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Sugar palm (Borassus flabellifer): potential feed resource for livestock in small-scale farming systems

Khieu Borin

The author's address is: Department of Animal Production and Health, Ministry of Agriculture, Forestry and Fisheries, PO Box 177, Phnom Penh, Cambodia (e-mail: borin@forum.org.kh).
Acknowledgements. The studies reported here were financed partially by the FAO/TCP/CMB/2254 Project, the International Foundation for Science (B/2353-1) and SAREC (research as partial fulfilment of the requirements for an M.Sc. in livestock-based sustainable farming systems).

PALMIER À SUCRE (BORASSUS FLABELLIFER): UN PRODUIT D'ALIMENTATION ANIMALE POTENTIEL POUR LES PETITES EXPLOITATIONS

Le palmier à sucre est un élément important de la vie rurale au Cambodge. Il fournit divers produits d'usage domestique. Les feuilles et le tronc servent de matériel de construction. Le suc, extrait des inflorescences, est traditionnellement transformé en sucre, consommé sous forme de boissons fraîches et fermentées, ou encore donné en nourriture aux cochons. Certaines parties de son fruit sont également consommées. Les études mentionnées dans l'article avaient au départ pour but de mettre au point de nouvelles utilisations du jus de palmier à sucre en tant qu'aliment énergétique pour les porcins. Pour ce faire, le rendement en jus des arbres appartenant à 12 ménages a été mesuré à intervalles mensuels pendant la saison de récolte 1995 (de janvier à mai). Dans les ménages pauvres, les porcs ont engraissé à un taux oscillant entre 250 et 550 g/jour lorsqu'ils étaient alimentés avec du jus frais de palmier à sucre et des quantités limitées (moins de 200 g de protéines/jour) de soja ou de poisson séché. Le rendement en jus s'est établi entre 2,7 et 7,5 kg/arbre/jour, sur une période de cinq mois, avec une concentration moyenne en sucre de 13 pour cent. Chaque arbre couvrant une superficie d'environ 50 m², il a été estimé qu'un tel rendement équivalait à une production de sucre de 10 à 27 tonnes par hectare et par an. Une telle productivité en énergie digestible est supérieure à celle de toutes les autres cultures, tempérées et tropicales, et est particulièrement remarquable si l'on considère que le palmier à sucre n'est jamais fertilisé.

PALMA DE AZÚCAR (BORASSUS FLABELLIFER): POSIBLE RECURSO DE PIENSOS PARA EL GANADO EN LOS SISTEMAS AGRÍCOLAS EN PEQUEÑA ESCALA

La palma de azúcar es un elemento importante de la vida rural en Camboya. Proporciona distintos productos para uso doméstico. Las hojas y el tronco se utilizan para la construcción. La savia obtenida de la inflorescencia tradicionalmente se ha transformado en azúcar, que consume la población en forma de bebidas frescas y fermentadas, o bien se administra a los cerdos. También se comen algunas partes del fruto. Los estudios descritos en el presente artículo se orientaron inicialmente a la búsqueda de aplicaciones alternativas del jugo de la palma de azúcar como pienso energético para los cerdos. En el curso del trabajo se midió a intervalos mensuales el rendimiento de jugo en árboles pertenecientes a 12 familias durante la temporada agrícola de 1995 (enero-mayo). Los cerdos de los hogares agrícolas pobres crecían a un ritmo comprendido entre 250 y 550 g/día cuando se les administraba jugo fresco de palma de azúcar y cantidades limitadas (menos de 200 g de proteínas/día) de habas de soja o de pescado seco. El rendimiento de jugo osciló entre 2,7 y 7,5 kg/árbol/día durante un período de cinco meses, con una concentración media de azúcares del 13 por ciento. Se estima que, puesto que cada árbol ocupa una superficie aproximada de 50 m2, ese rendimiento es equivalente a 10-27 toneladas de azúcares/ha/año. Este nivel de productividad de carbohidratos digestibles supera el de todos los demás cultivos, de clima templado y tropical, y es particularmente importante considerando que la palma de azúcar no se fertiliza nunca.

INTRODUCTION

The challenge facing scientists, researchers, extension workers and farmers in the next millennium is to find appropriate ways of utilizing the earth's resources to feed the predicted doubling of the human population while at the same time improving the living standards of rural people.

The pressure on the food supply will not only come from the increase in the population but from the deterioration in the natural resource base caused by factors such as deforestation, which causes flooding or drought; burning of fossil fuels, leading to global warming; and the pollution of soil and water by the overuse of agrochemicals such as fertilizers and pesticides. The effects of deforestation are especially serious in Cambodia, and in one area alone - around Tonle Sap Lake - the result has been a permanent fall in the lake's water level which has led to a reduction in the numbers of fish, a most important source of protein for the Cambodian population.
In order to respond to these issues it has been argued that, instead of exploiting resources for production of specific commodities, it is more appropriate to match the farming system with the available resources (Preston and Leng, 1987). The successful development of this strategy entails the identification of cropping systems that optimize the use of the basal resources of sunlight, soil and water to satisfy human needs for food, fuel, clothing and shelter. This approach takes a holistic view of human needs to include sociocultural, economic and environmental aspects, instead of individual crop or animal productivity as a unique paradigm.
This article illustrates the application of this approach, taking as an example the case of the sugar palm (Borassus flabellifer), the use of which has been a traditional feature of rural life in Cambodia. The sugar palm is one of the 200 genera and 1 500 species of palms that occur naturally in the tropics and subtropics. It attracted the attention of development scientists in the early part of this century but has since been largely ignored, presumably because its cultivation and utilization were not amenable to industrial-scale management and processing.
There is now renewed interest in the sugar palm as a result of two recent developments. One has been the declining availability and increasing cost of the fuelwood needed for evaporating the juice to make sugar; the second has been the demonstration (Khieu Borin and Preston, 1995) that the fresh juice could replace cereal grains in pig feeding.

SUGAR PALM PRODUCTS

Leaves

The leaves of the sugar palm are commonly used as materials for construction and domestic goods. Twenty-five to 36 leaves are harvested twice a year from the palms that are not used for tapping. Farmers believe that pruning negatively affects juice production. Almost all households in rural areas use palm leaves not only for thatching but also for the walls. The top young leaves are made into hats, boxes to store rice, baskets, fans, etc. In the past they were used as writing materials, especially by the monks.

Fruit

Each palm may bear eight to fifteen bunches of fruit with a total of about 80 pieces of fruit per year. The fruit generally contains two to three kernels which are eaten fresh or prepared as a sweet with sticky rice. The top part of immature fruit is also cooked as a vegetable. The fresh pulp around the kernels is reported to be rich in vitamins A and C (Morton, 1988). The mature fruit is soaked in water after which the wiry fibres are extracted. The yellow pulp is mixed with rice starch, folded inside a banana leaf and later steam-cooked.

Trunk

The less-productive palm trees are cut for timber when they are move than 10 m high and about 70 to 100 years old. The whole trunk is used by removing the soft middle part, and the strong, hard outer wood is used for house construction. This outer wood is more durable than other kinds of wood when used in the shade and protected from rain. The whole trunk can also be made into a small boat capable of carrying at least three people.

Inflorescences

Palms generally start to form inflorescences at the beginning of the dry season (November to January). The male and female inflorescences are carried on separate trees: the male tree begins to develop the inflorescence in November or December while the female tree commences one to two months later. Each palm may bear from eight to fifteen inflorescences per year. The male inflorescence lasts approximately 45 to 60 days and the female 60 to 70 days. Both male and female inflorescences are "tapped" for juice collection. Some palms, especially the female, also have inflorescences during the rainy season. Cambodian tappers have developed a technique to conserve inflorescences to be tapped after the normal harvest period.

Juice

The most important product of the sugar palm is the sap or juice, the production of which lasts for five to six months. Cambodian tappers use long bamboo poles with the stumpy remnants of leaf bases at the nodes that serve as rudimentary steps for climbing. These are rivetted permanently to the base of the trunk during the juice-collecting period. For safety reasons the tapper replaces the bamboo poles every production period (six to twelve months). When the trees are located close to each other, one or two long bamboo poles are used as an aerial "stairway" to facilitate movement between the trees, thus avoiding the need to descend and ascend each tree and permitting the tapper to use his time (there are no female tappers) more productively. Tappers are capable of tapping 20 to 30 palm trees twice a day provided an assistant is available at the base of the trunk to receive the collected juice.

 

W9980t18.JPG (61525 bytes)

Juice collection from a female palm in Takeo Province, Cambodia. Plastic bottles used for collecting the juice are those initially used for purified drinking-water
Récolte du suc d'un palmier à sucre potentiellement femelle dans la province de Takeo. Les bouteilles en plastique utilisées pour la récolte contenaient initialement de l'eau potable purifiée
Recolección de una posible palma hembra en la provincia de Takeo. Las botellas de plástico utilizada para recoger el jugo son las usadas inicialmente para el agua potable purificada

 

W9980t19.JPG (69939 bytes)

A palm juice tapper is slicing a female inflorescence for the afternoon juice collection
Incision de l'inflorescence femelle d'un palmier à sucre pour la récolte de suc de l'après-midi
Un extractor de jugo de palma está cortando una inflorescencia femenina para la recogida de jugo por la tarde

The inflorescences of the male and female palms are bound, beaten and then sliced for approximately five to eight consecutive days before juice can be collected. The tapping process is repeated every two to three days during the production season. The inflorescences can also be preserved for later use after being processed. A pair of rounded wooden mallets is used for the female inflorescences and flat wooden tongs for the male inflorescences. The small fruits around the female inflorescences should not be crushed during the preparation. The juice is channelled into a bamboo or plastic vessel. The bamboo vessel, called an ampong, has a diameter of 10 to 15 cm, a height of about 30 to 40 cm and can contain 2 to 4 kg of juice. For each tree an average of four to six collection vessels are used according to the number of inflorescences being processed at the one time. Collection is carried out twice daily (morning and afternoon) in order to limit exposure of the juice to contamination by yeast and other fermenting micro-organisms.
The most important technique for tapping palms is the processing of the inflorescence or spathe. Juice production from the inflorescences is stimulated by crushing the tissues without, however, completely destroying the cells of the crushed tissues. The time it takes from the com-mencement of tapping to the appearance of the juice depends on the experience of the tapper. According to the farmers in Bati district, Takeo Province, the flowers need to be crushed and kneaded for a period of five to eight days. The juice is then collected twice daily (early morning and late afternoon). It is usually possible to continue tapping a single spathe until it is reduced to a stump of about 10 to 15 cm. When the trees produce many inflorescences at the same time, the tappers are not able to collect juice from all of them. In this case, the inflorescences are sliced and crushed for the usual five to eight days and then preserved for juice collection some three to five months later.
The daily production of palm juice depends mainly on the skill of each tapper. When a tapper is replaced for a short period, the sap flow often diminishes on the day following this replacement. Kovoor in FAO (1983) reported that the flow of juice results from the stimulus produced by the manual operation of tapping, and thus depends on the physiological response of the palm. There is enormous variability in daily yield per tree and tree-to-tree juice production. Depending on the tree, weather and location, from one to seven inflorescences may be tapped at a time. The Table demonstrates that, although the rate of flow of the juice is reduced as the process continues, the Brix value (sugar content) increases.

Mean juice yield and Brix value (approximate sugar content) by farm, month, sex of trees and day of harvest
Rendement moyen en jus et valeur Brix (teneur approximative en sucre) selon l'exploitation, le mois, le sexe de la plante et le jour de récolte
Rendimiento medio de jugo y valor Brix (contenido aproximado de azúcar) según la explotación, el mes, el sexo del árbol y el día en que se recoge

 

Juice (kg/tree/day)

Brix value (%)

Farm family

   

Hay Yang

4.6

13.4

Houy Kiel

4.9

12.5

Pring Houy

2.7

14.3

Map Chreb

5.9

13.5

Sim Henn

4.0

15.9

Pauv Pauv

5.5

13.3

Tha Khorn

5.5

13.5

Thol Onn

6.0

12.2

Thorn Punn

4.4

12.8

Yem Khnol

7.5

11.6

Chhan Mak

3.9

13.0

Thorn Chreb

4.9

13.3

Mean

5.0

13.3

Standard error

±0.20

±0.14

Probability

0.001

0.001

Month

   

January

4.7

12.6

February

5.7

12.6

March

5.2

13.5

April

5.1

13.6

May

4.2

14.1

Standard error

±0.13

±0.09

Probability

0.001

0.001

Sex of trees

   

Female

5.3

13.4

Male

4.7

13.2

Standard error

±0.09

±0.06

Probability

0.001

0.005

Day of harvest

   

First

4.9

13.2

Second

5.0

13.3

Third

5.0

13.3

Standard error

±0.10

±0.07

Probability

0.665

0.534

The fresh juice starts to deteriorate naturally within a few hours after sunrise, especially during hot weather. When the juice is collected for sugar production, or as a drink for human consumption and for animal feeding, fermentation should be avoided as much as possible. The normal procedure is that the collection vessels are fumigated with the smoke of burning palm leaves or are sterilized with boiling water before being placed under the inflorescences. However, the juice can quickly become contaminated with wild yeasts carried by insects and airborne particles. In order to inhibit fermentation, at least partially, a piece of bark from the white meranti tree (Shorea cochinchinensis) is placed in the collection vessel while the juice is being collected. Another anti-fermentation agent, lime (calcium hydroxide), is available in local markets, but farmers do not use it, as they consider lime to have a negative effect on the quality of sugar and the fresh juice for drinking. It has been observed that the onset of fermentation is delayed when plastic bottles are used, presumably because they are easier to clean and sterilize.
The naturally fermented palm juice (teck thnot chhu) is a common alcoholic beverage in rural areas and is also used to make vinegar. Davis and Johnson (1988) reported that, when the juice is fermented through the action of airborne micro-organisms, an alcohol content of 5 to 6 percent may be reached. The upper alcohol limit is not necessarily set by the quantity of sugar available in the juice, which is always in excess, but because the natural fermenting organisms are killed at an alcohol concentration of 5 to 6 percent, leaving a large amount of fermentable substrate.
The juice yield varies according to the sex and age of the palm, the skill of the tappers, soil quality and the period of tapping. In a study carried out in 1995 (Khieu Borin and Preston, 1995) in 12 farm households with an average of 20 trees each, the yield varied from 2.7 to 7.5 kg per tree per day and the average Brix value (dissolved solids, measured by hand refractometer) was 13.3 percent. It was found that female palms produced on average 5.3 kg per day, compared with 4.7 kg produced by the male tree (Figure 1).

 

W9980t20.GIF (10670 bytes)

1
Sugar palm juice yield: by family, month of harvest and sex of trees
Rendement en jus des palmiers à sucre, par famille, mois de récolte et sexe de la plante
Rendimiento de jugo de las palmas de azúcar: efecto de la familia, el mes de la recolección y el sexo del árbol

 

Palm syrup and palm sugar

A considerable amount of energy is required to condense palm juice into syrup or sugar; about 4 kg of fuelwood is needed to produce 1 kg of palm syrup (Khieu Borin, Preston and Lindberg, 1996). Cambodian farmers continue producing palm syrup and sugar because they can still find free fuelwood and it is their main income during the dry season. However, if an opportunity cost were put on the fuelwood it would often exceed the value of the syrup produced.

Sugar palm juice is traditionally processed into three types of sugar: liquid sugar (sugar palm syrup), crystalline palm sugar and block sugar. The most common type consumed in rural areas is sugar palm syrup which is about 80 percent dry matter.

LIVESTOCK FEEDING IN CAMBODIA

The price of cereal grains and by-products used in pig and poultry feeding is increasing rapidly. The industrial livestock sector with guaranteed market outlets for its products is still able to absorb these cost increases. But the consequences for the landless and the poorest farmers are serious as competition develops between humans and animals for the same food supply. It becomes increasingly urgent, therefore, to develop alternative feeding systems for livestock which do not use cereal grains, but which make efficient use of the products derived from the plant resources that grow most abundantly in a tropical country such as Cambodia.

The technique of feeding liquid sugar-based diets to pigs was first developed and commercialized in Cuba using molasses derived from the processing of sugar cane (Preston et al., 1998). Later, in Mexico, the technology was modified to use the juice from freshly crushed sugar cane stalks (Mena, Elliot and Preston, 1981). In 1987 this system began to be applied widely in Colombia (Sarria, Solano and Preston, 1990) stimulated by the low market prices at that time for cane sugar. Artisan crushing of sugar cane for processing into brown sugar is a common practice in many Asian countries, and the alternative use of the fresh juice for pig feeding was well received in remote areas of the Philippines and Viet Nam where pig production offered a more profitable outlet for the sugar cane than raw sugar.
In Cambodia, the adaptation of the pig feeding system from sugar cane to sugar palm was relatively straight- forward, as in each case the soluble carbohydrates in the juice were a mixture of sucrose and the reducing sugars, glucose and fructose.

 

W9980t22.JPG (47824 bytes)

A pig producer is preparing pig feed by mixing sugar palm juice with freshwater fish silage ...
Un éleveur de porcs prépare la pâtée à base de jus de palmier à sucre et de poisson d'eau douce ensilé ...
Un productor de cerdos está preparando el pienso mezclando jugo de palma de azúcar con ensilado de pescado de agua dulce...

 

W9980t23.JPG (36871 bytes)

... which her husband is feeding to the pigs
... avec laquelle il nourrit les cochons
... que administra a los cerdos

An integrated farming system based around the sugar palm tree is an appropriate strategy for rural areas of Cambodia (Khieu Borin, 1996). Generally, in regions where sugar palms are found, each farmer owns at least ten sugar palm trees, which sets a limit on the scale of the livestock component. The juice from two palms (approximately 10 kg) contains sufficient digestible carbohydrate (about 15.4 MJ of digestible energy) to satisfy the daily needs of one pig averaging 50 kg live weight. Thus, ten palm trees per family can fatten five pigs. As in the case of sugar cane, there is virtually no protein in sugar palm juice, therefore some source of supplementary protein is needed. Traditional sources such as soybeans are not widely available in Cambodia and are expensive. The results summarized in Figure 2 were obtained in farm households (two pigs per family) where the protein supply was restricted to 150 g per day from soybeans with small amounts (about 500 g per day) of freshwater spinach (Ipomoea acuatica). The most important feature of this demonstration was that the farmers made more profit from feeding the palm juice to pigs than converting it into sugar when the fuelwood for juice concentration had to be purchased (Figure 3).

 

W9980t21.GIF (11698 bytes)

2
Average daily weight gain of pigs fed with sugar palm juice, and profit from rearing
Prise de poids journalière moyenne des porcins alimentés avec du jus de palmier à sucre et rentabilité
Aumento diario medio de peso de los cerdos alimentados con jugo de palma de azúcar y su rentabilidad

 

W9980t24.GIF (9466 bytes)

3
Comparative profit of different farmers from sugar palm trees used for sugar production or for pig rearing
Profit comparatif tiré par les exploitants des palmiers à sucre utilisés pour la production de sucre ou pour l'élevage de porcs
Beneficios comparados de distintos agricultores a partir de las palmas de azúcar utilizadas para la producción de azúcar o para la cría de cerdos

Another approach has been to use small waste fish commonly available from Tonle Sap Lake during January and February which is the traditional fishing period when the water flows out to the sea. During this period, small fish that are not suitable for human consumption can be purchased for less than US$0.06 per kilogram but, because the period when the small waste fish are available is short, they must be conserved. Ensiling with palm syrup (10 percent) and rice bran (40 percent) is a simple procedure. After removal of the intestinal tract, the fish are washed and placed in a bamboo basket for one to two hours to drain. They are subsequently mixed with the palm syrup followed by the rice bran and then sealed inside a polyethylene bag supported inside a ceramic container or in a hole in the ground. After 14 days the silage is ready for feeding to the pigs but it will remain in good condition for five to six months if anaerobic conditions are maintained.
A more common practice is to dry the waste fish in the sun. A demonstration was carried out in Samroung district, Takeo Province, with the participation of 15 farmers. The diet was 6.5 kg of palm juice, 1 kg of rice bran, 300 g of dried fish (approximately 110 g of protein), 5 g of salt and green vegetable according to availability. The average daily weight gain was 420 g per pig with a range of 220 to 580 g (Figure 4).

 

W9980t25.GIF (11318 bytes)

4
Performance of pigs fed on sugar palm juice, rice bran and sun-dried fish
Engraissement des porcs nourris avec du jus de palmier à sucre, du son de riz et du poisson séché au soleil
Rendimiento de los cerdos alimentados con jugo de palma de azúcar, salvado de arroz y pescado secado al sol


CONCLUSIONS AND RECOMMENDATIONS

The results of recent studies with the sugar palm in Cambodia have shown:

It is recommended that research be directed towards:


Bibliography

Davis, T.A. & Johnson, D.V. 1988. Current utilization and further development of the Palmyra palm (Borassus flabellifer L., Aracaceae) in Tamil Nadu State, India. Econ. Bot., 41(2): 23-44.
FAO. 1983. The Palmyra palm: potential and perspectives. By A. Kovoor. FAO Plant Production and Protection Paper No. 52. Rome.
Khieu Borin. 1996. The sugar palm tree as the basis of integrated farming systems in Cambodia.Contribution to Second FAO Electronic Conference on Tropical Feeds. Livestock Feed Resources within Integrated Farming Systems.
Khieu Borin & Preston, T.R. 1995. Conserving biodiversity and the environment and improving the well-being of poor farmers in Cambodia by promoting pig feeding systems using the juice of the sugar palm tree (Borassus flabellifer). Livestock Research for Rural Development, (7)2: 25-30.
Khieu Borin, Preston, T.R. & Lindberg, J.E. 1996. Juice production from the sugar palm tree (Borassus flabellifer) in Cambodia and performance of growing pigs fed sugar palm juice. In Sustainable Tropical Animal System, p. 1-11. Swedish University of Agricultural Sciences, Uppsala, Sweden. (M.Sc. thesis)
Mena, A, Elliot, R. & Preston, T.R. 1981. Sugar cane juice as an energy source for fattening pigs. Tropical Animal Production, 6(4): 338-344.
Morton, J.F. 1988. Notes on distribution, propagation, and products of Borassus palms (Arecaceae). Econ. Bot., 42(3): 420-441.
Preston, T.R. & Leng, R.A. 1987. Matching ruminant production systems with available local resources in the tropics and subtropics, p. 1-5. Armidale, New South Wales, Australia. PENAMBUL Books Ltd.
Preston, T.R., MacLeod, N.A, Lassota, L., Willis, M.B. & Velázquez, M. 1998. Sugar cane products as energy source for pigs. Nature, 219: 727.
Sarria, P., Solano, A. & Preston, T.R. 1990. Utilización de jugo de caña y cachaza panelera en la alimentación de cerdos. Livestock Research for Rural Development, 2(2): 92-100.

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