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Chapter 8
FEEDING SYSTEMS: STRAWS AND AGRO-INDUSTRIAL BYPRODUCTS
8.1 FIBROUS CROP RESIDUES
8.1.1 Factors influencing nutritive value
Introduction
In
many developing countries, and in Asia in particular,
ruminants are fed on straw from cereal crops (mainly rice and wheat). As
population pressure increases and the area devoted to food-crop production
is extended the use of crop residues and byproducts for animal feeding will
increase. In
countries with specialised livestock production
systems, straw is considered of such low feed value that it is often burned,
but in developing countries where livestock are integrated with cropping it
is a valuable resource.
Draught animals appear to be able to work and to maintain
body condition on a diet of mainly straw. Research on the utilisation of
straw by ruminants in developed countries has focused on the role of straw
as a roughage supplement in a concentrate diet. This aspect of the use of
straw is not important in the context of "matching livestock systems to
available resources". The following discussion emphasises the use of straw
as a basal diet and the use of supplements to increase productivity.
The nutritional value of straw (see Sundstol and Owen 1984)
varies according to a number of factors, including:
-
Cereal species (in general, oat, barley, sorghum and
millet straw are often of higher digestibility than wheat and rice
straw) (Table 8.1)
-
Variety and tannin content (see Table 8.2). There is a negative
correlation between tannin content and digestibility (Saini et al 1977)
-
Stage of harvest (eg. wetland rice is often harvested green)
-
Length of storage (which often depends on climate and storage
conditions)
-
Proportion of leaf to stem selected (see Table 6.1 )
-
Fertiliser application and soil fertility
-
Irrigation: straw from irrigated wheat had an in vitro digestibility
of41% compared with 34% for non-irrigated wheat (Kernan et al 1979)
-
Plant diseases
-
Weathering: leaf loss increases with time after removal of the grain
-
Maturity.
|
Table 8.1:
Straws from various cereal crops appear to be highly variable in
organic matter digestibility (in vitro) (OMD). The N content is
always low |
|
Wheat |
28-58 |
0.4-1.0 |
|
Oat |
34-68 |
0.4-1.0 |
|
Rice |
40-52 |
0.5-1.0 |
|
Barley |
34-61 |
0.4-1.0 |
|
Maize |
31-50 |
0.5-1.2 |
|
Sorghum leaves |
65-78 |
0.5-0.8 |
|
Source: Nicholson 1984 |
|
Table 8.2:
In vitro true organic
matter digestibility (True-OMD) and lignin content of sorghum
leaf and stem from 24
varieties grown under
the same conditions. Among leaves, 80% of the variation in
digestibility could be accounted for by the range in lignin
content. Higher lignin content was associated with the presence
of insoluble condensed tannins in the fibre fraction. Variation
in digestibility of both leaf and stem fractions of sorghum
straw is likely to influence productivity of livestock consuming
it and should be taken into account by plant breeders.
|
|
|
True OMD
(in vitro) (%)
|
Lignin (% DM) |
|
|
Mean (range) |
Mean (range) |
|
Leaf |
70 (62-79) |
6.0 (4.7-7.1) |
|
Stem |
65 (53-74) |
6.6 (5.1-9.1) |
|
Source: J D Reed, unpublished
data. |
All cereal straws have two characteristics in common:
There appear to be no toxic substances in straws, except when
they are mouldy. Rice straw, which forms a large proportion of the available
forage in developing countries, contains high levels of oxalate and silica
which are reported to be concentrated in the leaf rather than the stem. The
lignin content of rice straw appears to be less than in other straws.
When straws are fed to ruminants the primary limitations to
production are:
-
The slow rate of, and low total digestibility
-
The rate at which straw particles break down to a size
that can leave the rumen
-
The low-propionate fermentation pattern in the rumen
-
The negligible content of both fermentable N and bypass
protein.
Treatment of straws to increase digestibility
The
productivity of animals fed straw can be increased by treatment of the
straw to increase digestibility and feed intake, especially when combined
with correct supplementation. The use of treated straw with supplements also
allows the use of animals with higher genetic merit (Table 8.3). Methods
for industrial-scale treatment of straw with alkalis (eg. ammonia and
caustic soda) have been available for some time. In the developing countries
the major problem with this approach is to find methods that are both
acceptable and effective at the village level.
|
Table
8.3:
Milk
production and
change
in liveweight
(L Wt) in Zebu
and
Holstein/Zebu
cows in Bangladesh
on basal
diets
of untreated
or
ammoniated
rice
straw
(NH3-straw)
(urea ensiled).
The
native
animals performed
best
on
the
untreated
straw,
but
the
crossbreeds
were
superior
when
the
degradability
of
the straw
was
increased
by ammoniation.
|
|
|
Straw |
NH3straw |
|
Straw
intake
(g/d)
|
|
|
|
Local
|
- |
- |
|
Crossbred
|
5.2 |
10.2 |
|
LWt
change
(g/d)
|
|
|
|
Local |
-87 |
49 |
|
Crossbred
|
-211 |
168 |
|
Milk
yield
(kg/98
days) |
|
|
|
Local |
54 |
204 |
|
Crossbred
|
165 |
255 |
|
Khan and Davis 1981 |
In some European countries, caustic soda has been
used to increase the digestibility of straw for more than 40
years. A number of other techniques are being applied in large
enterprises (eg. ammoniation) but these methods have not been
generally accepted by small farmers. Methods for treating straw
with caustic soda are rarely economic, are difficult to apply
and are hazardous to people and animals. Thus, treating straw
with caustic soda is impracticable in most developing countries.
There are a number of ways in which ammonia can be used to
increase the digestibility of fibrous feeds, including methods that use
ammonia gas, ammonia in solution or ammonia generated from urea (see
Chapters 5 and 12). Ammoniation of straw appears to be potentially
applicable to a wide range of situations. The choice of the method of
ammoniation will depend on the cost and availability of ammonia gas
relative to urea. Ammonia gas lends itself to large operations where there
is the necessary infrastructure for distribution of ammonia in cylinders or
tanks. This may be readily done in oil-rich countries where ammonia gas is
manufactured for agricultural purposes.
For small-scale farmers it is more convenient to generate ammonia
from urea by the "wet-ensiling process" . Urea is a common fertiliser which
is often subsidised and which farmers have become accustomed to
handling. It poses no hazard to human health but farmers are
generally concerned about its possible toxicity to livestock.
Ammonia is generated rapidly from urea at high temperatures when
it is mixed with moist stra w, which makes the system
appropriate for tropical but not temperate countries. A source
of urease may also need to be added for the more inert crop
residues or fibrous byproducts (eg. bagasse; see Torres
et ai.
1982). The ground seed from Jackbean
(Canavalia ensiformis)
is being used commercially for this purpose in Colombia
(Preston 1987). Urea-ensiling appears to be less effective than
using ammonia gas because of the formation of ammonium
carbonate, which decreases the pH of the straw (Mason et
al. 1985).
Ammonia can be generated from other nitrogenous
materials such as chicken manure but these techniques are only
now being developed. The use of animal or human urine to ensile
straw has been researched in Bangladesh (see Davis
et al. 1983) and has
shown promise for application on small farms. It is, however,
essential to ensure an adequate level of urea in the urine.
Several other chemicals can be used to increase
straw digestibility including calcium oxide, acids and acid
gases (sulphur dioxide) or combinations of these. All these
techniques are experimental and have not yet been proved to be
applicable.
One method of treatment to increase the
digestibility of fibrous feeds which appears to have some
applications on an industrial scale is the use of steam at high
pressures. This may be feasible where this energy source is
available and inexpensive (ie. in sugar mills where there is
usually surplus steam). The technique appears to be particularly
appropriate for treatment of bagasse which is available on site
at the sugar mill and where the necessary technical knowledge
and equipment are also available.
Mineral content of straw
The mineral content of straws is generally low
and imbalanced but deficiencies are unlikely to be manifested
in animals at maintenance or working. For production of meat
and milk, requirements for minerals are increased many-fold and
supplements should be supplied. However, responses to mineral
supplements will only occur after the major nutrient imbalances
(protein and glucogenic energy) have been corrected. The mineral
composition of plants depends largely on the availability of
minerals in the soil and closeness to the oceans (for N a).
Calcium and phosphorus contents of straw are usually below
recommended levels and cobalt, copper, sulphur and sodium may
also be deficient. The high concentrations of oxalates and
silicates in rice straw also suggest that considerable amounts
of calcium and magnesium salts can be lost as silicates and
oxalates in urine and faeces.
8.1.2 Draught animals
Draught animals appear to work and survive on a
wide range of fibrous diets and are able to tolerate the low
digestibility of the diet and its low nitrogen content. Working
bullocks in Bangladesh consumed greater quantities of
ammoniated rice straw (ensiled with urea) than their pair mates
given untreated straw but there were no apparent differences in
work output or bodyweight change (Dolberg
et ai.
1981). Further evidence that working animals
require little protein supplementation is the finding that young
horses that were exercised grew at the same rate on a
low-protein diet as those on a highprotein diet that were not
exercised (Orton
et ai.
1985a). Recent work suggests that excessive
protein in a diet can slow the race horse (Glade 1983).
In
Pakistan,
Preston
(personal
observation)
observed
bullocks
driving
a press,
crushing
400kg
of
sugar
cane
per
hour,
working
alternate
shifts
of 3
hours
work followed
by 3 hours
for
feeding
and rest,
and found
that they
were
apparently
able
to
work
on
this
basis
for
24
hours
a day
almost
continuously
for
6
months
on
a
diet
of
only
sugarcane
tops.
In
contrast,
a diet
of
sugarcane
pith
of
higher
digestibility
(70%),
supplemented
with
urea
and minerals
barely
supported
maintenance
in
'growing'
steers
(Preston
et
al.
1976).
The
exclusive
use
of
sugarcane
tops
as
feed
for
working
oxen
is
common
practice
on
sugar
estates
with
a priority
for
employing
people.
Obviously
the
influence
of
exercise
on
nutrient
requirements
is
a
subject
requiring
a
great
deal
of
research
(see
Chapter
2).
8.1.3 Growing animals
Moderate
rates
of liveweight
gain
can
be
obtained
with
young
ruminants
on
diets
based
on
crop
residues
provided
that
a number
of
principles
are
applied.
These
are
discussed
below.
Green forage
A small
quantity
of highly
digestible
green
forage
appears
to
have
beneficial
effects
on rumen
function
on
diets
based
on
crop
residues.
The
results
in Table
8.4
indicate
that
such improvements
in the
rumen
ecosystem
carry
through
to
improved
animal performance.
Azolla
pinnata,
a water
plant which
grows
symbiotically
with the
N-fixing
alga
Anabaena
azolla,
appeared
to
be
even
more
effective
than
a
mixed
concentrate
meal
in promoting
liveweight
gain
in cattle
fed
a diet
of
wheat straw
and sugarcane
tops.
|
Table
8.4:
Small
amounts
of
the
water
plant
Azolla
pinnata
appear
to
be
as
effective
as
a balanced
concentrate
in
improving
the
utilisation
of
a diet
for
cattle
based
on
crop
residues. |
|
|
Concentrate* |
Azolla** |
|
LWt
gain
(g/d)
|
140 |
330 |
|
Feed
intake
(kg
DM/d) |
|
|
|
Wheat
straw+sugarcane
tops |
|
|
|
Supplement |
|
|
|
Total
|
3.6 |
3.0 |
|
Feed
conversion
(kg
DM/kg
gain) |
26 |
9 |
|
OMD
(%)
|
45 |
59 |
|
Source:
Singh
(1980).
1.*Contained:
65%
maize
meal,
15%
rice
bran,
16%
groundnut
cake,
4 %
minerals.
**2.8%
N in
DM;
81
%
digestibility
of
DM.
|
The
advantage of using the
foliages
oflegume
trees
as
"green"
supplements
is that
these
are
rich
in protein
(25
to 30%
in dry
matter),
at
least
part
of
which
appears
to
escape
rumen
fermentation.
According
to
Bamualim
et
al.
(1984)'
leucaena
leaf
meal
was
as
effective
in
stimulating
voluntary
intake
of a low-N
hay as
was
casein
infused
into
the
abomasum.
The
data
in
Table
8.5
and
Figure
8.1
confirm
the
effectiveness
of leucaena
foliage
as
a
supplement
for
cattle
fed
basal
diets
of
rice
straw.
In the
feeding
trial
in Colombia,
which
involved
36
weaner
steers
fed
ad
libitum
ammoniated
rice
straw
for 90 days,
fresh
leucaena
leaves
(2kg/d)
were
as
effective
as
500g/d
ohice
polishings
in stimulating liveweight
gain (from
200g/d
in unsupplemented
animals
to
550g/d
with the
supplements)
(Figure
8.1).
|
Table
8.5:
Leucaena
foliage
(+LF)
increased
dry
matter
intake
and
nitrogen
retention
in
cattle
given
diets
based
on
untreated
or treated
(sodium
hydroxide)
rice
straw
(NaOH-straw).
|
|
|
Untreated straw |
NaOH straw |
|
|
-LF |
+LF |
-LF |
+LF |
|
DM
intake,
kg/d |
5.1 |
6.6 |
3.6 |
3.9 |
|
DM
digestion,
|
38 |
42 |
47 |
48 |
|
N
retention, /d |
-6 |
+7 |
-6 |
+26 |
|
Moran
et
al.
(1983).
24
hours
with
4
% $olution
in
1:1
proportion.
|
 |
|
Figure 8.1:
Development of a cattle feeding system based on
ammoniated rice straw. In phase 1, the basal diet of 6 groups of weaner bulls
was ammoniated straw (ammonia gas); the supplements were rice
polishings at 0, 250 and 500g/d in the presence or absence of
fresh leucaena folzage (2kg/d). In phase
2, the treatments were ammoniated and
untreated rice straw with different levels of rice polishings.
In phase 3, the treatments were
ammoniated and untreated straw, the latter was supplemented with
urea/S (Source: Preston 1987) |
Lucerne
hay
comprising
13%
of
a
diet
based
on
maize
cobs
increased
liveweight
gain of
cattle
by
100%
when
the
basal
diet
was
untreated
and by
50%
when
the
maize
cobs
were
treated
with
ammonia
(Cook
et
al.
1982).
Bypass
nutrients
and glucogenic
compounds
The
role
of
these
nutrients
in
growing
animals
is discussed
in Chapter
4.
The
data
in
Table
8.6
are
from
experiments
in Australia
with
sheep
fed
oat
straw.
|
Table 8.6: Formaldehyde-casein (Formal-C), rapeseed
meal
(RSM) and sunflower
seed
meal
(SFM) (both meals with and without formaldehyde
treatment)
increased
fibre
digestibility,
dry matter
intake,
liveweight
gain and wool growth in sheep
fed
a basal diet
of oat straw. |
|
|
|
Urea
|
Formal-C
|
RSM
|
Formal-RSM
|
SFM
|
Formal-SFM
|
|
DM intake (g/d)
|
1316 |
1779 |
1750 |
1899 |
1909 |
1977 |
|
Digestibility
(%)
|
|
|
|
|
|
|
|
OM |
45 |
50 |
48 |
46 |
48 |
46 |
|
NDF
|
40 |
47 |
45 |
45 |
44 |
45 |
|
LWt
change
(g/d)
|
30 |
132 |
'140 |
144 |
144 |
157 |
|
Wool
growth (g/d)
|
4.5 |
11.0 |
10.5 |
10.1 |
10.1 |
11 |
|
Source:
|
Coombe
(1985).
|
|
|
|
|
|
Figure
8.2
and
Figure
8.3
relate
to
two
feeding
trials
where
the
pattern
of
response
to
the
supplement
was measured.
The
results
from
the
trial
in
Bangladesh
are
particularly
interesting
as
they
show
that a
daily
supplement
of
only
50g
of
fish
meal
to
cattle
tripled
productivity
on
a
diet
of
ammoniated
rice
straw
(Figure
8.3).
 |
| Figure
8.2:
Feed
intake,
wool growth and liveweight
gain of lambs given
barley
straw/urea
and a bypass protein
pellet
(cottonseed
meal
80%,
meat meal
8%,
soya bean
meal
10%,
minerals
2%)
(Source:
Abidin and Kempton
1981) |
 |
| Figure
8.3:
A small
supplement
of
fish
meal
dramatically
Increased
g1'Owth
in
live
and
carcass
weight
in
young
cattle
fed
a
basal
diet
of
ammoniated
(urea-ensiled)
rice
straw
in
Bangladesh
(Source:
saadullah
1984) |
Recent
research
in Thailand
and
Australia
(Table
8.7
and
Table
8.8)
provides
strong
support
for the
concept
that
the
critical
supplementary
nutrients
on a
straw-based
diet
are
bypass
protein,
starch
and long-chain
fatty
acids
(see Table
8.8).
High rates
of
growth
were
obtained
when
the
ammoniated
straw
(urea
ensiling
in Thailand
and
ammonia
gas in
Australia)
was
supplemented
with starch,
protein
and
oil
in byproduct
meals
that
are
known
to escape
rumen
fermentation
(Elliott
et
al.
1978a;
1978b).
|
Table
8.7:
Effects
of
supplementation
of
ammoniated
rice
straw
with
a mixture
of
fat,
protein
and rice
starch.
Young
Brahman
bulls
(36)
weighing
150kg
liveweight
were
used
in
an
experiment
lasting
153
days.
|
|
|
Supplement*, kg/d |
|
|
1 |
2 |
3 |
|
Feed
intake
(kg/d)
|
|
|
|
|
Rice
straw
|
5.81
|
6.22
|
4.35
|
|
Supplement
|
0.87
|
1.74
|
2.62
|
|
Total
|
6.68
|
7.96
|
6.97
|
|
LWt
gain
(kg/d)
|
0.47 |
0.84
|
0.93
|
|
Feed
conversion
|
|
|
|
|
(kg
DM/kg
gain)
|
14 |
9 |
7.5
|
|
Source:
Wanapat
et
al.
(1986).
*The
supplement
contained
rice
bran 65.6%,
broken
rice
22.0%,
soya
bean
meal
10.9%,
bone
meal
0.5%,
$alt
1.0% |
|
Table
8.8:
The effects
of
various levels
of bypass-protein
(largely
cottonseed
meal)
supplement
on the
live
weight
change
of cattle
(320kg
liveweight)
given a diet
of ammonia-treated
or
untreated
rice straw,
O.5kg
molasses/block
(15%
urea)
to
provide
fermentable
N,
and O.6kg
rice
polishmgs
to
supply
small
amounts
of starch
and lipid |
|
Straw preparation
|
Protein
meal)
(kg/d) |
LWt gain
(g/d) |
|
None |
0 |
38 |
|
|
0.4 |
365 |
|
|
0.8 |
292 |
|
|
1.2 |
306 |
|
Treated
with 3% NH3 gas |
0 |
236 |
|
|
0.4 |
497 |
|
|
0.8 |
601 |
|
|
1.2 |
639 |
|
Perdok and Leng
1987 |
The
interaction
between
ammonia
treatment
of straw
and response
to bypass
nutrients
is
illustrated
in
Figure
8.1
which
summarises
the
performance
of steers
fed
on
ammoniated
or
untreated
rice
straw.
During
phase
2 (approximately
260-350kg
liveweight),
there
were
linear
responses
in growth
rate
to
a supplement
of
rice
polishings
on both
ammoniated
and untreated
straw.
However,
2kg/d
of
the
supplement
was
needed
when
untreated
straw
was
given
compared
with
only
500g/d
to support
the
same
rate
of
liveweight
gain
on
ammoniated
straw.
The
interaction
continued
to
be
manifested
during
the
final
finishing
phase
of the
cattle
(350-450kg
liveweight),
when
urea
and
sulphur
were
sprinkled
on
the
untreated
straw.1t
can be
concluded
that ammoniation raised the availability of nutrients
from straw and also led to a more
balanced
array of nutrients to the
cattle
since
lower
levels
of dietary
bypass nutrients
were
needed
to optimise performance.
8.1.4 Long-chain fatty acids
Evidence
which demonstrates
the
benefits
of having a dietary
source
oflong chain fatty acids
in straw-based
diets
is summarised
in Figure
8.4. Lambs fed
ammoniated wheat
straw and minerals
increased
their
growth rate
and feed conversion
in response
to dietary long
chain fatty acids given
in the form of insoluble
calcium soaps (Ca-LCFA).
The response
was
only apparent when
bypass protein
was also given.
Subsequent
work
confirmed
the
interaction
between
LCFA and bypass
protein,
and showed
significant
increases
in carcass fatness
in response
to
the
LCFA
supplement
(given
as long-chain
fatty
acid prills) (van Houtert
and Leng
1987).
 |
|
Figure
8.4:
A supplement
of long-chainfatiy
acids
(as insoluble
calcium
soaps)
increased
the
growth
rate
of
lambs
fed
ammoniated
wheat
straw
and
bypass
protein
(Source:
van
Houtert
and Leng
1986).
|
From
the
discussion
in earlier
chapters
it
is
obvious
that fibrous crop residues
can only
support low milk yields
in ruminants because
of their
inability
to
supply
enough
protein
and glucogenic
energy
to
balance
the VFA
energy.
These
feeds
are
the
most,
and often
the
only,
available
resource
on
many
small farms ill developing
countries.
Therefore
every
attempt
should be made
to use
them as
efficiently
as possible.
Milk synthesis represents
a
greater
drain on critical nutrients
than any other
physiological
state
(Chapter
4).
In
view
of
the
nutritional
limitations
of most
crop
residues,
set
by
low
digestibility
and low
N content,
and the
high
demand
for
amino acids,
long-chain
fatty
acids
and
glucogenic
compounds,
milking
animals
must
be
given
high
priority
for
(i) the
available
supplements
and
(ii)
the
residues
that
have
higher
potential
digestibility
or
that
have
been
treated
to
improve
digestibility.
The
scientific
basis
for
feeding
milking
animals
on crop
residues
is
discussed
in the
following
section.
Effect of ammoniation
Upgrading
the
nutritional
value
of
straws
by
ammoniation
(urea
ensiling)
is
more
likely
to be
economically
justifiable
for
lactating
animals
than
for
animals
in
other
physiological
states.
In
most
circumstances
the
sale
value
of
the
extra
milk
produced
should
more
than
cover
the
cost
of
processing
the
straw.
|
Table
8.9:
Milk yields
and changes
in live
weight
(L Wt) in cattle
and buffaloes
fed
basal diets
of
untreated
and ammoniated
(urea-ensiled)
rice
straw
(NH3-straw) |
|
|
Milk
yield
(kg/d)
|
LWt
change
(g/d)
|
|
|
Straw |
NH3straw
|
Straw |
NH3straw
|
|
Cow1 |
1.1 |
2.3 |
-149 |
+109 |
|
Cow2
|
2.4 (4.6) |
3.4 (4.9) |
-266 |
+93 |
|
Buffalo3 |
2.4 (6.8) |
3.2(7.6) |
-17 |
+93 |
|
Sources:
Khan and Davis
(1981)
1.
All
cows
received
500g
of rice
bran/day
and 200g
of oiL~eed
cake/kg
of
milk.
2. All cows received
1.5kg
of concentrates/day.
3. All
buffaloes
received
1.0
kg of concentrates/
day.
Figures
in brackets
are
milk
fat percentages.
|
The
data
in Table
8.9
summarise
research
from
Bangladesh
and
Sri
Lanka
where
ammoniated
or
untreated
rice
straw
was
the
basis
of
the
diet
for
Zebu
and
buffalo
cows.
The
cattle
responded
significantly
to ammoniation
of
the
straw,
both
in
milk
yield
and
in
liveweight
change.
Ammoniation
of
the
straw
increased
feed
intake,
and
obviously
reduced
the
need
for
bypass
nutrients
since
the
amount
of milk
produced
per
unit of
concentrate
fed
was
increased
by an average
of 53%.
The
proportion
of the
total
diet
represented
by concentrates
was
reduced
from
an average
of
14%
to 9%
due
to increased
intake
of
the
treated
straw
(Table
8.10).
|
Table
8.10:
Ammoniation
of
rice straw
(NH3-straw)
permits
reduction
in
amount
of
concentrate
required
for milk
production |
|
|
Straw |
NH3
straw |
|
Concentrate
(%
diet
DM) |
|
Zebu
x Friesian
|
11 |
8 |
|
Zebu
|
21 |
14 |
|
Buffalo
|
11 |
5 |
|
Milk
produced (kg/kg concentrate) |
|
Zebu
x Friesian
|
1.
7
|
2.7 |
|
Zebu
|
2.8
|
4.2 |
|
Buffalo
|
4.0
|
6.0 |
|
Source:
Preston and Leng 1984 |
Effect
of green
forage
The
effect
of
green
forage,
in
the
form
of gliricidia
leaves
( Gliricidia
sepium),
is illustrated
in Figure
8.5.
On a
diet
of
untreated
straw, feeding
gliricidia foliage
at
approximately
15%
of
the
dietary
dry matter
increased
milk yield
by
22%.
With
ammoniated
straw as the
basal
diet gliricidia
comprised
10%
of
the
diet
and
milk
yield
was
increased
by
14%.
 |
| Figure
8.5:
Supplementation
with fresh
gliricidia
fohage
( G)
or ammoniation
of straw (urea
ensiling)
(TRS)
increased
milk yield
and body weight
gain of buffalo
cows
and
calves fed
a basal
diet
of rice
straw
and 1 kg/day
of concentrate
(RS).
Best
results
were
obtained
when
straw was
treated
with ammonia and supplemented
with gliricidia
foliage
(TRS/G)
(Source:
Perdok
et al.
1982).
|
Bypass nutrients
The
data
in
Figure
8.6
and
Table
8.11
illustrate
the
results
of trials
in
which
responses
to
different
amounts
of protein
supplements
were
measured.
In Bangladesh
there
was
a
linear
increase
in milk
yield
in Zebu
cows
when
fish
meal
was given
as
a
supplement
to
a basal
diet
of ammoniated
rice
straw.
Milk
yield
was
increased
by 23%,
fat
percentage
by
8%
and
liveweight
gain
by
110%
when
1000g of coconut
cake
were
fed
daily
to
lactating
buffaloes
in Sri
Lanka
on
a basal
diet
of
ammoniated
rice
straw
and
minerals.
 |
| Figure
8.6: Milk
yield
of
native
and
crossbred
cattle
fed
ammoniated
(urea-ensiled)
rice straw
in Bangladesh
was
increased
linearly
with.
small
amounts
of
fish.
meal
(0
to
400g/d)
(Saadullah
1984).
|
|
Table
8.11:
Supplementing
ammoniated
(urea
ensiled)
rice straw
with.
coconut
cake
increased
the
milk
yield
and
liveweight
gain
of
buffaloes
in S7'i
Lanka.
|
|
|
Coconut cake, kg/d |
|
|
0 |
1 |
|
Milk
yield
(kg/d) |
2.6 |
3.2 |
|
Fat
(%)
|
9.1 |
9.8 |
|
LW
gain (kg/d) |
0.1 |
0.21 |
|
Source: H Perdok, Unpublished data |
8.1.6 Wool growth
The
effects
of
strategic
supplementation
on
wool
growth
in
sheep
are
illustrated
in Figure
8.7.
Wool
growth
was
increased
when
either
a
protein
meal
(cottonseed
cake)
or
a readily-digestible
forage
(lucerne
hay)
was
the
supplement
in
a wheat-straw
diet
provided
with
fermentable
N
by
adding
urea
or
by
ammoniation
of
the
straw.
 |
| Figure
8.7:
Supplements
that
provided
rumen
"activators"
(lucerne
hay)
and/or
bypass
protein
(cottonseed
meal)
increased
the wool
g1'Owth
of sheep
fed
a basal
diet
of wheat
straw
that had been
sprayed
with urea
or ammoniated.
There
were
additional
benefits
when
the
sheep
were defaunated
(Source:
S H Bird,
B Romulo
and R
A Leng,
unpublished
data.)
|
The
combination
of
the
two
supplements
gave
the
best
results.
Responses
were
more
marked
when
the
straw
digestibility
was
increased
by
ammoniation
and when
the sheep
were
defaunated.
The
data presented
previously
(Figure
8.2)
suggest
that
the
optimal
wool
growth
response
in
growing
lambs
fed
a barley
straw/urea
basal
diet
occurred
when
the
protein
meal
(80%
cottonseed
meal,
10%
soya
bean
meal,
8%
meat
meal
and
2%
minerals)
comprised
about
30%
of
the
diet
dry
matter.
8.1.
7 Metabolic
disorders
associated
with ammoniation of feeds
Adding
ammonia
to
ruminant
feeds
to
provide
fermentable
N has
been researched
for
a number
of
years.
In
early
trials,
ammoniation
of molasses
was
highly
detrimental
because
the
ammonia
gas reacted
with
the
sugars,
increasing
the
temperature
and
apparently
resulting
in
formation
of
toxic
methyl
imidazole
compounds
which
induced
a severe
nervous
disorder
(Tillman
et
al.
1957,
Bartlett
and Broster
1958)
.
In
countries
with
a temperate
climate,
ammoniation
of
straw
(to
increase
digestibility)
requires
3-6
weeks
(versus
10
days
or less
in
the
tropics)
because
of
low
ambient
temperatures.
In
order
to
reduce
the
treatment
time,
methods
have
been
developed
in which
the
straw
is
heated.
Large
ovens
are
manufactured
in
Europe
to
treat
several
tonnes
of
straw at
90°C,
allowing
the
treatment
time
to be
reduced
to
one
day.
This
practice
has
been
commercialised
in Europe
and ammoniated
straws
have
been
fed
to
livestock
with
no
reported
ill-effects
(H Sundstol,
personal
communication).
However,
ammoniated
hays caused
bovine
hysteria
when
fed
to cattle
(for
review
see
LaBore
et
al.
1984).
The
problem
also occurs
occasionally
with
ammoniated
straw.
This
effect
may
be
related
to the
proportion
of
the
treated
forage
or
straw
in the
animal's
diet,
since
recent
research
in Australia
(with one
batch of rice
straw
and one
of w heat
straw) indicated
that bovine
hysteria
developed
whenever
the
treated
straw
comprised
a
large
proportion
(70-80%)
of the
diet
(Perdok
and Leng
1985,
1987).
In
studies
by
Perdok
and
Leng
(1985,
1987),
in
which
64 yearling
cattle
were
given
thermoammoniated
rice straw
from
a
failed
crop,
almost
all
the
animals
developed
hyperexcitability,
with the
following
symptoms: animals
were
restless
and blinked
rapidly, their
pupils
dilated
and
their
vision
was
apparently
impaired;
involuntary
twitching,
trembling,
loss of
balance
and
frequent
urination
and defecation
were observed.
In addition,
respiration
rate was
high,
heart
rate
was
low
and
the
animals
salivated
copiously;
they bellowed
and perspired.
The
most
obvious
and most
dangerous
symptom was sudden
stampeding:
the
cattle
galloped
in circles,
were
inclined
to collide
with
each
other
and
also
to run into
fences.
Often
the
animals galloped at
such
speed
that
they
broke
limbs,
and in one
instance
an animal
died.
The
symptoms
usually
lasted for
5
minutes and were
repeated
at 20- to
30-minute
intervals. The
affected
animals
appeared
normal between
these
attacks and tended
to
return
to
feed
on the
treated
straw.
The
condition
was also
induced
in animals
fed
the same
rice
straw
after
it
had been
treated
with ammonia
under
plastic
sheets
for
4 weeks
(Perdok
and Leng
1987).
The
syndrome
has
occurred
also
in
young
calves
suckled
by cows
consuming
a diet
containing
a major proportion of
ammoniated
rice
straw:
both cows
and calves
showed
symptoms.
Pasteurised
milk
from
these
cows also
caused
the
hysteria
when
fed
to calves.
Under some
circumstances
calves suckled
by
cows
fed
ammoniated
hays
have
died.
These
observations
indicate
that
the
toxic compound(s)
is transmitted
in milk
and is unaffected
by
pasteurisation
(Perdok
and
Leng
1987).
Bovine
hysteria
in
cattle
fed
straw
has
not so
far been
reported
from
Northern
Europe,
possibly
because
the
proportion
of
ammoniated
straw fed
rarely
exceeds
30%
of
the total
diet
in intensive
livestock
feeding
systems.
A recent
report
from Southern
Spain
(Cabrera
et
al.
(1987)
has,
however,
shown
that
in warm climates
feeding
ammoniated
straw
to
cattle
and
sheep
can
be extremely
dangerous.
Cabrera
et
al.
(1987)
reported
numerous
cases
of hyperexcitability
and death
in sheep
and
cattle
fed
straw
when
this
was initially
treated
with
ammonia
gas after
1100
hours
and
on
a
warm day
in
summer.
Ammoniation
through
urea
ensiling
is highly
unlikely
to
result
in toxic
compounds
being produced,
particularly
if the
moisture
content
of the
straw
is
kept
high.
It is
advisable,
however,
always
to prepare
straw
when
the
temperature
is
low.
The
transmission
of
toxic
compounds
in
milk
from cows
fed
ammoniated
forages
suggests
that
care
should
be
taken
in
feeding
ammoniated
forages
to
milking
animals.
8.2 FIBROUS AGRO-INDUSTRIAL BYPRODUCTS
There are a number of fibrous residues that, untreated, have
only limited application as the basal component in livestock feeds (eg.
bagasse, palmpressed fibre, cocoa pods and rice hulls). The limitation to
all these feed resources is their extremely low digestibility and, even when
supplemented with essential nutrients, intake is too low to support
maintenance. They are, however, often used as fillers and sources of
roughage in high-concentrate diets.
Most of these residues arise from industrial processing and
are therefore available in large quantities at the factory site. The
concentration of these byproducts at the factories is an incentive to
finding ways to use them as ruminant feeds by using 'relatively
sophisticated' technology to increase their digestibility. Techniques such
as briquetting, steam treatment and ammoniation can be considered under
these circumstances.
The factories where these residues are produced usually have
the infrastructure necessary to enable adequate servicing of the machinery
that is normally required for any large-scale industrial treatment of a
fibrous residue. Often the residue is used as fuel in the factory (eg.
bagasse, palm-pressed fibre and peanut hulls), but frequently there are
surpluses. Little research has been done on these residues, with the
exception of steam-treated bagasse which is now being used commercially in
diets for cattle in both Brazil (E L Caielli, personal communication) and
Colombia (Preston 1987).
Some of the original research on steam treatment of sugarcane
bagasse was done in Mauritius (Wong et al. 1974). Treating the bagasse
with high pressure (14kg/cm2) steam for 5 minutes raised dry
matter digestibility from 28 to 60% (rumen nylon bag method; 48 hr
incubation). Early attempts to use the treated bagasse as the basis of the
diet for growing cattle focussed attention on the need to supplement with
bypass protein (fish meal), LCFA and glucogenic precursors (maize grain)
(Table 8.12).
|
Table
8.12:
Calves
lose
weight
on
a diet
of
steam-hydrolysed
bagasse
(200°C
for
10
minutes)
supplemented
with
only
urea
and minerals.
Significant
improvements
in growth
and feed
conversion
wr'e
brought
about
when
fish
meal
(bypass
protein)
and/or
maize
grain
(glucogenic
energy
and oil) were
added
to the
diet.
|
|
|
Control |
Fish
meal
(0.25kg/d)
|
Maize
meal
( 1kg/d) |
Fish
meal
+ maize
(0.25kg+1kg/d)
|
|
Bagasse
intake
(kg DM/d) |
4.0 |
4.4 |
4.5 |
4.5 |
|
LW
change (kg/d) |
-0.17 |
+0.08 |
+0.16 |
+0.33 |
|
Feed conversion (kg DM/kg
gain) |
- |
34 |
23 |
12 |
|
Source: Naidoo et al 1977 |
The data in Figure 8.8 show how the commercial feeding system
was developed in Colombia, starting from the premise that the treated
bagasse should contribute the major part of the diet and that locally
available supplements should be used. The diet which gave the best results
(810g/d of liveweight gain), and which was chosen for the commercial programme, contained (%
dry matter basis): 53 steamed bagasse, 16 final molasses, 2 urea, 15
gliricidia foliage, 6 poultry litter, 7 rice polishings and 1 salt.
 |
|
Figure
8.8:
Development
of
a
cattle
feeding
system
based
on
hydrolysed
cane
bagasse
(steam
at
14kg/cm2
for 5
minutes).
The
same
8
groups
of animals
(weaned
bulls
of 180kg
initial
liveweight)
were
used
throughout
the
twelve
month
trial.
In
phases
1 and
2,
the
basal
diet
was
treated
bagasse
pith
supplemented
daily
with molasses/urea
(10%
urea),
gliricidia
foliage
(2%
of
liveweight
daily)
and
poultry
litter
(0.2%
of liveweight).
The
variable
was the
presence
or absence
of rice
polishings
(0.2%
of
liveweight,
RP).
In phase
3 the
treatments
were
untreated
bagasse
and
bagasse
pith,
with or
without the
rice
polishings.
In
phase
4 the
effect
of additional long fibre
was
studied
(from
African
Star grass
S G)
with the
basal
diet
using
treated
bagasse
and
with the
addition
of rice
polishings.
In phase
5, all
the
animals
were
given
the
best
diet
based
on
the
results
obtained
in
the
previous
phases
(Source:
Preston
1987). |
The
molasses was used
as a carrier
for urea
and also provided
trace elements;
gliricidia foliage
was the
source of fibre,
vitamin A and some
fermentable
and bypass protein;
poultry
litter provided
fermentable N and macro
(Ca, P, S) and micro (Cu,
Co,
Zn
etc)
minerals
and rice
polishings
was the
source
of nutrients
which improved the balance of amino acids and glucose
available in the
total nutrients absorbed and
this
increased
the
efficiency
of feed utilisation.
The
lipid
content of rice polishings was expected to be used
highly
efficiently
in this otherwise
low fat diet.
8.3
FRESHLY
HARVESTED
GRASSES
Elephant
(or
Napier
or King) grass (Pennisetum
purpureum),
guinea grass
(Panicum
maximum) and sugarcane
(Saccharum
officina
rum ) are among
the
highest
yielding
perennial
crops,
in terms of total
biomass production
per unit
area and
efficiency
of solar
energy capture.
Pennisetum
species
and
sugarcane
are
used
widely in the American
tropics as a reserve
crop ("ensilaje
vivo") for feeding
during the
dry season. Sugarcane
has the advantage
that its energy value
as feed increases
as it matures,
since
the
accumulation
of sucrose
more than compensates for
the increasing
lignification
of the
cell wall.
The
"stress"
of the dry season
(low soil moisture,
low
soil
N and [generally]
lower
air temperatures)
also stimulates
the storage of sucrose
in
the stem.
Pennisetum
yields
most
biomass
when it is harvested
at 6-month intervals
(Figure
8.9),
although it
is well
understood that
nutritive
value is highest when
harvesting is
over
shorter
intervals
(about
6 weeks). On the
farm, it is
difficult to
maintain
the
rigorous practice
of fertiliser
application,
irrigation
and
frequent
cutting and as a result the
N content and dry
matter
digestibility of
the
infrequently
harvested
forage
are
low.
 |
|
Figure
8.9:
Annual
biomass yields
from
sugar
cane
and
elephant.
grass
harvested
at different
intervals
(Source:
Alexander
et
al.
1979) |
Early
work with these
forages
emphasised
their
use
as "roughage"
supplements
in concentrate
diets for intensively
managed (usually
confined)
milking and fattening
cattle
and buffaloes.
This policy predicated
against the
efficient use of
these feed
resources
since the
drop in rumen pH when cereal
grain is fed
depresses
the
digestion
of fibre
(see
0rskov
and Frazer 1975).
In the following section examples are given of recent research in
which these forages have been the basis of the diet and have been
strategically supplemented.
8.3.1 Legume forages
In Costa Rica , lactating goats were fed a basal diet of King grass (Pennisetum
purpureum) supplemented with a fixed allowance of green banana fruit and
increasing amounts of the leaves of the legume tree Erythrina
poeppigiana. Total dry matter intake and milk production increased
linearly with legume supplementation (Figure 8.10). There was only a
minimal substitution of the King grass in the diet (intake fell from 690 to
600g dry matter / day).
 |
|
Figure
8.10:
Effect
on dry matter
intake
and
milk yield
of goats
of
supplementing
their
basal diet
of
King
grass
and banana
fruit
with foliage
of
Erythrina
poeppigiana
(Preston
1987).
|
In research in Colombia the foliage of the legume tree,
Gliricidia sepium, was given as a supplement to weaned steers fed a
basal diet of freshly harvested King grass during the dry season (Figure
8.11). Growth rate increased curvilinearly in response to increasing levels
of the legume foliage, with the optimum legume content of the diet being
about 30%.
 |
|
Figure
8.11:
Effect
of
increasing
levels
of
gliricidia
foliage
on
the
growth
rate
of weaned
bulls
(initial
weight
180kg;
4 animals
per
group) given
a
basal
diet
of King
grass
(Source:
ILCA
1986/87,
cited
by Preston
1987) |
Similar effects have been reported with West African Dwarf goats in Nigeria
fed combinations of Guinea grass (
Panicum maximum) and gliricidia (M.
van Houtert, personal communication).
Table
8.13:
Effect
of supplements
of
leaves
from
Gliricidia
maculata
on
performance
of
gl'owing
sheep
fed
a basal
diet
of
Brachiaria
mileformis.
Feeding
a supplement
of
gliricidia
to growing
sheep
on a basal
diet
of freshly
harvested
Brachiaria
multiformis
gave
a significant
response
in
bodyweight
gain
and
in wool
growth
when
the
legume
comprised
up
to 28%
of
the diet
(Table
8.13).
|
Table
8.13:
Effect
of
supplements
of leaves
from
Gliricidia
maculata
on
performance
of growing
sheep
fed
a basal
diet
of
Brachiaria
mileformis.
|
|
|
% Gliricidia in diet (DM basis) |
|
|
0 |
28 |
50 |
65 |
|
LW gain, g/d |
25 |
43 |
44 |
39 |
|
DM intake,
g/d |
530 |
610 |
690 |
690
|
|
DM conversion |
21 |
14 |
16 |
18 |
|
Carcass, kg |
10 |
12 |
12 |
12 |
|
Clean fleece, g |
280 |
350 |
320 |
360 |
|
Staple length,
cm |
4.3 |
4.7 |
5.4 |
5.5 |
|
Source: Kantharayu and Chadhakar 1981 |
Results
of studies
with
milking
cows
fed
diets
based
on
freshly
harvested
Setaria
grass
and
given
a
range
of
supplements
are
shown
in Table
8.14.
The
most
appropriate
supplement
was
groundnut
cake
since
it
maintained
body
weight and supported
the same
levels
of
milk production
in
cows
as
cereal
grain
or
molasses-based
supplements
fed
at twice
the
rate.
The
implication
is
that the
principal
deficiency
in
the
absorbed
nutrients
was
amino
acids
and this
was
effectively
corrected
by
the
ground
nut supplement,
which
provided
bypass
protein.
|
Table
8.14:
Effects
of
supplements
based
on
molasses,
cereal
brans/oil
cake or
groundnut
cake
on
milk
yield
and
liveweight
change
of
Friesian
cows
given
a basal
diet
of
freshly
harvested
grass
(Setaria
kazangula)
ad libitum. |
|
|
No suppl. |
Cereal/oil cake |
Molasses/urea |
Groundnut cake |
|
Milk yield, kg/d* |
6.1 |
7.6 |
6.8 |
7.9 |
|
LW change, kg/d |
-0.72 |
0.0 |
-0.83 |
0.13 |
|
Mapoon et al 1977
*Corrected for milk yield on standard diet before and after the
experimental period |
8.4 Sugar cane
Growing
sugarcane,
more
than
any
other
crop,
maximises
the
yield
of
biomass
per unit
area.
Sugarcane
is an ideal
crop
to optimise
biomass
utilisation
because:
-
Its
C-4
pathway
for
photosynthesis
confers
both high-yield
potential
and
efficient
capture
of
solar
energy
-
The
requirements
of the
large-scale
sugar
industry
have
promoted
agronomic
characteristics
in the
plant
which
facilitate
fractionation
-
Its perennial
growth
habit
and
disease
resistance
aid maintenance
of soil
fertility
and
reduce
soil
erosion,
allowing
monocultural
practices with
only
minimal
use of
inputs derived
from fossil
fuels.
There
are
a number
of
sugarcane byproducts
that
can be
used
in animal
feeds.
Details
of the
two
principal
methods
of
extracting
sucrose
from
sugarcane
and the
associated
crop
residues
and resultant
byproducts
are
outlined
in Figure
8.12.
Of
the
two
extraction
processes,
the
industrial
technology
produces
the
most
byproducts,
the
principal
one
being
molasses.
In
the
artisan
(small-scale)
system for
production
of "Gur"
(Indian
continent)
or
"Panela"
(Latin
America)
there
is
no centrifugation
and
therefore
no
final
molasses.
 |
|
Figure 8.12:
Residues
and byproducts from the
manufacture
of
sugar by
"factor'y"
and
"artisan"
methods.
Numbers
in brackets
indicate
approximate
quantities
(fresh
basis)
relative
to
cane
stalk = 100.
I
Source:
Preston
1983a).
|
8.4.2 Whole sugar cane
Urea supplementation
In
all
the
trials
discussed
here,
urea
was
added
to the
sugarcane
at
levels
that
would
satisfy
the
needs
of
the
rumen
micro-organisms
for
fermentable
nitrogen
(approximately
3% of the
dry
matter
of the
diet).
The
optimum level
was
validated
in an experiment
in which
urea
concentrations
were
varied
from
zero
to 4%
of the
sugarcane
dry
matter.
All
cattle
were
supplemented
with rice
polishings
(l kg/day)
and
minerals
(Figure
8.13). All
the
parameters
of
animal
performance
increased
curvilinearly
with
increasing
urea
in the
diet.
 |
| Figure 8.13. The relationship between the level of
urea in the diet and live weight gain, feed intake and feed
conversion of cattle a diet of sugar cane and 1 kg/d of rice
polishings (Alvarez and Preston 1976b) |
When
rice
polishings
were
absent from
the
diet,
sugarcane
intake
remained
low
and
the
animals lost
weight
irrespective
of urea
level;
the
only
positive
response
was in digestibility
(Ferreiro
et
al.
1977).
Cattle
growth rates
and feed
conversions
were
similar
when
a urea
solution
was sprayed
on
to the
cane
(as an aqueous
solution
or
in dilute
molasses),
or
was given
in a separate
feeder
as concentrated
(10%)
solution
in molasses.
Foliage from
food crops and legume trees
Cassava
tops
and leucaena
forage
given
as supplements
to cattle
fed
ad libitum chopped
whole
sugarcane
plus
urea,
increased
the cattle's
voluntary
intake
of the
total
diet
but
reduced
the
intake
of
sugarcane
(Meyreles
et al.
1977; Hulman
and Preston
1981); improvements
in
growth
rate
were
small
(from
-40
to +140g/day
with cassava as the
principal
supplement;
and from
60 to 200g/day
when
leucaena
was
fed).
A
supplement
of
sweet-potato
foliage
added
to a basal diet of
chopped
sugarcane
and urea
did not depress
intake
of the
cane and increased
total
dry matter
consumption
by 34%
(Meyreles and
Preston
1978a).
Liveweight
gain
was not
measured
in
this
trial
but
significant
improvements
in liveweight
gain
of cat tIe
were
observed
when
this
forage
was added
to a ration of derinded
cane
stalk (cane
pith) (see
Figure
8.18)
This
indicates
that
the
foliage
of sweet-potato
is one of
the
most
suitable
"protein-rich"
forages to
use
with
sugarcane.
The
reason
may
be its higher
rate of
degradability
in the
rumen
compared
with either
cassava
or leucaena
forage
(Santana
and Hovell 1979a,
b),
which
results
in a low rumen
"load"
while
at the
same time
it stimulates
rumen
function.
Fresh
banana
leaves,
which are
only
slowly
digested
in the
rumen,
were
particularly
unsuitable
as
a supplement
as
they
reduced
the
intake
of sugarcane
and resulted
in a lower
total
dry-matter
intake (Meyreles
and Preston
1978b).
A comprehensive
series
of
experiments
with sugarcane
as
a basal
feed
for cattle
was carried
out in Mexico
and the
Dominican
Republic
with
the aim of understanding
the
constraints associated
with feeding
this
crop
as the basis of the
diet
for
growing/fattening
and lactating
cattle
(Preston
and Leng
1978a,b).
The supplement
that
promoted
the
highest
level
of
productivity
was rice
polishings
given
at a
level
of
1015%
of
the
diet
dry
matter
(Figure
8.14
and
Figure
8.15).
Similar
conclusions
were
reported
by Creek
et al.
(1976),
who
fed
diets
of
59%
sugarcane
(drymatter
basis)
supplemented
with rice
polishings
and
cottonseed
meal
to
Boran
(Zebu)
cattle in Kenya.
 |
| Figure
8.14:
Effects
of
supplementation
with
rice
polishings
(which
supplies
bypass
protein,
bypass
starch
and oil)
on growth
rates
of Zebu
bulls
in Mexico
fattened
on basal
diets
of whole
sugarcane
which
has
been
chopped
or
derinded
by the
"Tilby"
separator
process
(Source: Preston
et al.
1976).
|
 |
| Figure
8.15:
Effect
of level
of
rice
polishings
supplementation
on
performance
of
cattle
given
free
access
to chopped
sugar'cane
and molasses
containing
10%
Urea
(Lopez
et al.
1976).
|
Rice
polishings
are
relatively
rich
in protein(amino
acids),
lipid and
starch,
which
are
the
critical
nutrients
that
need to
be
adsorbed
where
the
basal
feed
is
digested
solely
by rumen
fermentation.
Experiments
with
cattle
fitted
with
duodenal
cannulae
showed
that
the
greater
part of
the
starch
(broken
grain)
in the
rice
polishings
bypassed
rumen
fermentation
(Elliott et
al.
1978a);
the
amounts
of
microbial
and dietary
non-ammonia
nitrogen
arriving
at
the
duodenum
also
increased
in direct
proportion
to the
amount
of
rice
polishings
in
the
diet
(Elliott
et
al.
1978b)
indicating
that
rumen
bacterial
growth
was stimulated
and
also
that
protein
in
rice
polishings
was protected
from
rumen
fermentation.
The
development
of
a
sugarcane-based
feeding
system
for
dual purpose
(Brown
Swiss
x Zebu)
cows
and their
calves
was
described
by
Alvarez
and Preston
(1976b)
and Alvarez
et
al.
(1977,
1978).
Best
results
were
obtained
with
combined
supplementation
of
500g
of rice
polishings
per
day
and
restricted
grazing
(3 hours/day)
on
a
leucaena
"protein
bank"
(Alvarez
et
al.
1978).
Complete
substitution
of leucaena
for
the
rice
polishings
led
to
lower
milk
yields
and
loss
of
bodyweight
in the
cows
which
was attributed
to
mimosine toxicity
(Alvarez
and
Preston
1976a)
but
may
have
been
also
a result
of
a
lower
fat
intake.
Sugarcane
tops
are
the
traditional
feed
for
draught
animals
(cattle,
buffaloes
and mules)
employed
in the
harvesting
of cane
and
its
transport
to the
sugar mill
(see
Table
8.15).
The
utilisation
of
cane
tops by working
animals
has
apparently
not
been
studied.
Cattle
appear
to maintain
bodyweight
while
carrying
out
quite
arduous
work
on
a
diet
of only
sugarcane
tops.
It
appears
that
fermentative
digestion
of
cane
tops in the
rumen
provides
an
adequate
balance
of
nutrients
for
maintaining
bodyweight
when
the energy
(acetate)
available
(relative
to
protein)
is
reduced
by
work
(see
Chapter
4).
Implicit
in
this
statement
is
the
concept
that
work
increases
feed
intake.
|
Table
8.15:
Composition
of
sugarcane
tops
and
of the
rind
and pith
fractions
produced
by
the
"Tilby"
process.
|
|
|
Pith
|
Rind
|
|
|
Dry
matter
(DM)
(%)
|
22
|
39 |
27
|
|
Composition
(%
DM)
|
|
|
|
|
Protein
(N x
6.25)
|
1.4
|
3.2
|
2.7 |
|
Ether
extract
|
0.2
|
1.0
|
0.8 |
|
Total
sugars
|
46
|
24 |
27
|
|
Fibre
|
45
|
70
|
57 |
|
Ash
|
1.9
|
3.1 |
5.3
|
|
Sulphur
|
0.2
|
0.3 |
0.4
|
|
Source:
Ministry
of
Agriculture,
Mauritius
|
The
apparent
high
nutritive
value
of
cane
tops
for
draught
animals
contrasts
with
their
inability
to
support
growth
in
young
animals
without
supplementation.
The
data
summarised
in Figure
8.16
show
that
cane
tops
support
high
growth
rates
of cattle
only
when
appropriately
supplemented.
Growing
Zebu
steers
given
a
basal
diet
of chopped
sugarcane
tops
grew
at almost
700g daily
when
this
feed
was supplemented
with
urea
and
1kg
of
rice
polishings
per
day.
Liveweight
gain
was
the
same
on
chopped
cane
tops as
on
chopped
cane
stalk.
However,
feed
utilisation
efficiency
was
higher
on
the cane
stalk,
apparently
because
of its higher
content
of
solu
ble
sugars,
which
could
have led to a larger
proportion
of
propionate
in the
rumen
VFAs (see
Chapter
4).
 |
| Figure
8.16:
In a fattening
diet
f01'
cattle,
increasing
the
proportion
of
cane
tops
(replacing
chopped
cane
stalk) led
to
increases
in feed
intake
and liveweight
gain
but a
deterioration
in feed
conversion
efficiency.
The
basal
diet
was supplemented
with urea
and
1
kg
of
rice
polishings/day.
Source:
Ferreiro
and Pre-ston
1976) |
The
constraints
to
the
wider
use
of
sugarcane
tops
in livestock
feeding
are
the
economics
of harvesting
and transporting
the
voluminous
material.
Traditionally,
sugarcane
tops
have
been
collected
by
smallholder
farmers
using
draught
animals,
and
even
as "head
loads".
The
increasing
practice
of
burning
the
cane
prior
to
mechanical,
and
even
hand harvesting
has
reduced
considerably
the
quantity
of cane
tops
available.
Cane
tops are
one
of the
most
under-utilised
resources
even
in those
countries
in which shortages
of
animal
feed
and
of
fuel
are
most
evident.
When
they
are
fed
to
livestock,
however,
they
have
generally
been
used
inefficiently
because
of
the
lack
of
knowledge
of
the
need
for
"key"
supplements.
If
they
could be
treated
safely
(and
economically)
to
increase
fibre
digestibility
this
would
improve
their
feeding
value.
Urea-ensiling
has
been
effective
in this respec.t
(A.
Boodo,
unpublished).
In
the
late
1960s
a technology
(Tilby
Separator
Process-Figure
8.17)
was developed
for separating
the
cane
rind from
the
pith.
The
aim
was to
use
the
cane
rind in
the
manufacture
of compressed
boards
which
could
substitute
for
plywoods
that are
usually
imported
into
tropical
countries.
The
residual
pith was
to be
used
for
sugar
extraction
or
alcohol
production
or
as a
feed
for livestock.
 |
| Figure
8.17:
Simplified
diagram of
the
Tilby
separator
process
for
derinding
sugarcane.
(Source:
Lipinsky
and Kresovich
1982).
|
In
early
experiments
carried
out
by
Donefer
and
his colleagues
in Barbados
(see
Pigden
1972),
high
rates
of growth
were
observed
in cattle
fed
sugarcane
pith
when
it
was
supplemented
with
chopped
cane
tops
and
a concentrate
containing
an oilseed
meal
and urea.
Unfortunately,
these
promising
developments
have
not
led to commercial
application.
The
main limitation
is the
need
for
sophisticated
and expensive
machinery,
necessitating
a large-scale
plant for
economic
viability.
A factory
producing
compressed
board
would
need
a
production
capacity
of about
30 tonnes
of
board
per
day,
requiring
the
processing
of
400
tonnes
of
sugarcane
stalks.
This would
produce about
300
tonnes
of pith per
day-enough
to
feed
15,000
head of
cattle
..
While
this
size
of unit is
not
unusual
by
feedlot
standards
in the
USA,
it
is
quite
impractical
for
most
developing
countries,
where
the
use
of sugarcane
as an
animal
feed
has
most
potential.
A second
constraint
which
emerged
from
research
in
Mexico
(Preston
et
al.
1976)
was
the
realisation
that,
as
a feed
for
cattle,
the
pith was
little
better
than
the
chopped
whole
sugarcane
plant
when
both
were
adequately
supplemented,
even
though
sugarcane
pith
contains
a higher
concentration
of
soluble
sugars
than
chopped
whole
cane
(Table
8.15) and
thus
has
a potentially
greater
feed
value.
In fact
when
it was
supplemented
with
rice
polishings
(providing
bypass
protein,
starch
and oil)
at low
levels,
the whole
sugarcane
supported
higher
growth
rates
than the
derinded
stalk.
Only
at the
highest
level
of
supplementation
was there
an indication
that
animal productivity
was
higher
on
a basal
diet
of pith.
Nevertheless,
differences
were
relatively
small (Figure
8.15).
These
data
indicate
that
it
is
the
composition
of
the
supplement
which determines
animal productivity
rather
than minor
variations
in the
ratio
of
sugar
to
fibre
in
the
basal diet.
Meyreles
et
al.
(1979)
demonstrated
that there
is
potential
for
exploiting
the
higher
energy
value
of the
pith by rational
supplementation
(Figure 8.18).
In the
absence
of supplements
other
than
urea
and minerals,
animals did not
grow
on
a
diet
of sugarcane
pith. When
green
foliage
of
sweet
potato
was added
to
the
diet,
however,
growth rate
increased
to
about
500g/day
and there
was
a significant
response
to high levels
of urea
(400 to
600g/
day).
This can
be
interpreted
as
indicating
an increase
in microbial growth
in response
to an improved
rumen
microbial
ecosystem,
which.
may be
due
to the
supply
of
both readily
digestible,fibre
and
essential
nutrients
for
micro-organisms
(eg.amino acids,
peptides,
minerals
and, perhaps,
vitamins):
Supplementation
with cottonseed
meal
gave a similar growth response,
but apparently
without
stimulating rumen
function
because
feeding
the
higher
level
of
urea
had no
effect
on growth
rate.
The
combination
of these
supplements
was additive
and feeding
the
high
level
of urea appeared
to
stimulate
rumen
microbial
growth,
as indicated
by
the
60%
increase
in growth
rate
(Figure
8.18).
 |
|
Figure
8.21:
In
a cattle
fattening
diet
based
on ad
libitum
molasses,
sugarcane
tops
and
wheat
bran
(1
kg/d),
urea
was a more
effective
source
of
fermentable-N
than
poultry
litter'.
Poultry
litter
stimulated
growth
rate
when
added
to the
diet
(with
Urea),
which
was
appar'ently
adequate
in
fermentable-N
(Sourcee:
Meyreles
and
Preston
1982). |
Despite
the
possible
advantages
of using
sugarcane
pith rather
than
whole-cane,
in
some instances,
the
technology
needed
for
chopping
the
whole
sugarcane
plant is simpler
and
much
less
sensitive
to
economies
of scale
than
the
derinding
process.
Chopping
is
therefore
the
preferred
system
for processing
sugarcane
as a ruminant
feed
in
developing
countries.
8.4.5 Final molasses
Alternative
uses
of
molasses
as animal
feed
or
for power
ethanol
Molasses
is
the
only
"concentrated"
source
of fermentable
carbohydrate
that
is
widely
available
in the
tropics
and
which is not
a staple of the
human
diet.
Its
importance
as
a
livestock
feed
is
indicated
by
the
ways
in which
it can
be
used:
-
As a carrier
for urea, minerals
and other nutrients
for improving
the efficiency
of utilisation of low-N
diets (eg. crop residues,
sugarcane
and agro-industrial
bypro ducts )
-
As a strategic
drought feed
reserve
and as the
basis
of a supplement for routine
feeding
during the
dry
season.
Molasses
is
traditionally
used
to
manufacture
potable
alcohol
(eg. rum).
However,
since the oil
crisis enormous
efforts
have
been
made
to develop
production
of industrial
alcohol,
especially
as a substitute
for gasoline
(power-alcohol).
The
lack
of
technical
knowledge
of how
to
use
molasses
efficiently
in
livestock
feeds
has resulted
in much molasses
being
discarded.
Often
molasses
accumulates
in
the
storage
tanks
at the sugar
mills
and is discarded into
rivers.
Its opportunity
cost
is thus very
low,
which has been
a principal
argument
for its
use
in power-ethanol
production.
However,
the
recent
developments
in
the
use
of molasses
in
livestock
feeding
have
given
profitable
alternatives
that
are vastly
superior
economically
to the production
of power
alcohol
(Table
8.16).
|
Table
8.16:
Molasses
may have
a higher
economic
value
when
used
as an animal feed
than when
it is
converted
into power alcohol |
|
|
Opportunity
cost $/t |
Assumption |
|
Survival feeding
of
cattle in drought |
540 |
1 |
|
Substitute
for
cereals |
150 |
2 |
|
Fattening
cattle |
92 |
3 |
|
Supplementing
crop
residues/dry
pastures
for:
|
|
Milk production |
440 |
4 |
|
Prevent
body
weight
loss |
47 |
5 |
|
Power
alcohol
|
15 |
6 |
-
To keep cattle alive
for 6 months about 360~:g molasses/urea (1 %) is required.
The cost of a replacement animal is estimated at US$200.
After substituting the urea and distribution costs the
value attributable to molasses is approximately $540 per
tonne
-
The value of molasses
as a replacement for imported grain i .• estimated on the
basis that it has a substitution value of 75 % and assuming
that imported grain is US$200/tonne (CIF)
-
It is estimated that
used as the basal diet (70% of the total feed) for fattening
cattle 6kg molasses supplemented with 150g urea and 8kg
fresh legume forage supports a daily liveweight gain of
750g. The urea cost.. $0.045, the forage US$0.46 and the
liveweight gain is valued at US$0.87/kg
-
The daily con.oumption
of 500g of a molasses/urea block; (50% molaHes, 20% urea,
20% bran, 10% minerals) ha.. increased milk yield on a
strawbased diet by lkg/day (milk is worth to the farmers
US$0.20/kg
-
A daily intake of 1.
5kg of 8 % urea/molasses mixture prevents a weight 10H in
cattle of 200g/day and that this weight 10H costs US$0.50/kg
-
4kg molasses are
fermented to produce 1 litre of anhydrous alcohol. Costs
that are not included are the fuel for distillation and the
interest/depreciation on the investment in a distillery. A
barrel of oil (CIF) is assumed /,0 be worth $15.
|
There
is
an extremely
strong
argument
for
retaining
molasses as a livestock
feed in countries
that
suffer
dry seasons and periodic
droughts.
The
opportunity
cost of using
molasses
(which
may
be the
only
feed
available) in drought
regions
in the
tropics
is related
to the value
of a live
animal
and
the survival of
subsistence
farmers who
are dependent
on
draught
animals.
Molasses
is used widely
in
compounded
feeds
in
the industrialised
countries,
where
it is used
to improve
the
palatability and binding
properties
of
pelleted
feed as well as reducing
dustiness.
Only
low concentrations
(5-10%)
are needed for this
purpose; higher levels
make
mixing and pelleting difficult.
Because
the
molasses
comprises such a small proportion
of the diet,
no nutrient imbalance
is apparent.
In tropical
countries the quantities
of molasses
available
are large
relative
to other potential
feed
ingredients.
In
these situations
molasses can
be used in three
ways:
-
As a
fermentable carbohydrate
providing
the basis
of the diet
for ruminants
-
As a palatable
carrier
for
other
essential
nutrients
(eg. urea
and minerals)
to
supplement
fibrous
diets and
also
a gelling
agent
in the
production
of nutrient
blocks
-
As
a source
of trace
minerals
and
some
macroelements (eg.
sulphur,
calcium and potassium).
Many
attempts
have
been
made
to incorporate
molasses
into
relatively
inert
materials
such
as bagasse
and
bagacillo
(the
residue
after
extraction
of
the coarse
fibres
for
paper
and
particle
board
manufacture)
but
the
final product
is of
poorer
feeding
value
than
the
original
molasses
and is more expensive
due
to the
high
cost of
power
for mixing.
Supplementation
Research
was conducted
in Cuba
in the
late
sixties
aimed
at
developing
livestock
feeding
systems
in
which
molasses
was the
principal
ingredient.
At
the
outset
it
was
decided
that
molasses
should
be
fed
in
its
original
liquid
state in
order
to
reduce
processing
costs and to facilitate transport
and
storage.
The
successful
development
of
the
high-molasses
fattening
system
for cattle
(Preston
et
al.
1967)
exemplifies
the
use
of the
basic
principles
of
ruminant
digestion
and
metabolism
as outlined
in earlier
chapters.
These
include
optimising
rumen fermentation
by supplying
fermentable
N (urea) and
some
highquality
green
forage
and balancing
the
amount of protein
(amino
acids)
to VFA by supplementing
with a bypass protein
source.
The
original system
used
forages
such as elephant grass,
pangola grass
and
sugarcane
tops as the
roughage
source.
The
availability
of forage was restricted
to
0.8kg
dry matter/100 kg liveweight
to
encourage the
animal to
consume
large
amounts of molasses.
The
urea
level
was set
at 2.5%
of the
fresh
weight
of the
molasses to
provide
a ratio of fermentable
N
to carbohydrate
close
to the
theoretical
requirements
of rumen
micro-organisms.
Sulphur
supplementation
was
not
required
as
sulphur
dioxide
used
in
clarification
of cane juice and the
residual
sulphur
concentrated
in the molasses.
In
the
widespread
commercial application
of the feeding
system
in
Cuba, fish
meal (Peruvian)
was the
bypass-protein
supplement.
The
dramatic
effect of this
supplement
in raising
animal
productivity
on the
molasses-based
diet
is shown in Figure
8.19.
 |
| Figure 8.19. Addition of fish mealk to a basal diet of ad
libitum molasses-urea and restricted forage substantially improved
growth rate and feed conversion of cattle in Cuba (Source: Preston
and Willis 1974) |
Subsequent
developments
in the
use
of molassesbased
diets
have been
directed
to the
use of:
(i)
protein-rich
forages
that
supplied
much, and
sometimes
all, of the
bypass
protein
as well
as the roughage
(Table
8.17 and
Table
8.18);
and (ii) supplementation
with poultry litter
(Figure
8.20 and
Figure
8.21).
|
Table
8.17:
Leucaena
foliage
was
as
effective
as
groundnut
meal
in supporting
high growth
rates
in young
Friesian
bulls
fed
a
diet
based
on molasses/urea.
The
leucaena
replaced
both
the
forage
(native
grass)
and
the
groundnut
cake,
and
may thus
have
served
as a
combined
source
of
protein
and
roughage |
|
|
Leucaena
(% LW/d) |
Groundnut.
Cake
(g/d)
|
|
LW gain
(g/d)
|
790 |
740 |
847
|
597 |
742
|
|
Feed conversion
(kg/kg
gain)
|
9 |
12
|
10
|
10 |
10
|
|
Molasses
(%
of
diet)
|
79 |
68 |
62 |
73
|
53 |
|
Source: Hulman
et al 1977 |
|
|
|
Table
8.18:
The
foliages
of
cassava
or sweet
potato
was
used
as
the
l'oughage
supplement
in
a
molasses-urea
diet
for
fattening
bulls
in the
presence or absence
of
a supplement
of
soyabean
meal.
With
cassava
supplementation
there
were
no
benefits
from
additional
protein
indicating
that
it
was
a
better
source
of bypass
protein
than
sweet
potato
foliage. |
|
Forage
|
Sweet potato foliage |
Cassava foliage |
|
Soybean meal (g/d) |
0 |
400 |
0 |
400 |
|
LW
gain, g/d) |
650 |
850 |
850 |
870 |
|
Molasses
(kg/d) |
5 |
6 |
6 |
6 |
|
Forage (kg/d) |
13
|
13
|
10
|
10
|
|
Source: Ffoulkes and Preston (1978b) |
 |
| Figure
8.20:
Contrasting
effects
of legume
(leucaena
foliage)
and grass
(sugarcane
tops) as
the
roughage
supplement
in
a diet
based
on ad
libitum
molasses/u1'ea
with or without
supplements
of wheat
bran (1kg/d)
and/or
poultry
litter
(1.5kg/d)
(Source:
Meyreles
et
al.
1982).
|
 |
| Figure 8.21: In a cattle fattening diet based on ad
libitum molasses, sugarcane tops and wheat bran (1 kg/d), urea was a
more effective source of fermentable-N than poultry litter'.
Poultry litter stimulated growth rate when added to the diet (with
Urea), which was appar'ently adequate in fermentable-N (Source:
Meyreles and Preston 1982). |
There
is evidence
that,
on
molasses-based
diets,
poultry
litter
influences
the
pattern
of VFA
formation,
increasing
the
proportion
of
propionate
and decreasing
the
proportion
of
butyrate
(see
Table
5.2).
This
would
partly
explain
the
improved
growth
rates
and feed
conversions
associated
with
the
use
of
poultry
litter
in
molasses-based
diets
(Figures
8.20
and
8.21;
see
also
Meyreles
1984;
Herrera
1984).
Commercial
feeding
systems
based
on molasses
The
data
m
Tables
8.19
and
8.20
summarise
the
results
obtained
when
the
molasses
fattening
programme
was
used
commercially
in large-scale
feedlots
and
under
conditions
of
restricted
grazing
on
State
farms
in
Cuba.
|
Table
8.19:
Production
data from
a commercial
cattle
feedlot
(10,000
head)
in
Cuba
during the
years
when
a change
was made
from
an ad libitum
forage
(Pangola
grass)
plus concentrate
diet
to one
based
on
ad libitum
molasses/urea
and restricted
forage
and fish
meal.
The
high
losses
due
to
emergency
slaughter
and mortality
in the
first
year
of
high
molasses
feeding
were
due
to
molasses
toxicity
(cerebro-cortical
necrosis,
see
Preston
and Willis
1974).
|
|
|
Forage
1969 |
Molasses-based |
|
1970 |
1971 |
|
Total
LW gain (kg/d)
|
3,724 |
8,295 |
13,797 |
|
LW gain
(g/head/d)
|
430 |
880 |
890 |
|
Feed
conversion
(kg DM/kg
gain)
|
15 |
11 |
10 |
|
Deaths
(%)
|
0.1 |
1.0 |
0.2 |
|
Emergency slaughter (%)
|
0.1 |
1.0 |
0.2 |
|
Source:
Munoz
et
al. (1970).
|
|
Table
8.20:
Performance
of
bulls
fattened
commercially
in Cuba
on ad libitum
molasses/urea,
fish
meal
and
restricted
grazing
(3
hours/
day).
Results
are
for
11
units
each
with
400 animals |
|
|
LW
gain
(kg/d) |
Conversion
(kg/kg
LW gain) |
|
Molasses |
Fish meal |
Urea |
|
Worst
|
0.74 |
14.7 |
0.54 |
0.47 |
|
Mean
|
0.83 |
9.1 |
0.45 |
0.29 |
|
Best |
1.04 |
5.9 |
0.32 |
0.19 |
|
Source: Morciego et al 1970 |
8.4.6
Metabolic
disorders
on molasses-feeding
systems
Three
metabolic
disorders
may
occur
in
cattle
and
sheep
fed
diets
containing
more
than
50%
molasses:
-
urea
toxicity
-
molasses
toxicity
-
bloat.
Urea toxicity
This is discussed
since,
when
high
levels
of molasses are
used,
urea
is almost
invariably
included
in
the
molasses,
and urea intakes
may
be
as high as
300g/
day (eg.
in
a 500kg
dairy
cow consuming
10kg of the
molasses/urea
mixture
per
day).
However,
there
is
little
risk
of
urea
toxicity
since
the sugars
in molasses
and
ammonia
from
urea
are
quickly
used
in rumen
microbial
cell
growth.
Animals
that have
not previously
consumed
urea
can
be
safely
permitted
free
access
to molasses
containing
up to
3%
urea
without fear
of toxicity.
Toxicity
will
only
occur if the
urea
is not
uniformly
distributed,
or mistakes
have
been
made
in formulation.
Molasses toxicity
This is probably
the most serious problem associated with molasses feeding. For example, in the
first year following the introduction of the molasses/urea fattening system in
Cuba, mortality and emergency slaughter rates in a 10,000 head feedlot increased
from 0.1 % and 0.4% (when a forage-based diet was fed) to 1% and 3%
respectively, when the diet was changed to high levels of molasses/urea (see
Table 8.19).
Cattle suffering
from molasses toxicity salivate, stand apart in a "dejected" posture, usually
with their heads lowered; and frequently are found "leaning" against the fence
or feed trough. Invariably, eye-esight is affected and often the animal is
blind. When disturbed they have an unsteady and uncoordinated gait and this led
the "cowboys" in Cuba to refer to the affected animal as "borracho" (ie.
drunk!!).
The nervous
symptoms and blindness that were a feature of molasses toxicity indicated damage
to the brain and it was subsequently shown by Verdura and Zamora (1970) that the
clinical syndrome was indistinguishable from that of cerebro-cortical necrosis (CCN)
also known as polioencephalomalacia (Edwin et al. 1979). The necrosis in the
brain is readily seen and this allows rapid diagnosis.
The cause of the
necrosis is likely to be a decrease in the energy supply to the brain because of
either an absolute deficiency of alimentary thiamine, binding of thiamine
analogues produced in the rumen and/or through the action of thiaminase in the
rumen (Edwin et al. 1979), or a deficiency of glucose (Losada and Preston 1973).
The evidence for the last explanation is that rumen propionate levels were
extremely low (less than 10% molar) when the disease was induced in cattle
deprived of forage (Losada and Preston 1973), and that daily oral administration
of 400g of glycerol (a glucogenic substance frequently used in the treatment of
ketosis) prevented clinical symptoms of the disease (Gaytan et al. 1977). In
contrast, administering thiamine either intra-ruminally or intra-amuscularly did
not prevent the disease (Losada et al, 1971 ).
Recent work by Rowe
et al (1979a) introduced another element into the aetiology of molasses
toxicity. They confirmed that removing the forage from a molasses-based diet
induced symptoms of molasses toxicity, including brain necrosis, in which
neither blood glucose level nor the rate of entry of glucose into blood was
impaired. The most significant finding was that the absence of forage in the
diet caused a rapid reduction in the rate of turnover of rumen fluid to the
point of almost complete rumen stasis (from 1.5 to 0.5 volumes/day). Rowe et al.
(1979a) hypothesized that, under these conditions, the supply of both amino
acids and B-vitamins to the animal would be drastically reduced with a
consequent decrease in the availability of thiamine for brain metabolism. Another
explanation
is that
low rates of
turnover
of
rumen
fluid
might.
encourage
the
proliferation
of
slow-growing
bacteria
that
produce
thiaminase.
It
is
apparent
that
a number
of
factors
interact
in the
development
of
molasses
toxicity
(see Figure
8.22).
The
basic
defect
common to all situations
is the
disruption
of energy
supply to the
brain.
This
could
be
brought
about
by inadequacies
in the
absolute
supply
of blood
glucose
or
thiamine
(required
for
brain
metabolism
of
glucose)
or
both,
as well
as by
the
action
of
thiaminases
present
in the
feed
or
produced
by
the
rumen
microorganisms.
 |
|
Figure
8.22:
A summary
of some
factors
that may
affect
the supply
of
blood
glucose
and
its
utilisation
by the
brain
(Source:
Rowe
al.
1979a).
|
The
theory
that
glucose
deficiency
is the
main
cause
of
molasses
toxicity
seems
the
most plausible.
The
availability
of
glucose
to cattle
on molassesbased
diets
is
always
precariously
balanced
because
of the
low-propionate/high-butyrate
fermentation
of
molasses,
and
t.he
economic
pressure
to mini mise
true-protein
inputs.
Molasses
toxicity does
not
apparently
occur in sheep.
Sheep
fed
such
diets have
higher
propionate
fermentation
patterns
than
c.attle
which
lends
support
to
the
concept
of
glucose
being
primarily
involved
in the
syndrome.
Removal
of
forage
from
a
molasses-based
diet
givell
to sheep
does
not
result
in the
same
rumen
stasis
as in cattle
(Beveridge
and
Leng
1978).
Two
processes
may
separately,
or in
combination,
lead
to
excessive
use of
glucose
and a lowering
of blood
glucose
concentrations,
which
could
lead
to
brain damage.
These
are:
-
Periods of
exercise/excitement, which illcrease the utilisation of glucose, especially
by muscle (see Chapter 4)
-
Consumption of an
excessively large amount of molasses at one time, leading to a requirement
for glucose to clear the increased amounts of acetate absorbed. Molasses
ferments very rapidly in the rumen and animals normally eat "little and
often" throughout the day. Disturbance in this pattern, brought about by
poor management or inadequate trough space and therefore "dominance" by
some animals, could be the triggering mechanism for the over-eating.
This thesis
is supported by
observations of
periods of low
blood
glucose
levels
in cattle during experiments
which
involved
intensive
blood
sampling
(R A Leng
and
M H Ferreiro,
unpublished; also
Gaytan et al.
1977).
When
feeding
high-molasses
diets
to cattle
it is usual
to
restrict
the
supply
of forage,
either
to increase
intake
of
molasses
or
because
of
the
greater cost
of
forage
compared
to
molasses
(see
Table 8.20).
Inadequacies
in
either
the
quantity
or
quality
of forage
appear
to be the
main
causes
of
molasses
toxicity.
Thus,
the
incidence
of
molasses
toxicity
was
less when
wheat
or barley
straw,
rather
than
sorghum
forage
or maize
silage,
were
used
as the
forage
sources
in
molasses-based
diets.
Furthermore,
there
have been
no
reports
of
toxicity
when
high-protein
forages (eg.
leucaena
and
cassava
alld sweet-potato
tops)
have been
used.
Equally,
feeding
nutritious
and palatable
forage
appears
to
be the
best
cure
for affected
animals (T R Preston, unpublished
data) .
Recent
developments
in
the
molasses-feeding
system
have emphasised
the technical
and
economic
advantages
of feeding
high-protein
forages,
especially
from
leguminous
plants
such as
leucaena,
as
a combined
source
of
both
roughage
and
bypass
protein.
Including
such
forages
in the
diet
is
also
likely
to
offer
the
most
cost-effective
means
of
avoiding
molasses
toxicity.
Bloat
Bloat
is
the
retention
in the
rumen
of
gas,
either
free
or
trapped
in foam,
and
occurs
in
cattle
on
almost
all feeding
systems.
It is
more
prevalent
with
some
diets
(eg.
grazed
legumes
that
contain
high
levels
of
soluble
foaming
agents
such
as
saponins
and
proteins).
It is
not
a partic.ularly
serious
problem
with
molasses
feeding.
However,
relatively
high
incidence
of
bloat
(up
to 5%)
has
been
reported
where
access
to
the
molasses
is
occasionally
limited
(eg.
grazing
cattle
allowed
access
to
molasses/urea
only
once
or
twice daily)
and where
cattle
have
eaten
relatively
large
quantities
of
molasses/urea
over
short
periods.
A hypothesis
for
the
aetiology
of the
syndrome
is
as
follows.
In
animals
fed
molasses-based
diets,
an
organism
grows
in the
rumen
which
produces
considerable
mucilaginous
secretions
(Methanosarcina
bakerii
--
see
Rowe
et
al.
1979b)
and
which
can
reach
high
population
densities.
When
the
animals
consume
molasses
quickly,
the
rate
of fermentation
in the
rumen
is
high
(producing
considerable
quantities
of
carbon
dioxide
and methane),
the
pH falls
and
the
bicar
bonate
in
the
rumen
fluid is
converted
to CO2.
The
very
rapid
production
of
gas
in
the
presence
of
the
mucilagenous
organism
forms
a foamy
bloat.
A similar
train
of
events
is
reported
to
cause
feedlot
bloat
on
grain-based
diets
(Cheng
et
aI.
1975).
An
optimum level
of
rumen
ammonia
accelerates
fermentation
and therefore
bloat
may
be
controlled
by
using
a
source
of NPN
that releases
ammonia
more
slowly
than urea,
eg:
chicken
litter.
8.4.7 Sugar cane juice
The
extremely
low
fermentability
of
sugarcane
fibre
(Figure
8.23)
and the
negative
effect
this
had
on
voluntary
intake
of
the
overall
diet
was
the
reason
for
developing
methods
for
fractionating
the
crop
so
that
sugar
and
fibre
could
be
treated
as separate
entities.
 |
| Figure
8.23:
Rate
of
loss
of dry matter
from
nylon
bags
containing
washed
sugarcane
fibl'e,
pangola grass
or
a
sample
of
hay
grown in
Scotland,
suspended
in
the
rumen
of
a
steer
fed a
sugarcane-based
diet
(Source:
Fernandez
and
Hovell1978).
|
The
new
approach
to
fractionation
of
sugarcane
for
livestock
feeding
and fuel
production
was
first
developed
in
Mexico
(Preston
1980b).
The
aim was
to
achieve
only
partial
extraction
of
the
juice
using
simple
low-cost
cane
crushers,
of
the
kind developed
for
"panda"
and
"gur"
production.
This
reduced
the
investment
in machinery
and the
energy
cost
of
milling (stalks
are
passed
only
once
through
the
crusher).
The
justification
for
this
system
was
that
the
juice
is
a suitable
carbohydrate
resource
for
both
ruminant
and non-ruminant
livestock.
The
residual
sugar-rich
fibre
can
be gasified
to
make
"producer
gas"
to
substitute
for
gasoline
and
diesel
oil
(T
R Preston
and
A Lindgren,
unpublished
data).
Alternatively
it
can
be
used
as
a
component
of
the
diet
of
draught
animals or
small
ruminants
that
can readily
select
the
pith from
the
rind
(Preston
1987).
Supplementation
The
fermentable
carbohydrates
in sugarcane
juice
and molasses
are
sucrose,
glucose
and fructose.
Molasses
is
the
concentrated
soluble
residues
after
extraction
of
the sucrose
from
cane
juice.
It
is
therefore
richer
in minerals,
organic
acids
and
other
soluble
plant
components
than
cane
juice.
Diets
based
on
cane
juice
support
much
higher
levels
of
animal
productivity
than
those
based
on
molasses.
The
rates
of
growth
and feed
conversion
efficiency
recorded
in
studies
in Mexico
(Table
8.21
and Figure
8.24)
are
comparable
to
those
recorded
in intensive
grain-based
systems.
|
Table
8.21:
Holstein/Zebu
bulls
had higher·
g1'Owth
rates
and
better
feed
conversion
on a basal
diet
of fresh
sugarcane
juice
than
on molasses.
The
difference
was
especially
marked
in the
absence
of the
bypass
protein
supplement
(sunflower
seed
meal
SSM).
|
|
Basal
diet
|
SSM
supplement
(kg/d)
|
LW gain
(g/d) |
Intake
of molasses/cane juice
(kg/d)
|
Feed
conversion
(kg
DM/
kg
gain)
|
|
Molasses |
0.0 |
250 |
4 |
26 |
|
|
1.0 |
550 |
4 |
12 |
|
Cane juice |
0.0 |
800 |
23 |
7.4 |
|
|
1.0 |
1320 |
32 |
6.4 |
|
Source: Sanchez
and Preston 1980 |
 |
|
Figure
8.24:
Zebu
steers
had high
growth
rates
and efficient
feed
conversion
on sugar
cane
juice
supplemented
with
ammonia
and leucaena
foliage.
Additional
bypass
protein
from
fish
meal
increased
growth
rate
slightly
but
there
was
no
effect
on
feed
conversion
(Source:
Duarte
et
al.
(1982).
|
The
potential
for
use
of
cane
juice
is
considerable
because
microbial
growth
in the
rumen
on
this
feed
appears
to
be
highly
efficient;
Zebu
cattle
grew
at 800g
per
day on
minimal protein
intake
(5%
protein
in
the
diet
dry
matter
supplied
from
leucaena)
with
the
fermentable
N
provided
by
aqueous
ammonia.
This
is
in
contrast
to
the
average
grain-based
feeding
system,
in
which
at
least
12%
of
the
diet
dry
matter
is
protein.
It appears
that
on
a cane
juice
diet,
the
end-products
of
rumen
fermentation
are
better
balanced
and
therefore
support
much
higher
levels
of
animal
productivity
than
sugarcane
pith.
This
indicates
that
microbial
growth
in the
rumen
was
extremely
efficient
since
it must
have supplied
an almost
ideal
protein/energy
ratio
for
production
without
supplementation.
Two
observations
on feeding
cane
juice
to cattIe
are
pertinent
to
the
underlying
thesis
of
this
book:
-
Propionate
comprised
more
than
20%
of
the
total
VFAs
in
the
rumen,
giving
a high
glucogenic
energy
ratio
(G/E)
in the
animals
(Figure
8.25).
In
this
respect
the
juice
was
dearly
superior
to
molasses
-
The
population
of
protozoa
in the
rumen
of
animals
fed
cane
juice
was
lower
than
that.
in the
rumen
of
molasses-fed
animals
(ie.
10,000/ml
versus
1,000,000/ml
of rumen
fluid),
again
suggesting
efficient
microbial
protein
production
(D Harrison,
personal
communication;
Bird and
Leng
1978).
The
importance
of these
factors
as determinants
of
efficient
ruminant
productivity
are
discussed
in
Chapter
5.
 |
| Figure
8.25:
There
were
higher
molar
proportion
of
propionic
acid
and lower
proportion
of butyric
acid
in rumen
fluid
of cattle
fed
sugarcane
juice
than
with
cattle
fed
molasses
(Source:
Perez
et
al.
1981).
|
8.4.8 Residual pressed cane stalk
The
maximum
economic
benefit
from
the
use
of
sugarcane
juice
for
livestoc.k
feeding
will
only
be
realised
iftechnologies
are
developed
to
use
the
residual
pressed
stalk.
The
options
being
pursued
for
the
use
of
this
material
include:
-
Productiojn of charcoal
-
Conversion to producer gas (a
mixture of carbon monoxide, hydrogen and nitrogen) as a substitute for
diesel fuel
-
Feeding to draught animals
-
Feeding to small ruminants
(sheep and goats), allowing a high degree of selection (eg. by
providing twice the normal dry-matter in take) .
Making
charcoal
from
pressed
cane
stalk
is
simple
but
requires
briquetting
to produce
a readily
saleable
product
(Ffoulkes
et
al.
1980).
To
be
able
to
use
pressed
cane
stalk
for
producergas
production,
it
must
first
be
sun
dried
to
20%
moisture
content
and
chipped
into particles
of 10
to 20mm
in length.
A
gasifier
has been
designed
that
uses
dried
sugarcane
chips
(A Lindgren,
personal
communication)
.
A promising
development
is
the
potential
of
using
the
pressed
(extracted)
cane
stalk
as a basal
diet
for
small
ruminants.
When
it is available
immediately
following
juice
extraction,
goats
eat it avidly,
selecting
the
sugar-rich
pith and
rejecting
the
lignified
rind.
In
studies
in
Colombia,
goats on
a
mixed
diet
of
pressed
stalk
and
fresh
gliricidia
foliage
selected,
and apparently
preferred,
the
pith to
the
green
foliage
(Preston
1987).
8.5 Sisal bagasse and pulp
8.5.1 Introduction
Sisal
(Agave
fourcroydes)
is
a
source
of
fibre
for
twine,
ropes
and
carpets.
The
entire
leaf
blade
is
harvested
and
transported
to
the
factory,
and
there
are
thus
no
residues
in the
field.
However,
the
bagasse
that
remains
after
the
fibres
are
extracted
is potentially
useful.
The
bagasse
left
after
traditional
processing
contains
both long
and
short
fibres.
More
advanced
factories
extract
a greater
proportion
of
the
fibres
and
some
of the
saponins,
which
are
used
as
raw
material
for
the
manufacture
of
steroid
hormones.
The
byproduct
of
this
modified
process
is
referred
to
as
"pulp"
to
differentiate
it from
bagasse
(Riley
1984).
Data
on the
chemical
composition
of
both
these
byproducts
are
given
in Table
8.22.
Because
of the
high
content
of soluble
sugars
and the
high
moisture
content,
the
pulp
or
bagasse
begins
to
ferment
immediately
after
fibre
extraction
and most of
the
soluble
sugars
are
converted
to lactic
acid.
|
Table 8.22: The chemical composition of sisal bagasse and
pulp |
|
|
|
Sisal pulp |
Sisal bagasse |
|
|
|
Fresh |
Ensiled |
Fresh |
Ensiled |
Fresh |
|
Proximate
analysis
(%
DM) |
|
|
|
|
|
|
Crude
fibre
|
|
29
|
30
|
28 |
29 |
23 |
|
Crude
protein
|
|
5.3
|
4.9
|
5.3 |
5.5 |
6.3 |
|
Ether
extract
|
|
3.1
|
3.0
|
3.7 |
3.4 |
3.0 |
|
Ash
|
|
|
13
|
13 |
15 |
15 |
12 |
|
Water-soluble
CHO |
21
|
0 |
27 |
0 |
|
|
Mac1'O-minerals
(g/kg
DM)
|
|
|
|
|
|
|
Calcium
|
|
51 |
53
|
47 |
49 |
35 |
|
Phosphorus
|
|
1.1 |
1.0 |
1.0
|
1.2 |
1.5 |
|
Magnesium
|
|
8.0
|
8.0
|
9.0 |
10.0
|
8 |
|
Trace
minerals
(mg/kg
DM) |
|
|
|
|
|
|
Zinc
|
|
|
1.2 |
1.2
|
1.5
|
1.4
|
|
|
Copper
|
|
|
0.5
|
0.5
|
1.0 |
0.8
|
|
|
Cobalt
|
|
|
ND
|
ND |
ND
|
ND
|
|
|
Manganese
|
|
1.0 |
1.1 |
1.0 |
0.8 |
|
|
Iron
|
|
|
2.0
|
1.8 |
2.3
|
2.2
|
|
|
0rganic
acids
(%
DM)
|
|
|
|
|
|
|
Lactic
|
|
|
1.6
|
16.5
|
1.0 |
18.1
|
|
|
Citric
|
|
|
1.0 |
0.5
|
1.2 |
0.8
|
|
|
Oxali,
|
|
|
5.5
|
5.3
|
5.2
|
5.4
|
|
|
pH
|
|
|
4.0
|
3.9
|
3.9
|
3.8
|
|
|
Source:
|
Harrison
(1984).
|
|
|
|
|
|
The
constraints
associated
with
the
use
of the
pulp/bagasse
as
a feed
for
ruminants
relate
partly
to
the
content
of
organic
acids,
principally
lactic
and
oxalic
acids.
Phosphorus
and
some
of the
trace
elements
are
also
severely
deficient,
and thus
the
minerai
content
of
pulp
or
bagasse
is
highly
imbalanced
relative
to the
needs
of productive
animals.
Cattle
fed
only on
ensiled
sisal
pulp
for
a
long
period
developed
acidosis
and barely
maintained
bodyweight,
despite
the
reasonably
high
digestibility
(5060%)
of
the
feed
(Naseeven
and
Harrison
1981).
Attempts
to correct
only
the
acidosis
and the
mineral
imbalance
did not
increase
animal
productivity
(Naseeven
and
Harrison
1981;
Belmar
and
Riley
1984)
.
Research
in Mexico
on the
use
of sisal
pulp as
a feed
for
ruminants
(Rodriguez
1983)
is
a further
example
of the
application
of
the
principles
developed
in this
book,
namely
that
attention
should
first
be
given
to optimising
the
rumen
ecosystem
and then
to
correcting
the
protein/energy
ratio
with
bypass
protein
(Chapter
7). Only
after
these
two
steps
have
been
taken
are
responses
to supplementary
minerals
observed
(Figure
8.26).
 |
| Figure
8.26:
Sisal
pulp
is
relatively
digestible
(55-60%)
but
low in
fennentable-N,
protein
and minerals.
Supplementing
with
urea
and mineTals
had
no effect
on lamb
performance
until
green
forage
(foliage
from
the
tree
Brosium
alicastrum)
and/or
bypass
protein
(soybean
meal)
were
also
given
(Source:
Rodriguez
1983).
|
8.6 Bananas and plantains
Bananas
and plantains
provide
voluminous
amounts
of
crop
residues
which
are
normally
incorporated
into
the
soil for
mulching
and to
maintain
soil fertility.
When
bananas
are
grown
for
export,
up to 20% of
the
fruit may
be
rejected,
and these
are
often
discarded.
There
are
few
nutritional
constraints
to the
use
of banana
fruit as
feed
for
ruminants.
However,
it is
important
to
feed
the
material
while
it is green
and the
carbohydrate
is
still
in the
form
of
starch.
The
fruit
can
be
fed
as
a complete
bunch
(or "hand")
and
there
is
no
need
for
any processing.
The
fruit is
low
in nitrogen
and
the
skin is rich
in tannins. The
greatest
nutrient
deficiency
of
bananas
as a feed
for ruminants
is
fermentable
nitrogen
and
diets
containing
bananas
must
be
supplemented
with
urea.
Where
molasses
is freely
available,
the
most
convenient
procedure
for
supplementing
cattle
with urea
is to allow
the
cattle
free
access
to a urea/molasses
mixture
(10%
urea).
Cattle
will restrict
their
intake of this
supplement
to about
2kg/day,
which
provides
enough
urea
(200g/day)
to ensure
an adequate
level
of
ammonia
in
the
rumen
for
efficient
fermentation
(McEvoy and Preston
1976).
If
a
high-protein
forage
is fed
with
the diet,
either as
a legume component
of a pasture
in a restricted-grazing
system
or
as
a protein-rich
foliage
(eg.
leucaena
or gliricidia),
there
appears
to be
no
advantage
from
supplementing
with
a bypass-protein
meal.
Results
from
feeding
reject
bananas
to cattle
in Colombia
are
summarised in
Table 8.23.
|
Table 8.23:
Growths
rates
of
cattle
fattened
under
commercial
feedlot
conditions
in
Colombia
on reject
bananas
(40%
of diet
DM), chopped
elephant
grass
(42%)
and
Kudzu
legume
forage
(18%)
with
different
supplements.
|
|
Protein suppl. |
Initial LW
(kg) |
Daily gain (kg/d) |
Days on feed |
Comparisons |
|
No
supp!.
|
330
|
0.83 |
90 |
Female
adult
|
|
|
325
|
0.64
|
90 |
Male
adult
|
|
|
334
|
0.80
|
90 |
Female
old
|
|
|
325
|
0.88 |
90 |
Female
young
|
|
|
240
|
0.91
|
100
|
Male young
|
|
|
350
|
0.61
|
100 |
Male
old |
|
1kg/d
CSC |
381
|
1.15
|
60 |
+ sulphur
|
|
|
391
|
0.97
|
60
|
- sulphur
|
|
|
332
|
0.98
|
60
|
Ureal
|
|
|
|
|
|
Jllolasses
|
|
|
322
|
0.97
|
60 |
Aqueous
urea
|
|
2kg/d
CSC |
|
1.60
|
|
Chianina
x Zebu
|
|
|
|
1.14
|
|
Zebu
crosses
|
|
|
|
1.25
|
|
Zebu
bulls
|
|
|
|
1.10
|
|
Zebu steers |
|
|
|
1.66
|
|
Chianina
bulls
|
|
|
|
1.50
|
|
Chianina
steers
|
|
Source: Perex
and Roldan 1984
CSC cottonseed
cake |
8.6.2 Banana foliage
The dry
matter
in the
leaves
and
pseudostem
of
the
banana plant is relatively
digestible
(65 and
75%,
respectively;
Ffoulkes
and Preston
1978a).
Despite
this,
these
feeds
barely
support
maintenance
if
given
alone
to ruminants.
However,
when
ruminants
are
fed
banana
pseudostem
they
respond
to supplementation
with
urea,
highly
digestible
green
forage and
bypass
nutrients.
The
data
in
Figure
8.27 show that
cattle
increased
their
voluntary
feed
intake
significantly
when
the
chopped
leaves
and pseudostems
were
supplemented
with
sweet-potato
foliage
or with wheat
bran.
The
highest
feed
intake
was
observed
when
both
sweet-potato
foliage
and wheat
bran were
given
together.
 |
| Figure 8.27: Supplements of wheat bran (1kg/d) and/or sweet
potato tops (5% bodyweight, fresh basis) increased the voluntary
feed intake of cattle given a basal diet of chopped banana
pseudostcm, urea and minerals (Source:: Fernandez et al. 1981). |
Feeding
systems
based
on
banana
foliage
have
been
developed
in the
Seychelle
Islands
(Figure
8.28).
Acceptable
levels
of growth
were
obtained
in cattle
fed
the
banana
forage,
urea
and leucaena,
and there
was
an apparent
response
to additional
supplementation
with
banana
fruit.
 |
| Figure 8.28: Growth performance of crossbred (Jerrsey/Creole)
cattle in Seychelles fed a basal diet based on the whole banana
plant (pseudostem and leaves plus urea and minerals) and supplements
of fresh leuucaena foliage (3% bodyweight/d) alone or with some
reject banana fruit (3kg/d) (M Delpeche and T R Preston, unpublished
data). |
 |
| Sugarcane produces enormous amounts of biomass. Picture shows
sugarcane being chopped for feeding trials with cattle in Mexico
(Alvarez F) |
 |
| Crop residues are the major feed biomass for cattle 111
developing countries (China-Leng R A) |
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