Depletion of lipid, lean, and ash masses in food-restricted American black ducks /

Includes bibliographical references (pages 1495-1496).

We
investigated
the
rate
and order
of
depletion
of
lipid depots and other body components
in
American
black
ducks
(Anas
rubripes)
responding
to
food
restriction. Forty-one hatching-year ducks
were
placed
on
one
of
four
diets
to
induce
high
variability
in
body
composition. Regression analyses suggest
that
for
every
I
-g
decrease
in
body
mass, lipids decreased 0.53
g,
water
decreased 0.36
g,
ash-free nonlipid dry mass
(NLDM)
decreased 0.05
g,
and
ash
decreased 0.02
g. However,
depletion
rates
were not uniform
among
lipid
sources.
Both
lipid mass and lipid depletion rate
were
ranked
in
descending order:
subcutaneous, carcass, omental, and visceral. Despite disproportionately
low
depletion rates, intraperitoneal depots
were
depleted before subcutaneous or carcass lipids.
We
also found evidence
of
a sexual
difference
in endogenous
nutrient utilization
by
American black
ducks
in
response
to
food restriction. Males reduced
NLDM
(mostly
breast
muscle),
visceral
lipids, and
subcutaneous lipids concomitantly.
In
contrast. females
did
not utilize NLDM but
depleted
visceral
and subcutaneous lipids
at
rates
146-
175%
higher
than
males.
These data
suggest that relationships between depot and
total body lipid
masses
are
not
necessarily uniform. Furthermore,
it may
not
be
possible
to
apply
some measures
of
physiological condition equitably
to
both sexes
of
Anatinae.