Improved Rice Stram as Elephant Grass (Pennisetum purpureum Schumach) Substitute for Ruminants

INTRODUCTION

About
Ihdonesia

t h e human a n d rctmi n a n t p o p u l a t i o n s

of

kc:)%

in

are

Java

i nc:rea!si n g

annt-tal 1 y

e:.:pl o s i ctrl

tends

and t h e

hctnlan

of

p o p ~ t l a t i o n is

at. t h e r a t e o f 2.34%. T h e popctl a t i o n

to

decrease

the

agricctl tur-al

larld

avai lable

+or c:rc~p ancj g r a s s pr-odctct.i o n whi 1e

t h e demand

fur

and

Theref ore,

meat

milk

keeps

on

irtcreasing.

producztion i n J a v a h a s t o r e l y h e a v i l y f o r

ruminant.

feed

a n agro--i rtdust.ri a 1 by-.-products and c r o p residl-ces.
,

R i c e s t r a w i s t h e : l a r g e s t c r o p resitjice f o c t n d i n

being

17

However,

tcms

million

annually

(Anonymous,

Java

1982a)

.

it h a s l o w nutritional value due t o t h e -following

factors:

1.

Being

a matctr-e

proportion
a n d Aman,
2.

microbes.
7

.-t

.

*

It

it: c o n t a i n s a

cell wall s (Jackson,

of

amctng

cell wall

iC::eegstr-a e t a l .

,

1.986)

to

1904;

rumen

1973).

( R o x a s et a l . ,

1985a;

Hart

and

.

I t h a s a l o w m i n e r a l a n d v i t:.amir, c o n t e r ) t
a n d Aman,

through

1973; H a r t l e y ,

K s h a n i !::a S a n n a s g a l a a n d J a y a s c c r i y a ,

4.

Theander

cortcjti t u e n t s

b o n d s redctces t h e i r a v a i l a b i 1i t y

has a l o w nitrogen content

Manapat:,

1977a;

high

1984)

Inter1inking
chemical

plant residue,

1.9E14)

(Theander

Consequently, rice s t r a w a l o n e h a r d l y provides maintenance
f o r - r u m i n a n t s a n d r e q u i r e s .to b e t r e a t e d a n d

regui rement5

s u p p l e m e n t e d i n o r d e r t:o i n c r e a s e i t ' s n u t r i t i o n a l
Currently,

the

treatments

i n c r e a s e t h e a v a i l a b i l i t y of
physical

,

chemical

,

or i n c o m b i n a t i o n .
I b r a h i m ( 1 983)

some

However

literature.

Firstly,
of

,

W a l l-::er

(

major- d e f i c i e n t a r e a s a r e

in

the

recognized.

r i c e s t r a w p o r t i o n s measured i n
of

.Fi.tr-ther s t u d y w o u l d b e t o

nutritional

val. u e as + e e d .

s e l e c t i n g t.hose p o r t i o n s
S e c o n d 1y ,

s t r a w c h e m i s t r y is sti 11 s l i g h t .

to

increase

vivo.

The

provide

an

with

greatest

knowledge of

Alkali

straw

However,

used f a r treatment.

a

c h e m i c a l 1y

information

cell
will

a c i d s or o t h e r c h e m i c a l s a r e t o

T h i r d 1y ,

nutritionally
treated

more

is

organic

through d i s r u p t i u n of chemical bonds between
constituents.

rice

treatments,

t h e a v a i l a b i 1i t y of

c e r t a i n 1y h e needed i f

produce

( 19 8 4 ) .

t h e r e is n o i n f o r m a t i o n a b o u t t h e n u t r i t i v e v a l u e

for

wall

either

u s e d e i t h e r s e p a r a t e 1y

1 9 8 4 ) a n d F ' r e s t o n and Lxng

opportctnity

matter

,

t o

'These h a v e b e e n t h o r o u g h l y r e v i e w e d b y

Three

advantage

thoi.tght

used

b a s i c i n f o r m a t i o n is s t i l l l a c k i n g

different

main

be

can

c e l l w a l l s are

str-aw

biological

or

%hat

value.

t r e a t m e n t u s u a l 1y d o e s

balanced feed

s t r a w !should

be

and

be
not

t h e r e f ore,

supplemented

with

o t h e r i n g r e d i e n t s i n o r d e r t o ~ ~ t p p o ra nt i m a l p r o d u c t i o n .

-

aims of the research described below was ( 1 )

The
evaluate
straw

the nutritive value fur cattle of different rice

portions,

( 2 ) to

maximize

the

coef+icient of rice straw through treatments
combinations of alkalis,
r

vitro

to

in

value

of lime

with various

acids and white rot fungi

condition and then to test

under

digestibility

v i v o conditions,

under

selected

treatment

( 3 ) t o compare t h e

nutritive

treated rice straw with elephant grass

in

diets enrichecl with local I. y avai X able concentrates such as
cassava leaves and onggok.

LITERATURE REVIEW

to

Accor-ding

Bir-o

Pusat S t a t i s t i k

(1984)

62% o f

I n d o n e s i a n r i c e s t r - a w product.ion is p r o v i d e d b y J a v a .
1981

paddy f i e l d i n J a v a w e r e p l a n t e d w i t h

varieties

s h o w n i n T a b l e 1.

as

Government.

35

released

v a r i et.i e s

o b t a i rted

from

c u l t i h v a r s or v a r i e t i e s

crossing

(Anonymous,

new

rice

various

Further,

different

In

i n 1983

improved

between

the
rice

local

the

1983a). Rice s t r a w i n

I n d a n e s i a obv:i o u s l y i s a v a r - i a b l e p r o c l u c t w h i c h coma5 f r ' o m

a

c o n t i n u a l 1y e v o l v i n g m i x t u r e o f

var'ieties
when

arid c u l t i v a r s ,

long and s h a r t

and t h i s must b e k e p t

strawed
in

a t t e t n p t i n g t o re1a.k.e w o r l t j l i t e r a t ~ t r ec3n r i c e

mind

straw

t n t h e I n d u r i e s i a n si ti.tal.:i o n .

I.

R i c e Straw
Rice

i s t h e a e r i a l p a r t 0.f t h e r i c e

straw

l e f t after the grain

plant

There are a

h a s been harvested.

number o f r i c e s t r a w v a r i e t i e s h u t i n g e n e r a l t h e s t r a w
p o r t i o n s a r e as, r e p r e s e n t e d b y F ' i g ~ t r e 1.

1. Straw

P o r t i o n s and Their
The

of

lnwer p o r t i o n of

stems

which

w i t h a number- o f

Nutritive

Value.

s t r a w is composed
internodes

mainly

and

nodes,

are t h e p o i n t s w h e r e t h e l e a v e s e m e r g e .

upper

material

pc3rtion

is

c o n s t i t ~ t t e d mainly

c o n s i s t i n g of

and t h e l e a f

blade.

two parts,

The

of

leafy

t h e leaf

sheath

B n t a n i c a l p o r t i o n s of

various

T a b l e 1.

Percentage
distribution
of
varieties
planted
in
Java
(Siwi and K a r t ~ o w i n u t o , 1984)

--- -.----

---------.-.-------.

-.-

----..----

"---"----.-----W e s t

-----------.-

.-.--

-------- ----

JAVA
---------.--------------

Central

------- --.-.- -------.----.

-.-----------.---.-----------.-

rice
in
1981

East

--------------------

T o t a l rice f i e l d
( . 05)0 h a )
Pel it a

(% 1

0 3

.

1.8

Semeru

(%)

5.6

0.3

Ci s a d a n e

(%)

14.2

2. 1

1.5

17.5

13.2

0.2

L-ocal v a r i e t i e s
Local c u l t i v a r s (%)

T a ta1

N,

negligable.

25. O

------

.

1 (:)0 0

18.2

------

.

1 (:)a 0

.

0 5

IL
7

.-

(-)

6.7

---.---

100.0

Rachis

Leaf b 1ade
Internode

Node

Leaf sheath

F i g u r e 1.

Rice p l a n t ( O r y r a s a t i r ~ a )

s t r a w s a r e a s s ~ t m m a r i z e di n T a b l e 2 .

cereal

predominant
,

strrar-J,

.for t h e o t h e r c e r e a l s t r a w s .

chemical

3.

composition

and

higher

was

v i tri.)

krt

Prubabl y,

because

leaves

rice

have

the lower

d i g e s t i b i l i t y val.ue l o w e r t h a n t h e s t e m ,
portion

For

t h e ! s t r a w por.t.ior-1s a r e p r e s e n t e d i r s

d i g e s t i b i : l i t y of
Table

t h e s.traw shauld have a n u t r i t i v e

of
than

is

r i c e s t r a w b u t i n c o n t r a s t , s t e m is

for-

t h e fna.jor- p o r t : i o n

rice

Leaf

the

'T'hi a

upper portion.

suppor.ted

Hart

by

and

value

hypothesis
(1986)

Wanapat

who

r e p o r t e d % h a t t h e l o w e r p o r t i o n oS r i c e s t r a w h a d a n
irt

r j i t r o d r y matter d i g e s t i b i l i t y v a l u e h i g h e r t h a n

(42 v s 29%).

t h e upper portion

This

M a s

t.houyht t o

b e mmairll y d u e t o t h e h i g h e r c o r - t c e n t r - a t i o n o f
in

the

available

].paves.

i t should be noted

But

C r o m t h e l i t e r a t u r e are

data

silica

that

the

based

on

T e s t i n g c-tnder . i n r./ic/o c o n d i t i o n

labor-ator-y s t u d i e s .

i s r ~ ? q u i r e dt p c l a r i f y t h i s h y p o t h e s i s .

2.

The H i s t o l o g y o f

Schematic
internode
presented
tubular

C e r e a l Straws
d r a w i n g s o+ t y p i c a l s l e n d e r
cereal

straws

are

(Staniforth,

1979).

The

c:rass-.sections
in
part

2

Figure
is

made

a

stemmed

of

up o f

of

small

v a s c ~ t l a r t:)undl e s e m b e d d e d i n p a r e r i c h y r n a t o n s

tissue

over

with

o~cter layer
numerous

epidermis

layer

an

'Table 2.

.------

".--.--

Botanical
portiol-1s
(% dry matter)

-------

of

cereal

.-..----------------

-----.-----------.-.---------.----.--.--

Str'aws
Internode
ldnde
Sten)
..-.-------------.--"-"----"-.---.---.----"-"-------------------------------

straws

Leaf

Reference

-

40

6C.)

( 2 ) 'T'hearider and
A m a n (1984)

50

8

58

42

(:L)

Spring

58

4

62

38

Winter

65

7

72

28

Oat

I54

4

58

42

E a r l ey

.-J

€3

7

65

-*
3 .J

Rye

72

r

'7 7

Wheat

3

,=.

(2)

C:hemical
compnsi t i o n and
in
vitro
d i g e . - i t . i b i l i t y oS r i c e s t r a w p o r t i o n s
-..--- "-----------..-----------------.---------------.---.--.
--.--Stem
Leaf
R i c e st.raw
---.---. --- .---- -----. ..-----.-....-----KeCerences
I
N
S
b
CJ
L.
C
T a b l e 3.

--

...y

Crude
prot.ei n

5

4

b

- .- - ---------------.----NDfz

ADF

..Z

IVDMD
IVUMU

-

( 1 ) t:::shanil::a
S a n n a s g a la and
J a y a s u r i y a (1984)

7

-

( 2 ) H a r t a n d Wanapat
(1YNh)

4

---.-----.--------.--------------------

'73

76

73

.

.-.

-

(1)

-

--

.--

-"

...-

-

73

(4) Jackson

5C)

ZjU

r

45

--

-.

..-

(

-

-

-..

54

56

..-

(2)

34

80

56

.-

-

-

(3)

6

6

6

-

.--

.-..

(31

'7

i4 !

8

J

"

)

-----.----.--.--------..--- Silica

-.

74

-48

Lignin

-..

2

4

h

-."-"

6

----

-..

-.

1

---.-

.....

2 9 LIZ
.--..---------------------.--"----------------.-.----------------7..,-,
-..
31
.ad.
.--..
44 4'7

(1977)

-"

-- ----- -----

(I)

(2)
(1)

I, i n t e r n o d e ; N, n o d e ; S , s h e a t h ; B , b l a d e ; U, u p p e r ;
L , lower; C? complete;
I\IDF, n e u t r a l d e t e r g e n t f i b r e ;
HDF,
acid
detergent
fibre;
TVDMU, i n v i t v o d r y
matteldigestibility;
IVOlblD, i r t v . i t r o o r g a n i c
matter d i g e s t . i b i l i t y

Winter

Winter

t

Oats

Rice
Densely lignified tissue
Lignified parenchyma
Vascular tissue

Figure

2.

1Unlignified

tissue

Central lumen

15)Air

cavity

1-ransverse s e c t i o n s of t h e i n t e r n o d e s of
c e r e a l s t r a w s ( S t a n i f o r t h , 1979)

11
( t h i n-wall l e d
layer

and

t h e t i s s u e s of

.

The

occur

scl er-enchymatous

t h e vascular bundles

m o s t ligniCied tissues.

the

But l i g n i n

e l s e w h e r e and t h e d e g r e e of

increased
(

1 i v i ng c e l l s )

1984)

were

with plant maturity.

found

may

of

also

lignification
Theander and

e p i der-mi s ,

5.-7%

s c l e r - e n c h y m a t o ~ t st i s s u e a n d 65-69% a f

is

Aman

straws

t h a t tl?e i n t e r n o d e s o f cereal

cornposed

are

25-27%

parenchyrnatous

t.i s s u e s .
Y o s h i d a et al.
blade,

s h e a t h and s t e m of

:Leaf

deposited
bundle

i n t h e epidermal

sheaths,

layer

a

bullifornl

i n t h e leaf
si 1 i c a

rice,

a n d s c l e r e n c l - l y f n a t o u s artd

of

The

leaf

cells

epidermal

vascular

is s u r r o u n d e d

including

which are o f t e n d e s c r i b e d a s

cells,

was

bul l i f o r m cells,

cells,

( F i g u r e 3).

bundle cells;
by

(1962) r e p o r t e d t h a t

the
the

c e l l s t h a t a r e r e s p o n s i b l e f o r t h e f o l d i n g movements

of

t h e 1e a v e ' s .

phloem

and xylem s y s t e m s ,

sheaths
most1y

Vascular bundles,

ar-e

present.

containing

both

and surrounded by bundle

The

embedded i n mesophyl 1

vascular
but

bundles

are

scl er-enchymatous

t i s s u e is o f t e n l o c a t e d a b o v e and below t h e b u n d l e s .
In t h e leaf
that

90%

blade,
of

the

epidermal t i s s u e s .

Y o s h i d a et a l .
si 1 i c a w a s

(1962) estimated

deposi t e d

in

A r e p r e s e n t a t i v e p i c t u r e of

the
rice

Leaf b l a d e

Leaf sheath

Internode

F i g u r e 3.

Schematic
r e p r e s e n t a t i o n of t h e s t r u c t u r e s of
l e a f b l a d e , l e a f s h e a t h and s t e m of rice straw
i n r e l a t i c ~ nt o ~ iliica d e p n s i t i o n ( I-ocation
o f si l i c a d e p a s i t i o r t ; B , F L Il ~i , F o r m c e l l s ;
P,
Parenchyma;
US, b ~ t n del s h e a t h ;
V , V a s c ~ t al r
bc.tndXe ( P h l o e m 8z X y l e m ) : S , S c l e r e n c h y m a ; M ,
M e s u p h y l l ; SL, S i l i c a l a y e r ;
E , Empty s p a c e )
( Y o s t ~ i c l a e t a]. , 1 9 h 2 )

,

13

e p i d e r m a l t i s s u e is p r e s e n t e d i n F i g u r e 4.

I t shows

how c l i f f i c ~ t - 1 1 ti t ir;

f u r p l a n t d i s e a s e s or i n s e c t s t o

attack:

:L n c w t : . ~ .o n

t.he

main

where

photosynthesis

occc-tr-s.
Akin
in

(19'79) t r a t a g o r i z e d d i f f e r e n t p l a n t t i s s u e s

r e 1 a t i o n t.t:,

G r a s s e s w e r e shown t o f o l l a w a

organisms.
pattern:

mesophyll

degraded,
bundle

sheath

e p id e r i l i s

cells,

and

was

and

then

slowly

and

F'robably,
its;

conski tctents,

due

1 inl.::ages

general

most

readily

parenchymal
-Followed

by

degraded,

t i sst-tes w h i c h w e r e t h e m a s t

digestion.

content.

by

which

lignified
t o

phloem w e r e

and

f 011 owed

s c l er-enchyma

micro-

t h e i r d a g r a c l a b i 1 j. t y b y r u m e n

resistant

t o t h e h i g h

w i t.h

other

and

silica

cell

wall

t h e p a t t e r n s h o u l d b e recor-f irmed

in

rice s t r a w .

3. C e l l Wall C o n s t i t u e n t s

a

R e i rlc~
predominantly

8(3%),

t.he

r esi d u e ,

h a s a h i g h cell w a l l
constituents

hemi c e l l ul a s e ,
predominating

senile

lignin,
(Jacksun,

attached to t h e w a l l

being

straw

content.

(about

most1 y

minerals
1977a) ,

rice

cellulose,

with

silica

a n d some n i t r o g e n

( T h e a n d e r a n d Aman,

1 9 8 4 ) . The

n u t r i t i v e v a l u e of rice s t r a w l a r g e l y depends

upon

Figure

4.

-

Schematic
representation
of
rice
leaf
e p i d e r m i s in relation t o si 1 ikon deposition
(
, Location of silicon deposition; C,
Cuticle;
SL,
S i l i c a layer;
SC,
Silica
c e l l u l o s e membranes
(Yoshida et al., 1962)

15

the

a v a i l a b i 1i t y

of

t h e cell w a l l c o n s t i % u e n t s

to

d i g e s t i a n i n t h e ri.tmen.
(:elli.tlose is a l i n e a r p o l y m e r c o m p o s e d o f u p t o

10,000 p1,4 .- 1 i n k e d g l yct:)pyr-anosyl ~ t ntis ( F i g u r e 91
(Theander
largely

and

&man,

crystalline

1984)

.

form,

I t

occurs

as

organized

a

in

fibrils,

w h e r e t h e c e l l ~ t l o s ec h a i n i s t i g h t l y p a c k e d t o g e t h e r
in

compact

a g g r e g a t e s st.trrounded

of

matrix

The g l u c a n c h a i n s are

other cell w a l l constituents.
held

a

by

t o g e t h e r by hydrogen bonds both between

sugar

u n i t s i n t h e c h a i n and between a d j a c e n t c h a i n s .
Xylans

a s t h e main u n i t nf

straws,

cereals

backbone

of

h)

'

p o l y m ~ rzi a t i o n

and

Aman,

generally

to

1984).

>: y l a n 5

of

t h a n t h a t of

conformation,

grasses

is

The

cellulose.

cellulose

it

degree

of

(50-2C)C)

Havi n g
can

a

(Figure

1o w e r

much

from

have

1 , 4 1i n k e d : . c y l o p i r a n o s y l u n i t s

{Theander-

residues)

and

hemicellulose

si m i 1 a r

be

strongly

associat.ed with o t h e r polysiaccharides.
P;~?owleclge a b o u t
reviewed

1i y n i n

by Jung and Fahney

has

been

(1983).

c u r r e n t 1y

s t r u c t u r a l s t ~ t d i e ss o f a r h a v e b e e n o n wood
( F i g u r e 7).

o+

a

most

However,

lignins

L i g n i n is a f a m i l y o f r e l a t e d p o l y m e r s

three--dimensional

phenylpr-apane u n i t s .

structure,

made

up

of

I t i s g e n e r a l l y a g r e e d t h a t p-

0-

-

\

7f-op(-),o

-O

F i g u r e 5.

OH

H

H

O O H

H

C e l l c r l ose s t r c r c t c r r a

H

-I-

(Theander and Aman,

1984)

X = D-XYLOSE

A = 1-ARABINOSE

GA = D-GLUCURONIC A C I D ( R = H)
OR4-D-METHYL
I'
(R = CH3)

-

F i g u r e 6.

S c h e m a t i c s t r u c t u r e o f a :.:ylan
( T h e a n d e r a n d A m a n , 1984)

-

( h e r n i c e 1l u l o s e )

-I
H C - 0 [CH~OH]
I

I
HCOU

HOCH2
I

HC
I

HCOH

I

HCOH

F i g ~ t r e7.

I

C =0

Schematic s t r u c t u r e o f
the
main
u n i t s irt
g y m n a s p e r m 1 i g n i n ( I t ? r a n d e r a n d Aman, 1984)

19
coumaryl

are

,

important

1i g n i n

precursors i n

a

via

complex

( T h e a n d e r - a n d Aman,
of

1984)

t:.he

(Plorrison,

Table

.

process

digestibility

Linberg et

some

h e r n i c e l l u l o s e , as w e l l

of

The b i g g e r t h e c o n t e n t

19'7Yts,

gives

4

biosynthesis

dehydrogenation

monomers t h e l o w e r t h e

these

straws

( F i g u r e 8)

c o n i f e r y l and s i n a p y l a l c o h o l s

values

al.

for

,

of

1984).

cellulose,

a s cell w a l l s a n d l i g n i n - f r o m

s t r a w s and some o t h e r agr-icult u r a l r e s i d u e s .
Average
is

presented

mineral

o f m i n e r a l s i n cereal

content
in

T a b l e 5.
v a r - i es

content

agronomical

factors

and

mineral

widely

content of

depending

on

amount

cc~ntertts of

straw

1 e v e 1 s. C o b a l t

of
Leng

s t r a w s is g e n e r a l l y l o w

,

are

Calcium and
be1o w

u s u a l 1y

copper,

sulphur

and

rice s t r a w

the

s o d i ~ t m may a l s u b e

limiting.

average

a s h is a b o u t t h r e e t i m e s h i g h e r

c o n t e n t of

Xn

Cor

adequate

m a i n t e n a n c e a n d f o r wor-k b y r u m i n a n t s .

reczommended

the

According t o P r e s t o n and

i m b a l a n c e d b u t t h i s may b e q u i t e

phosphor(-ls

that

also with t h e

and

con t a m i n a t i n y s o i 1 .
(1984),

I t i s known

straws

t h a n i n t h e o t h e r s t r a w s a n d t h i s is m a i n l y d u e t o a
h i g h e r si 1 i c a c o n t e n t .
Althouqh

i t is a c c e p t e d t h a t s i l i c a is o n e

t h e major f a c t c ~ r sl i m i t i n g t h e d i g e s t i b i l i t y

of

values

Figure

8.

Schematic
str~lctt.tr.e o f
p-Co~tmaryl(I1,
C o n i f e r y l ( 1 1 ) and
S i n a p y l (111)
alcohols
(T'heander and Aman, 1984)

Tab 1(zl! 4.

- -..

--

Ch(sfit1c a l composi t.1on
o f some roctghages
(Theartder and Aman, 1984)

-

Rot-lghage

.._._ ..--..--.-..-- -.---...-----.-.-.-.--

Cell wall s

-----------.-..--

t4erni c e l l c t l o s e

------

C e l l u l ase

L ig n i n

44

'7

36

39

10

3(1)

31

11

14

39

11

15

C'

..JCI'..

13

Hat- 1ey s t r a w

81

27

Oat s t r a w

73

Ib

Paddy s t r a w

'79

26

Wheat s t r a w

130

Sor-ghum s t o v e r

74

Chickpea s t r a w

62

Li.tcerne s t r a w

b9

Sugarcane bagasse

82

29

Sugarcane t . r a s h

80

26

Faddy h u l l s

(36

C:c~tton seed h u l l 5

V1

_-__--_------------"_-_--"--__-----.---_.-.--------

-..--.-.- - - --- --.-

.-.-------

----------

I
-

T a b l e 5.

Contents of m i n e r a l s i n c e r e a l straws
(Theander and Aman, 1984)

-----------------------------.--------.----------------------------Mineral

Unit

B a r 1ey

Oats

-------------.---.-------.-.---.---

Rice

Rye

----------------..--------------

Spring
wheat

Winter
wheat

---------

Gsh

g /' I:g
:

60

59

1t39

3 (7

61

50

Silica

g / k ~

15

11

130

34

31

32

C::

g / I::g

9.B

11.8

10. O

Na

g i I::g

-"

0 5

.

0.5

0.5

S

g / I:(3
:

3.

2,

1.2

1.4

1.6

-

0. 0 5

Cn

111(7 /'::.I

g

.

14. (1)

.4

- ..-

(->

.

2,

21.9

13.2

-

-

2.5

1

.

0 09

....-

-

0.08

23
of

its

straws,

known.

chem:ical + o r m u l a i n p l a n t s is

J o n e s and Handreck

not

(1978)

(1967) and J o n e s

specrt-(1a t e d t . h a t i n s o i 1 ,

monosi 1i c i c a c i d s ( H 4 S i 0 4 )

could

atom v i a a

jain

t o a n a:.:ygen

hydrogen

bond

t h a t . b r i d g e s t w o i r o n atoms a s :

. ..O ( F e x Q 4 H 4 )

( O H ) :&i -0-H.

i t is l i k e l y t h a t s i l i c a c o u l d also b i n d

ThereSore,
iron

or

atoms s i n t i l a r t o t h a t i n

other

h e n c e may r e d u c e t h e i r a v a i l a b i l i t y i n
that

is t h e case,

silicates

in

The

and

straws.

If

c o n s i d e r a b l e l o s s e s of
are d u e t o

faeces

si 1 i c a i n s t r a w

soil

the

( T h e a n d e r a n d Aman,

content: of

salts

presence

as
of

1984).

straws

c r u d e p r o t e i n i n cereal

i s 1o w ,

4.--7% d e p e n d i n g ccpon v a r i e t i e s a n d f e r t i 1i z e r

applied

(Koxas e t d l . ,

and

Aman

most

(1984),

1i k : e l y

Meanwhile

t h e major p a r t o f t h e p r o t e i n

a s s n c i alred

van S u e s t

insoluble

1.985a). A c c o r d i n g t o T h e a n d e r

in

with

the

(1985) r e p o r t e d

acid-detergent

cell
that

is

walls.

nitrogen

e s s e n s i a 1 1y

is

i n d i g e s t i b l e i n ruminant d i g e s t i o n .

S t r c r c t u r e o f C e l l Walls

Rased
sitrc.tct.ures
si 1 i c a ,

re11

on
c3+

knuwledge

(:el 1 c.tl o s e ,

t:I-)~?1 cherni c a l

wall

o+

the

of

l-terni c e l 1 u l o s e ,

chemical
1i g n i n and

b o n d s t h a t i n t e r l i nl::i n g

ccmsti tctent

are p r o b a b l y

depicted

each
in

24
Figctre

C e l l ~ t l o s e may b e e i t h e r

9.

hydrogen

hnnded w i t h s i l i c a

Hydr-ugen

9).

hemi c e l l u l ose

arrd

S e t t e r - f i e l d and

Harley

Lignin

be

may

(1973)

Figure

to

attached

by

9).

cellulose

si 1 i ca br-i d g e s (see b a n d c i n F i g c t r e 9 ) .

through

may be

Lignin
throt-tgh 0-Si
of

indirect1y

between

suggested

see d i n

(

Figure

B a u e r e t al.

(1961),

(1973)

linkages

were

cell u l o s e

K e e g s t r a et a l .

and

(see g a n d c i n

or e s t e r

bindings

or

covalently

bond

c o v a l e n t 1y

with silica

linked

l i n l . : : a g e s (see b i n F i g u r e 9 ) . T h i s t y p e
be a l s o f o u n d

could

si 1 i c a

between

and

g l u c o r o n i c a c i d i n h e m i c e l l u l a s e s t r u c t u r e (see i i n
Figure

ester

?

L.i y n i n

(see a i n F i g u r e 9 )

linkage

through

may 1i n k h e m i c e l l u l o s e

ether

(see

linkage

j

and

in

through
cellulose

9).

Figure

H e m i c e l l u l o s r i s 1 i n k e d w i t h si 1 i c a p r o b a b l y t h r o u g h
c o v a l e n t u r h y d r o g e n bond

[see e a n d c i n F i g u r e 9).

In a d d i t i o n , hydrogen band between t w o g l u c u s e u n i t s
in

t h e c e l l u l o s e s t r c t c t t - t r e (nay b e f o r m e d b y

plants
of

(see k i n F i g u r e 9). I n m i c : r o s c o p i c a l s t u d i e s
J o n e s ct a l .

oat plants,

s i l i c a w a s a n i n t e g r a l p a r t of
cell

mature

wal.1

deposi t e d

and
in

c o n s t i tc.tents

they

(19h5) i n d i c a t e d

t h e t h i c k e n i n g of t h e

suggested

that

intimate association with
of

the

wall.

that

A

silica

was

the

other

p o s s i b i 1i t y

that

I = ' i g ~ t r e9.

F"o~jsi
bl e

c h e m i c a l 1i nk:ages between c e l l
wall
-.. , w a t e r - f o r m a t i o n ; a , ester
c a n s t i t ~ t e r t t s(
1 i n k a g e s b e t w e e n h e m i c e l l u l o s e a n d 11 i g n i n ; b ,
1 i nC::ages b e t w e e n 1 i g n i n a n d
si l i c a ;
c
S i -C1
h y d l - o g e n h a n d h e t w e e n si 1i c a a n d
c e l l u l ose
(however,
t . h e t:)ortd c o c ~ l db e a l s o p c l s s i b l e i n
f o r m o f c:ovaler-lt 1 i n k a g e s u c h a 5 i n b a n d e ) ;
d,
ester
1i n k a g e between
c e l l t.11ase
and
hemi e e l l u l ose; e , c o v a l ei-11:. b o n d b e t w e e n si 1 i ca
ancJ
hemi c e l l u l ose
( t h e bond
co~th
d
b e a 1so
possible
i n f o r m of h y d r o g e n bond s u c h a s i n
c j ; f,=c;
g , ;
h , hydrogen
br.nd b e t w e e n
5
1i a
a n d i ror.1 ( a d o p t e d f ram s o i 1
science) ;
i = ;
j , ether
1 i n k a g e b e t . w e e n 1i g n i n
and
I ,
hydrogen
bond
between
two
e e l l ul o s e ;
g l . u c n s e u n i t s i n cel l i r l a c ~ es t r u c t ~ l r e i

:.-:

,

26
p h e n o l i c tnoncxners o r - 1i g n i n ar-e 1i n k e d .to u t . h e r c e l l

t h r t 1e y

corsst i t u e n t . s wa5i r e p n r t e d b y

wall

(

1 9 7 5 ) who

ct!sed 1.01.ium m u 1 tif'lorum + ( w a g e .
I t i s n o t known how many b a n d s e a c h c o n s t i t u e n t
can

tu

use link

other

cell

wall

constituents.
1i n k a g e s are

Prohahl y the m o r e f r e q u e n t t h e chemical

t h e m o r e c l i f f i c t - t l t i t i s f t ~ rrt-{men m i c r o o r g a n i s m s t o
digest

t.he

cell

wall.

Morris a n d

Bacon

(1977)

s u g g e s t . e d the need t o c o n c e n t r a t e a t t e n t i o n upon t h e
I: y

a

l a n s t r u c t i . t r e r a t h e r t h a n a n t h e t l e r n i c e l l ul ose

as

d i g e s t i h i l i t : ~w a s r e p o r t . e d t a

be

whole.

Xylan

l o w e r when h i g h e r a r a h i n o s e c h a i n s w e r e f o u n d o n t h e
>: y l an

s2:ructure

enzyme

becat-tse o f

t h e redi.tc:ed

a t t a c k between a d j a c e n t ,

sites

unat.tached

for

xylose

~ t nt.s.
i

T h i s is r e p r e s e t - j t e d i n F i g u r e 1.0 I M o r r i s o n ,

1979b.

However,

xylose

ikself

Morris a n d H a c o n

(19'7'7) f o u n d t h a t

w a s less d i g e s t i b l e t . h a n

arabinase.

Hnrided ~ i l l c aw a s t h o u g h t t o b e s t a b l e i n
weal::

al1::al.i

slightly

anel

acid

r5:jcn:Lubil i z e d

(Jones,

1978)

t o Sor-m

si 1 i c a t e

when t h e ptl w a s n i n e o r m o r e
ct a 1 . ,

'1-hi s
c o ~ tdl

198r:i;

sctggests
be

(Ja(:l::son,

H a r b e r et a.1.

t.l-rat

(..\zed t o

d i g e s t i b i l i t y c:aused b y s i l i c a .

it

but

campounds

1981.; H a r t l e y ,

t:he

was

1977a; M~tdgal

ei t . h e r s t r c m g a c i d

reduce

both

or

hi ndrance

19f31).
a 1 l::al i

to

In a d d i t i o n , silica

F i g u r e 10.

The e f f e c t . of a r a b i n o s e suhr;t.itution an
the
d e g r a d a t i c ~ n o.f : . : y l a n s (
=
xylose;
0 =
arabinose;
& = sites of. m i c r o b i a l a t t a c k )
( M o r r i s a n , 177Yb)

can

h e d i s s o l v e d by h y d r a f l u a r i c a c i d

f 1uor.ide-csi 1 i c a t e

but

(HF) t o

c o m p o u n d is

this

form

toxic

to

a n i ma1 s.
Our k n o w l e d g e on t h e c h e m i s t r y o f
of

is 1i n r i t e d and w e h a v e t o

c r - c ~ phy-procli.tc:ts

~tporl i n f o r - m a t i on

d e r i ved from

wood.

In

major

deposit.iun l a y e r s namely,

wall,
of

the

secondary

According
af

componentv

to
the

Noqg1.e

hemicel l u l o s j e s ,

e

Keegstra

cell

primary

consi s t i n g

wall

.

and

Fritz

cel l u l a s e

(19761,

of

the

Sycamore

nricrof i b r i ls,

pectic. pol ysacchar i d e s and protein.
a].

(

1973)

st-tggested

that

occur i n t h e primary cell w a l l

cnmponerits

of

is d i v i d e d i n t o 2

primary cell w a l l

p s e u b o p l a t a n ~ l s ) are

rel y

str-c-tcture

the

cell

s e v e r a l l a y e r - s ( F i g u r e 11)

(Acer

the

p r i n c i p l e t h e cell w a l l

and

t h e cell w a l l

these

of

other

p1ant.s and t h e y proposed a t e n t a t i v e primary

higher

c e l l w a l l s t r u c t u r e shown

12.

i n Figure

t-lowever

,

it

seems t h a t t h i s a r r a n g e m e n t i s f o r y o u n g p l a n t s .

At

m a t u r i t:y

m o s t 1y

been tr-anslacated from t h e v e g e t a t i v e

to

parts
197'7b

)

p r o t e i n a n d s o l ~ t b l ec a r b o h y d r a t e s

.

the

grains

(Qnderson,

Consequently,

the

1978;

plant

have
plant

Morrison,

residue

c o r i s i st m a i n l y s t r ~ t c ~ t ~ t cr aarlb o h y d r a t e s p r o b a b l y
form of

c:rysta:lline.

w i l l

in

I t i s n o t known w h e t h e r l i g n i n

Warty l a y e r

1
PW,

Secondary w a l l l a y e r s

Primary w a l l

P
Ml,

F i g u r e 11.

Middle l a m e l l a

Schematic represent.ation of t h e v a r i o u s l a y e r s
of
an u n l i g n i f i e d cell w a l l of a h i g h e r p l a n t
( J u n i p e r , 1978)

11 111 Ill

F i g u r e 12.

11 Ill 111 111'1 1 - 1

A

-

t e n t a t i v e molecular s t r u c t u r e of
Sycamore
cell
walls
primary
, cellulose
el e m e n t: a r y
fibril
, xyloglucan
(hemicellulose)
protein
with
4*
a r a b inosy1
tetrasaccharides
glycosidicall y
to
t h e hydroxyprol i n e
residues;
attached
,total
pectic
pol ysaccharides;
,r h a ~ n r t o y aal c t u r o r t a r t m a i n c h a i rr o f
t.he p e c t r i c
pol ysaccharide;
1 , a r a b i n a n and
4-1 inl::ed g a l a c t a n
s i d e c h a i n s r ~ ft h e p e c t i c
p o l ymer- ;
-C$- , 3 r b - l i n L : e d a r a b i n o g a l a c t a n
a t t a c : h e d .to s e r i r t e o f t h e w a l l p r a t e i n ; --r-.
~ c n s c t b sit t t . \ t ~ ? ( S
ser y l
resi dc.ces o f
t1-t~ w a l l
p r o t . e i n 1 I f : I e e g s t r a e t a l . , 19.73)

-

-d+*

7-Y

,

31
and s i l i c a are d e p o s i t e d i n t h e p r i m a r y cell w a l l of
plant residues.

a

Rlt.hough

very ordered arrangement h a s

~3astc.tlated for- p r i m a r y c e l l w a l l s ,
I.::nown

;Jt..rni per-

(

19781 ,

anci T a l m a d g e et

t h a t s e c o n d a r y cel l w a l l

suggested

very little

the s e c o n d a r y

a b o u t t h e a r c h i t:ec: t ~ t r - . eo f

wall.

.j

type

is

palyphenylproparloid,

encr~rsted
liynin,

deposited

are

aromatic

i t r e a d i l y forms

and

(J~rnipcr-, 1978).

cell

(1Q73)

dl.

the

chemical bonds with a wide r a n g e of
constituernts

is

Into a certain

a f t e r - t h e cell h a s c e a s e d expanding.
cell

been

o t h e r cell

wall

Apart from l i g n i n ,

s e c o n d a r y c e l l w a l l s are m a r k e d b y a g r e a t a m o u n t o f

el l u l o s e d e p o s i t i o n (A1 b e r s h e i m ,
t o J o n e s et al.

Acccrrcliny
Handreck
(19'78)

(

136'7)

and

,

van

1965).
(19631,

v a n Soest a n d J o n e s
Eys

(1982)

(

silica

Jones

1968) , J o n e s

may

play

import.ant role i n l i m i t i n g cell d i g e s t . i b i l i t y
silica

in

t h e cell w a l l

is t h o u g h t

b e t w e e r 1 cell{-rlose m i c r o f i b r i 1 5 ,
pectins,

h e m i c e l l u l asp

and

to

analysis

c n n s t i t u e n % s of

can

since

o r t o i n t e r a c t wit.h

phenol ic

compounds

t h e r e are nu a v a i l a b l e methods of
which

an

polymerize

t h e r e b y d e c r e a s i n g t h e d i g e s t i b i l i t y n+ f o r a g e
present,

and

determine

the

t h e v a r i o u s w a l I. 1 a y e r - 5 .

.

At

chemical

cell

wall

5. F a c t o r s
Affecting
Chemical
D i g e s t i b i 1i t y o f C e r e a l S t r a w s .
One

v a r i a b i 1i t y

in

d i g e s t i b i 1i % y
respnnsibl e

their

chemical

for

the

The main

ar-e

v a r i a b i 1i t y

and

a p p l i c a t i o n of

fertilizer.

nlanagernent

practices

a n d K s h a n i l::a S a n n a s g a l a a n d J a y a s u r i y a
€3).

and

factors
genotype,

as

such

f a c t t h a t t h e r e is v a r i a t i o n between

g e n o t . y p e s w a s s h o w n b y R o e a s et

straw

the

is

composition

( T a b l e h a n d 7).

e n v i rc3nmen.t.,

The

cereal s t r a w s

t h e f e a t u r e s of

of

and

Composition

In

R o x a s c t al.

t h e work o f

v a r i et i es

al.
(

rice

(1985b)

1 9 8 4 ) ( T a b 1e

(1904),

rice

15

w e r - c g r o w n a t t h e same 1 o c a t i o n a n d h e n c e

environmental e f f e c t s w e r e minimized.

The

obtained

in

considerable

v a r i at.ion

i r l t h e c h e m i c a l c o r n p o s i t i o n a n d irr

digestibility

In

rice.

this

of

%he

Jayasuriya

st.t..rdy

indicate

results

~ ~ i t r c ~

s t r a w from d i f f e r e n t v a r i e t i e s
o.F

work

(1984),

C::shani l::a

Sannasgala

9 r i c e v a r i e t i e s w e r e grown

t w o main r i c e b r e e d i n g s t a t i o n s ,

so t h a t

of
and
at

variation

w o ~ tdl h a v e i n c l ~ r d e d e n v i r u n m e n t a l a s we1 1 a s g e n e t i c
d if +erences.
van

S o e s t . ef al.

o f f e r t i 1 i. z e r ,
light

(1.978) s u m m a r i z e d t h e e f f e c t

w a t e r appl ication,

intensity

on

chemical

temperature
compasit.ion

and
and

d i g e s t i b i l i t y i n f o r a g e s ( ' T a b l e 9 ) . However t h e y d i d

T a b l e 6.

V a r i a b i 1i b t y i n
chemical
composition
i%d r y
m a t t e r ) and in v i t r o
organic
matter d i g e s t i b i l i t y (IVOMD) of cereal
s t r a w s ( v a n Soest method)
---------------.------.-.-------------.---------.----------------.-----

-

Straw

-.-----.-----------------------Wheat

Oat

NDF

Range
Lignin

Range

-

-

76-03

79-82

8-10

8-15
-.

--

8-15

4(:).-45

40-43

40-45

40-43

49-63
43-53

49-&1
43-50

43.-55

43-58

Hemi c e l l u l o s e 17-28

25-26

Range
ADF

-

-

Range

-

Range

17-28

-

-

-

25-26

Silica

Range

-

-

1-8

1-3

Range

*

3!:)-50

References
Rice

- P e a r c e et a l . ( 1 9 7 9 )
54-71 Hoxas e t a l . (1985a)
'72-81 Kshani k a Sannasgal a
and J a y a s u r i y a ( 1984)
49-80 Anonymous ( 1982a)
49-81
5-12
3-16
5-16

-

8-10

(:el 1u l ose

Barley

-

P e a r c e e t a I . (1979)
Roxas e t a1. (1985a)
Anonymous (1982a)

Pearce et a l . ( 1 9 7 9 )
21-39 Anonymous ( 1982a)
3 1-35)

L

-

Pearce et a1.(1979)*
Cilderman (1776)
40-.71 Anon ymous ( 1982a)
40-7 1.

P e a r c e e t a1.(1979)
10-36 4nonymous ( 1982a)
10-36
- Pearce e t a l . ( 1 9 7 9 )
16-22 Roxas e t a l . (1985a)
5-8
E s h a n i k a Sannasgal a
and J a y a s u r i ya ( 1984)
4-24 Anonymous (1982a)
4-24
Winuqroho (1781)
Pearce et a l . ( 1 9 7 9 )
A1 derman ( 1976)
Roxas e t a l . (1985a)
Roxas e t a l . (1985b)
K s h a n i k a Sannasgal a
and J a y a s u r i ya (1784)
Anonymous ( 1982b)

34-48

C a l c u l a t e d b y a d d i n g l i g n i n t o c e l l u l o s e and s i 1 i c a c o n t e n t s 3
NDF,
neutral
detergent
fibre;
ADF, a c i d d e t e r g e n t f i b r e

Table 7 .

Variability
i n
chemical
composition
i%d r y
m a t t e r ) and i n v i t r ~ . ) o r g a n i c
m a t t e r d i g e s t i b i l i t y (IVOMD) o f c e r e a l
straws
!Weende
method)
(Anonymous,

1982a)

Crude
Ether
fibre
e:.:tra:.:t.
..................................................................................

s-irLaw

-T DhI

Crude
Ash
p r o t e i r~

P VUMD

------------------------

5-

Rice

24-38

1

Corn

--77--34

Sweet
p o t a t o e s 14-29

.-

41-51

3-.-7

1-2

4'7--62

:3-'7

I-' .J

35--5'7

8-14

f.7

l ~ - -L,J, - i c 41-.-4'7
17

1i:)-2r+

34-42

4,5--5(:)

26-55

4 1-70

Li3-65

Tabel 8. Vari abi l i t y of chemical composi ti an and
i n v i t r o urganic
matter digestibility
(IVOMD) af rice straw

n varieties
Crude protein
I\IDF' ( % )

15

5 - 9

(%)

54

Lignin ( % )
Silica

(%)

IVOMD I % )

f.~efe!e-~-~e.
Roxas

5
I&

--

71

- ;la
-

22

31 - 4 6

et ai.

(

1985a)

I.::shani
k a Sannasgal a
and Jayasuri ya ( 1984)

T a b l e 9.

I n . f l c t e n c e u.f e n v i r o n m e n t a l f a c t o r s upon
cocnposition
and
digestibility
oS
f o r a g e ( v a n S o r s t e t a l . , 1978)

------.----------.---------------------

-----------_--_-....._
-__--.-----_--_

---.

_..-.----

N ltrogen
.-.-

Water

---------------------.--

------------------------

Temp.

L.i g h t

Yield

-4.

.C

+

+

WSC*

-

-

-.

+

Cell w a l l content

+
.....

.+

.t.

-

Lignin content

-4.

-4.

+

-.

Digestibility

+.-.

-

-

+.

+k

Water s o l c t b l e c a r b o h y c i r a t e s

-

s7

not

explain

how

these

factors

influencing

An a t t e m p t t o p r e s e n t r e a s o n s w i l l b e

digestibility.

g i v e n i n t h e f 01 1 o w i n g p a r a g r a p h s .
to

Accord1 ng
increasing
improve
are

either

Jones

and

Handrecl::

e i t h e r I\J or F'

fertilizers

amount of cereal y : i e l d b u t t h e

the

more 5 u s c e p t . i b l e .to f i r n g a l a t t a c k s .
thr

reduce

(19671,

n u t r i . t i v e v a l u e of

the

will

plants

This

crop

will

residues.

from

Increasing t h e nitrogen f e r t i l i z e r application
C::g N / h a t e n d e d t o i n c r e a s e t h e c r u d e

0-120

c:untent
VY't r ~ )

protein

t h e s t r a w f r o m 5.8 t o 6 . 3 % b u t

of

digestihi1it y

not

was

( K o x a ! ~e t

ni trogen appl i c a t i o n

the

increased

by

the

1985b).

dl.,

in

Most

n i t r o g e n is p r o b a b l y a t t a c h e d t o c e l 1 w a l l s t r u c t u r e
and

i t is n o t r e a d i l y a v a i l a b l e f o r rumen

(van

Snest,

available

Nn

1985).

on

the

paddy

s i l i c a when

fieldsheavilywithNandP.

straw

on

J o n e s a n d Handrecl::

t h e addition of

(1967)

fertilizing

Yoshidaet

(1959) d e m o n s t r a t e d a marked i n c r e a s e i n growth
production
silica

such

dl.

and

f a r r i c e p l a n t s grown i n t h e p r e s e n c e of

('Table

apl ication

are

data

e f f e c t of f e r t i l i z e r s

qua1 i t y a f ter h a r v e s t .
suggested

other published

microbes

are

10).

The

advantages

increasecl r e s i s t a n c e

a s b l a s t a n d brown d i s e a s e s ,

and

o.f

to
to

silica
d i 5eases
insects

T a b l e li':).

E + + e c t 0.f: s i 1 i c a p r e s e n c e on g r o w t h o f
r i c e p l a n t s ( Y o s h i d a e t al., 1959)

-------.----------..--

-.-----.--.-.-..---

---.--.-----

-.-----.-------------Si F e r t i l i z e r
-.------.-.---------.---

-----

- ------ ----. --

I

Shooth l e n g t h

----------------------

(app.

1--

rm,

-.. --.--

+
--. --.- ------------.- -----------

..
s ma)

Transpiration*
Grain t o t a l

Leaf b l a d e

15

12

1400

(DM)
(%!

L e a f s h e a t h 8~ stem
Leaves

92

90r:)

number p e r - - g r o u p

SiC12 c o n t e n t

85

("1

.
0.1

(%)

s Grams o f

water

19.2

0 1

(%)

___----_-----_-.-..---..-------.---.-.-----.----

.2

-- ..-.--..--..- -.- --.-.--- -

l o s t p e r gram o f

13.7
12.4

-----------.-

d r y w e i g h t p e r day

39

st-tch

a s r i c e b o r e r anti l e a f

spider,

e f f i c i e r i c ~ y of p:l a n t w a t e r e c o n o m y .

and

increased

They a 1so showed

that

h e i g h t : o f t h e p l a n t was i n t r r o a s e t i b y 8%.

wi II

pr-ovi d e

rrlore

a r e a s exposed t o

si 1 i. c a

Tt~c highest

the

sun1i g h t

were

(:oncentrat.i. o n s

This

in

1e a v e s w h e r e t h e p h o t o s y n t h e s i s m o s t 1y o c c u r .
a l l o w some p r o t e c t i o n a g a i n s t p l a n t

w i l l

.

the
This

parasites

a n d d i seases.
is a b s o r b e d h y r-ice p l . a n t s i n t h e

Silica
of

fnonosi 1 i c i c
The

1967).

acid

,

H 4 S i U4

the

Handrecl::,

Harldreck

p r o c e s s is p a s s i v e d e p e n d i n g upon

silica
15'67;

parts

exposed

yr-own

irr

~cptaC::e b y

dry

plant.%

ta
r

areas

the

and
Plant

t h e s u n l i g h t or p l a n t s
1e

ly

to

have

higher

t . h e r e f ore i t i 5 e x p e c t e d

t.rans[:,ira.tior.l r a t e s ,
this

r n a t ~ ? r i + ~wl o u l d h a v e a h i g h e r

than

shaded

plant

(Jones

1 9 7 11 .

S a n g s t e r and P a r r y ,
directly

,

1"tie h i g h e r t h e r - a t e , t h e

p l a n t t r a n s p i r a t i o n rate.
higher

( J o n e s and

form

p a r t or p l a n t s

si I i c a

grown

that

content
in

cool

areas.
According
deposited

in

to

van

three

Eys

1ocati o n s

i n t r a c e l l ~ ~ l a r ,i n t e r c : e l l u l a r ,
which

w a s mainly responsi bl e f

digestibility.

(1982),

silica

being

cJr i n t h e c e l l
01-

was

ei t h e r
wall

r e d { - c c in g c e l 1 w a l I.

S t ~ t des
i whi c h sc.tggest.ed

t h a t si 1 i c a

40
tji

d n a t r-edctcze t h e d i g e 5 t . i b i 1 i t y o f

t.ha.t

of

mos.t

the

i n t r a c e l . l ul, iar-

and

than

c:ell

in

the

s:i l i c a h a d

Jones,

deposited

(Mlr~son, 19'71).

Qther

r;i 1 i c a h a d r e c i u c e d

imp1 y t h a t l a r g e q u a n t i t i e s o f

et

Smith,

19hB;

in

rather

b e e n d e p o s i t e d i n the c e l l w a l l s

had

imp1 i e d

1o c a t i o n s

s t u d i e s wl-jic:h i n d i c a t e d t h a t :
diqestlbility,

beer,

i n % e r c e l1 u l a r

w a l l s

straw,

al.,

the

silica

( v a n Soest a n d

1971).

uni t

One

i n c r e a s e i n si 1 i c a c o n t e n t r e d u c e d d i g e s t i b i 1 i t y
( S m i t h et a l . ,

one u n i t

Soest a n d J o n e s ,

of

a v a i l a b i 1i t y

Water
S ~ C ~ W I It c 3

been

Duantitative determination

f o r e a c h l o c a t i o n is n o t y e t a v a i l a b l e .

silica

was

or t h r e e I - t n i t s ( v a n

9 7 1 ,

1968).

dur-ing t h e growing

lC?B1;

(Jones

and

P~trser,

1982

1985b).

With

rice,

reported

that

lowering

Jones
the

meast-(re

rice

in

the

leaf

.

and

Handr-ech

result

rainfall
in

content

a c c ~ t m ~at tl i o n

blades hut they

did

not

before

and

Based on t h i s n h s e r v a t i a n ,

during t h e

1c)~er-

J rt

growing
~/x'tr.c:r

al.,

(1967)

water

soil

r ~ o t si.ir-131,-is i rlq t . h a t a r e s o i 1 w a t e r c o n t e n t
higher

1967;

a n d H o w a s et

d i g e s t i b i l i . t y ut: t h e l e a f

a f t e r .treatment

have

tiandrecl.::,

r - e d u c e d t r a n s p i r a t i o n ancl r e d u c e d t h e
silica

period

a + +e c t s t r a w qi.tal i t y a f t e r g r a i n s

harvested

Winctql-.ohm,

of

by

i t is

due

period,

organic

to
will

matter

41
d i y e s . t i b j . l it y
1981;

vali.tes

F'c.trser,

1982).

f o r wheat.

straw

H i g h s o i l water

(Win~tgroho,

content allows

t h e t r a n s p j . r a t i on r a k e t o i n c r e a s e hence
the

plant:.

s i l i c a content.

r e p o r t e c l that:

P a t e 1 and

increasinq
Shah

t h e cr(..tde f i h r - e c o n t e n t uf

was h i g h e r when t h e wheat was i r r i g a t e d

(1957)

wheat

straw

(41 v s 31%).

Probably t h e straw obtained from t h e i r r i g a t e d areas
wot-tld

h a v e s i 1i c a c o n t e n t h i g h e r t h a n t h a t o b t a i n e d

+ram t h e n o n - - ir r i g a t e d a r e a s .

al.
had

(1985b) showed t h a t

I n contrast.,

Haxas et

i n t h e wet season r i c e s t r a w

a 17% ! s i l i c a cuntcr-llz v s 15% i n t h e d r y

season,

and t h a t s t r a w o b t a i n e d i n t h e wet season had an

in

cjitro organic matter valire higher than t h a t obtained
i n

t h e d r y seasnn

r - e s u lt s

between

differences
silica

i n

(48 v s 44%).
the

between

two

s t u d i e s may

plant

c e l l walls,

The d i f C e r e n c e

species

i n

It i s

cjue

i n

effect

of

soil

transpiration
different

water

rates

plant

content

and

s i 1i c a

apecirs

upon

the

relative

deposition

i n order t h a t

the

important

a + u r t h e r s t u d y b e undertaken t o observe

that

to

depositing

o r between seasons

r ~ fs a i 1 w a t e r c o n t e n t .

magni t u d e

be

i n

effect

i n
on

s t r a w qua1 it y (ran b e e s t a b l i s h e d .
Higher
transpiratior-I

temperatures
rates

i n

r,timu1a t e s

p l a n t s which i n

higher
turn

are

42
1 ik e l y

t o

higher

c:oncentrations

Higher

1 igt3.t i n t e n s i t y may i n c r e a s e

t.her-eby
plants
i.rnder

reduce

straw

f : > r o v i dng
i

thror-rgh

s i li c a

of

h i gher

i n

I.evels

ca~tsing

cell

walls.

photosynthesis

of

nutrients

i n

i t c o i . ~ l db e t?:.:pected t h a t : st.raw o b t a i n e d

;anc:l

t:ondi t i ons waul d be o f

these

i f

t.iowever-,

qctal it y

t.he

higher

h i qher

light

value.

intensity

i s

accompanied b y a h i g h e r t e m p e r a t u r e t h e n t h e e f f e c t s
of

t h e t w o c l i m a t i c f a c t o r s on s t r a w q u a l i t y w i l l

be

c o n f ounded.
&rite

apart from t h e e f f e c t o f

on st.r-ak~q r - t a l i t y ,

rr,aturity
reduc:ec.J

and d i g e 5 t i b i l i t : y

content

of

increase w i t h

digestibility.

1978;

Morrison,

pr-oceedi ng

with

a

Therefore,

g r a i n harvest.

yrain

decrease

wheat

be

1979a).

harvest

harvest
i n

S t a n i f o r t h and C o l l i n s

date

t h e y d i d not.

straw

i t i s n o t wise t o delay

mentioned a reduct.ian i n t h e q u a l i t y o f

However,

plant

(1978) r e p o r t e d t h a t t h e c r u d e f i b r e

period

si mu1taneoi.ts1 y

the

wall

wheat and b a r l e y s t r a w i n c r e a s e d o v e r a

khr-ee--weel.::

when

i s call

of: t h e m a t e r i a l would

( N i l m a n and D a l y ,

Manl.ey and Wood

the

the proportion that

t h a n c e l l content. w i l l

rather-

climatic factors

was

delayed

(1979)

wheat

straw

one

week.

o b s e r v e t h e same e f f e c t when

w a s grown d u r i n g w i n t e r .

F'robably t h e lower

4J
'7

t..e~nperaki.tr-es

have

wot..tl d

j.

n f 1 uel-tcecj

result

the

t t - I I - C I L I ~ ~~ : ~ ~ ' . . c ~ d ~ t a( : : si nlgc ~ ~ ~c : eh arn g e i n

the

relative

~ ~ r a p c 3 r " t i o n0.f:
s c e l l r - ~ a l . 1 5a n d c e l l c o n t e n t : .
In
lead

addition,

.to

1.oss o.F I:)rit::tle

the

alter

quality

inflc.tencec1

% e a v e s whi'ch

+:.tern r a t . i n a n d

leaf:

t3.f:

straw.

the

timr?

w i l l

:in i:t.tr-n

will.

d e l a y i n g . t h e har-\./er?t

lhe

t ~ y {nethocl of:

af:+ect t h r

ratio

harves.t.

may

end
be

also

Mechanical

and

t h r - e ! s h i n g h a r v e s t : : i t - ~ g m e t h o c l s c a n cat-ts;e h i g h e r d r i e d 1e a f

I c)e;s compar.ec:l t:n rnanctal h a r v e s . t i rtg d o n e w i t t l

a 17cJ

ife

.t:racli t i a n a l

I-t

y
5imt.tl.t:anec:)c.t~l

cart b e ~ t s e d.to el i m i r ~ a . k e rac:hi s C r o m

t h e s%:r-aw.

I.:

F i a c h i s cqc.ta1i.t.y

uii:,:t:.it~,-eof: rit:e

:Leaf a17(:J

~3~ .l r i t e r I - t ~ s e ,

h a v e beet-) har-\cest:.ed

sc3lltble
I t

Re!searcl-t

and

l o s s e ! ~o f

j.

r1ut:r.i t i v e

value

n v e s t i g a t e t:he

tl-Iei r i rltrt.?racI:.i CJIVI

w i l l . t i m e cot-tsc.tming,

a1-1rJ

in~iect
the

.it:.r.aw.

t:here arc

to

or- p o u r

r t c . t t r i c r t t s s u c h as;

seems
the

and

a +t e r g r a i n s

s t r a w .t.cn f u n g a l

j.n

i n f l t..tence

(::oliec:ted

I:)e%ayecj c:o:Llec::%ri(317,

,,

a

(Wir~r..tgrohc:~,
1981).

sterri

car-bc:jhyclratre
that

which

)

abet-tt ha1.f: t h a t : o f

a n d i minec:li a t e l y ,

~ - r i , l l e:.:po:se

a % t a c \ : : sa n d prc3,nol:s

1.5

..;t:rap~shat.tld b e

: % t o r r ~ r al p p r - a p r i a t e l y ,

st:oragc,

t-I

( a n l-ani

a

oil

L.3~ct

many
04:

factors

the

ef f e c t of t h e

straw

qua1i t y

neces!zary i f

the

that

straw.
+;actors

obviously
ultimate

44

goal

is

.f. e e d i r i (1

.

t o mak:e

c t s e cjf s t r a w i n

ma:.:imum

ruminant

I 1 Straw T r e a t m e n t s
A s p r e v i a u s l y ment i o n e d t h e a b u n d a n t e n e r g y s t o r e d

in

c e l l e t l o s e a n d h e m i c e l lr-{lose c o n t e n t

the

cell

is n o t r e a d i l y a v a i l a b l e f o r d i g e s t i o n

w a l l s

trapped with o t h e r c e l l wall

1i g n i n

53.1 i c a

and

pr-ovi d e

t:hr-or-rgh

c:nnstituents

c h e m i c:al

cnnstrain t s

p h y s i cal

by

T h e c e l l ctl u s e a n d h e m i c e l l u l ose

rumen m i c r o o r g a n i ! s m ~ , .
are

straw

of

sctch

as

1 i nC::ages

that

aggai n5.t w i r ~ d or

water

lodginq.
Ef f a r t s h a v e b e e n made u s i n g p h y s i c a l
chemical. t r e a t m e n t s ,
to

combinations

1 i g n o c e l l ul.o s i c:

biological

treatments,

treatments,
and t h e i r

i n c r e a s e t h e e n e r g y a v a i l a b i 1i b t y

in

c r o p resi d u e s .

1. P h y s i c a l T r e a t m e n t s .

The

a i m of

main

t h e treatment

is

t o

reduce

p a r t i c l e s i z e or

t o i n c r e a s e t h e s u r f a c e area p l a n t

ti s s u e

b y - . p r - o d u c t s wktich a r e

of:

crop

microbial. attack:.

Light mechanical

a s m i 1 1i n g , g r i n d i n g ,
more

p1 ar7.t

microbial

t i 8sr-tez

digestion.

e:.:posed

procedt-rres

t o
st-tch

c h o p p i n g ancl c h e w i n g may c a u s e
t.n

be

more

t-lowever

,

a v a i 1a b l e

for

c e l l u l ose

and

45

a r e s t i I. 1 t r a p p e d b e t . w e e n 1 i g n i 1-1

hemi c e l J. ~ . tos;e
1

s i l i c a i n t h e t i s s u e s hence preventing

and

total

their

a v a i l a b j . l i t : . y ,For r u m e n d i g e s t i o n .
If

slrruc.ture is s u b j e c t e d t o v e r y

t.he c e l l w a l l

f i n e m i l : L i n g , f o r e:.:ample
vibratory

ball

constituents

milling,

can

( S t o n e e t al.,

be

all

to

nearly

100%

(1904) mentioned that.

Walker

digestibility

m i 1 1 i n g t i m e was e : . : t e n d e d

a1I

words,

wall

even

up t o 8 h a u r s .

1i n k a g e s

ii984),

effect
This

ball.
on

milling did
chemical

imp1 i e s t h a t

d o e s n o t r e v e a l t h e d e g r e e of

other
between

According

not

between

c:ell

of

composi t i o n

cellulase availability

i % may mean t . h a t a m e t h o d t o m e a s u r e t h e

strength

a

have

composi t i a n

chernical

in

96% i f

In

c o n s t i t u e n k s had b e e n removed.

Walker

s a m p 1 es.

and

chemical and physical

significant

and

m i l l i n q and

p a r t s of t h e c e l l w a l l

d i y e s t e t j up

1969).

67% c a r b o h y d r a t e

t o

ball

woad b a l l rni 1 l e d f o r 1 0 m i n u t e s r e s u l t e d

spruce

cell

through

c:unsti t.uents

wall

bond
in

1i g n o c e l l u l o s i c c r o p r e s i d u e s n e e d s t o b e d e v e l o p e d .
I t is r - c p o r t e d t h a t r e d u c i n g t h e p a r t i c l e s i z e
s t i m ~ t l a t e i n c r e a s e d i n t a k e d u e t o a h i g h e r rate

passage
rat. i on
1972).

but

the digestibility coefficient

i s of t e n decreased

But,

( M i nsan

t h e f i n a l i n t a k e of

p r a c t i c a l 1y i m p r o v e d

,

196i3;

of

will

of
the

Dune+ er

,

d i q e s t i l ~ l ee n e r g y i s