ANNEX B
A Review of Integrated Livestock-Fowl-Fish Farming Systems

Medina N. Delmendo
FAO Regional Office for Asia and the Far East
Bangkok, Thailand

Abstract

Traditional and current practices in integrated farming are reviewed and show that it is concentrated in Asia. The chemical composition of animal wastes and organic compost produced by Chinese methods are summarized and published information on rates of application to fish ponds is discussed. The design of integrated animal-fish units and the formulation of animal feeds are identified as key factors in farm productivity and profitability. Economic analyses are included from selected examples of pig-fish, chicken-fish and duck-fish farms.

Introduction

TRADITIONAL FARMING IN ASIA

The bulk of agriculture production in Asia is undertaken by farmers whose landholdings are too small and fragmented. The application of modern technology and large-scale production are not feasible solutions to their present problems of low income and low productivity.

For centuries, the small farmers have sustained themselves by practicing various kinds of crop diversification and integrated farming systems. Aside from crop production, most small farmers have such livestock as a few head of cattle or buffalo, one or two pigs and a small flock of ducks or chickens. Where there is adequate water supply, a small fish pond is maintained.

Livestock-fowl-fish farming, combined with crop raising, is a workable pattern of integration as exemplified by the well-known Chinese small-scale farming system. The small farm raises pigs and/or ducks, in addition to crops, rotated in accordance with the seasonal climatic cycle. The animals, particularly ducks and pigs, are sources of animal protein, in addition to the fish. Pigs are fed with aquatic plants combined with kitchen leftovers, and animal manure serves as fertilizer for the crops, vegetables and fish ponds. This is a system where practically nothing is wasted. An ecological balance is maintained and a sufficient variety of products are obtained to meet the farm family's needs in terms of food and cash income.

This practice and a variety of other integrated farming systems continue to be used in many Asian countries: each system developed mainly through long years of experience of individual farmers. Unfortunately, no data are available on their technology; neither is there information on economics and yields. One reason for this is perhaps because the small farmers have always been considered as operating at subsistence level and have not gained the attention of economic development planners in the past.

In recent years, however, as information on the agriculture-aquaculture production techniques used in China has spread, the importance of integrated farming systems has begun to be more and more appreciated. National and international organizations are now beginning to take a fresh look at the traditional farming systems practiced in Asia, to obtain a better and fuller understanding of how these systems have sustained the small farmers and to find ways and means of making them more viable for the social and economic well-being of the small farm and rural communities.

Existing Livestock-Fish Farming Systems

PIG-FISH FARMING

The Chinese consider a pig as a “costless fertilizer factory moving on hooves” (FAO 1977a). The annual manure produced by 20 to 30 pigs is equivalent to 1 t of ammonium sulphate applied to the soil. The pigs are fed largely on kitchen wastes, aquatic plants and crop wastes. The sale of meat, bones and bristles after slaughter more than cover the cost of labor and feed. The pig-raiser obtains an annual yield of about 3 t of pig manure which is free. Pig-fish farming is therefore widely practiced in China, not only for meat needs but also to supply manure to fish ponds. Collective as well as individual pig-rearing is promoted. A target of one pig per person has been set and the total number of pigs raised in the country rose to 233 million from 57.8 million in 1976.

Although the pigs are not reared directly over the pond itself, the wastes are collected, made into compost and applied to the farmland and fish ponds. In some places, liquid manure from the oxidation tanks of bio-gas plants is conveyed to the fish ponds through small ditches running through the pond dikes (FAO 1977b).

A similar system is found in Vietnam, particularly in the cooperative and state farms where meat production, mainly pigs, is undertaken on a large scale. The manure is prepared into compost and applied as fertilizer to vegetable plots and fish ponds. The washings from pigsties are also channeled to the ponds.

In most Asian countries, e.g., Thailand, Malaysia, Singapore, Hong Kong and Indonesia, pigs are either reared over the ponds or at the edges so that the wastes can flow down into the ponds. Feeds consist of leftover food from households or restaurants; water lettuce, (Pistia stratiotes) (grown in the ponds) mixed with rice bran; water hyacinth, Eichornia crassipes (chopped and cooked with abattoir wastes) and peanut cake, corn meal and soybean meal whenever available and cheap.

Pig-vegetable-fish integration in Malaysia is also a successful operation. Although the fish yield is low, the returns are higher compared to the raising of pigs alone due to the high labor and feed inputs in rearing pigs. The overall system is viable and the vegetables serve as food for the pigs.

Thailand practices integrated poultry-pig-fish farming, particularly in the central plain where the water supply is abundant. Here, a three-tier system is applied where poultry is raised above the pigsty over the fish pond. In the poultry-pig-fish combination, the chicken manure is eaten by the pigs and whatever is left unutilized is washed down to the pond with the pig manure, both as fish food and fertilizer. The total production of a 1.5 rai* area using this combination is 4,000 kg of catfish (Pangasius pangasius) 8,000 kg of pigs and 15,330 chicken eggs. Vegetables are also produced. (Kamchai, ** pers. comm. 1979).

Fish production in pig-fish farming operations ranges from 2,000 to 5,000 kg/ha/6 mo. The number of animals kept averages 10 pigs/rai (about 60/ha). The fish and pig raising periods are 6 mo, which means that a farmer can produce two crops a year. The fish used are mainly tilapias stocked at the rate of 25,000 to 30,000/ha (Petcharoen and Charoensrisuk 1977).

Pig-fish farming is practiced in North Sulawesi (Christian area) and Bali (Hindu area), but not in the majority of Indonesia, on account of cultural and religious considerations. Djajadiredja and Jangkaru (1978), however, found integrated farming systems, such as sheep-fish, horse-fish, duck-fish, poultry-fish and crop-fish combinations in West Java (see also Djajadiredja, Jangkaru and Junus, this volume). Compared with crop-fish integration, the yield and income derived from livestock-fowl-fish combinations are much higher. Fish production combined with animal production averaged 6.22 t/ha/yr, compared to 1.31 t/ha/yr when combined with crops.

In the Philippines, an initial trial on pig-fish farming has shown encouraging results with tilapia, common carp and snakehead. Wastes from 40 and 60 pigs/ha were used in combination with total fish stocking densities of 10,000 and 20,000/ha (see Cruz and Shehadeh, this volume). Experiments on pig-fish farming have also been undertaken in Illinois, U.S.A. by Buck et al. (1978). Fish kills were encountered in two instances; these were attributed to oxygen depletion and poor water quality. Measures must be taken to guard against fish kills.

* 1 rai = 1,600 m²
** Kamchai lamsuri, Farm Kakikarn Co., Ltd., 295/36 Suriwong Rd., Bangkok.

DUCK-FISH FARMING

Central Europe has perhaps the most extensive duck-fish farming production activities after centuries of development (Woynarovich 1979; this volume). Duck-fish farming expanded rapidly in Central Europe after World War II when animal protein shortages became severe. Through exchange of experiences, practical fish culturists developed the technique of maintaining brood ducks and mass rearing day-old and 14- to 21-d-old ducklings, which are prerequisities for duck-fish culture on a commercial scale. Experiments conducted in the German Democratic Republic showed an average increase in carp production of 100 kg/ha with 300 ducks/ha kept on the ponds. In Hungary, 300 to 500 ducks/ha give fish yields of 500 to 800 kg/ha in 150 d (Woynarovich 1979; this volume).

In Hong Kong, about 58% of integrated fish farms raise ducks and about 8% raise geese (Sin 1979; this volume). The production of fish in ponds with ducks may be a little lower than those without, but it uses 25% less feed and therefore has lower production costs. The number of ducks ranges from 2,500 to 3,500/ha/yr to yield 5 to 6 t/ha of duck meat and 2,750 to 5,640 kg/ha of fish (Sin and Cheng 1976).

In Vietnam, raising 1,000 to 2,000 ducks/ha on ponds increased the average fish yield to 5.0 t/ha/yr compared to 1.0 t/ha/yr without ducks.

Duck-fish farming is still at an experimental stage in India. Demonstration trials have yielded 4,323 kg/ha/yr with 100 to 150 ducks/ha (Sharma et al. 1979). Nepal has also introduced duck-fish farming with assistance from the Food and Agriculture Organization of the United Nations (FAO) and the United Nations Development Program (UNDP), and initial production estimates of 1.0 to 1.5 kg/ha/yr are considered feasible (Woynarovich 1979).

The high productivity of Laguna de Bay lake in the Philippines is helped by manure from the commercial duck farms on its shores and by the domestic wastes draining into it. The duck population in this area is more than 700,000, raised in about 4,000 duck farms. This lake produces annually 39,055 t of finfish; 27,552 t of prawns, and 98,683 t of snails: an average of 430 kg/ha (Shimura and Delmendo 1969). Aquaculture in enclosures was introduced in the lake in 1971 and gave yield of 4 t/ha/yr (Delmendo and Gedney 1974), making full use of the high productivity water.

OTHER LIVESTOCK-FISH FARMING

Cattle are too large to be kept over ponds but they can be raised in feedlots within a fish farm area and their manure applied to the ponds. This is practiced in Israel where cattle manure is collected from stalls and stored in tanks near the ponds for later application. Schroeder (1978) reported that using organic manure as the sole nutrient in fish ponds gave 75% of the yields attained by using supplemental grain feeds and 60% of the yields attained by using protein-enriched pellets. Manure applied at the rate of 200 to 1,000 kg/ha/d increased fish yields from less than 500 to more than 4,000 kg/ha, representing fish growth of 20 to 40 kg/ha/d, without supplemental feeding. Intensive use of manure in conventionally-fed fish ponds doubled the fish yields with half the normal supplemental feed requirements.

In the United States, tilapia in manured ponds grew at 16.0/kg/ha/d compared to 25.8 kg/ha/d for ponds fed with commercial pellets. No significant difference was found between fish from the manured and pellet-fed ponds. Although the yields from manured ponds are significantly lower than pellet-fed ponds, their profitability is higher where manure is available at a nominal cost. The cost of tilapia production in pellet-fed ponds was $0.41 kg/compared to a range of $0.02 to $0.21/kg for manured ponds. (Collis and Smitherman 1978).

The above practices show that animal-fish farming can give high fish yields, comparable to intensive fish rearing using supplemental feeds. The organic nutrients in the animal manures fertilize the ponds and stimulate the growth of fish food organisms.

Animal Wastes

THE QUANTITY OF WASTES PRODUCED BY LIVESTOCK AND POULTRY

The amount of wastes excreted daily by an animal is directly proportional to its total live weight. Taiganides (1978) calculated the quantity of wastes produced by different animals (Table 1). The availability of organic nutrients for field crop production depends on the handling, treatment and storage of wastes, but this variability should be minimal for wastes added directly to ponds from animals over or adjacent to the water. In addition to direct addition of feces and urine to fish ponds, any leftover animal feed rations may also be used as nutrient inputs.

China has a long history of intensive use of animal and domestic wastes for agriculture and a total annual organic fertilizer use (mainly from pigs) of about 1,689 million tons: equivalent to 8,320,000 t of nitrogen (N), 5,092,000 t of phosphorus (P) and 9,671,000 tons of potassium (K). Estimates of the annual tonnage of manure production/Animal are as follows: cow, 6.0; pig, 3.0; goat or sheep, 0.8 and poultry, 0.025.

CHEMICAL CHARACTERISTICS OF ANIMAL WASTES

Taiganides (1978) reported that animal manures contain the major inorganic nutrient components (N, P, K), in addition to such trace elements as Ca, Cu, Zn, Fe and Mg. The major nutrients come from the feeds fed to animals, of which 72 to 79% N, 61 to 87% P and 82 to 92% K are recovered from the excreta. Urine comprising only about 40% by weight of the total daily waste excretion has higher N and K levels than feces. P is contained mainly in the feces except for pigs which have high urine levels.

NPK fertilizer use in aquaculture is well known but the application rates vary with pond soil type and water quality. The quantity and fertilizer quality of animal wastes also vary according to species, size and age, feed and water intake, and environmental factors. Their availability is also influenced by the type of waste management practices used (Taiganides 1978).

N in animal wastes may be in the form of NH₃, NH₄, NO₃ and NO₂, the levels of which vary considerably. Gaseous NH₃ can easily be lost to the atmosphere, and handling can affect other losses of the various forms of N. In solid waste handling, losses of N may vary from 20% in deep pits to 55% in open feedlots, whereas in liquid handling, N losses range from 25% for anaerobic systems to 80% under aerobic conditions (Taiganides 1978).

Table 1. Farm animal waste output and waste composition: TLW represents total live weight (after Taiganides 1978).

In general, pig and poultry wastes contain higher P levels than cow manure. P is bound to solids in most animal wastes and therefore handling losses are minimal.

Animals fed with high roughage rations will excrete more K than those fed on high concentrate rations. The vegetative plant parts contain higher K levels than grains (Taiganides 1978).

Based on the data in Table 1, 30 pigs (TLW 1,500 kg) will excrete 7,650 kg wastes/day comprising 58.5 kg N, 10.5 kg P and 12.0 kg K. For comparison, 2,500 laying hens (TLW 5,000 kg) will excrete 33,000 kg wastes/day comprising 495 kg N, 170 kg P and 145 kg K.

The number of animals required to supply the appropriate quantity of organic nutrients can be estimated but their initial and final weights should both be taken into consideration.

ANIMAL WASTES IN AQUACULTURE AND FISH YIELDS

Animal wastes applied to fish ponds serve as fertilizer and are also consumed by some fish. Suspended organic matter is used by bacteria while the soluble nutrients are taken up by phytoplankton and larger plants. The possible pathways for animal waste utilization in a fish pond are shown in Figure 1.

METHOD OF APPLICATION

There are different ways of handling animal wastes for aquaculture, depending on existing practices for waste utilization and management.

In China, animal and human excreta are utilized in agriculture and aquaculture. These are prepared in different ways depending on local circumstances. The techniques of homemade manure preparation have been developed through centuries of traditional practice and experience and have now been standardized (FAO 1977a).

The highly integrated nature of Chinese farming facilitates the efficient recycling of animal wastes in agriculture and aquaculture. The farmers keep the optimum number of animals in balance with farm land and fish ponds, to supply the manure required. For fish ponds, 30 to 45 pigs/ha is deemed adequate to supply the organic fertilizer required for the year. The pig wastes are usually applied as compost.

COMPOST PREPARATION AND USE

Composting is a widely known technique and the methods used in China are presented here.

Figure 1. A diagrammatic representation of the breakdown of animal manure in fish ponds and its nutrient pathways in the polyculture of Chinese and common carps.

Animal manure is collected and placed in composting pits located in one corner of the field or farm. The pits are usually circular, measuring 2.5 m bottom diameter, 1.5 m deep and 3.0 m top diameter (Figure 2). Each pit is filled by layering river silt (7.50 t)/rice straw (0.15 t) mixture, pig or cow manure (1.00 t) and aquatic plants or green manure crops (0.75 t) in 15 cm layers. The top is covered with mud and a water column 3 to 4 cm deep is kept at the hollowed surface in order to create anaerobic conditions. This minimizes the N losses. The contents of the pit are turned over after 1, 2 and 2.5 mo after which the compost is ready. In the first turning over, 0.02 t superphosphate is added and throughly mixed with the organic material, adding water to ensure moist conditions. Superphosphate is added because the compost is mainly intended for crops. Most collective farms process manure in the same way for both crop lands and fish ponds, varying only the quantity of superphosphate added according to the type of crop or ponds.

Each pit produces about 8 t of compost, adequate to fertilizer a 0.1 ha of crop land. The chemical composition of the compost as % wet weight is as follows: N, 0.30; P, 0.20; K, 0.25, and organic matter, 7.8 to 10.3. The carbon:nitrogen (C:N) ratio is 15 to 20:1 (FAO 1977a).

Compost is applied to fish ponds in China at levels ranging from 5 to over 10 t/ha, depending on the type of soil, as three applications during the fish culture period (6 to 8 mo), with the first application greater than the last two and applied during pond preparation before stocking with fish.

Figure 2. Pits used for composting pig manure with a river silt-rice straw mixture and green manure in the Yueh Chi Commune, Wu County, Jiangsu Province, China: a. and b., two pit designs; c. the layering system used-stripling, silt/straw mixture; double crosshatching, stable manure; single crosshatching, green manure (Source: FAO 1977a).

In other countries such as the Philippines, dry chicken manure is added to fish ponds in combination with inorganic fertilizer. The manure is usually brought from distant farms and it entails added costs. The Chinese technique is a classic example of a truly integrated production system where all the manure needed is available. Alternative forms of manure, such as liquid manure and sludge, are considered below.

LIQUID ANIMAL MANURE

Liquid manure is obtained from the anaerobic fermentation of animal manure in bio-gas plants or by mixing fresh manure with water. Animal wastes collected in open tanks or pits and mixed with water can be used as fertilizer in fish ponds, but this requires transport, handling and storage facilities even when the animals are raised within the same farm. The handling of this type of liquid manure is quite difficult.

Liquid manure or effluents from bio-gas digesters are, however, easier to handle as they can be conveyed to delivery points through small canals or pipes. From Chinese experience, the dilution of animal manure for biogas generation may be through any of the following mixtures:

1. 20% urine, 30% human excreta and 50% water.
2. 10% human excreta, 30% animal manure, 10% straw and grass, and 50% water.
3. 20% human excreta, 30% pig manure and urine, and 50% water.
4. 10% each of human and animal excreta, 30% marsh grass, and 50% water.

Crop wastes, grass and other vegetable material are allowed to decompose for at least 10 d before adding them into the digester.

A 10 m³ capacity bio-gas plant is the standard size for a household in China; it produces about 10 m³ of sludge and 14 m³ effluent/yr. The levels of available N, P and K are as follows: sludge—650 ppm N, 40 ppm P, 9,400 ppm K; effluent—500 ppm N, 15 ppm P, 2000 ppm K. The sludge is 35% organic matter (FAO 1977a).

The sludge and effluent are applied to the land with irrigation water or as a top dressing for crops. The effluent is called “fertile water” and is used in fish nurseries as well as growout ponds as feed and fertilizer. The sludge is also used as a base manure.

FRESH, UNTREATED ANIMAL MANURE

The application of fresh, untreated animal wastes to fish ponds is common in Asia, where pigsties and chicken coops are sited over the ponds.

Although this is a widespread practice, the numbers of animals used/unit area of pond surface have not been standardized. Only in China have the rates of application of manures been established.

The application of fresh untreated animal manure to fish ponds has given high fish yields, but excessive amounts can cause fish kills due to oxygen depletion in the water. This problem has lacked adequate investigation because of the lack of quantitative knowledge on the numbers of animals and the quantity of manure appropriate for specific aquaculture operations. The techniques for integrated agriculture-aquaculture have yet to be standardized and at present vary according to individual skills and experience.

Animal wastes delivered to fish ponds undergo decomposition through bacterial action and this process uses dissolved oxygen (DO), creating a biochemical oxygen demand (BOD). This is often the greatest single factor determining the pond water DO. Schroeder and Hepher (1979) reported that such oxygen depletion could be predicted from BOD measurements in manured ponds. The BOD can also be estimated from the % dry matter content of manures.

Manure is applied to ponds at daily rates of more than 1.5 t/ha under Israeli conditions. Table 2 gives the 24-hr BOD at 30°C for various organic fertilizers and feeds used in Israeli ponds. These observations may be a useful guideline for the management of manured ponds in the tropics to avoid dangerously low DO, particularly at night when no photosynthetic activity takes place.

Table 2. The 24-hr Biochemical Oxygen Demand (BOD) for various fish foods and manures used for pond fertilization (after Schroeder 1975).

LEVELS OF ANIMAL WASTE APPLICATION TO PONDS AS FERTILIZER

The rate of organic manure application in ponds varies with the type of manure, pond conditions and the local climate.

In China, compost applications in ponds range from 5,000 to over 10,000 kg/ha/yr: equivalent to range of 15 to 30 kg N; 45 to 90 kg P₂O₅, and 12.50 to 25.00 kg K₂O/ha/yr. These nutrient levels approximate to the most economic levels applied elsewhere using inorganic fertilizers. For instance, in Taiwan, 40 kg/ha of P₂O₅ is regarded as the most efficient level of superphosphate application and if the natural productivity of the pond is high, about half this amount is needed. Supplying N, P and K from an inorganic fertilizer was found to be more expensive than the use of superphosphate alone; it also failed to give higher yields (Lin and Chen 1967).

In mainland China, the customary use of 30 pigs/ha of pond provides about 58.5 kg N, 10.5 kg P and 12.0 kg K/ha, assuming an individual average live weight of 50 kg and using the factors in Table 1.

Buck et al. (1978) used 60 to 85 pigs/ha, which is equivalent to a fresh manure application of 180 to 255 t/ha/200 d, assuming an average output of 3 t/pig/yr. The pigsties in this case were located over the pond which therefore received all the urine and solid wastes. The nutrient loading of these ponds was higher and, consequently, the fish yields were also higher compared to the average yield in China. The relationship between organic waste loading and yield requires further investigation.

Woynarovich (1979) reported that in Taiwan, duck-fish operations produce an average of 3,500 kg/ha/yr of fish. Polyculture, selective harvesting and stocking, and high density of ducks ranging from 1,000 to 1,500/ha are practiced. The fish yields from similar operations in Hong Kong are higher ranging from 2,750 to 5,640 kg/ha/yr with about 2,000 to 2,400 ducks/ha.

Based on an estimated manure output/duck of 6 kg/40 d or 150 g/d (Woynarovich 1979), the level of duck manure application in Taiwan is 150 to 225 kg/ha/d. In Hong Kong, it is 300 to 360 kg/ha/d.

In addition to the references on manure pond experiments given above, the following contain information relating waste loading to fish yields: Allen and Hepher (1979), FAO (1977b), Moav et al. (1977) and Rappaport and Sarig (1978). The information available shows that ponds receiving from less than 0.5 t to more than 1.0 t/ha/d can give fish yields of from 1,500 kg to more than 8,000 kg/ha/yr, according to local conditions. It should now be possible to design a balanced animal-fish operation, taking into account the feed requirements of the animals, waste output, pond area and fish yields.

Design of Animal-Fish Production Units

There is a wide variety of animal-fowl-fish integrated farming combinations in operation in Asia, but an appropriate integrated farming production unit has yet to be developed which would be practical and viable enough to be adopted by small farmers under different local conditions. The present system practiced in China provides examples to follow, but here land is consolidated into communal farms which allow full integration of aquaculture and agriculture. Most Asian countries have small, fragmented landholdings of individual ownership and the cost of all farm inputs have therefore to be shouldered by an individual farmer. The technological and economic aspects of integrated farming systems should be clearly demonstrated to small farmers, to promote the maximum use of limited resources and inputs.

A small integrated farming system such as that practiced in Singapore—originally described by Ho (1961) and discussed by Bardach et al. (1972)-has a fish pond at the bottom of a sloping farm land. It includes fruit trees, rootcrops, vegetables, chickens and pigs. Natural drainage and agricultural runoff are conserved and utilized in the fish pond. This principle is also beginning to be used in Nepal where much of the land has steep slopes and terrace farming is practiced. Crop rotations are used in the terraces and the lowest plots are used as fish ponds. Ducks are also kept but are not confined to the ponds.

For flat terrain such as the central plain of Thailand, elevated ridges are made for crop raising and the borrow pits between the ridges contain water for fish culture and for irrigation of some crops (e.g., corn and vegetables). The perimeter of the farm is usually planted with bananas, coconuts, papayas or leguminous trees, such as Leucaena glauca. In some cases, the farm is divided into two areas separated by a dike: water space for fish culture and a farm plot housing the pigs and the chickens under one roof. The manure from these animals serves as fertilizer for the pond and for crops. Where there is only one small plot and an adequate water supply, the operations may be restricted to animal and fish raising. When two plots are available, these are rotated each year between fish and crop raising. Thus, organic material at the pond bottom becomes used for crop production. This system is illustrated in Figure 3 and Plates 1 and 2.

Although these systems are being practiced, there are no data available to show the effects of size on their production economics. The number of animals, crops produced and the land-use allocation of the farms vary widely and the farm management techniques employed depend on the interest and experience of individual farmers. In most cases, emphasis is on one product only and the rest are not given proper attention. This is mainly due to lack of financial resources for additional inputs and lack of technical know-how on the synergistic relationships of integrated systems.

From the information available on animal waste output and the waste loading levels appropriate for fish ponds, the number of animals to be kept for agriculture-aquaculture integration can be calculated. A demonstration unit of 2,400 m² (1.5 rai) has been successful in Thailand, combining 42 pigs (weaners) and 60 hens with growing corn and leafy vegetables and raising 4,000 kg of fish/yr. More data are still needed, however, to determine the smallest production unit which would be viable for the average small farmer, particularly where landholdings are less than 1.0 ha.

Animal Feeds

The high cost of feed is often the major constraint to intensive livestock and fish production. Most farms are therefore under extensive management and small farmers lack the financial resources to intensify their operations.

One approach to reducing the cost of feeds is to produce them within the farm, e.g., feed crops. Pigs can subsist on kitchen wastes mixed with vegetables. Tubers, bananas, coconut meal and grain by-products are also suitable components for pig rations, along with other ingredients rich in carbohydrates, protein and green fodder. Example of feed formulations are shown in Table 3 and of daily feed quantities in Table 4 (COVECO E-104). Green aquatic vegetables, such as water spinach (Ipomoea aquatica) mixed with rice bran and kitchen leftovers are commonly used in family scale pig rearing. Bananas, coconut and Leucaena glauca are also grown and their fruit and leaves, except for coconut leaves, are used for pig food. Water spinach can be planted along the pond margins or in a shallow portion of the pond but its growth is never allowed to expand to cover the surface area of the pond. It is harvested 30 d after planting and at weekly intervals thereafter by cutting its vertical branches. A hectare of pure I. aquatica can give an average yield of 90 t/yr (Eddie and Ho 1969). The nutrient contents of I. aquatica and rice bran are given in Table 5.

Figure 3. Diagrammatic representation of a small-scale integrated farming system employing rotation between two level plots of land, as practiced in the central plain of Thailand.

Plate 1. A small-scale integrated farming system employing rotation between two level plots of land, as practiced in the Central Plain of Thailand (see also Figure 3).	Plate 2. Detail from the system depicted in Plate 2, Figure 3 of the equipment used for keeping chickens above pigs in an animal home projecting over water. The pigs eat chicken droppings and the pig manure fertilizes the water

Rice bran should not exceed 30 to 40% of the total pig feed ration or else soft pork is produced.

In Vietnam, the main materials used for pig food are water spinach and Azolla, which make up about two-thirds of the rations. These are mixed with one-third rice bran and 2 to 3% fish meal. A farm with 6,000 pigs devotes 50 ha to growing water spinach and Azolla.

The green cooking banana (Musa paradisiaca) is another good pig food, whether ripe or green, giving a food conversion ratio of 3.55 (Clavijo and Maner 1975). Banana-based pig foods may be supplemented with rice bran, maize or fish meal. Banana leaves can also be fed to pigs. Bananas grow well and fruit all year round (FAO 1977c).

Table 3. Feed formulations for pig farming in the tropics (after COVECO E-104).

Table 4. Daily feed quantities for pig farming in the tropics: growing mash from 15 to 50 kg and fattening mash thereafter (feed formulations in Table 3). (Source: COVECO E-104).

Sweet potato tubers can also be grown as a pig feed substitute or supplement. They grow well in warm humid climates, even in poor soil, and withstand drought. They can be harvested every 3 mo. The young leaves and stems are also edible (FAO 1977d).

Water management in small fish ponds should be developed according to local conditions and synchronized with the other farm activities. Ideally, a small farm should be self-sufficient in the material inputs required for animal and fish production. A combined effort is therefore needed by agriculturists and aquaculturists to design balanced systems for integrated agriculture-aquaculture production. For fish production, the quantity of manure loading in ponds could range from 1 to more than 1.5 t/ha/d: higher than the range quoted above. The farmer must, however, prevent fish kills due to oxygen depletion and take such precautions as providing aeration.

Table 5. Evaluation of water spinach (Ipomoea aquatica), rice bran and cooking bananas (Musa paradisiaca) as pig feedstuffs.

Table 6. Economics of polyculture and duck-fish systems of selected Hong Kong farms of three size categories: US$1.00 = HK$5.00 (after Sin and Cheng 1976).

Marketing and Economic Aspects

There appears to be no significant difference in the taste and texture of flesh of fish grown in manured ponds and those fed commercial diets. Allen and Hepher (1979) report that fish from ponds receiving well-treated domestic wastes taste as good or even better than fish grown in waste-free ponds. Similarly, Moav et al. (1977) report good flesh color and intramuscular fat levels for fish grown in intensively manured ponds. Examples of the economics of manured pond fish culture are given by Rappaport and Sarig (1978) and Sin and Cheng (1976). There is little detailed information on the economics of pig-fish farming operations in Southeast Asia, but Petcharoen and Charoensrisuk (1977) and Djajadiredja and Jangkaru (1978) give data for a few family farms in Thailand and Indonesia (Tables 7 to 9).

Table 7. Expenditure (excluding depreciation) and income for some integrated pig-fish farms in Thailand: US$1.00 = 20 Baht (after Petcharoen and Charoensrisuk 1977).

Table 8. Costs and returns from a 1,000 m² chicken-fish farm, holding 100 layer chickens/yr in Tasikmalaya, West Java in 1977: US$1.00 = Rp 627 (after Djajadiredja and Jangkaru 1978).

		Quantity	Cost or value (Rp)	Percent (%)
Capital Investment
Land value		1,000 m2	1,000,000
Construction
Building and equipment		12 m2	150,000
Chickens		100	120,000
	Total (A)		1,270,000
Operating costs
Fish seed: Common carp and tilapia		250 kg	100,000	19.2
Chicken feed		3,600 kg	216,000	41.5
Labor:	Permanent labor	12 man-months	72,000	13.8
	Seasonal labor	36 man-days	14,000	2.7
Maintenance and repairs			17,500	3.4
Interest (12%)			32,400	6.2
Taxes			2,000	0.4
Depreciation:
	Chicken house (20%)		30,000	5.8
	Chicken layers (30%)		36,000	6.9
	Total (B)		520,000
Income
	Fish	625 kg	250,000
	Eggs	1,200 kg	660,000
	Total (C)		910,000
Profit (C-B)			390,000
Rate of return on capital Investment				30.7
Rate of return on operating costs				74.9

Table 9. Costs and returns from a 1,000 m² duck-fish farm in Garut, West Java in 1977: US$1.00 = Rp 627 (after Djajadiredja and Jangkaru 1978).

		Quantity	Cost or value (Rp)	Percent (%)
Capital investment
Land value		1,000 m2	1,000,000
Construction		-	-
Building and equipment		-	120,000
Ducks		300	600,000
	Total (A)		1,720,000
Operating costs
Fish seed: Common carp		140 kg	70,000	4.3
Nile tilapia		87.5 kg	26,250	1.6
Duck feed		16.9 tons	1,014,000	62.0
Labor:	Permanent labor	12 man-months	144,000	8.8
	Seasonal labor	40 man-days	16,000	1.0
Maintenance and repairs		-	72,000	4.4
Interest (12%)		-	86,400	5.3
Taxes		-	2,000	0.1
Depreciation:
	Duck house (20%)	-	24,000	1.5
	Duck (30%)	-	180,000	11.0
	Total (B)		1,634,650
Income
	Common carp	280 kg	140,000
	Nile tilapia	350 kg	105,000
	Eggs (incubated)	33,600	1,176,000
	Ducklings	1,000	600,000
	Low quality ducks	40	60,000
	Total (C)		3,019,000
Profit (C-B)			1,384,350
Rate of return on capital investment				80.5
Rate of return on operating costs				84.7

Acknowledgments

This writer would like to thank the International Center for Living Aquatic Resources Management for their kind invitation to participate in this Conference.

Gratitude is also conveyed to Dr. H. R. Rabanai, Senior Aquaculture Development Officer, South China Sea Fisheries Development and Coordinating Programme, and Dr. H. Chaudhuri, Deputy Director, SEAFDEC, Institute of Aquaculture, for their comments on the manuscript.

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Delmendo, M.N. 1977. Environmental and engineering considerations in the development and management of aquaculture projects in flood plains. Joint (South China Sea Programme/ Southeast Asian Fisheries Development Center) Workshop on Aquaculture Engineering (with emphasis on small-scale aquaculture projects), Volume II -Technical Report, SCS/ GEN/1977/15 Iloilo City, Philippines. p. 75–83.

Mendola, D. 1976. Aquaculture Energy Primer/Aquaculture. p. 129–141. New Alchemy Institute, Woodshole, Massachussetts.