Placentophagia and taste aversion conditioning
501
An important determinant of the effectiveness of TAC
in Subgroup LP was the success of the experimenter in
preventing placentophagia during the first parturition, prior
to instituting TAC: the Spearman rank order correlation
coefficient between the number of placentas eaten during
the first parturition and the placentophagia index during
the second was +.94 (p<0.01).
All 6 females in Group SP showed complete consump-
tion of their own placenta during the second parturition.
By contrast, 5/9 of the LiCl group (Group LP) expressed an
aversion to their own placenta during parturition (p = 0.04,
Fisher test). Five of the 6 females in the saline group
consumed the donor term placenta presented just after
parturition. The difference between this group and the LiCl
group on the postpartum test (1/9) was significant (p =
0.01; Fisher test). In summary, the administration of TAC
during the first parturition (particularly if placentophagia
only occurred in conjunction with LiCl) altered placento-
phagia both during and just after the second parturition.
Observation of Maternal Behavior
During the perinatal period, the 4 females in the
Lid-injected group (Subgroup LP) that had exhibited
placentophagia during parturition also severed the umbilical
cords and cleaned all their pups. Among the 5 animals
showing an aversion to placenta, 2 failed to clean 1 pup
each and 4 failed to sever the umbilical cords on a large
number of pups in their litters. Although all the females in
the saline-injected group (Group SP) exhibited placento-
phagia during the perinatal period, 2 of the 6 females did
not clean all the pups in their litters. With the obvious
exception of placentophagia, no significant difference in
perinatal maternal behavior could be detected between the
saline and Lid-injected groups.
When observed at 2 days postpartum, all the females in
the Lid-treated group (Subgroup LP) built nests, nursed
their young and retrieved their litters within the 15 min
test. Five females lost at least 1 pup from their litters. The
number of pups lost tended to be small, ranging from I to
3, with the mean being 2.0 ± 0.4. Although most of the
females in the saline-injected group (Group SP) continued
to show maternal behavior at 2 days postpartum, there was
a high incidence of pup mortality. All the animals in this
group lost at least 1 pup from their litters. The number of
pups lost tended to be large, ranging from 1 to 16, the
mean being 5.7 ± 2.2. Although a larger number of females
in the saline groups exhibited pup loss when compared to
the Lid-treated group, this difference was not significant (p
= 0.09; Fisher test).
Two-week postpartum test
All the females in the LiCFtreated group (Subgroup LP)
exhibited placentophagia in the test 52 days after TAC.
Since only 4 of the 9 females had eaten placenta during
parturition, this increase was significant (p = 0.03 ; McNemar
test). All 6 females in the saline group (Group SP) exhibited
placentophagia in the test after the control interval. The
saline-injected females showed no change from their re-
sponse to placenta at parturition.
Response of nonpregnant females
Females in Subgroup LP had been given an injection of
LiCI following the consumption of donor term placenta
after the first parturition. During the test after the first
control interval, which occurred at 38 days after the first
parturition, all of the LP females continued to exhibit
placentophagia.
A comparison between Subgroup LP and Subgroup LP
revealed a significant difference (p - 0.02, Fisher test).
Whereas more than half of the females in the pregnant
group manifested an aversion to placenta at the second
parturition, none of the females in the nonpregnant group
gave any indication of an aversion after the first control
interval.
The response of the nonpregnant group in Experiment 3
(LP) can be contrasted with the response of the nonpreg-
nant groups in Experiment I (Subgroup CP) and in
Experiment 2 (Group P). Whereas the nonpregnant groups
from Experiments 1 and 2 exhibited an aversion after the
first control interval, the nonpregnant group in Experiment
3 did not. The comparison between LP and CP was
significantJp = 0.004; Fisher test) as was the comparison
between LP and P (p = 0.009; Fisher test).
When observed after the second control interval (52 days
after conditioning) all females in Subgroup LP continued to
exhibit placentophagia as in the test after the first control
interval. The results of the second control interval (2 week
postpartum for P females) tests performed on the 3 groups
in Experiment 3 revealed that all groups were exhibiting
placentophagia at this time.
To summarize the results of Experiment 3, a taste
aversion to placenta, induced at parturition, was expressed
at the next parturition; the expression of the aversion was
contingent upon limiting the number of placentas eaten
during the first parturition (just prior to TAC), females
eating more than one placenta during the first parturition
showing no aversion to placenta during the second. An
aversion conditioned at parturition was not expressed
during a subsequent nonpregnant period. The saline-
injection procedure did not lead to the expression of an
aversion to placenta during the second parturition.
DISCUSSION
The role of prior parturitional experience with placenta
can be elucidated by making comparisons between inexperi-
enced (Exp. I) and experienced (Exp. 2) females. Nonpreg-
nant females, even those with prior parturitional experience
with placenta, can acquire an aversion to placenta by TAC.
The aversion was induced with equal facility in both virgins
and nonpregnant primiparae. The aversion could still be
observed in both groups after an interval of 25—30 days.
Thus nonpregnant females can acquire an aversion to
placenta, and express it on both a short-term and long-term
basis.
If females were impregnated after the completion of
TAC, the aversion to donor placenta could alter the
consumption of naturally-delivered placenta during a subse-
quent parturition. TAC was particularly effective in modi-
fying parturitional placentophagia when TAC was induced
in virgins and tested at the first parturition. These females
had very little exposure to safe placenta before the onset of
conditioning, learned safety of placenta having been kept to
a minimum. After conditioning, these inexperienced fe-
males clearly responded to donor placenta and their own
placenta in the same manner, refusing to consume either
variety. Females that lacked parturitional experience with
placenta did not demonstrate an ability to distinguish