Effects of oil drench on growth rate of cattle fattened on grass, supplemented with molasses, rice bran or rice straw

Nguyen Thi Hong Nhan, Nguyen Trong Ngu, Vo Van Son, T R Preston^* and R A Leng^**

College of Agriculture, Cantho University, Cantho, Vietnam
nthnhan@ctu.edu.vn   ;   ntngu@ctu.edu.vn   ;   vvson@ctu.edu.vn
^*UTA Colombia, AA48 Socorro, Santander, Colombia
trpreston@mekarn.org
^**PO Box 814, Coolum Beach 4573, Australia
rleng@ozmail.com.au

Abstract

This study was conducted to investigate the effects of defaunation in cattle received different sources of carbohydrate. The hypothesis to be tested was that growth responses of cattle to a drench of soybean oil would be greater in the diet based on molasses compared with rice straw. Experimental design followed a 3*2 factorial arrangement of three basal diets and with or without an oil drench at 6 ml/kg live weight (LW). Individual treatments were MGU (30 % molasses + 70% grass + 50 g urea/100 kg LW), RGU (50% rice straw + 50% grass + 50 g urea/100 kg LW) and RGR (45% rice straw + 45% grass + 10% rice bran). Thirty growing cattle of 132-144 kg were allocated to 6 treatments (5 replicates per treatment) and the trial lasted for 90 days.

Intakes were affected in the first 30 days after oil drench, but over the whole period these values were similar in defaunated and faunated cattle. However, among rations, molasses supplementation has provided a significantly higher DM intake (p<0.01). Changes in live weight of cattle were not statistically different although at the end of the experiment, cattle received oil tended to growth faster than the other group (p=0.07). Diets and oil drench had strong effects on daily weight gain of cattle (p<0.01) with highest average daily gain (p<0.01) on treatment MGU. Nevertheless, due to a high proportion of molasses in the diet, the cost of MGU treatment was higher compared to the other two treatments. The diet with inclusion of rice straw and urea (RGU) offered a lowest cost and thus greater benefit was found in this group.

In conclusion, the introduced system of feeding grass with rice straw and urea supplement with an oil drench resulted in more financial profits to the farmers than the system normally practiced.

Key words: cattle, economic benefits, growth, oil drench

Introduction

Strategies to develop animal production systems in the tropics, which are sustainable and applicable, must be based on locally available feed resources. Economic viability depends on achieving optimum level of animal performance with minimum inputs of cost, scarce concentrate and protein supplements. In Vietnam, rice straw is abundant in most provinces and molasses is also widely available. Moreover, researchers have found that molasses, a by-product of sugar production, is one such a component that can replace cereal grains as a component in diets for beef cattle production. Molasses is traditionally used by farmers in Vietnam as a feed for pigs and cattle.

In principle, it is possible to improve the feeding value of rice straw with a number of treatment techniques that have been developed (Trach and Thom 1998). A feeding trial carried out in An Giang province (Nhan et al 2003) confirmed the advantages of the oil drench in increasing the live weight gain of local Yellow cattle fed on untreated rice straw supplemented with cassava foliage. In a similar trial in Lao, live weight gains of 289 g/day were reported in local Yellow cattle fed rice straw and cassava foliage and given the same oil drench (Vyrapheth 2002 Missing). According to Seng et al (2001), the oil drench has a defaunation effect which may improve rumen cellulolysis thus increasing straw digestibility and intake, and eventually animal growth.

It is therefore proposed to measure the responses of growing cattle to the oil drench with a basal diet of molasses compared with rice straw with the hypotheses that (i) there will be positive effects of defaunation by soybean oil in cattle at local conditions and (ii) the research will establish a basis background for an economical way of fattening cattle in Vietnam.
 

Materials and methods

Location and animals

The experiment was carried out in co-operative farms in Angiang province. Five farmers, who traditionally fatten cattle on rice straw and grass, were selected to participate in the study. Thirty Sindhi x Yellow cattle of 132 - 144 kg were allocated to 6 treatments according to a 3*2 factorial design with 5 replicates per treatment. The animals were vaccinated against foot and mouth disease and dewormed before the initiation of the experiment. They were housed in individual pens; drinking water and rumen supplement (1.5% sulphur, 5% salt, 5% bone meal, and 73.5% rice bran) were available at all time. Cattle were fed totally in shed for the whole experimental period of 90 days.

Feeds and treatments

Rice straw was purchased from local farmers and Hymenachne acutigluna grass was planted in the farms and harvested at 30 day interval (Photo 1).

The animals were fed on three basal diets with or without oil administration at the beginning of the trial to provide totally six treatments:

• MGU: 30 % molasses + 70% grass (DM basis) + 50 g urea/100 kg LW
• MGUO: similar to MGU with oil drench at 6 ml/kg LW
• RGU: 50% rice straw + 50% grass (DM basis) + 50 g urea/100 kg LW
• RGUO: similar to RGU with oil drench at 6 ml/kg LW
• RGR: 45% rice straw + 45% grass (DM basis) + 10% rice bran
• RGRO: similar to RGR with oil drench at 6 ml/kg LW

Feed ingredients were supplied three times per day. To prevent selection, grass and rice straw were chopped and mixed together and they were offered at 30% above the observed intake in the previous day. Rice bran was prepared with some water so that cattle could eat it easily. Molasses and urea were diluted in water and sprayed on the feeds given to individual cattle.

Measurements

Cattle were weighed (Photo 2) on consecutive mornings at the beginning and after 30, 60 and 90 days of the trial. Feed intake and residues were measured daily and representative samples were collected and bulked weekly for chemical analysis including DM, CP and ash (AOAC 1990) and NDF and ADF (Van Soest . At the end of the experiment, an economic estimation was drawn based on the difference between benefit of cattle growth and other expenses during the fattening period.

Data analyses

All data were coded for subsequent statistical analysis using General Linear Model (GLM) in Minitab Software (version 13.2). Sources of variation were treatments and errors.

Results

Diet composition

Chemical composition of the feed ingredients is presented in Table 1.

Feed intake and growth rate

Intake and changes in LW of cattle are shown in Table 2.

In the first period (0-30 days) when cattle were still affected by a sudden supply of oil, there was a tendency of lower feed intake in all treatments with oil drench. After 30 days of oil administration, the trend of DM intake was changed to an opposite direction, in which oil drench has slightly stimulated feed consumption. However, in both cases the difference did not reach the significant level (p>0.05). Among treatments, inclusion of molasses and a higher proportion of grass in the diet (Treatment MGU) resulted in higher DM intake (p<0.05) compared to urea (RGU) or rice bran (RGR) supplementation in both factors: no oil (5.09 vs. 4.08 or 4.54 kg, respectively) and oil drench (5.19 vs. 4.25 or 4.46 kg, respectively).

Changes in LW of cattle were not statistically different over the trial period although at the end of the experiment, cattle received oil tended to growth faster than the other group (p=0.07). However, diets and oil drench had strong effects on daily weight gain of cattle (Figure 1), excepting for the first period where no significant difference found.

At day 60 and 90 and over the whole period, irrespective of oil factor, highest and lowest values of average daily gain (ADG) (p<0.01) were on treatment MGU and RGU, respectively. If oil drench was taken into account, its positive effects on ADG could be observed clearly at day 60, for example, with the same ration MGU cattle in oil drench group gained 0.733 kg/day while this data in the other group was 0.513 kg/day. On average of 90 days, ADG in defaunated cattle was higher (p<0.01) than in normal animals.

It was the oil factor but not diet that most influenced the DM feed conversion (Figure 2).

In all treatments, cattle supplemented with soybean oil improved DM feed conversion from 15 to 25% (p<0.01).

Economic benefits

Cost of ingredients and the products sold at the end of the experiments are indicated in Table 3.

Based on changes and input and output, feed cost calculated per kg live weight gain is shown in Figure 3.

Due to a high proportion of molasses in the diet, the cost of MGU treatment was highest. The treatment with inclusion of only urea (RGU) offered a lowest cost and therefore higher benefit was found in this group.

Discussion

Many studies reported so far on the effect of defaunation on feed intake and animal performances have not led to the same results. The current findings are in line with those investigated by Ankrah et al (1990) and Chaudhary and Srivastava (1995) that DM intake was not influenced by defaunation. However, in the study of Ankrah et al (1990) defaunation did not affect growth rate and thus feed conversion was also not different between faunated and normal groups, which are contradictory to our study. Other authors (Santra and Karim 2000; Eugène et al 2004) seem to agree on the conclusion of better feed conversion efficiency in defaunated compared to faunated animals.

In addition, it was hypothesized and confirmed by Eugène et al (2004) that better feed conversion efficiency may lead to a higher yield of nutrients absorbed, which is in turn useful for maintenance and growth of defaunated animals. In this study, an increase of 12 - 24% in growth rate was found and comparable to many reports, for instance, in lambs (Bird and Leng 1985; Santra and Karim 2002) and in cattle (Nhan et al 2001; Seng et al 2001). The explanation for higher growth rate in all treatments might have been due to improved DM digestibility (Nhan et al 2007) or reduced methanogenesis as well as an increased microbial and dietary protein flow to the duodenum as discussed by Santra and Karim (2002).

It is well known that responses of growth rate depend mainly on feed and supplements available for the animals. Irrespective of oil factor, molasses - a source of readily fermentable carbohydrate has shown its potential in improving cattle performance since it has provided a source of carbon backbone as well as energy for fermentation activity of rumen bacteria that are capable of digesting carbohydrate and balance the protein and volatile fatty acid (Preston et al 1967). The elimination of protozoa also lead to a more efficiency of energy available in the rumen since protozoa require energy for their maintenance (Coleman 1975). In addition, a combination of molasses and green forage supplemented with urea has formed a large proportion of propionate and reduced butyric. All of these factors have contributed to explain for a better growth rate of animals. Similar results were also reported elsewhere by Khalili et al (1993) and Iwuanyanwu et al (1990). In contrast to molasses, rice straw provided a high proportion of structural carbohydrate which were slowly fermentable in the rumen and thus it took longer time to digest and more energy was needed (Leng 1990). Another source of supplement in this study was rice bran, a source of bypass nutrients including protein, starch and fat. Though most of starch from rice bran escape from rumen degradation and provide nitrogen in the duodenum (Elliott et al 1978), its contribution to cattle growth was lower compared to molasses.

To farmers, the efficiency of application a new technique is evaluated through the economic status. Although they have to invest a little more at the start of the fattening period, after three months, an increase of 14 - 28% benefits could be achieved due to an improved cattle grow performance. Therefore, in term of economic effect, the RGU and RGR diets and an oil drench were suggested for fattening cattle at house-hold level.
 

Conclusions

• A single dose of soybean oil (6 ml/kg live weight) to cattle fed on grass supplemented with molasses, rice bran or rice straw has improved growth rate and economic profitability.
  
  

Acknowledgements

The authors wish to acknowledge the support for this research from the MEKARN Regional Project, financed by SidaSAREC of Sweden. This research was also supported by the International Foundation for Sciences (IFS), Stockholm, Sweden, through a grant to the second author (Grant Agreement No B/3369-1). The authors are also grateful to the farmers' cooperative in An Giang province for providing the facilities and assistance during the trial.
 

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