By—=pmdœcîs and wastes
83
poultry waste in the diet.
There
appeared to be poor utilisation of the
waste
and
amino
acids
were
not
efficiently incorporated into the fish biomass.
For
fish
to
utilise
NPN
an
analogous microbial process to that occuring in
ruminants would have
to be present.
Although large populations of intestinal
micro—flora are
found
in
ÎiSh,
in carp
this
micro—flora does not
appear
to
utilise NPN
and
then
to
be
digested and absorbed by the fish.
In
spite of
the
essentially negative results found with dried poultry wastes fed to carp,
a
relative
of
the
carp,
the
goldfish, has been shown to grow better when fed
with
a
30% dried poultry waste/70% salmon feed pellet than when fed with
salmon
feed pellet alone.
In
Israel
considerable work has been
done
in
combining manuring and the
feeding of pelleted diets to fish.
Whereas
in manured ponds, without
supplementary feeding,
a
certain
level
of
fish production is reached,
even
a
relatively small amount of low protein pelleted feed (25—100 Kgs per ha.
of
25% protein pellets) added to the manured ponds increases the yield
considerably.
The
economics
of
such
an
operation has been analysed and it
has
been
shown
that
the
profit break—even point between the use of manure and
of
feeds
occurs
at
a
given relation to the price of feeds.
Only when fish
are
relatively cheap is it more profitable to grow them with manure only
(Wohlfarth and Schroeder,
1979).
Similar work has
been
carried out
in South
Africa
by Prinaloo and Schoonbee (1984).
The direct
use
of
duck
manure
with
fish
culture has
been practised for many
years
in
the
Far East
and
in Hungary,
and experiments in Israel, have shown
this
to be
an
efficient
system.
The
ducks
performance are superior to their
land growth rate.
Viability and cleanliness are improved while the average
daily gain of fish is not significantly different from the fish in ponds
receiving mixtures of dried poultry manure plus supplementary feeding.
WASTE B1PRODUCTS
Traditionally a number of organic by—products and wastes have been used in
animal
feeding (Rock,
1976).
Most
of
these materials have been
assessed as
possible fish feeds.
Whether
one
should regard the use of leaves and pond
weeds
as
wastes,
unless
they are residues from another agricultural operation,
is problematic.
Although the common carp does consume macrophytes,
these
are
rarely used as supplementary feeds.
The
grass
carp,
however, which is a
voracious
plant feeder,
is
another
matter.
This
fish has been
the
subject of
much
investigation.
The
growth rate of these fish fed both with aquatic
weeds, for example Hydrilla and Lemna (duckweeds) or with Eichornnia (water
hyacinth),
and terrestrial
grasses
such
as
Napier grass,
and with
leaf
material
such
as
cabbage leaves, has been studied.
Stocking density and
temperature are,
as
usual,
important but growth can be good in intensive
mture when these
fish
are
fed on such natural
plant feeds
(Shireman, Colle
and Rottman,
1977; Riechert and Trede, 1977; Kilambi and
Terrestrial
grasses,
however,
perform in some instances as a superior feed
to aquatic macrophytes.
For example the growth rate of grass carp fed with
hybrid Napier grass has been found to be nearly three times that of fish fed
on
the
aquatic Weed, Hydrilla, and five times that growth attained with
Ceratophyllum (Venkatesh and Shetty, 1978).
Fresh
duckweed
feeding,
however,
in intensive culture situations does appear to give better growth than in the
feeding of 100% ryegrass pellets (Shireman. Colle and Rottman, 1978).
Leaf protein concentrate prepared from waste sugar cane tops and other leaf
residues has been fed experimentally to carp with success, giving good growth
rates,
However,
leaf protein may contain substances which inhibit protein
digestibility, for example, chlorogenic acid which is found in leaf protein
imubits the attack of proteolytic enzymes like trypsin 0Î chymotryps1n
(Jan,
Hsu and
1977; Ogino, Cowey and Chiou,
1978; Gwiazda, Noguch1, Kltamura
and Saio, 1983).
83
poultry waste in the diet.
There
appeared to be poor utilisation of the
waste
and
amino
acids
were
not
efficiently incorporated into the fish biomass.
For
fish
to
utilise
NPN
an
analogous microbial process to that occuring in
ruminants would have
to be present.
Although large populations of intestinal
micro—flora are
found
in
ÎiSh,
in carp
this
micro—flora does not
appear
to
utilise NPN
and
then
to
be
digested and absorbed by the fish.
In
spite of
the
essentially negative results found with dried poultry wastes fed to carp,
a
relative
of
the
carp,
the
goldfish, has been shown to grow better when fed
with
a
30% dried poultry waste/70% salmon feed pellet than when fed with
salmon
feed pellet alone.
In
Israel
considerable work has been
done
in
combining manuring and the
feeding of pelleted diets to fish.
Whereas
in manured ponds, without
supplementary feeding,
a
certain
level
of
fish production is reached,
even
a
relatively small amount of low protein pelleted feed (25—100 Kgs per ha.
of
25% protein pellets) added to the manured ponds increases the yield
considerably.
The
economics
of
such
an
operation has been analysed and it
has
been
shown
that
the
profit break—even point between the use of manure and
of
feeds
occurs
at
a
given relation to the price of feeds.
Only when fish
are
relatively cheap is it more profitable to grow them with manure only
(Wohlfarth and Schroeder,
1979).
Similar work has
been
carried out
in South
Africa
by Prinaloo and Schoonbee (1984).
The direct
use
of
duck
manure
with
fish
culture has
been practised for many
years
in
the
Far East
and
in Hungary,
and experiments in Israel, have shown
this
to be
an
efficient
system.
The
ducks
performance are superior to their
land growth rate.
Viability and cleanliness are improved while the average
daily gain of fish is not significantly different from the fish in ponds
receiving mixtures of dried poultry manure plus supplementary feeding.
WASTE B1PRODUCTS
Traditionally a number of organic by—products and wastes have been used in
animal
feeding (Rock,
1976).
Most
of
these materials have been
assessed as
possible fish feeds.
Whether
one
should regard the use of leaves and pond
weeds
as
wastes,
unless
they are residues from another agricultural operation,
is problematic.
Although the common carp does consume macrophytes,
these
are
rarely used as supplementary feeds.
The
grass
carp,
however, which is a
voracious
plant feeder,
is
another
matter.
This
fish has been
the
subject of
much
investigation.
The
growth rate of these fish fed both with aquatic
weeds, for example Hydrilla and Lemna (duckweeds) or with Eichornnia (water
hyacinth),
and terrestrial
grasses
such
as
Napier grass,
and with
leaf
material
such
as
cabbage leaves, has been studied.
Stocking density and
temperature are,
as
usual,
important but growth can be good in intensive
mture when these
fish
are
fed on such natural
plant feeds
(Shireman, Colle
and Rottman,
1977; Riechert and Trede, 1977; Kilambi and
Terrestrial
grasses,
however,
perform in some instances as a superior feed
to aquatic macrophytes.
For example the growth rate of grass carp fed with
hybrid Napier grass has been found to be nearly three times that of fish fed
on
the
aquatic Weed, Hydrilla, and five times that growth attained with
Ceratophyllum (Venkatesh and Shetty, 1978).
Fresh
duckweed
feeding,
however,
in intensive culture situations does appear to give better growth than in the
feeding of 100% ryegrass pellets (Shireman. Colle and Rottman, 1978).
Leaf protein concentrate prepared from waste sugar cane tops and other leaf
residues has been fed experimentally to carp with success, giving good growth
rates,
However,
leaf protein may contain substances which inhibit protein
digestibility, for example, chlorogenic acid which is found in leaf protein
imubits the attack of proteolytic enzymes like trypsin 0Î chymotryps1n
(Jan,
Hsu and
1977; Ogino, Cowey and Chiou,
1978; Gwiazda, Noguch1, Kltamura
and Saio, 1983).