Availability and use of feed resources in crop–animal systems in Asia

Agricultural Systems 71 (2002) 59–73 www.elsevier.com/locate/agsy

Availability and use of feed resources in crop– animal systems in Asia C. Devendra a,*,1, C.C. Sevilla b a International Livestock Research Institute, PO Box 30709 Nairobi, Kenya Institute of Animal Science, University of the Philippines, Los Ban˜os, The Philippines

b

Abstract Feed resources and nutrition constitute the principal technical constraints to ruminant production in Asia. Four main categories of feed resources are potentially available for use in smallholder crop–animal systems. These are pastures (native and improved grasses, herbaceous legumes and multi-purpose trees), crop residues, agro-industrial by-products (AIBPs), and non-conventional feed resources (NCFRs). Priorities for the use of crop residues in terms of nutrient potential and animal species are indicated. Of the technologies developed to improve the nutritive value of crop residues, more attention has been given to chemical treatment of cereal straws than to supplementation. However, a failure to demonstrate costeffectiveness has discouraged on-farm adoption. The production of fodder from food crop systems and the establishment of multi-purpose trees and shrubs are potentially important for insuring adequate feed supplies for ruminants and improving soil fertility, but there has been limited adoption on small farms to date. Equally, there is significant potential for the more effective use of locally-produced AIBPs and NCFRs, all of which are under-utilised currently. # 2001 Elsevier Science Ltd. All rights reserved. Keywords: Asia; Crop–animal systems; Feed resources; Crop residues; Forages; Supplementation

1. Introduction Feed resources are a major component of economic animal production in Asia. Their availability and efficiency of use in specific agro-ecological zones and in smallholder production systems dictate to a very large extent the performance of both ruminants and non-ruminants. Their importance is reflected further in the following: * Corresponding author. Tel.: +603-7983-9307; fax: +603-7983-7935. E-mail address: [email protected] (C. Devendra). 1 Current address: 130A Jalan Awan Jawa, 58200 Kuala Lumpar, Malaysia. 0308-521X/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved. PII: S0308-521X(01)00036-1

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1. Critical assessments of livestock research priorities in Southeast Asia (Devendra et al., 1997) and South Asia (Devendra et al., 2000) indicate that feed resources and nutrition are the principal technical constraints affecting production. 2. Costs of feed, as a percentage of total production costs, account for about 50– 60% of those in ruminant feeding systems, and 65–80% in industrial systems. 3. Inadequate adaptive research that promotes wide adoption and use of appropriate technologies has resulted in continuing poor performance of animals in rural areas. 4. Ruminant production systems are unlikely to change in the forseeable future, although shifts within the systems toward intensification are envisaged (Mahadevan and Devendra, 1986; Devendra, 1989). 5. The recent Asian economic crisis has made farmers more wary of large production costs, especially feed costs, and industrial production systems that depend heavily on external inputs. The significance of improved animal nutrition on productivity and the wider role and contribution of animals are, therefore, the most important considerations in sustainable crop–animal systems. This paper focuses on the availability of feed resources and their use in smallholder crop–animal systems.

2. Types and availability of feed resources Four main categories of feeds are potentially available for use on small mixed farms in Asia. These are pastures (native and improved grasses, herbaceous legumes and multi-purpose trees), crop residues, agro-industrial by products (AIBPs), and non-conventional feed resources (NCFRs). Poor quality native grasses and the fibrous residues of a wide range of crops form the principal feeds for ruminant livestock on small mixed farms. Tethered or free-grazing animals utilise the native grasses, often communally, from rangelands, forests, fallows, wastelands, roadsides and cultivated areas after crop harvest. Where animals are kept in confinement, grasses are cut and carried to the livestock. Zero-grazing is common on intensively-cropped small mixed farms in southeast Asia and in the highlands of south Asia. The largest areas of rangelands (approximately 43 million ha) are found in south Asia, in the arid/semi-arid and highland regions of Bhutan, India, Nepal and Pakistan (Devendra et al., 2000). Mountain rangelands in this sub-region (including the Tibetan Plateau of China), for example, occupy an area of approximately 2.0 million km2. In southeast Asia, there are only some 14 million ha of native grasslands, the largest areas being found in Indonesia, with smaller areas in countries such as Cambodia, the Lao PDR and Thailand (Devendra et al., 1997). However, in many regions, native grasslands are in decline due to changes in land use. Crops, including forages, grown specifically for ruminants represent a relatively small component of the available feed resources on the mixed farms. These are usually associated with the irrigated systems in south

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Asia, particularly in India and Pakistan. This does not, however, detract from their potential importance in feeding systems for ruminants, and much more can be done to extend their use. On the other hand, production of leguminous crops grown as a cash crop at the end of the wet season and before the onset of the dry season is a very common practice on small farms. Cereal straws and stovers are by far the most important crop residues (Maehl, 1997). AIBPs are less fibrous, have relatively more digestible nutrients, and are often high in protein. Good examples of AIBPs are the oilseed cakes and meals (e.g. copra cake, rice bran, cottonseed meal and oil palm kernel cake). NCFRs are identified separately and include all those products that have not been used traditionally in animal feeding. These feeds are diverse and include cocoa pod husks, rubber seed meal, distiller solubles, shrimp waste, leather shavings and poultry litter (Devendra, 1992; Devendra et al., 2000). The type of agro-ecological zone, the extent and intensity of crop production determine the quantity and availability of feed resources. In the more favoured irrigated and lowland rain-fed areas of southeast Asia, multiple cropping giving two to three crops of rice annually generates up to three times more straw than is produced in the upland areas, where only one rice crop is grown. Similarly, in India, Singh et al. (1995) have reported that the proportion of rice grown in lowland irrigated, lowland rain-fed and upland areas was 42, 42 and 10%, respectively. The availability of such feeds, together with the animal species raised, will determine the type and intensity of the crop–animal system that develops. An attempt has been made to determine the supply of each of these categories (other than pastures), based on earlier calculations of the total availability of cereal straws (Devendra, 1997), AIBPs from field crops, tree crops and NCFRs specific to Asia (Devendra, 1992). These estimates are presented in Table 1. Rice and wheat straws alone contribute about 57% of total availability, and if maize, millet and sorghum are included the contribution would increase further to about 78%. Although NCFRs contribute about 38% of total availability, with approximately 80% of these feeds mostly suitable for ruminants, they are currently grossly underutilised in farming practice. In individual countries in Asia, the use of rice straw for animal feed is significantly higher. For example, in Thailand, Wanapat (1990) reported that 75% of the rice straw from rain-fed upland farms, and 82% from Table 1 Availability of non-forage feed resources in Asiaa Category

Quantity (million t) b

Cereal straws (rice and wheat) Feeds from field cropb Feeds from tree cropsb NCFRs Total a b

Contribution (%)

672.2 67.2 0.8 455.8

56.5 5.6 0.0 37.9

1196.0

100.0

Sources: Devendra (1992, 1997). These categories are considered traditional feeds.

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lowland farms was collected by small farmers for use as feed (Table 2). In Bangladesh, Saadullah et al. (1991) found that 74% of rice straw was used as animal feed on small farms. In most countries in Asia, all buffalo, a large proportion of draught and beef cattle, and small numbers of sheep and goats are maintained largely on cereal straws. Devendra et al. (1997) have estimated that rice straw is the principal fibrous residue fed to over 90% of the ruminants. Rice straw is especially important during periods when other feeds are scarce; from time of planting through to harvest, when animals have limited or no access to grazing, and whenever drought or some other factor causes crop losses. The maximum intake of rice straw per 100 kg liveweight in Asia is about 1.0–1.2 kg. For southeast Asia, the average intake of straws by swamp buffalo and catt1e (determined by using adult liveweights of 350 and 200 kg, respectively) is 1.0 kg of rice straw per 100 kg liveweight. However, straws are not used exclusively for animal feed. For example, in south Korea, Im and Park (1983) reported that only 15% of rice straw was used for animal feed; most of the residue was used as fertiliser (46%) and for fuel (20%). In some areas of the Indo-Gangetic Plains of India, 80% of rice straw and 40% of wheat straw are burnt after harvest and, therefore, are never used for livestock feed (Devendra et al., 2000). Thus, values for the availability of crop residues do not necessarily reflect the extent of their utilisation as animal feed.

3. Priorities for use of feed resources The types of feed resources, their approximate crude protein contents and nutrient potential, and the animals that make best use of them are shown in Table 3. The good quality feeds have a high nutrient potential because of high energy, protein and mineral contents. Thus, they are used mainly in production rations for non-ruminants (pigs, poultry, ducks) and also for ruminants producing milk and meat. The mediumquality feeds are also useful for promoting production in both ruminants and nonruminants. The third category, consisting of low-quality crop residues, provides the main source of energy for the maintenance of adult livestock, including animals used for draught purposes such as swamp buffalo, cattle, camels and equines. Table 2 Utilisation of rice straw in Asia Country

Purpose

Total availability (%)

References

Bangladesh Korea

Feed Feed Fertiliser Fuel Feed Feed Feed

74.4 15.0 46.0 20.0 75–82 25.0 30.4

Saadullah et al. (1991) Im and Park (1983)

Thailand China Southeast Asia and othersa

Wanapat (1990) Wang (1996) Devendra (1997)

a The countries involved are Cambodia, China, Indonesia, Laos, Malaysia, Mongolia, Myanmar, Philippines, Thailand and Vietnam.

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Table 3 Priorities for the use of non-forage feed resources in Asiaa Type of feed

Nutrient potential

Species (product/service)

Good quality (e.g. oilseed cakes and meals, cassava leaves) >35% CPb

High-protein, high energy supplement, minerals

Pigs, chickens, ducks, ruminants (milk, meat)

Medium-quality (e.g. coconut cake, palm kernel cake, sweet potato vines 15–35% CP

Medium-protein

Pigs, chickens, ruminants (milk, meat)

Low-quality (e.g. cereal straws and stovers, palm press fibre) <15% CP. Most cereal straws 6–8% CP.

Low-protein, very fibrous

Ruminants (meat, draught), camels, equines

a b

Source: Devendra (1997). CP, crude protein (N6.25).

Egan (1989) further subdivided crop residues into three classes. The first group contains residues that are low in cel1 wall contents, high in crude fibre and lignin, with low in vitro digestibility (30–40%) and intake. These are not improved greatly by chemical treatment. The second class contains residues with relatively low cell wall contents of medium digestibility (40–50%), and capable of some improvement with chemical treatment. The third group contains residues that are relatively high in cell wall contents, not as highly lignified, with high digestibility (50–60%) and intake. Most cereal straws and stovers have lower nutritive values than the haulm from grain legumes or vines from root crops such as sweet potato. In defining priorities for the use of feed resources, it is important to take into account the differences between and within groups, especially for the crop residues. Priorities for their use will depend, amongst other things, on the quantities available, the relative nutrient contents, and potential value to individual ruminant species.

4. Available technologies to improve nutritive value of crop residues Increasing the efficiency with which crop residues are utilised by livestock has been a major theme of technology development since the 1970s. In the case of cereal straws, the central objective has been to overcome the inherent nutritional limitations of low digestibility, low crude protein, poor palatability and sheer bulk. These include chemical treatment and the use of supplementation (energy, nitrogen and minerals). 4.1. Chemical treatment The chemical and biological procedures to upgrade cereal straws have been reviewed in some depth by Chaudhry (1998). Chemical treatment, in particular, has

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been an effective way of improving the nutritive value of straws. Several alkali compounds, including hydroxides (particularly sodium hydroxide) and ammonia, have received a great deal of attention experimentally. Various wet and ‘‘dry’’ processes have been tried using sodium hydroxide. Ammonia is less hazardous than sodium hydroxide and contributes towards nitrogen enhancement of the straw as well as increasing the energy value. The variables affecting the efficiency of treatment include the length of the straw (unchopped or chopped), its moisture content, and the level and method (spraying or impregnation) of chemical application. The value of the treated straw to livestock will depend on the feeding regime (with or without additional ingredients), the species of animal and the objective of the production system. Devendra (1997) has concluded that far too much attention has been given to the chemical treatment of straw, at the expense of supplementation strategies. Arguably, supplementation is more likely to be applied in farming practice than chemical treatment of straw although, currently, the use of supplements on small farms is also low. Much of the research work has been confined to the experimental station, with few attempts to transfer the technology through large-scale testing on-farms. The failure to demonstrate cost-effective results has discouraged farmer adoption. 4.2. Supplementation Feeding of cereal straws alone results in perpetual poor productivity in animals on small farms in Asia. Thus, considerable work has been conducted experimentally on supplementation of feeds of poor nutritive value. Several alternative supplementation strategies have been pursued, the commonest being the use of purchased protein supplements such as cottonseed and oilseed cakes, and the installation of multi-nutrient blocks as licks, often consisting of molasses, urea and minerals. Supplements serve two essential functions. Firstly, they promote efficient microbial growth in the rumen. Secondly, they increase protein supply for digestion in the small intestine through the provision of by-pass or rumen non-degradable proteins. One impressive example of the use of supplementation comes from Henan Province, China, where cottonseed cake (CSC) was used to supplement straw for beef production (Dolberg and Finlayson, 1995). A supplement of 2.0 kg CSC/day gave daily growth rates of 600–700 g in 2-year old crossbred cattle. The feeding period was halved from 36 months to 18 months when only 0.5 kg CSC/day was fed. At 4.0 kg CSC/day, the feeding period was further reduced to almost 10 months. Economic analysis indicated considerable financial benefits to farmers. Feeding urea-treated straw alone gave an additional profit of US$ 26/head. With CSC supplementation, this increased tenfold. The most profitable treatment was 2.0 kg CSC/day, and supplementation significantly reduced the dependence on more expensive purchased concentrates. Increased beef production, making optimum use of local feeds, is clearly a viable activity on small-scale farms with good market access. Despite the potential economic benefits, supplementation to ensure high animal productivity at the small farm level is very haphazard. In south Asia, for example, AIBPs and NCFRs contribute < 10% to feed requirements in farming practice

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(Devendra et al., 2000). Yet, AIBPs and NCFRs jointly constitute some 43% of available feed resources in Asia. The low utilisation of supplements is associated with poor farmer appreciation of the value of supplementation; an inadequate knowledge of types and ways of using supplements; the high cost of purchased concentrates; and an ignorance of opportunities for on-farm preparation of supplement mixtures. The weakness of extension services has resulted in few demonstrations of supplementation being undertaken on small farms. Therefore, the prevailing tendency is to use supplements only to provide nutrients, often at high cost, during critical periods of feed shortages such as in the dry season. Nevertheless, the potential for more effective use of AIBPs and NCFRs on small mixed farms is enormous.

5. Potential for fodder production Grasses and legumes are the cheapest feeds for ruminants but are highly seasonal, being abundant during the wet season and becoming scarce during the dry season (Islam et al., 1995; Sevilla and Obsioma, 1996). The availability of forages on smallholder mixed farms in Asia depends on the agro-ecological zone, size of farm, cropping intensity, labour availability, tillage requirements and socio-economic factors. The introduction of improved forage species for ruminants can promote the sustainability of cropping systems. In addition to their feeding value, which is well documented, improved forages (particularly legumes) can make an important contribution to erosion control by providing cover, and to increased soil fertility by enhancing nutrient and organic matter levels. Options include the under-sowing of food crops such as rice with annual or perennial herbaceous legumes as inter- or relay-crops; the introduction of leys as sequence crops in rotations; the improvement of fallows; the establishment of leguminous cover-crops in perennial tree crop plantations; and the development of agro-forestry systems that include multi-purpose trees. Forages will be dealt with in depth in another review within this special issue. However, for completeness in the discussion of feed resources, some mention of forages will be made here. 5.1. Forages in annual food crop systems A considerable volume of experimental data are available to show that significant production of green and dry matter can be obtained from forage crops sown in annual cropping systems in the different countries of Asia. For example, in India, the green fodder yields of summer forage crops, planted before wet season rice, ranged from 7–24 t/ha. In a rice–wheat–cowpea cropping sequence, 11.5 t/ha of grain, 17.2 t/ha of straw and 24.0 t/ha of green fodder were produced, whilst oats, berseem and lucerne planted after rice harvest resulted in dry matter yields of 6.4, 6.5 and 5.2 t/ha, respectively (Hedge and Pandey, 1989). Sun hemp, as an intercrop in mung bean and pigeon pea, can produce grain and forage yields of 5.0 and 12.0 t/ha, respectively (Miah and Carangal, 1987; Rebancos et al., 1991). In a rain-fed lowland ecosystem in the Philippines, rice–mung bean, and rice–mung bean/siratro

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(Macroptilium atropurpureum) were compared with rice in traditional monoculture (Carangal et al., 1994). The average mung bean fodder yield was 0.85 t/ha, whilst the dry matter yield from the forage legume siratro was 4.59 t/ha. An additional 3.5 t/ha from the last clipping of siratro was available as green manure for the following rice crop. The yields of rice following the inter-cropping of mung bean and siratro were 4.39 t grain/ha and 4.33 t straw/ha. The adoption of the rice–mung bean+siratro cropping pattern on 1000 m2 of land can produce a total of 1.0 t of forage containing 53% total digestible nutrients (TDN) and 12% crude protein, sufficient to support one cow for 4 months of the dry season (Carangal and Sevilla, 1993). In Pakistan, a study on silage showed that inter-cropping cowpea with maize at a 30:70 ratio increased crude protein yield from 1.32 to 2.48 t/ha and dry matter yield from 15.9 to 17.2 t/ha. Maize and cowpea silage had a higher crude protein content and digestibility and a lower pH than silage made from maize alone (Azim et al., 2000). However, despite impressive results from on-station trials, the extent of production of forage crops on small mixed farms is restricted, and is observed most commonly in the irrigated systems of south Asia (Devendra et al., 2000). For example, forage crops have been sown in smallholder irrigated farming systems in India on 30% of the cropped area in four northern states (Haryana, Punjab, Rajasthan, Uttar Pradesh). In Pakistan, 15% of the cultivated area (mostly in Punjab Province) has been sown to forage crops in the irrigated systems. In both countries, the traditional fodders grown under irrigation in summer include pearl millet, maize, sorghum, cowpea and, in winter, berseem (Trifolium alexandrinum), lucerne (Medicago sativa), rapeseed and oats. In Bangladesh, the legume Lathyrus sativus has been integrated into rice cropping systems on small mixed farms to mitigate feed shortages for dairy cattle. This practice has resulted in increased biomass availability and an improvement in the organic matter and nitrogen contents of the soil. Milk yields were increased and milk composition improved 20–40% (Akbar et al., 2000). In the rain-fed production systems of Asia, the adoption of food crop–forage systems on small farms is still very low. Nevertheless, considerable potential exists in these areas, where most of the ruminants are found, to develop improved forages. In south Asia (Bangladesh, India, Nepal, Pakistan), for example, there are 14.6 million ha of rice fallows that could be used for the establishment of leguminous forages without interfering with crop production. In fact the inclusion of legumes would contribute to improved soil fertility. Currently, the constraints to adoption by farmers include the high labour requirements and low cash returns (Garrity and Becker, 1994). Often the inclusion of forages as a secondary crop in food crops is unacceptable to many farmers as there is no immediate monetary benefit from this practice. In considering the availability of fodder in annual cropping systems, it is worth noting that weeds (many of them gramineous) can be utilised by livestock. A typical fresh herbage yield from common grass weeds associated with lowland rice is 16 t/ ha, of which 63% are eaten by livestock, mainly Echinochloa crusgalli, E. colonum, E. cruspavonis, and Leptochloa chinensis (Furoc and Javier, 1979). In rain-fed lowland rice, Medrano (1982) reported dry matter yields from weeds of 2.03 t/ha, of

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which 60% were grasses. Rice bunds also contribute to feed availability and have a potential to produce forage legume dry matter yields of 5–50 kg/100 m2/year (Gutteridge, 1983), and a grass dry matter yield of >10 t/ha/year (IRRI, 1988). 5.2. Forages in tree crop systems There is considerable potential, particularly in southeast Asia where there is an estimated area of 210 million ha, for improved land use and increased income through pasture improvement in the perennial tree crop systems (Devendra et al., 1997). Examples of ruminant–plantation crop combinations include cattle under coconut, oil palm and mango; sheep under coconut, rubber and durian; and goats under coconut. In the past, most attention has been given to the integration of cattle with coconut, especially the tall traditional palm varieties. In coconut the light penetration is relatively constant and bright throughout the life of the crop, which benefits the understorey. Non-productive weed species in plantations can be replaced with productive improved species. In rubber and oil palm, especially, leguminous cover crops have been planted for weed control and contribute to the early growth of trees through nitrogen accretion. A detailed coverage of forages in plantation crops is given by Shelton and Stur (1991). 5.3. Fodder trees and shrubs The many advantages and uses of multi-purpose trees and shrubs have been described by Devendra (1988, 1993). Leucaena leucocephala has been the species used most extensively on small farms in Asia, although Gliricidia sepium gained some popularity as a substitute for Leucaena during the psyllid outbreaks in the 1980s. Table 4 summarises the benefits of feeding Leucaena to livestock. The role

Table 4 Benefits of supplementing cattle diets with Leucaena Feeding regime

Forage supplement

Country

Significant responsea

Results

References

Rice straw Sugar cane tops Rice straw Urea-treated rice straw Rice straw

Leucaena Leucaena Leucaena Leucaena Leucaena

Philippines Philippines Philippines Thailand Thailand

LW gain LW gain LW gain Milk yield LW gain

Reduced costs – – Reduced costs Reduced costs

Rice straw+dried poultry litter+ concentrate

Leucaena

Philippines

LW gain

Reduced costs

Sevilla et al. (1976) Lopez et al. (1981) Le Trung et al. (1983) Promma et al. (1984) Cheva-Isarakul and Potikanond (1985) Le Trung et al. (1987)

Rice straw

Leucaena

Thailand

Increased milk yield

Reduced costs

Wanapat (2000)

a

LW, liveweight.

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of multi-purpose trees and shrubs in the nutrition of farm animals is especially significant in the harsher, drier environments of the arid/semi-arid zones as well as in the hills and uplands of the humid parts of Asia during summer. Table 5 shows the range of biomass yields of leguminous trees grown for animal feed in annual food crop systems. The variations in values are due to differences in agro-ecological zone (reflecting climatic and edaphic conditions), season and density of planting, and cutting interval and height. However, the overall extent of utilisation of trees and shrubs as fodder in smallholder mixed farming systems is still limited. For example, in Nepal, despite the fact that some 60 species of trees and shrubs are being utilised for animal feed on small farms (Pandey, 1982), only 2 kg of fresh leaves from these sources constitute a given ration during the peak of feed scarcity. In a coconut-growing area of Sri Lanka, rations for cattle and buffalo contain only eight and 12%, respectively, of Gliricidia sepium (Ibrahim and Jayatileka, 2000). Nevertheless, the potential value of multipurpose trees and shrubs in small farm systems has been highlighted by Nitis (1989). He estimated that if the agricultural lands of Asia were planted to 230 multi-purpose trees and shrubs per hectare, with a dry matter yield of 7.0 kg/tree, 150 t of extra fodder could be produced annually. This could support 155 million animal units when fed at 18% of the ration, or 56 million animal units when given as the sole diet for the duration of a 6-month dry period. A number of systems, incorporating multi-purpose trees and shrubs, have been developed for small mixed farms in Asia. The three-strata forage system (TSFS) was developed on Bali, Indonesia to provide livestock feed throughout the year (Nitis et al., 1990). The system contains three strata of fodder trees, shrub legumes and grasses/herbaceous legumes on an area of 0.25 ha. The improved pastures are utilised by cattle in the wet season, the shrubs in the mid-dry season, and the trees in the late dry season. A core area at the centre of the plot can be planted to commonly-grown cash crops such as maize, soyabean and cassava. The increased forage production in this system allows higher stocking rates and liveweight gains

Table 5 Dry matter yields of some leguminous trees and shrubs Species

Yields

References

Sesbania

215–412 g/tree 9–11 t/ha 1162–2115 g/tree 0.95–1476 g/tree 13–27 t/ha 418–2500 g/tree 1.4 t/ha 288–930 g/tree 814–3352 g/tree 860 g/tree 15.4 t/ha

Yuhaemi and Ivory (1994)

Desmodium rensonii Gliricidia sepium Flemingia macrophylla Erythrina Calliandra Leucaena leucocephala

Oka Nurjaya et al. (1991); Kaligis et al. (1990) Sukanten et al. (1995, 1997) Halim (1992) Kaligis et al. (1990) Nitis (1999); Kaligis et al. (1990) Oka Nurjaya et al. (1991); Kaligis et al. (1990) Halim (1992) Siregar (1984)

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equivalent to 375 kg/ha/year compared with 122 kg/ha/year in a non-TSFS. Additionally, the system increases farm income by 31%, reduces soil erosion by 57% and increases soil fertility. Some five million tonnes of fuel wood (meeting 64% of annual needs) are produced from 2000 shrubs and 112 trees logged twice a year. Average gross margin/ha/year from the TSFS farms was US$ 74 more than that on the non-TSFS farms (Arga, 1990). The system was integrated onto small mixed farms on Bali in 1984, and by 1988 there were 141 units in operation. The TSFS has been institutionalised by law in Indonesia, and is being adopted increasingly in south Asian countries such as India as well as in sub-Saharan Africa. Fodder trees and shrubs have also been used in a conservation farming scheme called sloping agricultural land technology (SALT) described by Laquihon and Pagbilao (1994). SALT is a simple, applicable, low-cost method of upland farming, developed for small farmers. It is a form of alley farming in which annual and perennial crops are grown in bands 4–5 m wide between contoured rows of leguminous trees and shrubs. The latter are planted thickly in double rows to form hedgerows. When the hedge reaches 1.5–2.0 m in height, it is cut back to 40 cm and the cuttings are placed in the alleys as a mulch and green manure. Rows of perennial crops are planted on every third alley created by the contoured hedgerows. The unoccupied alleys are sown with cereals, grain legumes and other annual crops. The average monthly income to one family from 1 ha of the SALT is approximately US$ 52. As a consequence of the success of the SALT, three more variants have been developed. These are the simple agro-livestock technology (SALT-2), sustainable agro-forestry land technology (SALT-3) and small agro-fruit livelihood technology (SALT-4). SALT-2 is a goat-based agro-forestry project with a land use comprising 40% agriculture, 40% livestock and 20% forestry. SALT-2 is generating a monthly net profit of approximately US$ 213 and is producing 4700 l of goat milk per year for sale or home consumption. Additionally, 16 t of manure per year are produced. The various SALT farms established by government and non-government organisations in the Philippines now occupy over 5000 ha, and the technology has become the basis for the extension efforts of the Department of Agriculture to develop some 24 million ha of sloping uplands. The woody species used in the system include Calliandra calothyrsus, L. leucocephala, L. diversifolia, G. sepium, and Flemingia macrophylla. The technology has been extended for use elsewhere in the region in India, Sri Lanka and Laos. Additional to the high levels of proteins, minerals and vitamins, the potential of fodder trees and shrubs is also enhanced by the presence of many complex chemical constituents which have anthelminthic, antimicrobial, antiprotozoal and antiseptic properties. However, the presence of bio-active groups of compounds such as alkaloids and phenolics, particularly tannins, limits the use of some fodder trees and shrubs (Lowry, 1989). Plants containing over 5% tannic acid have anti-nutritional properties (McLeod, 1974), with dysphagia, decreased milk yield, haematuria and urinary problems reported by Singh and Joshi (1990). On the other hand, low levels of condensed tannins in fodder trees and shrubs have been found to form a complex with proteins within the rumen, thus preventing excessive protein degradation (Barahona et al., 1997).

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6. Conclusions Currently, levels of animal performance are low in the small mixed farms of Asia. Production is seriously constrained by a combination of feed deficits at critical periods, poor nutritional management, and poor technology application at the farm level. Future strategies for improved utilisation of animal feeds need to be identified that are based on a knowledge of the availability and potential nutritive value of feeds, the production objectives and the production systems themselves (Devendra, 2000). These strategies should promote the development of appropriate technology that can be adopted readily at the farm level. Deficits in feed availability need to be addressed through the increased and more efficient use of locally-produced crop residues, AIBPs and NCFRs, all of which are under-utilised in the region. Furthermore, there is a need to capitalise on the considerable amount of research work that has been conducted in Asia with improved forages over the last 25 years. Suitable cultivars that have been selected for environmental adaptation are available for introduction into both annual and perennial cropping systems. Also, emphasis needs to be given to the greater use of multi-purpose trees, improved feed conservation and strategic supplementation. Unsophisticated feeding systems should be developed that synchronise feed availability with the nutritional requirements of animals throughout the year.

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