Livestock Research for Rural Development 24 (3) 2012 Guide for preparation of papers LRRD Newsletter

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Effect on growth performance of ducks of supplementing a basal diet of rice bran with water spinach, duckweed or ensiled taro leaves

Sengsouly Phongphanith, Visam Vilaysack, Sangkhom Inthapanya and T R Preston*

Faculty of Agriculture and Forest Resources, Souphanouvong University, Lao PDR
* Finca Ecológica TOSOLY, AA 48 Socorro, Colombia


Growing Muscovy ducks (n=36) were fed a basal diet of rice bran mixed with three sources of protein-rich vegetative plants: Water spinach, Duckweed and Taro leaf silage. The bran and supplements were mixed in equal parts on fresh basis and fed ad libitum.

Supplements of fresh duckweed and water spinach supported growth rates of 26.5 - 27.5 g/day. Supplementation with ensiled taro leaves led to lower feed intakes and growth rates. DM feed conversion was similar on all diets in the range of 5.28 - 5.66.

Keywords: feed conversion, green feeds, liveweight gain, local feed resources


Poultry production is a common activity in Southeast Asia, and is a major source of livelihood for over a million people in the rural areas. In the last two decades, Asian duck production  has become increasingly important, accounting for up to 87% of the world's duck population, and duck meat and egg production has increased  more than four  times (Chein Tai and Jui-Jane Liu Tair 2001).

Ducks are reared traditionally by poor farmers for their livelihood. Duck production is one component of integrated farming systems which are regarded as being part of a sustainable development in agriculture. They can be integrated with rice, orchards, cash crops, livestock and fish (Bui Xuan Men 2010). Thus, the stakeholders not only can develop their livelihoods without accumulating debts, but also can get extra income through off-farm and non-farm activities (Le Thanh Phong et al 2007).

At smallholder level, many farmers have not enough money to buy the high quality protein sources such as fish meal and soybean meal that are the basis of intensive livestock feeding systems. However, they are able to grow many plants the leaves of which are relatively high in protein. Examples of these potential protein sources are the foliages from duckweed, water spinach, cassava, Taro and sweet potato. 

Duckweeds (Lemna spp) sre small green plants belonging to the family Lemnaceae. They grow on natural pond surfaces. They are fast growing and when adequately fertilized may contain up to 40% protein in DM (Porath et al 1979; Bui Xuan Men et al 1995; Skillicorn et al 1993; Leng et al 1995). Duckweed protein has a well-balanced array of essential amino acids, better than most vegetable proteins (Table 1) and closely resembles animal protein according to Culley and Epps (1978).

Water spinach (Ipomoea aquatica) grows in marshy or wet sandy areas or floating on water in many parts of tropical regions in the world (Bruemmer and Roe 1979). The plant has creeping, hollow, water-filled stems and shiny green leaves, and large purple or white 2-5 cm long funnel-shaped flowers. It is used as human food and animal feed throughout Southeast Asia (Gohl 1975). The fresh leaves and stems contain from 20 to 31 % crude protein on a DM basis (Bui Huy Nhu Phuc 2000; Ly Thi Luyen and Preston 2004; Prak Kea et al 2003; Chhay Ty and Preston 2006; Chhay Ty et al 2007; Phiny et al 2008; Sokha et al 2008), apparently with a better balance of essential amino acids than soybean (Table 1).  

Table 1:  Major essential AA in the “ideal protein”, soybean meal and leaves of selected protein-rich leaves (Adapted from Preston 2006)


Ideal protein

Soybean meal

Water spinach

Cassava leaves

Sweet potato leaves


New cocoyam


g AA/kg N*6.25














































As proportion of lysine = 100






























Composition of fresh leaves, g/kg fresh matter












Composition, g/kg DM



Crude protein








Crude fibre


















Taro (Colocacica esculenta) is a tropical food crop with high potential because of the high yield of the roots (or corms) and foliage. The leaves are rich in protein and are easy to ensile (Rodríguez et al 2009), a process which has been shown to reduce markedly the concentrations of calcium oxalate (Hang and Preston 2010),  an anti-nutritional compound that causes irritation of the skin and mouth and can be a limiting factor in consumption of the fresh leaves according to Tiep et al (2006). Silage made from the leaves and stems of Taro was successfully fed to ducks by Giang et al (2010) and Chhay Ty et al (2011).

The objective of the present study was to evaluate three vegetative plants as potential sources of protein for ducks fed a rice bran basal diet.

Material and methods


The experiment was conducted from December 2011 to February 2012 in the farm of the Faculty of Agriculture and Forest Resources, Souphanouvong University, Luang Prabang province, Lao PDR.

Experimental treatments and design

Growing ducks were fed a basal diet of rice bran and assigned to 3 dietary treatments with 3 replicates in a Completely Randomized Block Design (CRBD), as follows:

Animals and housing
Muscovy ducks (n=36) of 40-60 days age were purchased from farmers and raised in pens (4 ducks per pen) made from bamboo and wood (Photo 1) with dimensions of: width 0.5 m, length 0.5 m and height 0.5 m. There were spaces in the pen floor to let the feces go through. The house was made of bamboo with a thatch roof and open sides to facilitate ventiliation.

Photo 1. Muscovy ducks and experimental house

Feeding and management

The ducks were adapted to the experimental feeds for one week before collection of data. The ingredients were fed as a completely mixed ration, in the ratio of 50: 50 fresh basis. The ducks were vaccinated against bird flu before the experiment started.

The duckweed (Photo 2) and Taro leaves (Photo 3) were collected from areas around the University where they were growing naturally. The water spinach was planted in the University farm. Rice bran was bought from the market. Feeds were offered three times per day at 07:00 am, 11:30 am and 16:30 pm; water was freely available.

The duckweed (Photo 4) was collected each morning and mixed immediately with the rice bran in quantities sufficient for one day. The leaves and stems of water spinach were combined and chopped into small pieces before mixing with the rice bran (Photo 5).Taro leaves were made into silage . After harvest the leaves were chopped into small pieces of  around 2-3 cm of length (Photo 6) and exposed to sunlight for 24 hours to reduce the moisture before making the silage. The ensiled taro was put in sealed plastic bags and stored for 14 days before being fed to the ducks. Each day sufficient silage for the daily feed was removed from the bags and mixed with the rice bran.  Between successive meals the mixtures of rice bran and vegetative supplements were stored in the shade prior to feeding.

 Photo 2. Duckweed growing naturally in ponds  around the University campus  Photo 3. Natural growth of Taro around the University campus

Photo 4. Duckweed was mixed into the diet with no further processing Photo 5. Chopping the water spinach before feeding Photo 6. Chopping the Taro leaves prior to ensiling them
Data collection and analyses

The ducks were weighed at the start and afterwards at 7-day intervals. Feeds offered and refused were recorded daily, and representative samples taken every 7 days to determine N following procedures of AOAC (1990) and DM by micro-wave radiation (Undersander et al 1993).

Statistical analysis

Growth rates of the ducks were calculated as the linear regression of average live weight of the ducks per pen (Y = g) on time (X = days). The data were analyzed by the General Linear Model (GLM) option of the ANOVA software of Minitab (2000).  Sources of variation were:: supplement and error.

Results and discussion

Chemical composition

The crude protein content of the duckweed (Table 2) was at the lower end of the range (14 to 40% CP in DM) reported by Rodríguez and Preston (1996) and Keansombath Lampheuy (2003).  The crude protein in the Taro leaf silage was similar to what was reported (24.8% in DM) by Rodriguez et al (2006) for leaves of New Cocoyam (Xanthosoma sagittifolium), a plant from the same family as Taro (Colocacia esculenta). The crude protein in water spinach was slightly higher than values reported by Kean Sophea and Preston (2001) and Le Thi Luyen and Preston (2004), where the range was from 18 to 20% in DM. These authors showed that the protein content was increased by fertilization with urea or biodigester effluent N. It was also apparent from their data that the crude protein in the biomass of water spinach was dependent on the actual proportions of leaves and stems in the material harvested, as the stems had only some 25% of the level of protein found in the leaves.

Table 2. Chemical composition of feed ingredients


DM, %

CP in DM, %

Rice bran






Taro leaf silage



Water spinach



Growth rate and feed conversion

DM intakes, final live weight and daily weight gain were similar for supplements of duckweed and water spinach, both of which were better than the supplement with taro leaf silage (Table 3; Figures 1 and 2).  The growth rate with Taro leaf silage was inferior to that reported by Giang et al (2010) for a mixed diet of rice bran and taro silage made from combined leaves and stems. In the present experiment the taro leaf silage was prepared without additives, which may have had a negative effect on palatability of the feed when mixed with the rice bran. It has been shown that the quality of the taro silage is better when taro stems (which are rich in soluble sugars) are combined with the leaves in the ensiling process (Rodríguez and Preston (2009).

Table 3. Mean values of feed intake, live weight gain and DM feed conversion for ducks fed a complete mixed diet based  on rice bran  and supplements of duckweed (DW), water spinach (WS) or  ensiled Taro leaves  (TS)







DM intake, g/day  
Rice bran 132 121 78.4 5.49 0.005
Duckweed 14        
Water spinach   18.6      
Taro leaf silage     18.7    
Live weight, g          













Daily gain






DM intake, g/day












ab Mean values in the same row without common letter differ at P<0.05

Figure 1. Effect of supplements of duckweed, water spinach or Taro leaf silage, in  mixed diets with rice bran, on DM intake of ducks

Figure 2. Effect of supplements of duckweed, water spinach or Taro leaf silage, in  mixed diets with rice bran, on live weight gain of ducks

There are advantages of working with ensiled Taro foliage as it avoids the need for daily harvesting (Rodríguez and Preston 2009). A further advantage is that the harvesting of the foliage can be done at the optimum time in terms of the physiological development of the plant. Practical experience indicates that harvest intervals of about 20 days are most appropriate, such that the older  leaves and stems are harvested just before leaf senescence leaving the two youngest leaves to initiate the next growth cycle.



The senior author expresses his gratitude to the MEKARN program financed by the Sida project for providing the opportunity and the budget to do the research. Thanks are also given to Souphanouvong University, Faculty of Agriculture and Forest Resources for providing infrastructure support and laboratory assistance.


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Received 21 February 2012; Accepted 28 February 2012; Published 4 March 2012

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