Ammoniated rice straw or untreated straw supplemented with a molasses-urea block for growing Sindhi x Local cattle in Vietnam
Bui Van Chinh, Le Viet Ly,
Nguyen Huu Tao, Pham Van Thin and T R Preston*
Animal Husbandry Research Institute, Hanoi,
Vietnam *Centro para la Investigación en Sistemas Sostenibles de
Producción Agropecuaria, AA20591, Cali, Colombia
Summary
An important economic issue, which has not been adequately
evaluated, is the relative effectiveness of ammoniation using
urea as compared with supplementing untreated rice straw with a
molasses-urea block. The present trial was designed to compare
these two systems. Growing crossbred heifers (Sindhi X Local
Yellow cattle) were fed either (ARS) ammoniated rice straw
(ensiled with 2.5 kg urea, 0.5 kg of lime [Ca(OH)2]
and 0.5 kg of salt/100 kg air dry straw) or untreated straw and a
molasses-urea block (MUB) (final molasses 50, urea 10, salt 5,
lime 8, sugar cane bagasse 27%). Growth rates were consistently
higher on the ammoniated straw compared with the MUB supplemented
untreated straw. Improvement was 25% (P=.001) mainly because of
an almost 50% increase (P=.001) in intake of straw when it was
ensiled with urea. Total DM intake also tended to be higher with
the ammoniated straw treatment (P=.13) but the slight differences
in feed conversion were not significant (P=.42). On both
treatments the straw was offered at levels only slightly
exceeding measured intake (about 20% above) thus there was little
opportunity for selection. It is possible that if, in the present
experiment, the untreated straw had been offered at a much higher
level (100% above intake) then growth performance would have been
the same on both treatments but with cost advantages for the MUB
treatment. This hypothesis will be tested in the next series of
trials on this topic.
KEY WORDS: Rice straw, ammoniation, urea-ensiling,
molasses-urea blocks, cattle, Vietnam, growth.
Introduction
Rice straw is the most abundant feed resource for ruminant
animals in Vietnam especially during the dry season. Methods for
increasing its nutritive value by ammoniation using urea or
anhydrous ammonia are well established (Sundstol and Owen 1984)
and are being applied in many countries in Asia. When urea is
used in the wet ensiling system, the usually recommended level is
4 kg urea per 100 kg air-dry straw, little over half of which
remains in the straw when this is finally fed to the animal.
Earlier observations in Vietnam (Bui Van Chinh, unpublished data)
indicated that the amount of urea could be reduced to 2.5 kg/100
kg straw provided an additional 0.5 kg of lime [Ca(OH)2]
and 0.5 kg of salt were also added.
It is generally believed that the response to ammoniation has
two components: an increase in digestibility due to partial
saponification of the lignin-cellulose-/hemicellulose linkages
and a greater feed intake arising from the greater supply of
ammonia to the rumen microorganisms.
The feeding of molasses-urea blocks is another related
technology widely used for improving animal performance on
fibrous crop residues bringing about increases in feed intake and
also in digestibility (Leng and Preston 1984; Sansoucy 1986; Bui
Xuan An et al 1992).
An important economic issue, which has not been adequately
evaluated, is the relative effectiveness of ammoniation using
urea as compared with supplementing untreated rice straw with a
molasses-urea block. The present trial was designed to compare
these two systems.
Materials and methods
Twenty growing crossbred heifers (Sindhi X Local Yellow
cattle) were divided into two uniform groups and fed either (ARS)
ammoniated rice straw (ensiled with 2.5 kg urea, 0.5 kg of lime
[Ca(OH)2] and 0.5 kg of salt/100 kg air dry straw) or
untreated straw and a molasses-urea block (MUB) (final molasses
50, urea 10, salt 5, lime 8, sugar cane bagasse 27%). The
experiment was carried out at the Bavi State farm in North
Vietnam and extended through the summer (150 days) and winter
seasons (90 days). The animals were weighed at monthly intervals
and feed intake recorded daily.
Results and discussion
Mean values for weight gain, feed intakes and conversions are
given in Table 1. Growth rates were consistently higher on the
ammoniated straw compared with the MUB supplemented untreated
straw, in both summer and winter periods. The overall improvement
was 25% (P=.001) mainly because of an almost 50% increase
(P=.001) in intake of straw when it was ensiled with urea. Total
DM intake also tended to be higher with the ammoniated straw
treatment (P=.13) but the slight differences in feed conversion
were not significant (P=.42).
On both treatments the straw was offered at levels only
slightly exceeding measured intake (about 20% above) thus there
was little opportunity for selection. An interesting new approach
to improving the nutritive value of fibrous roughages is to offer
them at levels exceeding by some 100% the expected level of
intake (Ahmed et al 1990). This procedure permits the
animal to select the more nutritious component of the roughage
and results in higher intake of material of higher nutritive
value (Vargas et al 1992).
It is possible that if, in the present experiment, the
untreated straw had been offered at a much higher level (100%
above intake) then growth performance would have been the same on
both treatments but with cost advantages for the MUB treatment.
This must be the hypothesis to test in the next series of trials
on this topic.
| Table 1: Effect
of ammoniation of rice straw or supplementation with
molasses-urea block (MUB) on performance of growing
heifers during consecutive periods in summer (150 days)
and winter (90 days) in Hanoi province |
 |
| |
Ammoniated |
Untreated
straw |
SE(Prob=) |
| |
straw |
+ MUB |
|
|
| Initial wt
(kg) |
|
|
|
| Summer |
156 |
156 |
|
| Winter |
224 |
210 |
|
| Mean |
190 |
183 |
±17(.06) |
| |
|
|
|
| Final wt (kg) |
|
|
|
| Summer |
224 |
210 |
|
| Winter |
264 |
243 |
|
| Mean |
244 |
227 |
±16(.19) |
| |
|
|
|
| LWt gain
(kg/d) |
|
|
|
| Summer |
.453 |
.360 |
|
| Winter |
.444 |
.367 |
|
| Mean |
.449 |
.363 |
±.0096(.001) |
| |
|
|
|
| Intake straw
DM (%LWt) |
|
|
|
| Summer |
1.62 |
1.1 |
|
| Winter |
1.7 |
1.17 |
|
| Mean |
1.66 |
1.17 |
±.029(.001) |
| |
|
|
|
| Total DM
(%LWt) |
|
|
|
| Summer |
2.63 |
2.34 |
2.56 |
| Winter |
2.27 |
2.14 |
2.13 |
| Mean |
2.47 |
2.22 |
±.099(.13) |
| |
|
|
|
| Feed DM
conversion |
|
|
|
| Summer |
11.3 |
11.9 |
|
| Winter |
12.7 |
13.3 |
|
| Mean |
11.8 |
12.7 |
±.72(.42) |
|
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