Measuring responses to an oil drench and bypass protein (cassava foliage) in local (Yellow breed) cattle fed rice straw and a rumen supplement
 

Sypraseuth Khonglalien, Bounlieng Khoutsavan, Phonepaseuth Phengsavanh and T R Preston^*

^Livestock Research Centre, National Agriculture and Forestry Research Institute,
P O BOX 7170, Vientiane, Lao PDR.
p.phengsavanh@cgiar.org
* UTA-TOSOLY - Finca Ecológica
AA # 48, Socorro, Santander, Santander del Sur, Colombia

Abstract

The experimental animals were 20 females of local “Yellow cattle” about one year of age, average 100 kg live weight, with 10 animals allocated to each of two experiments. In experiment 1, The treatments were a single drench on day 1 of soybean oil at levels of 2, 3, 4, 5 and 6 ml oil/kg LW.  In experiment 2, the treatments were cassava hay at 0, 0.3, 0.6, 0.9 and 1.2 kg DM/100 kg of LW (approximately 0, 0.75, 1.5, 2.25 and 3 g protein/kg LW). .In each case the design was a production function using regression analysis to relate responses (live weight gain and feed conversion) with inputs (oil drench or cassava hay). Animals in the group receiving different levels of cassava hay also received 5 ml of oil by drenching at the start of the trial. Animals in the group drenched with different levels of oil also received 1.2kg /day of cassava hay/100 kg live weight. All cattle were fed ad libitum rice straw and a rumen supplement block (13% urea, 3% diammonium phosphate, 1% sulphur, 5% salt, 5% CaO, 30% rice bran, 43% molasses).

Growth rate was significantly increased by oil drench and supplementing with cassava foliage. There was strong relationship between cassava foliage intake and growth rate, and a weaker relationship between levels of oil drench  and growth rate.  The oil drench significantly reduced the protozoa population. However, there was a rapid re-infestation of the small protozoa, mainly Entodinia,  to a level comparable to the control groups. Only a few large protozoa, mainly (Polyplastron and Holotrichs) were observed.  In addition, rumen ammonia concentrations tended to be lower in oil-drench animals.  Feed intake was not affected by level of cassava foliage nor  by the oil drench.

Keywords: Cassava foliage, growth, , oil drench, protozoa, rumen ecosystem, Yellow-cattle 

Introduction

To improve the growth of cattle, farmers in the central region of Vietnam, have the custom to drench their animals with one litre of groundnut oil at the start of fattening them on rice straw and roadside grass. This practical observation was taken up by researchers at Cantho University, who showed that the oil eliminated the protozoa from the rumen and that the cattle grew faster (Nguyen Thi Hong Nhan et al 2001). The findings from Vietnam were further developed in work in Cambodia using fresh cassava foliage as a farmer-produced protein supplement (Seng Mong et al 2001). As in the Cantho findings all the rumen protozoa were eliminated by the oil treatment, however, there were differences in the rate of re-infection. The small protozoa (mainly Entodinia) were re-established within one month of oil treatment but the large protozoa (Holtrichs and Isotrichs) were still absent 3 months later. Feeding cassava foliage raised the growth rate of small local cattle (“yellow” breed) from 27 to 97 g/day but the oil drench further increased this to 346 g/day and the feed conversion rate was dramatically improved.

These findings have great significance for the more efficient utilization of rice straw in Laos as strong efforts are now being made to stop the burning of straw. Also farmers are accustomed to grow cassava for forage.

The purpose of this study was to determine response curves to both the oil and the cassava foliage in order to develop economic models for application of this technology in Laos.
 

Material and Methods

Location

The experiment took place from August to November 2006 at the Livestock Research Centre of The National Agriculture and Forestry Research Institute.

Treatments and design

20 females of the local “Yellow” cattle breed of about one year of age (100 kg live weight) were used as the experimental animals. Two separate response curve studies were done each with 5 levels and 10 animals. One study was on levels of soya bean oil given as a single drench on day 1 (2, 3, 4, 5 and 6 ml oil/kg LW) with sun-dried cassava foliage at the rate of 1.0 kg/100 kg live weight.  The second study was with levels of sun-dried cassava foliage (0, 0.30 0.60 0.90 and 1.20 kg DM/100 kg LW) (approximately 0, 0.75, 1.50, 2.25 and 3 g protein/kg LW) after a single oil drench on day 2 of 6 ml/kg live weight.

Feeds and management

The basal diet was untreated rice straw and a multi-nutritional block (13% urea, 3% diammonium phosphate, 1% sulphur, 5% salt, 5% CaO, 30% rice bran, 43% molasses), both offered free choice (20% above recorded intake for the straw). Cassava was planted for management as semi-perennial forage. Fertilization was with biodigester effluent at rates of 700 kg N/ha/yr, divided in 6 applications, applied at the beginning and after each harvest. The required area for growing cassava was 2000 m². The first harvest was at the beginning of the trial (?? days after planting) and a second harvest 56 days later. The stems were cut 70 cm above ground level and the foliage (leaves, petioles and green stems) sun-dried for 1-2 days before being stored in large plastic bags. Soya bean oil was purchased in the market. For the oil response study the level of sun-dried cassava foliage was constant at 1 kg/100 kg LW. For the protein response study, the oil drench was given once to all animals on day 2 at the rate of 6 ml/kg LW.

Measurements

The cattle were weighed at the start (day 1), fasted overnight and given the oil drench the following morning (day 2). Samples of rumen fluid were taken by stomach tube at the time of weighing on day 1 and subsequently at 30 day intervals,  Live weights were recorded every 2 weeks, always in the morning before offering fresh feed. Feed intake was recorded daily. Samples of rice straw and cassava foliage offered and refused were taken daily for determination of DM, The dried samples were pooled on a weekly basis for determination of residual moisture and N. Rumen samples were acidified to stop the fermentation prior to analysis for ammonia and counting of protozoa. DM was determined done by micro-wave radiation (Undersander et al 1993) and N and ammonia according to AOAC (1990).

Statistical analysis

The data were analysed according to the analysis of variance procedure using the general linear model (GLM) in SAS (Statistical System) version 31.2.

Results and discussion

Chemical composition of the feeds is given in Table 1..

Supplementation with cassava foliage increased total feed dry matter intake of animals; the oil drench had no effect on this parameter. Both the oil and cassava foliage increased the growth rate and improved the feed conversion. The highest growth rate was achieved with the combination of oil drench and cassava foliage supplementation (Table 2). Live weight gain was linearly related to levels of oil drench (Figure 1) and cassava foliage intake (Figure 2).

Figure 1. Relationship between size of oil drench and live weight gain	Figure 2. Relationship between level of suuplementation with sun-dried cassava foliage and live weight gain

Feed intake and growth rate increased and feed conversion rate was better when cassava foliage was included in the diet. This is agreement with the report of Do et al. (2001) who used fresh cassava foliage as a supplement for cattle fed rice straw, and Ffoulkes and Preston (1978) who fed fresh cassava foliage to cattle fattened on a diet of molasses-urea. Cassava hay, made by sun-drying the fresh foliage (Wanapat et al 1997), was used to replace part of the concentrate fed to Holstein*Zebu dairy cows with no loss in milk production. Supplementing rice straw with fresh cassava foliage increased the intake of straw and the growth rate of local (Yellow) cattle in Cambodia (Seng Mom et al 2001). These reports and the results of the present experiment confirm that cassava foliage fed fresh, after sun-drying or as a leaf meal, can replace conventional protein meals as a source of bypass protein in diets for ruminants.

The rumen pH was not affected by the oil drench nor the cassava foliage supplement (Table 3). This result is in agreement with findings of Newbold and Chamberlain (1988) who found that defaunation or refaunation had no effect on rumen pH. In contrast, Nguyen Thi Hong Nhan et al. (2001) reported that pH was lower in defaunated animals. The method of sampling rumen fluid by stomach tube, with variable degrees of contamination by saliva, could be the explanation of the failure to observe differences in the present study. 

Neither the quantity of the oil drench nor the level of cassava foliage had any effect on rumen pH, but depressed ammonia levels and the protozoa population after 30 days with tendencies for values to remain lower at 90 days (Table 4 and 5). The lower concentration in oil-drenched animals is in agreement with results of various authors (Kayouli et al 1983/84; Nguyen Thi Hong Nhan et al 2003). Protozoa have high capacity for proteolytic and deaminase activities and there is an increase in the rumen outflow of protein from bacteria and fungi in the absence of protozoa. Kayouli et al (1984) found that defaunation or reduction in the protozoa population leads to an increase in the bacterial population, which uses ammonia as the source of nitrogen for cell synthesis. Thus more ammonia is being used when the bacterial population is increased. The reduction in ammonia concentration could thus be due to high rate of ammonia assimilation by bacteria, as well as reduced sources of ammonia entering the pool when protozoa are absent or present in small numbers.

                       Holotrich protozoa                                   Entodiniomorp protozoa                                                

The protozoa began to return within one week of giving the oil drench, and the small ciliate protozoa population reached a level corresponding to non-oil animals within 2 weeks. However, there was a significant reduction of large protozoa in oil-drenched animals throughout the 90 day trial. In non-oil animals, the large protozoa comprised 7% of the total protozoa biomass, compared to only 1% for the oil-drenched animals. The difference in numbers of large ciliate protozoa between treatments markedly affects the total protozoa biomass because large ciliate protozoa are about 100 times bigger than entodinia. The higher biomass of total protozoa means more competition for space and food with other micro organisms.  Furthermore, large ciliate protozoa (holotrichs and polyplastrons) have longer turnover rates and only a small percentage of these protozoa wash out from the rumen while small entodiniomorphid protozoa have a similar turnover rate to the turnover rate of the rumen fluid of cattle and sheep. Protozoa contribute little to total microbial outflow from the rumen (from 5 to 20%) (Bird et al 1979; Bird and Leng 1984). Thus reducing the protozoa biomass in the rumen will lead to increased availability of microbial protein to the host, and increase in N retention as a consequence of defaunation as was reported by Bird et al (1994) and Santra and Karim (2000).

Conclusions

• The response curves to oil and to cassava foliage are positive and linear over the range of 3 to 6 ml oil/kg live weight, for oil drench, and 0.3 to 1.2% live weight (DM basis) of sun-dried cassava foliage.

• Cattle fed on untreated rice straw can grow faster with improved feed conversion when the straw is supplemented with cassava foliage and the animals are drenched at the beginning of fattening with cooking oil at the rate of 6ml/kg live weight

Acknowledgements

The authors would live to acknowledge the Swedish International Development Authority (Sida /SAREC) supported regional MEKARN project for financial support of this research. We are also grateful to staff members of Livestock Research Centre, National Agriculture an Forestry Research Institute of Lao PDR.

References

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