Livestock Research for Rural Development 4 (3) 1992

Citation of this paper

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)

 

References

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Sansoucy R 1986 The Sahel: Manufacture of molasses-urea blocks. World Animal Review 57:40-48

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(Received 5 July 1992)