Physiological Psychology
1973, Vol. 1. No. 3. 297-300
Food and water intake prior to parturition in the rat*
MARK B. KRISTALt and RICHARD S. WAMPLERft
Kansas State University, Manhattan, Kansas 66502
Food and water intakes were measured in pregnant rats to determine whether parturition in rats is preceded by
significant changes in food and water intake. Three diets of different palatability and caloric value were used. Over the
last 5 days of pregnancy, pregnant rats were found to ingest more calories∕day than nonpregnant rats, and females with
prior ρarturitional experience (multiparous) ingested more than virgin or primiparous females. Pregnant rats also
ingested significantly greater amounts of fluid when compared to nonpregnant rats, and multiparous rats (pregnant or
not) ingested greateɪ amounts of fluid than did virgin or primiparous pregnant rats. On the last day of pregnancy, the
intake of solid foods or a liquid diet did not change significantly, but the intake of either water or 5%. sucrose solution
was significantly reduced.
Little is known about the ingestive antecedents of
parturition. Examining immediately prepartum ingestive
behavior may provide clues to internal physiological
changes taking place as well as providing information
about the female’s motivation to eat placenta.
Decreases in food intake just prior to parturition have
been reported in certain of the ungulates such as the cow
and mare (Fraser, 1968). These periods of hypophagia,
however, are usually intermittent, are a characteristic of
the late prepartum period, and are Usuallyaccompanied
by the discomfort of labor (Fraser, 1968). Changes in
food and water intake in rodents during late pregnancy
have received little or no attention in the literature.
Graphs presented by Barnett and Burn (1970) to
describe various oral behaviors (chewing, feeding, and
drinking) during late pregnancy and early lactation
indicate that mice exhibit a slight decrease in food and
water intake on the last day of pregnancy, but this
phenomenon was not described in detail, We expected
that rats would demonstrate the same decrease in food
and water intake observed in mice prior to parturition,
but preliminary observations in our laboratory indicated
that rats manifest a relatively normal level of food intake
in the last 24 h of pregnancy. The present study was
then undertaken to examine food and water intake in
the rat over the last 5 days of pregnancy.
To test for a change in ingestion brought about by an
alteration of taste preference during the last 24 h of
pregnancy, three diets of different degrees of palatability
were used.
METHOD
Subjects
Thirty-nine female rats of a Sprague-Dawley-derived strain
"Supported by National Institute of Mental Health Training
Grant MH-O8359 to Kansas State University and Nutrition
Foundation Grant 428 and Public Health Service Grant
MHI-1894 to Richard S. Wampler. We wish to thank Eugene
Albrecht and Richard L. Sprott for their help.
↑Now at the Department of Psychology, SUNY Buffalo, 4230
Ridge Lea Road, Buffalo, New York 14226.
Now, at the Department of Psychology, Purdue
University-Fort Wayne, Fort Wayne. Indiana 46805.
(Carworth CFE), 100-150 days of age and weighing 250-350 g,
were used. Twenty-three of these were virgins (inexperienced),
and 16 had given birth to more than one litter (multiparous).
The females were housed in individual wire-mesh cages and
maintained on a 12/12-h day-night cycle throughout the
experiment. Vaginal smears were taken daily from the
nonpregnant females, and intakes on the day of cstrus were
excluded to eliminate the depression in food and water intake
observed during estrus (Tarttelin & Gorski, 1971).
Procedure
Nine virgin females and six experienced females were
time-bred with proven breeder males. When copulation was
indicated by the presence of sperm in the vagina, the female was
considered to be in the first day Ofpregnancy. The ad lib diet of
tap water and food pellets (Purina Lab Chow) was continued
until the 14th day of pregnancy, the beginning of the third
trimester. At that time, the pregnant females were assigned to
one of three diet groups, each comprising three inexperienced
and two experienced females. The first group (Diet 1) received a
premeasured quantity of tap water and food pellets each day,
the standard laboratory diet. A sheet of paper was placed under
the cage to catch spillage. The paper was removed each day and
dried for 24 h before the amount of spillage was determined.
Tap water was presented in 100-ml glass founts (Wahmann,
Baltimore), which were refilled each morning in conjunction
with the presentation of pellets.
The second group (Diet 2) received a more palatable diet,
consisting of a drinking solution of 5% sucrose and a high-fat
diet made of two parts of ground laboratory chow (Purina) and
one part vegetable shortening (Crisco) (Corbit & Stellar, 1964).
Paper was placed under each cage to catch spillage. The dish was
weighed each morning and replaced every third day. The sugar
water was presented in 100-ml glass founts and replenished twice
daily.
The third group (Diet 3) received a less palatable and less
Calorieally dense form of the “eggnog” developed by Teitelbaum
and Epstein (1962), consisting of 240 ml Similac (Ross), 50 mi
reconstituted whole egg, 100 ml of 50% (w/v) sucrose solution.
9g dry ground baby cereal (Gerber Mixed Cereals), 150 ml
distilled water, and I ml∕100ml solution of 10% Formalin as a
preservative.
Fourteen virgin and 10 multiparous females were used as
nonpregnant controls. The females were divided into the
following groups: five virgin and three multiparous females
received a diet of pellets and tap water (Diet 1); four virgin and
three multiparous females received a diet of high-fat mash and
sucrose solution (Diet 2); and five virgin and four multiparous
females received a diet of eggnog (Diet 3). Each nonpregnant
female received 11 or 12 days of constant exposure to the diet.
All food and waler intake determinations were made at the same
time daily.
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