Rau Dua (Ludwidgia adscendens) as component of recycling systems in pig production in the Mekong Delta of Vietnam

Le Thi Men  

College of Agriculture & Applied Biology
Can Tho University, Vietnam
ltmen@ctu.edu.vn
 

Abstract

The farming system should incorporate the principle of recycling so that residues are managed as substrate for more production. Integrated farming systems are based on the premise that there are complementary activities to be played by the different components within the system. The residues from one activity are the inputs for the next cycle, applies specifically to the farmland. Recycling organic waste and integration is the way to maximize use of natural resources, and decrease dependence on purchased inputs. These present  capacities can generate conversing the organic waste recycled to become the production of pig meat reality. Water plants (Lemna spp, Ipomoea aquatica, Eichhornia crassipes, Ludwidgia adscendens…) are valuable plants for decontaminating water charged with organic effluents. They could play a high potential when used as components of sustainable integrated farming systems.

Rau Dua, RD (Ludwidgia adscendens) yield was estimated on 4 farms in the Mekong Delta. On 2 farms the RD was fertilized by pig manure compost and on 2 farms by using digester effluent. On each farm 120 m² of water surface was divided into 4 plots for growing and harvesting RD in 2 first cuttings. The RD fresh biomass yield per harvest (tonnes/ha) was 19.2 on pig compost and 19.0 for bio-digester effluent. The contents of DM (11.7 %) and CP (20.3 % in DM) of RD were not different between the two types of fertilizers. An on-farm trial was carried out using Ludwidgia adscendens in pig diets to evaluate the replacement as part of the protein supplement. 24 Yorkshire-Baxuyen type pigs, comprising an equal number of castrated males and females with initial mean live weight of 57 kg were used. The trial was designed as a randomized block with four households and three dietary treatments. The basal feed was the same for the three treatments and was based on rice-by products, a protein supplement replaced by Ludwidgia adscendens at 0 % (RD0), 25 % (RD25) and 50 % (RD50). The daily weight gain and feed conversion ratio were not affected by dietary treatment. Feed cost per kg weight gain was more effective for  RD50 (13,306 VND) than for RD25 (13,815 VND) and RD0 (15,486 VND). Overall, these results indicate that usage of natural resources as supplements in pig diets can be recommended to get more benefit, and protect the environment by decontaminating livestock effluent wastes.

Key words: Biomass, compost, effluent, feed cost, natural resources

Introduction

The farming system should incorporate the principle of recycling so that residues are managed as substrate for more production. Integrated farming systems are based on the premise that there are complementary activities to be played by the different components within the system. The residues from one activity are the inputs for the next cycle, which applies specifically to the farmland. Recycling organic waste and integration is the way to maximize use of natural resources, and decrease dependence on purchased inputs. These present  capacities can generate conversing the organic waste recycled to become the production of pig meat reality. Water plants (Lemna spp, Ipomoea aquatica, Eichhornia crassipes, Ludwidgia adscendens…) are valuable plants for decontaminating water charged with organic effluents. They could play a high potential when used as components of sustainable integrated farming systems (Preston 1995).

The livestock production in the region is concentrated to small-scale farms and the crop residues from the farm are utilized as livestock feed and compost for organic fertilizer. Animal manure is a potential replacement for chemical fertilizer and is traditionally used by poor farmers in Vietnam. However, it is not properly managed so that the efficiency of utilization of the manure is not high. The introduction of low-cost biodigesters in Southeast Asia (Bui Xuan An et al 1997) has made it possible for small - scale farmers to convert manure into biogas and a nutrient-rich effluent.

Rau Dua (Ludwidgia adscendens) is a vegetable herb, available and readily consumed by humans and/or animals in the Mekong Delta (Ogle et al. 2001). The herb is creeping and floating on the water suface in the rural area. Its stem is slender, rooting at the nodes and leaves are alternate, flowers are white, solitary in the axil of the leaves and capule long, vilous and contaning numerous seeds. The extract of the whole herb cures fever, hermaturia or hemorrhagic dysentery (Dan et Nhu 1990). The vegetable samples contain the nutritional values of dry matter (13.8 %), and in the DM, CP (22.4 %), EE (5.2 %) and Ash (9.8 %). It is often applied in pig diet by farmers in the Mekong Delta (Xuan Dung 2001). When Ludwidgia adscendens cultivated in ponds fertilized with pig manure, the fresh biomass yield was 19.7 tonnes/ha and 1.9 tonnes/ha as DM. The contents in DM basis of CP, EE, CF and ash were 23.2, 4.9, 6.2 and 10.7%, respectively.   

The content in dry matter basis of lysine was 0.93%, threonine 0.91 % and methionine 0.61% for whole plant, respectively. There was higher level in total lipid of linoleic acid (C18:2 = 25.9 %), and alpha-linolenic acid (C18:3 = 29.9 %) (Men et al 2007, 2008).

The hypotheses

·         Rau Dua (Ludwidgia adcendens) can grow well in water surfaces fertilized by pig manure compost or biodigester effluent and produce a high fresh yield in a recycling model for small holders in the Mekong Delta.

·         Rau Dua can replace a part of the protein supplement in a diet for fattening pigs without affecting the pig performance and with benefit to farmers.
 

Materials and methods

Ludwidgia adcendens cultivation

The trial was conducted in Tan Phu Thanh village, located around 20km from Cantho city. The economy of the village is based mainly on agriculture, of which fruit production ranks in first place, and rice production is the important component of the farming systems. In addition, livestock production includes pigs and fishery and other water resources that are vital to the well-being of the village. Based on the practical situation, 4 families raising pigs were selected and divided into 2 groups, the first has a plastic bio-digester and the other do not have biodigester. Each household had 120 m² of water surface divided into 4 plots for growing two types of Ludwidgia adcendens from root stems, spacing 3-4 cm. The fertilizer used was pig manure compost or digester effluent. The fresh biomass was harvested after 40 days for two cycles. The whole plants were measured and the content of DM analysed by micro-wave radiation (Undersander et al 1993).

Feeding trial

The 24 Yorkshire-Baxuyen type pigs comprising equal numbers of castrated males and females had 57.5 ± 7.3 kg mean initial live weight. The experimental design included 3 dietary treatments, replicated in 4 farms, within which pigs were allocated to the treatments. There were 2 pigs (castrated male and female) in each pen, and they were given the experimental diets three times daily. The daily allowance was restricted to about 3.5 % of body weight. There was free access to drinking water.

Samples of each feedstuff were taken in each farm, and the contents of DM, CP, CF, EE were analyzed according to AOAC (2000); ME was estimated according to NIAH (1995). All pigs were weighed at the initial, and final time point of the trial. Feed refusal in every pen was collected every day.

Statistical analyses

Data were analyzed by ANOVA using the Basic statistics and General Linear Model of Minitab Statistical Software version 13. Sources of variation were treatments, blocks and error. The Tukey test for paired comparisons was used to separate means when the differences were significant at the 5 % level.

Results and discussion

Ludwidgia adcendens yield                                                                                                  

Fresh biomass yield of two varieties of Ludwidgia adcendens fertilized with biodigester effluent or pig manure compost are shown in Table 1.

Photo 1. The Ludwidgia adcendens Com cultivated  in the households by using biodigester effluent (B)  and pig manure compost (C)
Photo 2. The Ludwidgia adcendens Xanh cultivated  in the households by using biodigester effluent (B) or pig manure compost

Pig production

Chemical compositions of the feedstuffs used in the on-farm trial and the experimental diets are shown in Tables 2 and 3.

Growth and feed conversion did not differ among diets. Feed cost per kg weight gain (VND) was effective improved for RD50 (13,306; 86 %) than for RD25 (13,815; 89 %) and RD0 (15,486; 100 %) (Table 4).

Conclusions

·         Recycled organic waste and effluent can be used for growing natural feed resources such as Ludwidgia adcendens in small holder farms

·         Ludwidgia adcendens  can be used as a protein supplement to reduce feed costs of pigs in the integrated farming system

 

References

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    Preston, T.R. 1995 Tropical animal feeding. A manual for research workers. FAO animal production and health paper 126: 305 pp. Rome. 

Undersander D, Merten D R and Thiex N 1993. Forage analyses procedures. National Forage Testing Association. New York.  

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