Matings
set
up
between
males
and
females
of
each
strain
(litter
1)
-
2
Females
allowed
to
complete
first
lactation
(litter
1)
-
3
Females
treated
with
gonadotropin
and
mated
with
CD-1
males
(litter
2)
-
4
Biological
pups
counted
(litter
2)
and
replaced
with
ten
CD-1
pups
(cross-foster
litter)
Cross-foster
litter
weight
and
number
of
surviving
pups
recorded
daily
for
each
female
through
day
8
postpartum
Equipment
and
supplies
Funnel
feeders
(Research
Products
International,
Mt.
Prospect
IL)
Nestlet
pads
(Ancare,
Bellmore
NY)
Reagents
and
solutions
Pregnant
Mare
Serum
Gonadotropin
(PMSG)
Human
Chorion
Gonadotropin
(hCG)
Procedure:
Mating,
cross-fostering,
and
monitoring
Mice
are
maintained
on
2020X
pelleted
food
(Harlan
Teklad)
except
where
noted.
Matings
are
set
up
between
males
and
females
of
each
strain
to
allow
all
females
to
complete
one
lactation
(litter
1).
Females
are
given
2.5
IU
of
Pregnant
Mare
Serum
Gonadotropin
(PMSG)
i.p.
at
noon
followed
by
2.5
IU
of
Human
Chorionin
Gonadotropin
(hCG)
i.p.
46
hours
later.
Immediately
after
the
hCG
injection,
females
of
each
inbred
strain
are
mated
to
CD-1
males
(litter
2).
Note
that
CD-1
females
and
CD-1
males
are
mated
at
the
same
time
to
produce
litters
for
cross-fostering.
At
day
15
of
pregnancy,
females
from
inbred
strains
are
switched
to
a
powdered
form
of
AIN-93G
(Harlan
Teklad)
dispensed
in
funnel
feeders.
Each
female
is
given
a
single
nestlet
pad
on
day
15
of
pregnancy
to
provide
standardized
material
for
nest
building.
On
day
1
postpartum,
the
number
of
pups
born
to
each
inbred
female
is
recorded
(litter
2).
Biological
pups
(litter
2)
are
removed
from
the
cage
on
day
1
and
replaced
with
ten
neonatal
(day
1)
CD-1
pups
(cross-foster
litters
are
adjusted
so
that
all
have
similar
weight).
Litter
weights
and
surviving
pup
numbers
are
recorded
daily
through
day
8
postpartum.
Data
collected
by
investigator
Number
of
biological
pups
born
(litter
2,
from
CD-1
sire)
Average
daily
cross-fostered
litter
gain
(calculated
daily
based
on
litter
size)