 days
Ž .
for up to 5 weeks post-treatment tests 1–5 or until consumption of novel food did not differ significantly between groups.
In order to allow time to carry out procedures and observations for each treatment, Ž
. the timing of all procedures pre-treatment, treatment, and post-treatment was staggered
by 30 min for each treatment group: for example, C group rats had their SDS taken away at 1630 h the previous day and received their novel food between 0830 and 0900
h; TC group rats’ SDS was removed at 1700 h and they received novel food between 0900 and 0930 h; and T group rats’ SDS was removed at 1730 h and novel food was
presented between 0930 and 1000 h.
Minitab for Windows was used for all data analyses. The study was carried out under Ž
. a UK Home Office license, in accordance with the Animals Scientific Procedures Act,
1986.
3. Results
There was a number of responses common to all compounds. With the exception of thiabendazole at 100 mgrkg, at least 86 of rats ate 1 g of the novel food during its
first presentation prior to treatment, and consumption was similar among all treatment Ž
w x
. groups one-way analysis of variance ANOVA : P 0.05, Table 1 ‘Pre-treat’ . For all
compounds and dose rates, consumption of ‘novel’ food in post-treatment tests by Ž
. Ž
. control group rats TC and C was similar one-way ANOVA: P 0.05, Table 1 and
generally increased over time. Responses specific to the different compounds and doses were as follows.
3.1. 17a Ethinyl oestradiol 4 mg r kg 3.1.1. Treatment
No obvious symptoms of malaise were observed after intubation in any group. When SDS was provided 2 h after treatment, 29 rats investigated the food within 1 min, and all
E.L. Gill
et al.
r Applied
Animal Beha
Õ iour
Science 67
2000 229
– 240
234
Table 1 Ž .
Ž .
Ž . Mean consumption of novel foods by treated T , treatment control TC and control C groups of rats before and after treatment with 17a ethinyl oestradiol,
cinnamamide, or thiabendazole NS P 0.05;
U
P s 0.05–0.01;
UU
P s 0.01–0.001;
UUU
P - 0.001. Ž
. Ž .
Compound and food Group
n Mean 1 S.E. food consumption g
Pre-treat Post-treat 1
Post-treat 2 Post-treat 3
Post-treat 4 Post-treat 5
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
17a ethinyl oestradiol 4 mgrkg T
11 3.2 0.30
- 0.1 0.03
- 0.1 0.01
0.1 0.06 -
0.1 0.02 -
0.1 0.04 Ž
. Ž
. Ž
. Ž
. Ž
. Ž
. Ž
. Novel food s biscuit and cinnamon
TC 12
2.8 0.30 3.4 0.36
5.1 0.61 6.7 0.72
6.7 0.62 6.6 0.64
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
C 11
3.2 0.33 4.7 0.35
4.7 0.74 5.7 0.66
5.4 0.50 5.5 0.53
UUU UUU
UUU UUU
UUU
ANOVA P-value NS
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
Cinnamamide 160 mgrkg. T
11 3.6 0.32
1.0 0.35 2.2 0.54
3.8 0.83 4.2 0.68
5.3 0.55 Ž
. Ž
. Ž
. Ž
. Ž
. Ž
. Ž
. Novel food s oats, sugar and almond
TC 10
3.7 0.30 4.2 0.51
6.2 0.71 5.5 0.65
5.6 0.59 4.8 0.59
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
C 10
3.6 0.35 4.2 0.56
5.6 0.41 6.6 0.57
3.8 0.35 4.8 0.39
UUU UUU
U
ANOVA P-value NS
NS NS
Ž .
Ž .
Ž .
Ž .
Thiab’zole 100 mgrkg T
8 3.4 0.32
0.6 0.14 1.7 0.49
3.6 1.04 Ž
. Ž
. Ž
. Ž
. Ž
. Novel food s biscuit and cinnamon
TC 7
1.7 0.31 3.3 0.72
4.4 0.48 5.0 1.19
Ž .
Ž .
Ž .
Ž .
C 7
2.2 0.42 3.6 0.68
4.4 0.52 4.0 0.77
UU UUU
UUU
ANOVA P-value NS
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
Thiab’zole 200 mgrkg T
12 3.4 0.37
0.2 0.06 0.7 0.29
1.8 0.47 3.0 0.71
3.1 0.60 Ž
. Ž
. Ž
. Ž
. Ž
. Ž
. Ž
. Novel food s oats, sugar and almond
TC 12
2.9 0.49 4.2 0.39
5.6 0.47 5.2 0.57
5.4 0.39 5.7 0.52
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
C 11
3.5 0.29 5.3 0.52
5.7 0.32 5.6 0.43
5.3 0.55 6.4 0.32
UUU UUU
UUU UU
UUU
ANOVA P-value NS
rats had investigated after 66 min. At 24–48 h after treatment, T rats showed a marked Ž
. reduction in consumption of SDS 33–70 daily pre-trial consumption , although none
appeared unwell. Consumption returned to normal over the following 6 days and the first post-treatment test was carried out 8 days after treatment.
3.1.2. Post-treatment tests All rats investigated the novel food in their bowl during the 30 min trial, but
Ž consumption varied significantly between groups for all five post-treatment tests one-
. way ANOVA: P - 0.001, Table 1 . Consumption by T rats was negligible in all
post-treatment tests, whereas that of TC and C groups was at least that of the treatment day. In the course of the 30 min trial, some T rats dug in the food bowl with their
Ž .
forepaws, some chewed their bedding pica , and most eventually retired to their
bedding and either slept or sat inactive. These behaviours were not seen in TC or C rats, most of which ate continuously for much of the 30 min trial. Consumption of SDS diet
remained at pre-trial levels between post-treatment tests. Ž
. Additional post-treatment presentations carried out at ca. 3-week intervals were
made with T group rats to determine the time to extinction of the CTA generated by this compound. These demonstrated a gradual attenuation of the aversion over time for most
Ž .
rats, although three continued to eat - 1 g after 11 post-treatment tests 6 months ; complete attenuation of the aversion by all individuals occurred after 15 post-treatment
Ž .
tests 11 months . At 14 months after the first treatment, the possibility of regenerating Ž
. this aversion to the same food through a second intubation of oestradiol 4 mgrkg was
Ž .
investigated in six T rats the other five had either died of old age or been euthanised . In all five post-treatment tests carried out weekly after the second intubation, all six rats
ate - 0.1 g of food.
3.2. Cinnamamide 160 mg r kg 3.2.1. Treatment
After treatment, no signs of illness were recorded in groups TC and C, but some individuals in group T became listless and excessively sleepy. Although most rats
investigated the SDS within an hour of its presentation, one T group individual did not approach for 4 h, and another took 8 h. All individuals appeared well the
Ž .
following day 24 h after treatment , and normal consumption of SDS was resumed by all rats within 3 days. The first post-treatment test was carried out 7 days after treatment.
3.2.2. Post-treatment tests In all trials, all rats investigated the ‘novel’ food in their bowl. Consumption varied
Ž significantly between groups in the first three trials one-way ANOVA: P s 0.025–0.001,
. Table 1 . In the first trial, consumption by T rats was negligible, although most
individuals spent much of the 30 min at their food bowl. During the next two trials, consumption by T rats increased but was still less than that of groups TC and C. By
Ž trials 4 and 5 there was no significant difference between groups one-way ANOVA:
. P 0.05, Table 1 . Consumption of SDS diet remained at pre-trial levels between
post-treatment tests.
3.3. Thiabendazole, 100 mg r kg 3.3.1. Treatment
Ž Consumption of novel food before treatment differed between groups one-way
. ANOVA: P s 0.009, Table 1 ‘pre-treat’ , with most being eaten by T rats and least by
TC rats. This may be related to the generally low consumption of novel food by these Ž
. rats 22r36, 61, rats ate 1 g and resultant small sample. It is not known why the
uptake of the biscuit and cinnamon novel food by these rats was poor as the source and formulation of the food was the same as for oestradiol when a 94 uptake of 1 g was
achieved.
No signs of malaise after intubation were observed in any rat and all investigated the SDS within 10 min of its introduction into the cage. Consumption of SDS resumed
normal levels immediately after treatment. 3.3.2. Post-treatment tests
All rats investigated the novel food. In the first two trials, consumption varied Ž
. significantly between groups one-way ANOVA: P s 0.001 , with T rats eating negligi-
Ž .
Ž .
ble amounts Table 1 . However, in trial 3 3 weeks after treatment , all but two of the group T rats increased their consumption of novel food and the mean consumption was
Ž not significantly different to that of the other groups one-way ANOVA: P 0.05,
. Table 1 . No further post-treatment tests were carried out with these rats.
3.4. Thiabendazole, 200 mg r kg 3.4.1. Treatment
After treatment, four of the T group rats appeared sleepy and withdrawn, and some showed pica. All rats approached the SDS food within 2 h and all but one ate overnight.
Normal consumption of SDS returned to all but one T group rat within 2 days, and to all the groups within 4 days.
3.4.2. Post-treatment tests In all five post-treatment tests, consumption differed significantly between groups
Ž .
one-way ANOVA: P - 0.006, Table 1 , with T group rats eating less novel food than the other groups. A degree of individual variation in response to thiabendazole at this
Ž .
dose was recorded; the three largest rats in the group 530–550 g males ate nothing in all post-treatment tests, while the majority of T group rats increased their consumption
during post-treatment testing.
3.4.3. Comparison of CTA between compounds In order to account for the difference in consumption between the two different
Ž .
‘novel’ foods see ‘pre-treat’ column in Table 1 , for each T group rat we calculated the percentage differences in consumption between pre-treatment and each post-treat-
ment test. Means were calculated for each test compound and post-treatment test, and compared between compounds by Kruskal Wallis one-way ANOVA by ranks.
Fig. 1. Amount of novel food eaten during each post-treatment test, expressed as the mean percentage of the amount eaten on treatment day. Error bars are 1 S.E. Os17a ethinyl oestradiol, C s cinnamamide,
T200 s thiabendazole 200 mgrkg, T100 s thiabendazole 100 mgrkg.
Ž Significant differences existed for all post-treatment tests P F 0.005 for all tests, Fig.
. 1 , with oestradiol inducing the greatest reduction in consumption and cinnamamide and
100 mgrkg thiabendazole the least.
4. Discussion
