Variation in nutritive quality between morphological components is less for rice straw than for wheat straw. Wheat straw stems have a lower quality than stems of rice straw, while leaves and leaf sheaths of wheat are of better quality than of rice. Variation in voluntary organic matter intake, and in vivo and in sacco organic matter digestibility was studied with straw of 10 rice varieties grown in two locations (highland and lowland) in two years in Indonesia. Variation in nutritive quality was observed between varieties. Variation in DOMI was higher than in vivo OMD. In sacco degradation parameters were poor predictors of in vivo OMD and DOMI. Grain yield of the rice varieties studied was positively correlated with DOMI

Bruchem, J., van

Hartutik

Hermanto

Orskov, E.R.

Siti Chuzaemi

Soebarinoto

Wageningen Yield 

NUTRITIVE VALUE OF STRAW, WITH SPECIAL REFERENCE TO 
WET-SEASON RICE STRAW AS RELATED TO VARIETY AND LOCATION 
OF GROWTH IN EAST-JAVA, INDONESIA 
Soebarinoto1, Siti Chuzaemi1, Hermanto1, Hartutik1, 
J. van Bruchem2 and E.R. 0rskov3 
SUMMARY 
Variation in nutritive quality between morphological components 
is less for rice straw than for wheat straw. Wheat straw stems 
have a lower quality than stems of rice straw, while leaves and 
leaf sheaths of wheat are of better quality than of rice. 
Variation in voluntary organic matter intake, and in vivo and in 
sacco organic matter digestibility was studied with straw of 10 
rice varieties grown in two locations (highland and lowland) in 
two years in Indonesia. Variation in nutritive quality was 
observed between varieties. Variation in DOMI was higher than in 
vivo OMD. In sacco degradation parameters were poor predictors 
of in vivo OMD and DOMI. Grain yield of the rice varieties 
studied was positively correlated with DOMI. 
INTRODUCTION 
Fibrous crop residues and agricultural by-products do play an 
essential role in the seasonal feed-plan of integrated 
smallholder crop-livestock farming systems in the tropics. The 
nutritive value of such low quality fibrous feeds for ruminants 
is affected by stage of maturity at harvest, the method of grain 
harvesting and the post harvest storage conditions. Variations 
in cutting height, growing conditions and harvesting and 
threshing procedures can result in large differences in the 
nature of leaf and stem material collected at the threshing site 
(Egan, 1987). Next to metabolizability and the efficiency of 
utilization of the absorbed nutrients, the nutritive value of 
fibrous feeds is largely determined by voluntary intake. Chemical 
characteristics are relatively poor predictors of the intake of 
digestible organic matter and thus of the fibrous feed's 
nutritive potential (0rskov et al., 1989). They found that in 
barley and wheat straws, whether or not treated with anhydrous 
ammonia, covering an in vivo digestibility range of 343-596 g/kg, 
in vitro digestibility and in sacco degradation characteristics 
were closely associated to feed intake and animal performance. 
After a comparison of wheat and rice straw, this paper discusses 
various aspects of the nutritive value of wet season rice straws 
with special reference to recent results obtained in Indonesia. 
Faculty of Animal Husbandry, Brawijaya University, JaIan Hayjen Haryono 161, Malang, Jatim, Indonesia 
Department Tropical Animal Production, Agricultural University Wageningen, PO Box 338, the Netherlands 
Rouett Research Institute, Greenburn Road, Bucksburn, Aberdeen AB2 9SB, Great Britain 
388 
Nutritive value of straw 
CHARACTERISTICS OF WHEAT AND RICE STRAWS 
The morphological variation of cereal straws varies considerably 
(Doyle et al., 1987). As a proportion of the whole plant, 
excluding grain, wheat stem can range from 33% to 53% and rice 
stem from 22% to 34%. In addition to a genetically induced 
variation, it is obvious that these values are affected by 
harvesting height and growing conditions. Contrary to wheat straw 
(stem 24-36%, sheath 45-63% and leaf 58-77%), the variation in 
vitro organic matter digestibility (IVOMD) amongst plant parts 
showed to be less in rice straw (stem 43-75%, sheath 38-56% and 
leaf 45-60%). The grinding energy needed for physical reduction 
showed a comparable picture. Average values were 213, 122 and 81 
J/g for wheat straw stem, sheath and leaf, respectively, whereas 
for rice straw values of 168, 147 and 133 J/g were reported. From 
these observations the conclusion seems valid that both physical 
and fermentative degradation of wheat straw stem is inferior to 
stems of rice straw, but that with sheaths and leaves the 
opposite seems the case. In rice straw stems, however, the energy 
needed for physical reduction remains high relative to its 
digestibility. Accordingly, relatively to OMD, eating rate of 
rice straw was lower as compared to wheat straw. 
Time of harvesting may also significantly affect the straw's 
nutritive value. Pearce et al. (1988) clearly showed in wheat 
straw that initially after flowering the straw's neutral 
detergent solubles increased as caused by a production of 
photosynthates in excess of requirements for grain development. 
Thus the gradual decrease in OMD starting 20 - 30 days prior to 
flowering was temporarily equalized. However, a further decrease 
in OMD was observed soon after grain maturity, associated with 
a decrease in neutral detergent solubles. Thus in view of the 
straw's nutritive value, the timing of harvesting is presumably 
of an utmost importance, since the level of storage 
carbohydrates, fructans in wheat and starch in rice, retained in 
straw are critical to the straw's feeding value because of their 
high digestibility. 
VOLUNTARY INTAKE OF WHEAT AND RICE STRAW 
The intake of rice straw is influenced by various factors, 
amongst others by physical and chemical characteristics, 
palatability and degradability, differences in feeding conditions 
such as the amounts offered and the frequency and form of 
feeding, and finally the physiological state of the animal. 
Whether with rice straw with a comparatively lower variation in 
digestibility between plant parts, selection for different plant 
parts plays a less important role as compared to wheat straw, is 
not quite clear. According to Doyle et al. (1987), for whole 
plant material, relatively to in vivo OMD, OMI, eating rate and 
IVOMD were lower with rice straw as compared to wheat straw. 
The latter authors also pointed out that the intake of straw may 
be related to the previous nutritional history of the animals. 
Animals in good condition may be able to recycle more nutrients 
389 
Soebarinoto et al. 
into the reticulo-rumen and thereby increasing microbial growth 
in the reticulo-rumen, and consequently intake. 
NUTRITIVE VALUE OF RICE STRAWS IN INDONESIA 
In East-Java, 10 rice varieties (Table 1) were planted at two 
locations: Mojosari (lowland, regosol, 28 m above sea level) and 
Malang (highland, alluvial soil, 435 m above sea level). First 
transplanting (I) was done in early March 1988 in the wet season. 
Harvesting was in May-June at the onset of the dry season. This 
wet-season planting (II) was repeated in 1989. Intake and in vivo 
digestibility of the rice straws were tested with young 
fat-tailed sheep with a body weight of 20 - 25 kg. Rice straw was 
Table 1 In vivo organic matter digestibility (g/kg) of 10 rice 
straw varieties, grown at 2 locations (lowland: 
Mojosari; highland: Malang) in the wet season of 1988 
and 1989 
Variety 
A. IR 36 
B. Batang Pane 
C. IR 54 
D. IR 64 
E. Citandui 
F. Progo 
G. Cisadane 
H. Krueng Aceh 
I. Kapuas 
J. Tuntang 
Mean2 
1988 
461 
457 
414 
457 
454 
483 
367 
473 
464 
468 
450 
Mojosari 
1989 
476 
495 
471 
486 
468 
449 
514 
458 
502 
529 
485 
1988 
390 
471 
422 
457 
422 
486 
469 
531 
487 
468 
460 
Malang 
1989 
463 
471 
398 
440 
454 
477 
525 
497 
530 
489 
474 
Mean1 
448 
474 
426 
460 
450 
474 
469 
490 
496 
489 
468 
Note: - least significant differences (LSD), P <0.05: 1) 46.2; 2) 29.2 
Table 2 Voluntary intake of digestible organic matter (g/kg 
MW) of 10 rice straw varieties, grown at 2 locations 
(lowland: Mojosari; highland: Malang) in the wet 
season of 1988 and 1989 
Variety 
A. IR 36 
B. Batang Pane 
C. IR 54 
D. IR 64 
E. Citandui 
F. Progo 
G. Cisadane 
H. Krueng Aceh 
I. Kapuas 
J. Tuntang 
Mean2 
1988 
18.0 
18.3 
11.5 
11.8 
14.8 
13.5 
12.7 
19.2 
16.5 
16.1 
15.2 
Mojosari 
1989 
17.2 
18.1 
15.7 
17.7 
16.1 
15.3 
18.6 
14.8 
19.1 
20.5 
17.3 
1988 
10.4 
16.5 
13.8 
12.2 
13.9 
16.9 
13.7 
17.5 
18.9 
18.8 
15.3 
Malang 
1989 
17.1 
18.8 
13.2 
16.5 
15.6 
18.3 
18.0 
16.0 
22.8 
21.5 
17.8 
Mean1 
15.7 
17.9 
13.6 
14.6 
15.1 
16.0 
15.8 
16.9 
19.3 
19.2 
16.5 
Note: - least significant differences (LSQ), P < 0.05: 1) 2.96; 2) 1.87 
390 
Nutritive value of straw 
offered at a level of 10 - 20 % excess and was supplemented with 
about 18 g DM/kg MW of concentrates containing about 20 % crude 
protein. The season I in vivo digestibility trials were run in 
the period December 1988 till June 1989; of the season II rice 
straws in the period December 1989 till April 1990. Tables 1 and 
2 show the rice straw's organic matter digestibility (OMD) and 
voluntary intake of digestible organic matter (DOMI), 
respectively. 
Voluntary intake of rice straw OM was slightly positively related 
to the straw's OMD (R2 = 0.16, P < 0.01). Hence the variation in 
DOMI with a coefficient variation (CV) of 17.2 % exceeded that 
of OMD (CV = 8.1 % ) . 
DIGESTIBILITY OF RICE STRAW 
The in vivo digestibility of rice straw is highly variable. In 
such highly fibrous material only a minor part of the OM is water 
soluble. In addition to this it seems that the fractional rate 
of passage of the liquid phase from the reticulo-rumen is low. 
A pilot experiment with sheep fed on urea- ammonia treated rice 
straw as a basal feed in Indonesia revealed 6.1 %/h for the 
liquid phase (Co-EDTA) . Hence digestion occurs almost 
quantitatively by fermentation, predominantly in the 
reticulo-rumen. A minor part, generally less than 10% of the 
fermentation products emerge from the hind gut. Digestion in the 
small intestine is almost limited to the microbial biomass 
synthesized in the reticulo-rumen, of which the true protein 
digestibility approximates 85% (Storm et al., 1983; Van Bruchem 
et al., 1989) . 
The extent to which the feed is degraded in the reticulo-rumen 
depends on its water soluble part, which presumably is degraded 
almost quantitatively by the rumen microbes, and the water 
insoluble part. This water insoluble part in turn can be divided 
into a part which is truly resistent to microbial degradation and 
a potentially degradable part. Of the latter part the extent of 
degradation is related to a lag phase related to rate of 
attachment of the microbes as well as subsequently the rate of 
colonization, the in situ fractional rate of degradation and the 
residence time in the reticulo-rumen. In turn the residence time 
is determined by the rate of physical degradation of large into 
small particles and the subsequent passage of the latter to the 
omasum. 
In temperate cereal straws a close relationship was found between 
in sacco OM degradation characteristics and in vivo 
digestibility. These biological measures were found to be 
superior to chemical analyses. This can easily be understood 
based on the above theoretical considerations. However, in rice 
straw the picture thus far obtained is less clear. In Table 3, 
the rice straw's in sacco degradation characteristics, determined 
in sheep according to Mehrez and 0rskov (1977), are presented. 
391 
Soebarinoto et al. 
The multiple regression of IDOM versus S, D, t' and kd gave 
results as presented in Table 4. 
Table 3 Effect of variety and location of growth (lowland, L; 
highland, H) on in sacco OM degradation of wet-season 
rice straw (mean of seasons I and II) 
Variety 
A. IR 36 
B. Batang Pane 
C. IR 54 
D. IR 64 
E. Citandui 
F. Progo 
G. Cisadane 
H. Krueng Aceh 
I. Kapuas 
J. Tuntang 
Mean 
L 
189 
210 
200 
198 
177 
192 
200 
215 
208 
186 
198 
s' 
H 
186 
168 
163 
162 
180 
163 
157 
178 
183 
195 
173 
L 
481 
463 
401 
378 
402 
405 
380 
400 
425 
487 
422 
D2 
H 
408 
416 
363 
381 
290 
345 
390 
437 
439 
378 
385 
f 
L 
330 
328 
399 
424 
422 
403 
420 
385 
367 
327 
380 
3 
H 
406 
417 
474 
457 
530 
493 
453 
386 
379 
427 
442 
L 
5.5 
6.1 
6.5 
6.3 
6.5 
5.2 
6.4 
6.2 
5.8 
4.2 
5.9 
t'4 
H 
8.1 
5.7 
7.0 
5.5 
6.5 
6.0 
6.0 
4.7 
6.6 
7.6 
6.4 
kd6 
L 
2.7 
3.1 
2.7 
3.3 
3.1 
3.1 
3.0 
3.7 
2.9 
2.8 
3.0 
H 
3.3 
3.0 
2.4 
3.1 
3.4 
3.1 
2.4 
3.0 
3.3 
3.0 
3.0 
Notes: 1) S: water soluble part (g/kg), estimated as (a) in the exponential equation: 
a + b * (1 - exp(-c * (t-t')); least significant difference (LSD, P < 0.05) 9.6 
2) D: water insoluble but potentially degradable part (g/kg), estimated as (b); 
LSD (P < 0.05) 14.1 
3) R: truly undegradable part (g/kg), equivalent to 1000 - (a + b); LSD (P < 0.05) 7.6 
4) t': lag phase (h); LSD (P < 0.05) 3.29 
5) kd: fractional rate of degradation of D, estimated as c (%/h); LSD (P < 0.05) 1.38 
Figure 1 Observed DOMI values versus DOMI values fitted from 
the multiple regression analysis vs. S, D, t' and kd 
IDOM obaarvod values (g/kg MW) 
O Highland Unity A Lowland 
392 
Nutritive value of straw 
Table 4 Prediction of DOMI 
characteristics 
Factors 
from OM in sacco degradation 
Equations 
S 
D 
S + D 
t ' 
S + D + t ' 
kd 
S + D + t ' + kd 
20.1 - 0.20*S 
8.6 + 0.19*D 
10.1 - 0.05*S 
16.9 - 0.09*t ' 
9.3 - 0.05*S 
12.1 + 1.44*kd 
5.7 + 0.01*S 
0.18*D 
+ 0.19*D + 0.09*t' 
+ 0.18*D - 0.03*t' + 1.16*kd 
R2 
0.072 
0.211 
0.215 
0.002 
0.217 
0.084 
0.262 
Figure 2 Nutritive value (DOMI) of rice straw as related to 
grain yield. Mean of two wet-season crops and two 
attitudes (letters indicate varieties, see Table 1) 
25 
5 
o 
î 
a 
2 O 
a 
20 
15 
10 
J , » ' 
y Y 
T» 
»T 
4 5 
Grain yield (ton/ha) 
In Figure 1, the fitted DOMI values as derived from this multiple 
regression analysis are plotted versus the observed DOMI values, 
showing a somewhat less clear cut relationship as compared to the 
temperate cereal straws (0rskov et al., 1989). In line with the 
differences in truly undegradable OM residue (R) between lowland 
and highland (see Table 3), 48-h OMD was lowest for highland rice 
straws. Somewhat surprisingly, this difference was not reflected 
in the in vivo OMD (see Table 1). 
It thus seems that further research is needed to elucidate why 
in rice straw the in sacco OM degradation characteristics are 
such poor predictors of in vivo OM digestibiJity.fSince the rice 
straws were offered in excess, perhaps par!: of this absent 
relationship could be explained by selection. Generally, however, 
393 
Scjarinoto et al. 
the rice straw residues did not exceed 20% of the quantity 
supplied, so that these residues can hardly be expected to 
account for this. It would also be possible that due to 
differences in physical characteristics the rates of physical 
degradation of large into small particles differ. Finally, the 
rate of passage to the omasum may differ, due to the consistency 
of the reticulo-ruminal contents and the shape and/or functional 
specific gravity of the small particles. Possibly, in experiments 
with Cr-mordanted rice straw particles such differences could be 
identified. 
RELATION BETWEEN GRAIN YIELD AND STRAW QUALITY 
Identifying the most suitable rice variety is first of all 
related to its grain yield. The straw's quantity and quality have 
to be regarded as a second priority. This is elaborated in this 
workshop in the paper by De Wit et al. (1993). Hence, it is 
worthwhile to investigate the relation between straw quality, 
straw quantity and grain yield. Figure 2 is a pictorial 
presentation of this relationship as derived from the data 
obtained in Indonesia, showing that as averaged over both 
altitudes and seasons the straw's nutritive value fortunately 
seemed positively related to grain yield. This possibly could be 
explained on the basis of a variation in photosynthetic capacity, 
and the fact that harvesting took place at a stage that the straw 
was still greenish, and the excess of photosynthates produced 
were as yet not completely stored in the grain. These 
observations are not in line with those of Erickson et al. 
(1982), who observed in barley a poor relationship between grain 
yield and straw quality. 
CONCLUSIONS 
Significant differences between in vivo OMD, DOMI and in sacco 
degradation parameters were found for straw from 10 rice 
varieties grown in Indonesia. Variation in DOMI was higher for 
DOMI than for in vivo OMD. In sacco degradation characteristics 
could only explain 26.2% of variation in DOMI. No significant 
effects of location of growth (highland or lowland) on in vivo 
determined quality parameters were found, but in sacco 
degradability was significantly better for straw of rice 
cultivated in highland than for rice grown in lowland. A positive 
relation was observed between grain yield and DOMI for the ten 
rice varieties studied. 
ACKNOWLEDGEMENTS 
The authors gratefully acknowledge financial support provided by 
the Commission of European Communities. 
394 
Nutritive value of straw 
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395 


Nutritive value of straw, with special reference to wet-season rice straw as related to variety and location of growth in East-Java, Indonesia.

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