KRISTAL AND WAMPLER
AMOUNT OT WATER INGESTED I ml ∕dθ ∕)
Fig. 1. Intake of tap water and sucrose solution in pregnant
females prior to parturition and in nonpregnant females.
300
attributable to the high water content of the diet.
In summary, (1) pregnant females ingested a greater
number of calories per day than did nonpregnant
females; (2) females with prior ρarturitional experience
ingested a greater number of calorics per day than
females which had never given birth; (3) females ingested
a relatively constant number of calories per day
regardless of the palatability of the diet; (4) pregnant
females ingested a greater amount of fluid than did
nonpregnant females; (5) pregnant females exhibited a
significant decrease in intake of water or 5% sucrose
solution, but not of solid food or eggnog, on the last day
prior to parturition; (6) the intake levels of tap water
and of sucrose on the last day of pregnancy did not
differ, regardless of the magnitude of the difference seen
in pregnant females prior to the last day; and finally,
(7) when only a fluid diet was available, caloric intake
was stable through the last day of pregnancy and did not
decrease on the last day as did fluid intake on Diets 1
and 2.
DISCUSSION
The caloric intake of the pregnant and nonpregnant
rats on all diets in the present experiment is in general
agreement with gross energy intake values of pregnant
and nonpregnant adult rats reported by Warner (1962).
Warner reported that nonpregnant female rats ingest
about 52 kcal∕day and that pregnant rats ingest about
76 kcal∕day while feeding on a diet of pellets and water,
Tire greater intake of the pregnant females is expected,
because the pregnant females are laying down body fat,
manufacturing milk, and sustaining fetuses. The higher
intakes of multiparous females can be attributed to the
significantly higher body weights of those females when
compared to virgin or ρrimiρarous females.
Although the total caloric intake of the pregnant rats
on Diet 2 in the present experiment was greater than the
values reported by Warner, the increased caloric intake
may be attributed to the higher palatability of both
high-fat diet (vs pellets and eggnog) and of 5% sucrose
solution (vs water). On the last day of pregnancy, the
intake of the fluid component of Diets 1 and 2
decreased, but no change was observed in the intake of
the solid component of the diets. At that time, the total
caloric intake value of Diet 2 returned to a level closer to
that reported by Warner. The decrease in the caloric
intake of Diet 2 on the last day of pregnancy is the
result of a substantial decrease in the intake of 5%
sucrose solution.
Tlie present experiment provides clear evidence that
the intake of fluids of low caloric density decreases
slιarply on the last day prior to parturition. When a fluid
of Iiiglier caloric density is presented and no alternative
diet is available, the diet appears to be treated by the rat
as if it were solid food, and no significant decrease is
seen on the last day. Tlie lower intake of eggnog (Diet 3)
by multiparous pregnant females (base level), in
comparison to other rats on the same diet, is
inconsistent with that of the other groups (see Table 1),
but may be attributed to the small N. One of the two
females showed unusually low intake values.
On a diet of pellets and water, the normal water∕food
ratio for rats of approximately 2 ml water∕gram of food
eaten is markedly reduced on the last day of pregnancy,
while the absolute level of solid food ingested remains
constant. This decrease in fluid intake cannot be
attributed to the discomfort of labor or to the lack of
time available to devote to ingestion, since either
condition would also produce a decrease in food intake.
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(Received for publication May 21, 1973;
revision received June 11, 1973;
accepted June 18, 1973.)