Duck production in the Mekong Delta and taro (Colocasia esculenta) foliage as feed supplement

Nguyen Tuyet Giang

Department of Animal Husbandry and Veterinary Medicine,

Angiang University, Vietnam

ntgiang@agu.edu.vn

Duck production in Vietnam

Vietnam is a country situated in Southeast Asia with a population of 85.79 millions and an area of 331,114 km². Vietnam has a paddy rice culture and approximately 70% of the population lives in the countryside, and 90% of households raise poultry. According to Doan Xuan Truc (2001), Vietnam ranks 5th in ASEAN and 47th in the world in poultry meat and egg production. Traditionally, poultry are kept in small scale system, in the back yard and close to farmers’ houses. As study of Hall et al. (2006) showed that small scale farmers in Vietnam keep poultry for cash income and food, and raising poultry is a form provides a small proportion of total household economic activities (5-10%) compared to more intensive enterprises (20-85%). According to a FAO (2004) classification, poultry production (including ducks) diversifies into sectors depending on the management and marketing system: industrial integrated system (integrated farms with various components are managed under high biosecure procedures); the industrial sector (commercial poultry production system with moderate to high biosecurity and birds/products usually marketed commercially; birds are kept indoors, completely inhibited from contact with other animals); semi-commercial sector (low to minimal biosercure level in which birds are housed in cages; open sheds allowed spending time outside the shed) and the sector of village or backyard production, which is under or without biosecurity, and birds and products are sold or consumed locally.

In Vietnam, there is also another standard using herd size as standard to classify the poultry sector, which can be found in both rural and industrial sectors. There are 400,000 small and medium scale farms with 50 to 5000 head of poultry and at least 8 million households use small scale systems with less than 50 poultry head. Vietnam has many advantages to enhance duck production. Firstly, the natural resources with appropriate climate conditions, a large number of rivers, as well as canal networks, are suitable for developing duck production. Vietnamese farmers have a long experience of raising ducks; they can utilize local feed sources that are cheap and available through out the year. Vietnam is ranked 4th in the world, after China, France and Thailand (Doan Xuan Truc 2001) in duck production. Products from duck production are meat, eggs and feathers. In addition, salted duck eggs have become a product into some Asian markets in recent years. The duck is a water fowl that can easily adapt to different environments, with or without water. Ducks are raised mostly for meat and egg purposes. Farmers like to keep ducks because of the low investment, utilizing local materials for housing; ducks are well resistant to common diseases and grow well on locally available feed resources. Ducks are easily raised with low nutritional feed inputs but they rapidly bring benefits, with short life cycle, high growth development and productivity. In addition, ducks can be seen widely in the rural and remote areas where farmers are stakeholders, although they are facing handicaps in accessing to appropriate technologies, information, market and help services (Shan-Nan Lee 2009).  

Among the agroecosystems, the Red River Delta, Mekong River Delta and North East regions accounted the highest proportion of poultry (Desvaux Stephanie et al. 2008). According to Bosma et al. (2005), since livestock requires less and lower land quality than cultivated plants, farmers invest more in livestock activities, raising ducks or chickens, fish or pigs, buffaloes or cattle, for example. In fact, raising ducks for eggs involves a risky investment for the smallholder in the Mekong Delta. In contrast to chickens, ducks may lay eggs everywhere, and then need to be fenced and restricted by nets, also in order to keep the birds safe at night. Also a bedding of straw or rice husks should be prepared to protect the eggs from breaking. For intensive systems, the flock size varies from about 500 to 5000 ducks. Landless farmers generally start with smaller flocks and expand slowly in order to minimize the investment and labour.

Raising systems

Scavenging free range system

Vietnamese farmers have a long experience of scavenging ducks in the backyard or garden. Complete scavenging systems or semi-scavenging are most suitable for most local duck breeds (Nguyen Thi Kim Dong 2005). Most stakeholders apply this system because they can start with a small size flocks (5-50 ducks) in the backyard or garden. Although this system is distinguished by low feed offer, with or without housing, farmers can profit from products they get (meat and eggs). If predators are a problem at night, the open areas or pens can be covered by inexpensive net or wire mesh (Dean and Sandhu 2006). Ducks can effectively be fed home wastes or cheap by-products (such as rice bran or broken rice) 2-3 times per day; they also have free access to other feed sources in rivers, pond or areas of the rice fields (Bui Xuan Men 1996). 

Integrated systems

In the Mekong Delta, farmers use many traditional ways to raise ducks, of which the integrated systems are the most common. Bui Xuan Men (1996) mentioned that besides scavenging, a very traditional system, which is not very profitable. Ducks can be raised along with growing rice but do not harm the plants in the early stage of growth, before flowering. After the brooding stage (at more than 1 week of age), ducklings are let into the rice fields (20 days after transplanting until flowering). Ducklings can find and consume snails and insects in the rice field. While scavenging, ducklings can consume weeds, swim and stir the mud around the plant roots without harming the rice plants. Ducks’ excreta also fertilize and stimulate rice growth. In this way, farmers can save money for pesticides, herbicides as well as chemical fertilizer. The second model is raising ducks in the post-harvest rice fields. Commonly, both laying and meat type ducks are reared. Above 3 weeks of age, ducklings can consume whole rice grains. After harvesting, ducks can scavenge in the rice field leftover or fallen rice grains, insects, shellfish, frogs, weeds, fish and water plants. Today, varieties of high yielding rice are preferred, and after the harvest just takes, it only takes a few days to start a new crop. In such circumstances, this system becomes less flexible. Ducks can also integrate with fish (Le Hong Man 2002) to get higher fish yield (an increase of 30–40% in comparison with fish without duck integration) due to the duck manure and waste feed. Duck houses are often built above or near the fish pond, where herbivorous and omnivorous fish can be reared such as carp, roach and tilapia. Duck are kept in a house at night and allowed to range freely during daylight. They scavenge snails, crab, algae, plankton, fingerings and other available feeds in the pond. Generally, the number of ducks can ranges from 200–300/ha. After 2–3 years, both duck and fish yields start to decrease, since the ponds are full of sludge and become toxic to the fish. The sludge collected from the pond is a good source of organic fertilizer for the gardens and rice field. The third integrated model is also applied, and is referred to research carried out by Islam et al. (2004). They reported that thirty ducks and four fish species were introduced along with rice. Ducks were allowed to graze during the day and then were confined in houses built on the corner of the land. No supplement was supplied for the fish. The rice yield was lower than the culture with fish only. However, farmers could also benefit from the increase in the yield of fish and eggs from ducks.

Intensive duck production systems

According to Dean and Sandhu (2006), commercial duck production can be categorized into two types: absolute confinement and semi-confinement. The modern intensive total-confinement system is clearly differentiated by high duck density, high capital investment for housing, commercial feed and labour (Nguyen Thi Kim Dong 2005). Feed is supplied as well balanced rations; floor is design to eliminate wetness, and water troughs are installed such that ducks can not spread water. The intensive system is mainly found in agro-industrial zones or in peri-urban areas. Exotic and improved duck breeds are commonly reared in this system, mostly for meat. Ducks grow fast and are killed at early stage with high productivity. To semi-confinement system, duck housing is similar to confinement system, except that ducklings after 2-3 weeks can be allowed outdoors during the day.

However keeping ducks is risky; diseases may kill the birds in a flock within a few days. Due to disease outbreaks, it was a negative experience when some farmers took out loans with high interest rates or sold land to refund and restart with ducks. It also recognized that the duck production in small flocks creates many challenges for outbreak control. Farmers are keeping these flocks and even some intensive farms are unaware of biosercurity and seek veterinary service if their poultry have health problems. The transportation of birds should be under the government control. It is a concern that the free-ranging system plays an important role in AI spread in Vietnam, especially in remote areas where these are interactions between ducks of different villages (Edan et al. 2006).

Common ducks

According to Nguyen Thi Kim Dong (2005), common ducks are crossbreds of male Cherry Valley (imported to Vietnam since 1975) and female Pekin Ducks. Other common ducks are crosses between male Super-Meat ducks (meat type ducks imported from the United Kingdom in 1989) and female crossbred ducks (between Cherry Valley and Pekin ducks). According to various studies carried out recently, common ducks reach normal slaughter weight at around 9-10 weeks of age. Common ducks can grow at a similar rate to the Muscovy although they consumed double the amount of duckweed than Muscovy ducks (Men et al. 1996). Common ducks are preferred by farmers in the peri-urban and rural areas due to their ability to utilize low quality feed (by-products and natural forages), but the feed conversion rate is poor (Nguyen Thi Kim Dong 2005; Bui Xuan Men et al. 1995).

However, the pure breeds are facing a problem that they are being lost. A sign of this is that people can not recognize the difference between breeds in the field. In the Mekong Delta, for example, ducks that are called “Tau” but now look very close to the Khaki Campbell since the indigenous pure breeds have become less common and have been crossed with other different breeds (Desvaux Stephanie et al. 2008).

The nutrient requirements of ducks

Ducks can grow well, whether by scavenging or consuming a complete ration. However, the feed offered should contain enough nutrients and balance in ration regarding to the requirements for grow, maintenance and reproduction. Their need can be differ, depending on the stage (age) of birds and the production purpose (Table 1).

Feeds for ducks

Ducks are easy to raise under various management conditions. They can grow faster and reach higher performance earlier in a commercial system (semi- or fully-confinement), if supplied commercial feeds with balance a formula for each development stage. These systems are now widely applied, but rarely found in rural and remote areas where there is a lack of appropriate technologies and financial supports. However, ducks are preferable because of their good adaptation to local feed resources, such as household waste, agro-industrial by-products and forages.

The Mekong Delta region is the biggest “rice basket” of the country. Annually, rice mills produce large quantities of grain for export, as well as the by-products (rice husk, rice bran and broken rice). The broken rice is not as valuable as rice grain but it also can be exported or used locally for human consumption. Rice bran is the outer layer of brown rice kernel (after separating the husk) which is removed while milling brown rice to white. Rice bran, a rich source of nutrients and pharmacologically active compound, is currently used as livestock feed, and is also used for oil production (Tahira et al.2007). According to Houston (1972), rice bran accounts for 5-8 percent of paddy rice (whole grain). Commonly, in Vietnam, the rice mills produce three kinds of rice bran: the initial bran (mixed with rice husk fragments) and two types of bran produced in the polishing process which is very fine and have higher nutritional value than the initial bran. In the Mekong Delta, rice bran is cheaper than rice grain and broken kernels, so it is the most widely available feed resource for duck production.

The Mekong Delta is also well-known for fish and shrimp production (Le Viet Ly 1994), thus their by-products are available in large amount. Commonly, fish meal and soybean meal are widely used to supply protein; a good balance amino acids are suitable for all livestock species. However, due to the increasing oil price and the competition with human demands, local feed resources are a good alternative in terms of convenience and maximum net profit. Recent studies have shown that expensive feedstuffs can be replaced by alternative cheap ingredients without reducing the feeding value. Nguyen Thi Kim Dong (2005) for example found that soybean meal can be replaced by soya waste at up to 60% and using ensiled shrimp waste could replace fish meal (around 20%) without any effects on the growth performance of growing crossbred ducks, thus resulting in higher incomes for farmers. Study carried out on meat type ducks under Vietnamese farming conditions also showed that meat and bone meal as well as poultry by-product meal can fully replace fish meal (Nguyen Quang Dat and Yu Y  2003).

Duckweed (Lemna spp.) is easily grown in lakes, ponds and lagoons and has a high content of organic matter and crude protein (86.0 and 40.2%, respectively). In one experiment carried out on growing ducks, Khanum et al (2005) found that because of the low dry matter content and low crude protein digestibility ducks had poor growth performance, and duckweed could only included at around 50% in duck diets without negative influences on carcass quality. Farmers can produce duckweed in lagoons near their homesteads and/or may collect it from natural sources as feed to their ducks. This will help to reduce feed costs by about 50%. Nguyen Duc Anh and Preston (1997) asserted that duckweed can be fed as non-conventional protein source to support ducklings (5-20 days of age) growth performance. Duckweed can be used to totally replace the soybean meal but the protein is utilized is less efficiently than the protein in soybean because of the lower digestibility. Nguyen Thi Hong Nhan et al. (1997) reported that Trichantera leaf meal can be used in diets for laying ducks, hens and quails.  In the case of fattening ducks, they were given free access to fresh leaves of Trichantera or water spinach (the basal diet including broken rice, soybean and fish meal). The intake was around 70-80 g DM/duck/day. The authors asserted that soybean or fish meal can be reduced by 10% if the ducks had a free access to either Trichantera leaves or water spinach, with no negative influence on growth performance or carcass quality.

Taro (Colocasia esculenta) in the Mekong Delta

Nutrient composition

Taro, which belongs to the Aracea family, can be cultivated or collected from the wild in the Mekong Delta, particularly on the banks of ponds and along rivers or canals. Some taro species (Colocasia antiquorum and Colocasia gigantea ) which have a  large corm or palatable stem can be used for human consumption, while  Xanthosoma sp., Alocasia sp. Alocasia cucullata and Alocasia macrorrhiza (giant taro/giant elephant ear) can be used both as food and animal feed. Wild taro (Colocasia esculenta) originates from India and Southeastern Asia. It is a perennial herb 1.5 m tall, with thick stems, very small corms, and with leaf blades of around 60 in length and 50 cm in width. Wild taro is abundant particularly in wet lands since it is highly resistant to pest and diseases. The wild taro leaf has a high nutritive value, with 22.5-26.3% crude protein (Malavanh Chittavong et al. 2008b; Chhay Ty et al. 2007). However, in common with other species of the Aracae family, calcium oxalate (an anti-nutritional factor), is found in all parts of the plant, causing irritation in the throat and mouth epithelium and indirectly affecting the digestibility. Another constraint of taro is the high content of fibre (in taro leaves, crude fibre is around 17.1-18.3% of DM, Chhay Ty et al. 2007 and Malavanh Chittavong et al. 2008b).

Uses of taro as animal feeding

Taro is used for feeding livestock not only in Vietnam but also in other tropical countries. A survey in Cambodia on taro varieties and their use reported that taro is a common plant grown or developing naturally near the houses, in the forests, ponds, streams and canals but farmers rarely fed taro to their pigs because of the itchiness (Pheng Buntha et al. 2008b). Others researchers also evaluated the use of wild taro (Colocasia esculenta) in growing crossbred pigs (Chhay Ty et al. 2007, Nguyen Tuyet Giang 2008 and Pheng Buntha et al. 2008a) and Mong Cai gilts (Malavanh Chittavong et al. 2008a).

Processing methods and their influence on the nutritional value of taro

A major constraint to livestock production is the lack of animal feed resources (Kayouli and Stephen 1999). Many by-products and forages are not available through out the year; and therefore, it needs to be stored with appropriate processing methods.

Taro contains an anti-nutritional factor, namely calcium oxalate, which causes irritation on contact. This substance is present in all parts of the taro plant. Leslie and Patrick (1979) stated that the density of calcium oxalate crystals in corms increases rapidly in the early stage, then decreases in older and larger corms. Ravindran et al. (1996) showed that calcium oxalate was a main factor contributing to anti-palatability and anti-nutritive effects. Exceptions for corms that can be cooked for human consumption, Cambodian farmers rarely use taro petioles and leaves for animal feeding. In order to reduce the itchiness of taro caused by the calcium oxalate content, most farmers boil taro before feeding it to their pigs or add sugar palm syrup after boiling, while others applied salt, frying or sun drying (Pheng Buntha et al. 2008b).

There are various ways to process taro in order to store it and reduce the density of calcium oxalate crystal content, such as cooking, sun-drying, soaking and ensiling (Table 2).

Ensiling is a process that has been applied to preserve carbohydrate rich materials, with or without additives (Machin 1999). The particular feature of ensiling is the fermentation of feed with organic acids produced by bacteria. Ensiled forages are a good feed source animals, as monogastrics can digest all enzymically digestible components in the small intestine and fibrous materials are fermented quickly in the large intestine then easily absorbed as nutrients. This method is suitable and easy to apply for smallholders under tropical conditions because it is safe, takes less investment and results in significant incomes.

Taro (leaves or the mixture of petioles and leaves) are harvested and chopped into small pieces. The size of the fragments depends on what type of animal is reared.  Then, taro pieces are partially sun-dried to reduce the moisture content and packed tightly into plastic bags or containers. The bag should be sealed tightly to prevent contamination by air. Chhay Ty et al. (2007) mixed taro with rice bran and salt (10 kg rice bran, 0.5 kg salt and 89.5 kg taro leaves), and the silage was stored in normal temperatures for 30 days before being used. The purpose of this procedure was to reduce the content of calcium oxalate. Other additives can be used to stimulate the fermentation of bacteria and improve the palatability, such as molasses (Du Thanh Hang and Preston 2010 and Malavanh Chittavong et al. 2008a), and sugar palm syrup (Pheng Buntha et al. 2008a). 

Du Thanh Hang and Preston (2010) showed that neither ensiling nor different methods (sun-drying, soaking and cooking), affected the crude fibre content of taro leaves. However, Malavanh Chittavong et al. (2008a, b) reported that the fibre content in taro leaves was reduced by ensiling.

Effect of taro foliage on the growth performance of common ducks

Fresh taro leaves

The DM and CP intakes were significantly different among treatments in which ducks were offered by basal diet with five feeding levels (3, 4, 5, 6 and 7% of BW) and fresh taro leaves fed ad libitum. The increasing fresh taro leaves intake was to compensate for the reduced amount of basal diet. The result is consistent with the study carried out by Nguyen Thi Kim Dong (2005). The mineral as well as vitamin content of the fresh taro leaves can meet the demand of ducks, confined by the similar growth performance of confined common ducks (FCR and ADG) between diets, with and without a premix of vitamins and minerals.

In spite of ducks being able to consume high amounts of a bulky and fibre-rich feeds, the growth rate is poorer than if they are given a low fibre and high-energy diet. The growth performance of ducks in the present study was lower than of ducks fed "A" molasses substituted for broken rice and rice polishings at 15 or 30% in the diets (Bui Xuan Men and Vuong Van Su 1990). There was a relationship between the percentage of taro leaves intake in dry matter intake and the length of caecum as well as the weight of abdominal fat. The more taro leaves consumed, the less fat stored and the longer caecum length. The fibrous bulk in the digestive tract could be the reason for the increase in ceacum length.   

Silage of taro foliage (leaves and stem)

The ensiling process applied in forages should lead to an increase in the concentration of metabolizable energy in the diets, and therefore to improved performance in terms of growth rate and feed conversion. In fact, there were no differences in growth performance, but there were major effects on the carcass, with linear decreases in carcass percentage and in abdominal fat as the level of taro silage in the diet was increased.  These responses can be considered as positive in terms of carcass quality of the product and the opportunity to use local available forage which grows wild in the Mekong delta.

It is apparent that the ensiled taro foliage (leaves plus stems) has a relatively high nutritive value. The observations in this experiment do not permit conclusions to be made as to the relative nutritional values of the leaf and stem in the ensiled product. Rodríguez and Preston (2009) concluded that ensiling the combined leaf and stem of New Cocoyam (Xanthosoma sagittifolium) was a simpler process than ensiling only the leaf. When leaves were ensiled alone a source of fermentable carbohydrate (sugar cane juice) had to be added. However, it was found that the stem contained appreciable amounts of soluble sugars, and thus there was no need for an additive when the leaves and stems were ensiled together.  Dao Thi My Tien et al. (2010, unpublished data) also observed that the stems of taro (Colocasia esculenta) contained high levels of soluble sugars (up to 40% in the DM) and that this facilitated the ensiling process of the combined taro leaves and stems.

Conclusions

·       Vietnam is an agricultural country with huge annual rice production, so the by-product (rice bran) from mills is abundant. This is a cheap and available feed resource for duck production.

·       Taro foliage can be supplemented to local feed resources for common ducks to bring economic benefit for smallholders in Mekong Delta. 

•       Live weight gain was reduced from 30 to 20 g/day, and FCR was poorer, when the basal diet of rice bran, broken rice and SBM, was restricted to 3% of LW (as DM) with fresh Taro leaves ad libitum

•       There was no effect on ADG and FCR of including a mineral-vitamin premix when Taro leaves were also fed

•       Growth rates of ducks were:

Ø      The same over a range of ratios of rice bran and taro silage from 80:20 to 40:60

Ø     8% higher when the feeds were given as a mixture rather than separately

•       Calcium oxalate in taro leaf-stem silage was lower than in fresh taro leaves

•      Calcium oxalate in taro leaf-stem silage was lower than in fresh taro leaves

•      There was a positive effect on carcass quality (lower abdominal fat) from supplementing rice bran with taro silage.

•      Smallholders farmers in the Mekong Delta can get significant economic benefits from fattening common ducks as using the local feed resources (rice bran and taro foliage) that are very cheap compared with commercial feeds and widely available in the region and are safe for ducks.

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References

Bosman Roel H, Cao Quoc Nam, Udo Henk M J, Verreth Johan A J and Visser Leontine E 2005: Agriculture Diversification in the Mekong Delta: Farmers’ Motives and Contributions to Livelihoods,

Bui Duc Lung and Le Hong Man1999: Feeds and feeding poultry. Agricultural Publishing House, Hanoi, Vietnam. Pp. 211.

Bui Xuan Men 1996: The Role of Scavenging Ducks, Duckweed and Fish in Integrated Farming Systems in Vietnam, from http://www.fao.org/ag/AGAinfo//////resources/documents/frg/conf96pdf/men.pdf

Bui Xuan Men and Vuong Van Su 1990 A molasses in diets for growing ducks. http://www.lrrd.org/lrrd2/3/vietnam2.htm

Bui Xuan Men, B Ogle and T R Preston  1996: Duckweed (Lemna spp) as replacement for roasted soya beans in diets of broken rice for fattening ducks on a small scale farm in the mekong delta, from http://www.lrrd.org/lrrd8/3/men831.htm

Bui Xuan Men, B Ogle and T R Preston 1995: Use of duckweed (Lemna spp) as replacement for soya bean meal in a basal diet of broken rice for fattening ducks, from http://www.lrrd.org/lrrd7/3/2.htm

Chhay Ty, Khieu Borin, T R Preston and Sokveasna Mea 2007: Intake, digestibility and N retention by growing pigs fed ensiled or dried Taro (Colocasia esculenta) leaf as the protein supplement in basal diets of rice bran/broken rice or rice bran/cassava root meal. Livestock Research for Rural Development. Volume 19, Article #137, from  http://www.cipav.org.co/lrrd/lrrd19/9/chha19137.htm

Dao Thi My Tien, Nguyen Tuyet Giang and Preston T R 2010: A note on ensiling banana pseudo-stem with Taro (Colocasia esculenta) leaves and petioles

Dean W and Sandhu T 2006: Duck housing and management, from  http://www.duckhealth.com/housmngt.html

Desvaux Stephanie, Vu Dinh Ton, Phan Dang Thang and Pham Thi Thanh Hoa 2008: A general review and a description of the poultry production. Agricultural Publishing House, from http://www.aitoolkit.org/site/DefaultSite/filesystem/documents/Review%20of%20Poultry%20Production%20in%20Vietnam.pdf

Doan Xuan Truc 2001: Poultry production in Vietnam has a bright future. WORLD POULTRY-Elsevier Volume 17,No 2. '01, from http://www.worldpoultry.net/backgrounde/the-future-of-central-american-poultry-is-tough-6188.html

Du Thanh Hang and T R Preston 2010: Effect of processing Taro leaves on oxalate concentrations and using the ensiled leaves as a protein source in pig diets in central Vietnam, from http://www.lrrd.org/lrrd22/4/hang22068.htm

Edan M, Bourgeois Luthi N, Gautier P and Guerne-Bleich E 2006: Free ranging ducks and risks in Avian Flu disease in Vietnam, from http://www.sciquest.org.nz/crusher_download.asp?article=10003445

FAO 2004: Recommendations on the Prevention, Control and Eradication of Highly Pathogenic Avian Influenza (HPAI) in Asia

Hall David C, Benigno C and Wantanee Kalpravidh 2006: The impact of avian influenza on small and medium scale poultry producers in South East Asia (preliminary findings), from http://ageconsearch.umn.edu/bitstream/21348/1/sp06ha07.pdf

Islam S S, Azam M G, Adhikary S K and Wickramarachchi K S 2004: Efficiency of integrated rice, fish and duck polyculture as compared to rice and fish culture in a selective area of Khulna district, Bangladesh, from http://198.170.104.138/pjbs/2004/468-471.pdf

Kayouli Chedly and Stepen Lee 1999: Silage from by-products for smallholders, from http://www.fao.org/docrep/005/X8486E/x8486e0l.htm

Khanum J, Chwalibog A and Huque K S 2005: Study on digestibility and feeding systems of duckweed in growing ducks, from http://www.lrrd.org/lrrd17/5/khan17050.htm

Le Hong Man 2002: Duck-fish integration in Vietnam, from http://www.fao.org/docrep/004/ac155E/AC155E15.htm

Machin D H 1999: The potential use of tropical silage for livestock production, with special reference to smallholders, from  http://www.fao.org/ag/AGP/AGPC/gp/SILAGE/HTML/Paper5.htm

Malavanh Chittavong,  T R Preston and B Ogle 2008b: Ensiling leaf of Taro (Colocasia esculenta (L.) Shott) with sugar cane molasses.  Livestock Research for Rural Development. Volume 20, supplement, from http://www.cipav.org.co/lrrd/lrrd20/supplement/mala1.htm

Malavanh Chittavong, T R Preston and B Ogle 2008a:  Effect of replacing soybean meal with a mixture of Taro (Colocasia esculenta (L.)Schott) leaf silage and water spinach on apparent digestibility in Mong Cai gilts at two stages of gestation.  Livestock Research for Rural Development. Volume 20, supplement, from http://www.cipav.org.co/lrrd/lrrd20/supplement/mala3.htm

National Academy of Sciences 1994: Nutrient Requirements of Poultry. Ninth Revised Edition, 1994, page 42- 43, from http://www.nap.edu/openbook.php?record_id=2114&page=42

Nguyen Duc Anh and T R Preston 1997: Evaluation of protein quality in duckweed (Lemna spp.) using a duckling growth assay, from http://www.lrrd.org/lrrd9/2/anh92.htm

Nguyen Quang Dat and Yu Y  2003: Total replacement of fish meal by meat and bone meal and poultry byproduct meal in meat duck diet, from http://nationalrenderers.org/assets/duck_feeding_trial.pdf

Nguyen Thi Hong Nhan, T R Preston and Dolberg F 1997: Use of Trichantera gigantea leaf meal and fresh leaves as livestock feed, from http://www.lrrd.org/lrrd9/1/nhan91.htm

Nguyen Thi Kim Dong 2005 An evaluation of brewery waste as a replacement for concentrates in diets for growing crossbred common ducks. Tropical Animal Health and Production. 36 (7): 715-729.

Nguyen Tuyet Giang 2008 Taro (Colocasia esculenta) silage and water spinach as supplements to rice bran for growing pigs. http://www.mekarn.org/msc2008-10/miniprojects/minpro/giang.htm

Pheng Buntha, Khieu Borin, T R Preston and B Ogle 2008a:  Digestibility and nitrogen balance studies in pigs fed diets with ensiled taro (Colocasia esculenta) leaf as replacement for fish meal.  Livestock Research for Rural Development. Volume 20, supplement, from  http://www.cipav.org.co/lrrd/lrrd20/supplement/bunt2.htm

Pheng Buntha, Khieu Borin, T R Preston and B Ogle 2008b:  Survey of taro varieties and their use in selected areas of Cambodia.  Livestock Research for Rural Development. Volume 20, supplement, from http://www.cipav.org.co/lrrd/lrrd20/supplement/bunt1.htm

Ravindran V, Sivakanesan R and Cyril H W 1996: Nutritive value of raw and processed colocasia (Colocasia esculenta) corm meal for poultry, from http://cat.inist.fr/?aModele=afficheN&cpsidt=3009224

Samli H E, Senkoylu N, Akyurek H, Agma A 2006: Using rice bran in laying hen diets, form http://www.agr.hr/jcea/issues/jcea7-1/pdf/jcea71-18.pdf

Shan-Nan Lee 2009: Improved Duck Production of Small-Scale Farmers in Asia. http://www.agnet.org/library/ac/2007g/

Sunell Leslie A  and Healey Patrick L  1979: Distribution of Calcium Oxalate Crystal Idioblasts in Corms of Taro (Colocasia esculenta), from http://www.jstor.org/pss/2442567

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