Small ruminants integrated with tree cropping
Types of tree-cropping systems
Effects of animal integration on the parent crop
Effects of primary crop management on small ruminants
Economic aspects
Choosing between goats and sheep
Research and development
Potential goat and sheep population increase
References
C. Devendra
The author is Senior Programme Officer in the Division of Agriculture, Food and Nutrition Sciences Division, International Development Research Centre (IDRC), Tanglin PO Box 101, Singapore 9124. His principal responsibility is the Animal Production Systems Program in Asia and he is leader of the Small Ruminant Project Group.This article concentrates on the importance of integrating small ruminants with tree crops as a production system, drawing attention to research and development issues related to the process of integration, and the potential benefits of achieving this especially in Southeast Asia and the South Pacific.
In many developing countries, two potentially important objectives of animal production are the maximization of food production and the generation of supplementary cash incomes. These have been achieved, for example, by the large-scale development of increased milk production from mainly Holstein-Friesian cross-bred cattle or the wider use of milch buffaloes. With small ruminants in the Asian region, the two objectives present a much greater challenge since these species have not as yet made a parallel impact. Increasing their productivity is therefore an important objective. This is further justified by such species being identified with the poorest people in agriculture, in pastoral systems ranging from the arid and semi-arid tropics to complex crop-livestock systems in the humid tropics; and by the projections made by the Technical Advisory Committee (TAC) of the Consultative Group on International Agricultural Research (CGIAR) on the annual increase in demand for goat and sheep products and milk from all animals up to the year 2000 (FAO, 1985), which indicate that the gap is widening faster than for any other food commodities.
Since expansion can result from improvements to production systems, it is relevant to enquire into, and examine, prevailing and alternative avenues of food production specifically in terms of potential increased production. In this context, integrated small ruminant and tree-cropping systems represent an underestimated, unexplored and potentially important avenue for increasing food production in Southeast Asia and the South Pacific (Devendra, 1979; Mahadevan and Devendra, 1985). These systems were identified as meriting high priority in research and development at the FAO Expert Consultation on Small Ruminant Production in the Developing Countries held in Bulgaria in 1986 (Timon, 1986) and, more recently, at the International Research Centre/Small Ruminant Collaborative Research Support Program Workshop on Small Ruminant Production Systems in South and Southeast Asia (IDRC/SR-CRSP, 1987). Failure to have given importance to this system in the past was a result of the emphasis on the traditional systems of managing ruminants (roadside, communal and stubble grazing, tethering- and cut-carry-feeding methods), which are consistent with the thrust on arable rather than tree cropping in Asian agriculture.
This system is especially feasible in South and Southeast Asia and the Pacific islands because of the area under tree crops (coconuts, oil-palm and rubber) and is especially common in the humid and subhumid regions where there is intensive crop production. Although not new, the system has not been given adequate attention to ensure more complete utilization of the land. Its advantages are:
- increased fertility of land via the return of dung and urine
- control of waste herbage growth
- reduced use and cost of weed-killers
- reduced fertilizer wastage
- easier management of the crop
- distinct possibilities of increased crop yields consistent with greater economic development, including the sale of animals and their products.
Weed control costs, for example, are about US$34-43/ha (Velayuthan and Choo, 1986), which can be substantially reduced by using small ruminants. It has recently been reported that a 16-26 percent saving in the cost of weed-killers was obtained by using sheep (Ani, Tajuddin and Chong, 1985). An additional advantage inherent in the system is the presence of abundant shade offered by the trees. This creates an environment that reduces heat stress on the grazing animals.
Given these advantages, and considering the large area under such tree crops as coconuts, oil-palm and rubber, the potential carrying capacity and offtakes of meat (goat meat and/or mutton) from the land are therefore enormous. Many of the Pacific island territories, notably Papua New Guinea, Vanuatu, Fiji, the Solomon Islands and Western Samoa, have large land areas under coconuts, which provide potential for the integration of goats or sheep.
In Indonesia, Rika (1983) reported that on-native pasture the stocking rate was six animals/ha. On improved pasture, with Centrosema pubescens, siratro (Macroptilium atropurpureum) and Brachiaria decumbens, the stocking rate increased to 12 goats/ha, which also resulted in very good animal performance and healthy kids.
There are a number of tree-cropping systems in Southeast Asia, the importance of which is related to primary or secondary functions. Nitis (1986) refers to examples of crops of the following systems:
- Fodder production: acacia (Acacia sp.), Leucaena leucocephala- Fruit production: cashew (Anacardium occidentale), coconuts (Cocos nucifera), mango (Mangifera indica), oil-palm (Elaeis guineensis) and tamarind (Tamarindus indica)
- Manure production: Caliandra eryophila, L. leucocephala
- Protection and shade: Ficus sp., L. leucocephala
- Wood production: C. eryophila, Gliricidia sepium and Erythrina variagata
- Miscellaneous: ornamental or ceremonial reasons, e.g. Ficus religiosa.
This article, however, focuses on coconuts, oil-palm and rubber in view of their economic importance and extensive area in the region. During the period 1966-82, this area increased annually by about 1.6 percent (Asian Development Bank, 1985).
Table 1 summarizes the limited published data on the magnitude of stocking rates with specific reference to goats and sheep under these crops and indicates that, of the three tree crops, least work has been done with oil-palm. This point is associated with the fact that the introduction of goats or sheep is most advantageous during the first four years of the oil-palm's life, after which there is a marked reduction in the availability of dry matter. This is because of decreased light penetrating the canopy of the plant compared to rubber (about 10 percent daylight in oil-palm and very much higher in rubber). There are thus greater opportunities for growing fodder, either grasses or leguminous forages. Legume cultivation, for example, enables the stocking rate to be increased significantly; the amount of nitrogen utilized by the animals increases as also does that excreted in the faeces and urine (Chee and Devendra, 1979).
Increased fodder production has also been achieved by use of rubber and palm-oil mill effluents in the plantations, with concurrent savings in the cost and use of organic fertilizers. On the other hand, the oil-palm plant provides an abundance of feed by-products, all of which are potentially valuable for utilization by small ruminants (Devendra, 1978), and which have been fed intensively in situ in the plantations (Dalzell, 1978). Some of the factors affecting feed availability and their utilization in large oil-palm and rubber plantations have recently been discussed (Wan Mohamed, 1987).
The integration of small ruminants with coconuts, oil-palm or rubber raises a number of issues because of the interaction with the primary tree crop. Given the many varied agro-ecosystems in the region, adaptative research may be necessary to meet the requirements of different situations. Specific sets of recommended practices will also need to be adjusted for individual tree crops and their peculiarities. The process of integration will finally need economic analyses of cost:benefit results to demonstrate the viability of the system.
The recently concluded IDRC/SR-CRSP Workshop on Small Ruminant Production Systems in South and Southeast Asia addressed many of these issues thoroughly, and the effects of animal integration on the parent crop and conversely, on the animals, which are given below, are worth noting.
1. Summary of published data on stocking rates under tree crops in Southeast Asia
Récapitulation des données publiées sur les taux de charge des cultures arborées en Asie du Sud Est
Resumen de datos publicados sobre la densidad de pastoreo en tres tipos de cultivos arbóreos en Asia Sudoriental
|
Tree crop |
Location |
Type of vegetation |
Approximate DM availability (tonnes/ha/yr) |
Species |
Stocking rate (animals/ha) |
Reference |
|
Coconuts
|
Sri Lanka
|
- |
- |
- |
- |
|
|
Improved |
- |
Sheep |
12.0 (est.) |
Rajaguru (1987) |
||
|
Philippines
|
Native |
4.0 |
Goats/sheep |
7-8 |
Parawan and Ovalo (1987)
|
|
|
Improved |
10.8-14.6 |
Goats |
27-28 |
|||
|
Improved |
10.8-14.6 |
Sheep |
25-27 |
|||
|
Malaysia |
Native |
0.8-1.2 |
Goats/sheep |
3-5 |
Devendra (1976) |
|
|
Indonesia
|
Native |
- |
Goats |
6.0 |
Rika (1983) |
|
|
Improved |
- |
Goats |
6-12 |
|||
|
Oil-palm
|
Malaysia |
Native |
0.51-6.52 |
Goats/sheep |
3-36 (est.) |
|
|
Malaysia |
Native 3 |
- |
Sheep |
30-37.5 |
Pillai, Thiagarajan and Samuel (1985) |
|
|
Rubber
|
Malaysia
|
Native |
0.5 |
Goats/sheep |
2.0 (est.) |
Devendra (1976) |
|
Native/Improved |
- |
Goats |
8.0 |
Lee et al. (1978)
|
||
|
|
- |
Sheep |
10.0 |
|||
|
Native |
- |
Sheep |
0.2-1.0 |
Wan Mansur and Tan (1982) |
||
|
Native 4 |
- |
Goats |
2.0 |
Mohamad Jaafar and Mohd Khusahry (1983) |
||
|
Native/legumes |
1.4 |
Goats/sheep |
6.0 |
Tan and Abraham (1980) |
||
|
Native |
15-17 |
Sheep |
15-17 |
Pillai, Thiagarajan and Samuel (1985) |
1 Old oil-palm (above 3 years)
2 Young oil-palm (below 3 years)
3 Immature palms
4 With concentrate supplements
Note: est. = estimated value
A wide variety of issues must be considered in this complex interaction. The following are not listed in any particular order of priority, but refer to a number of important examples. It is by no means an exhaustive list.
- Possible damage to leaves or bark of the primary tree by the grazing or browsing animal: greater precautions must be taken in introducing goats in rubber plantations because of possible damage to the bark. Young coconut, oil-palm and rubber trees are more susceptible to browsing.- The beneficial effect of the animal in weed control, sparing herbicide use and costs; the complementarily of animal and chemical weed control must be studied.
- Beneficial effect of the animal in browsing lower, senescent leaves.
- Possible transmission of plant diseases from pasture plants to the trees.
- Soil compaction by grazing animals.
- Soil organic matter and nitrogen fertilizer from animal excrete and urine.
- Soil moisture depletion by the forage crop; higher evaporation rate if ground cover is overgrazed.
- Animal damage to latex collection cups with rubber cultivation.
- Possible reduction of rodent population (important in oil-palm plantations) with grazing.
The following issues are relevant to the effects of primary crop management on the animals. These issues merit continuous monitoring and research.
- The residual effect of herbicides (contact versus systemic) and its duration.- Adjusting grazing rotations to cultural and harvesting practices, for example, in possible consumption, indigestion and death of the animals as a result of latex consumption in rubber plantations. Problems of metabolic disorders or even nutrition imbalances are also likely in the ingestion of fruitless of oil-palm fruit bunches, rubber leaves and seeds.
- Possible effects in areas where rodenticides have been used.
- Presence of toxic compounds in forage plants when effluents are discharged (for example, palm-oil mill effluent) on the land and in streams; there are also the effects of oil-palm by-product build-up.
- Mineral imbalances and toxicities are likely to be a problem. A case in point concerns copper levels which can be as high as 30-35 ppm (well above the daily requirements of small ruminants).
Most of the animal-related issues are common to other intensive, mixed crop-livestock farms. However, the following are unique to the tree crop-livestock association.
- Time of introduction of animals is critical so as not to cause damage to the parent crop with reduction in yield and serious economic consequences. With oil-palm, for example, the optimum time for introduction is four to five years of age to avoid any damage to the leaves.- Intensity of grazing and carrying capacity will be affected by the space occupied by the trees, and the amount of light penetrating the canopy.
- Fencing and/or shepherding of animals will be influenced by labour availability and, on large estates, by requirements for movement of machinery.
- Many by-products of tree-crop processing are readily available which are potentially valuable for small ruminant feeding and strategic supplementation. These are: coconuts - coconut meal; oil-palm - palm press fibre, palm kernel cake, palm-oil mill effluent (pome); and rubber - rubber seed meal. In addition to these there are other non-conventional feed resources such as cassava leaves (Manihot esculenta Crantz), which are also extensively used in these situations (Devendra, 1985b).
- There are a number of management-related issues, and some of the more important ones include the use of tree legumes such as leucaena (Leucaena leucocephala) and sesbania (Sesbania grandiflora) as feeds, fuel and as a fence line; supplementation; provision of water and mineral licks; conservation of crop residues and forages for dry season use; hours of available grazing per day; control of predators; labour availability; complementarily of sheep and goats and possibly also cattle in mixed grazing systems; manipulation of the breeding season to take best advantage of seasonal feed availability; type and regularity of drenching, and housing requirements.
- The animal health problems of major importance include endoparasites (especially in grazing systems), ectoparasites (e.g. scabies) and respiratory diseases such as pleuropneumonia. These need to be regularly monitored and appropriate control measures adopted, for example, regular drenching.
An example of the economic benefits of integrating goats with oil-palm is a case history of an oil estate in Malaysia where a portion of the grazing land within the estate was allocated to the workers for grazing their animals. In the first two years (1980 and 1981), only cattle were grazed. In 1982 and 1983 goats were also introduced, in view of their economic importance and capacity to supply both meat and milk to the estate.
The comparison of the grazed and non-grazed area involving both young and mature trees is valid in that it involved the same hectarage and, more particularly, since both areas were of the same soil type. The total cattle and goat populations were both approximately 80 and 220 animals respectively. It can be seen in Table 2 that the differences in yield over the four years due to the effect of grazing cattle and goats was between 2.15 and 5.16 tonnes of fresh fruit bunches/ha/year with a mean value of 3.52 tonnes of fresh fruit bunches/ha/year. When translated into the total area grazed and value per tonne of fresh fruit yield, the economic advantage is conspicuously substantial.
2. The effect of mixed cattle and goat grazing on the yield of fresh fruits in oil palm cultivation in Malaysia
Effets du pâturage mixte de bovine et de caprins sur le rendement en fruits frais des plantations de palmiers à huile en Malaisie
Efecto del pastoreo mixto de vacunos y caprinos sobre el rendimiento de fruta fresca en un cultivo de palmas de aceite en Malasia
|
Year |
Grazed area Yield of fresh fruit bunches |
Non-grazed area Yield of fresh fruit bunches (tonne/ha/yr) |
Difference Fresh fruit bunches (tonne/ha/yr) |
|
1980 |
30.55 (C) |
25.61 |
4.94 |
|
1981 |
17.69 (C) |
15.87 |
1.82 |
|
1982 |
25.12 (C & G) |
22.97 |
2.15 |
|
1983 |
23.45 (C & G) |
18.29 |
5.16 |
|
Mean |
24.20 |
20.69 |
3.52 |
Note: C = cattle; C & G = cattle and goats
Source: Devendra (1985)
Malaysia has a combined total hectarage of approximately 4.3 million under rubber and oil-palm. Thus, even if only half of this crop area is utilized by animals, assuming a carrying capacity of three animals/ ha, the total number of animal equivalents is of the order of 5.2 million, which is substantial. Based on ten years' research, Ani, Tajuddin and Chong (1985), have reported that integration of sheep with rubber gave a 15-25 percent saving in cost of weed control and that, together with the sale of animals and manure, sheep could give a return of 15 percent on investment. Pillai, Thiagarajan and Samuel (1985) have estimated this saving to be approximately US$ 57 per ha.
More recently, the gross margin of returns from sheep integrated with mature oil-palm has been reported by Tan (1987) based on a study also made in Malaysia over two years. The project involved 50 pregnant ewes. Net farm income was calculated from a consideration of fixed and variable costs and gross production incomes (see Table 3). It can be seen in Table 3 that the net farm income was approximately $M15 000. This is equivalent to $M7 500/year A or about $M 150/ewe/year.
It is important to consider certain criteria for the choice of either goats or sheep appropriate for integration with tree-cropping systems. The following factors are particularly worthy of mention.
Feeding behaviour. Goats are inquisitive animals and essentially browsers (Devendra and Burns, 1983). This feature enables a greater selection intensity than sheep which, by comparison, are grazing animals. In situations where there is less grass and a higher proportion of shrubs and other forages, goats are likely to make more efficient use of this herbage. Sheep are generally more docile than goats. Quite often both goats and sheep are run together to enable maximum utilization of the available herbage.
Relative price of meats. The relative price of either goat meat or mutton has an important bearing on the choice of animals. Presently, the price of goat meat is much higher (approximately two to three-times that of mutton), simply because of inadequate supply.
Availability of animals. The availability of animals for breeding, and therefore for slaughter, is an important consideration. Sheep are currently more easily imported than goats, which favours the former in development programmes. On the other hand, there is a high demand for good-quality breeding goats which fetch high prices.
Survivability. This important characteristic is breed-specific and an important component of biomass production and lifetime productivity.
3. Gross margin from sheep integrated-with mature oil palm
Produit brut de l'élevage ovin dans des plantations de palmiers a huile adultes
Beneficios brutos de la integración de ovejas con palmas de aceite adultas
|
Gross production income | |||
|
|
Sales of animals |
2 450 20 | |
|
|
Net inventory change of sheep 1 |
18 425.00 | |
|
Total ($M) 2 |
20 875.20 | ||
|
Variable costs | |||
|
|
Brooms and basins |
55.70 | |
|
|
Ropes |
15.50 | |
|
|
Medication |
237.40 | |
|
|
Milk supplements |
123.50 | |
|
|
Salt |
62.50 | |
|
|
Hired labour |
1 002.00 | |
|
|
Miscellaneous costs |
62.40 | |
|
Total variable costs ($M) |
1 559.00 | ||
|
Gross margin ($M) |
19 316.20 | ||
|
Fixed costs | |||
|
|
Depreciation costs 3 | ||
|
|
|
Shed |
3 911.46 |
|
|
|
Fencing |
416.00 |
|
Total fixed costs ($M) |
4 327.46 | ||
|
Net farm income ($M) |
14 988.74 | ||
|
Overhead costs |
| ||
|
|
- Shed |
9 778.65 | |
|
|
- Fencing |
1 040.00 | |
1 Based on the change in value of sheep relative to numbers from over the two years
2 US$1.0 = $M2.60 approximately
3 Depreciation rate = 20 percent of total capital expenditure per year
Source: Tan (1987)
4. Comparative biomass production between indigenous goats and sheep in Malaysia
Comparaison de la production de biomasse des caprins et des ovins indigènes en Malaisie
Producción comparativa de biomasa entre cabras y ovejas autóctonas en Malasia
|
Species |
Average live weight of female |
Litter size |
Survivability at 12 months 1 |
Average weight at slaughter |
Biomass production 2 |
|
(kg) |
(kg) |
(kg) |
|||
|
Goats |
22 |
1.8 |
1.44 |
20 |
28.8 |
|
Sheep |
22 |
1.1 |
0.88 |
18 |
15.8 |
1 Mortality rate is 20 percent
2 Survivability x average slaughter weight
Source: Devendra (1985)
Market for meats. Both goat meat and mutton have a fluctuating high income demand, which is particularly apparent in the Near East markets. The attendant factors that merit consideration are: type of meat required (goat meat or mutton); methods of slaughter; processing; cost of transportation; live animals or frozen carcasses; carcass quality and taste preferences; economic benefits of the export trade.
Biomass production. This component is the net effect of combining the inherent biological qualities in the species as well as good husbandry. It is influenced by such factors as age at first breeding, length of reproductive cycle, interval between parturitions, litter size, lifetime productivity and mortality. It is therefore of interest to compare the relative abilities of both species to produce biomass, a portion of which is sold for profit as meat. Table 4 produces the results of this comparison. It is evident that although the average live weight of adult does or ewes is about the same, litter size is a most important determinant of biomass production when other factors, such as the level of husbandry and mortality rates, are similar. In this case, goats produced about 82 percent more biomass than sheep in Malaysia.
There exist, therefore, several research and development issues concerning integrated systems. Recognizing these, the IDRC/SR-CRSP (1987) Workshop recommended research and development into a number of areas in these systems which include:
- intensity of grazing and carrying capacity- possible alteration of the normal planting density of the primary tree crop to accommodate longer productivity from the herbage
- optimum times for introducing the animals for specific tree crops in agronomic and economic terms
- dual-purpose value of the legume cover for the animals and the plantations
- small ruminant management issues (e.g. grazing system, by-product utilization, mineral imbalances, toxic problems, etc.)
- economic aspects of integration.
According to FAO (1988) data, 24.2 million hectares of land under permanent crops currently exist in South and Southeast Asia (see Table 5). This area is essentially unused and is potentially valuable if some of it can be integrated with either goats or sheep for meat production using available knowledge and by suitable interventions. The impact of integration is shown in the following calculations. Assuming an average stocking rate of four goats or sheep/ha, which is typical for rates involving natural vegetation under coconuts, oil-palm and rubber (see Table 1), and if only 10 million ha were integrated with these species, there will be an increase of 40 million animals. At an approximate slaughter weight of 20 kg, the potential increased meat production 400 000 tonnes, assuming a dressing percentage of 50 percent.
5. Land use in Asia and the South Pacific
Utilisation des terres en Asie et dans le Pacifique Sud
Utilización de la tierra en Asia y el Pacífico Sur
|
Type of land use |
Area (106 ha) |
% of total |
|
Arable land and permanent cropland |
396.5 |
18.2 |
|
Permanent pasture |
522.7 |
24.1 |
|
Forest and woodland |
313.2 |
37.7 |
|
Other land |
727.00 |
33.5 |
|
Total land area |
831.7 |
100.0 |
Source: FAO (1988)
6. Projected goat and sheep populations in Asia and the South Pacific (106)
Projection des populations caprines et ovines en Asie et dans le Pacifique Sud (106)
Poblaciones proyectadas de caprinos y ovinos en Asia y el Pacífico Sur (106)
|
Category |
19871 |
20002 |
20003 |
|
Goats |
256.1 |
316.0 |
336.0 |
|
Sheep |
237.0 |
277.1 |
297.1 |
1 The base year 1987
2 Based on annual growth rates of 1.8 and 1.3 percent for goats and sheep respectively
3 Potential increase due to integration of goats and sheep with permanent crops (see text, for explanation)Source: FAO (1988)
Table 6 demonstrates the goat and sheep population over approximately ten years. The cumulative increase will be about 1723 percent from the base year in 1987, and in addition there could be a 6-7 percent increase through integration of 40 million small ruminants. These projections assume that there will be concurrent improvements in reproductive efficiency, improved systems of management and reduced losses from health and diseases. Further expansion in the use of the land under tree crops will depend on the demonstration that the integration of small ruminants with tree crops is clearly associated with definite economic benefits. Whether these projections can in fact be achieved in the future represents the challenge of exploiting this particular production system much more thoroughly.
The development of small ruminants is, therefore, especially significant in integrated systems in the Asian and South Pacific regions. The importance is associated with issues of sustainability, including their wider use in agroforestry systems with complementary advantages of forage production, supply of fuelwood, improvement of soil fertility, permanent soil cover and economic land use. These and other issues need to be addressed thoroughly in research and development teens in the search for efficiency in the utilization of integrated tree-cropping systems and small ruminant genetic resources in Asia and the South Pacific.
Ani, B.A., Tajuddin, I. & Chong, D.T. 1985. Sheep rearing under rubber. In Proc. 9th Ann. Conf. Malays. Soc. Anim. Prod., Serdang, Malaysia, p. 117-123.
Asian Development Bank. 1985. Agriculture in Asia. Statistical appendices. Manila, ADB.
Chee, Y.K. & Devendra, C. 1979. The nitrogen cycle role of legume and animals in rubber cultivation. In Proc. Workshop on Nitrogen Cycling in the South east Asian Wet Monsoonal Ecosystem, Chiangmai, Thailand, p. 109-112.
Dalzell, R. 1978. A case study on the utilization of oil palm mill effluent by cattle and buffaloes. In Devendra, C. & Mutagalung, R.E., eds. Proc. Symposium on Feedingstuffs for Livestock in South East Asia, Serdang, Malaysia, p. 132-141.
Devendra, C. 1976. Goat production on small farms in South East Asia. In Proc. Integration of Livestock with Crop Production at Small Farm Level FAO Expert Group Meeting on Livestock Programmes for Small Farmers and Agricultural Labourers in Asia and the Far East, Bangkok, Thailand, p. 176-210.
Devendra, C. 1978. Utilization of feedingstuffs from the oil-palm. In Devendra, C. & Mutagalung, R.E., eds. Proc. Symposium on Feedingstuffs for Livestock in South East Asia, Serdang, Malaysia, p. 116-131.
Devendra, C. 1979. Goat and sheep production potential in the ASEAN region. Wld Anim. Rev., 32: 33-41.
Devendra, C. 1985a. Integrated farming systems involving small ruminants. In Proc. 3rd Asian-Australasian Anim. Sci. Congr., Vol. 1, p. 146-156.
Devendra, C. 1985b. Non-conventional feed resources in Asia and the Pacific. 2nd ed. FAO/Regional Animal Production and Health Commission for Asia and the Pacific (APHCA). Bangkok, Thailand, FAO.
Devendra, C. 1987. Herbivores in the arid and wet tropics. In Hacker, J.B. & Ternouth, J.H., eds. The nutrition of herbivores, p. 23-46. Sydney, Academic Press.
Devendra, C. & Burns, M. 1983. Goat production in the tropics. 2nd ed. Farnham Royal, Commonwealth Agricultural Bureaux.
FAO. 1985. TAC review of CGIAR priorities and future strategies. Rome.
FAO. 1988. Selected indicators of food and agriculture development in the Asia-Pacific region, 1977-87. Regional Office for Asia and the Pacific, Bangkok, FAO.
IDRC/SR-CRSP. 1987. Small ruminant production systems in South and Southeast Asia. Devendra, C., ed. Proc. of a Workshop, Bogor, Indonesia, 6-10 October 1986. Ottawa, IDRC.
Lee, K.A., Wan Mohamed, W.E., Ng, L.M., Ng, F.C. & Phang, A.K. 1978. Performance of sheep and goats under rubber - preliminary results. In Proc. Integration of Animals with Plantation Crops, p. 206-212.
Mahadevan, P. & Devendra, C. 1985. Present and projected ruminant production systems of South East Asia and the South Pacific. In Proc. Int. Workshop on Forages in South East Asia and South Pacific Agriculture, Bogor, Indonesia, p. 7-11.
Mohamad Jaafar, D. & Mohamad Khusahry, M.Y. 1983. Supplementation with selected feedstuffs for sheep grazing under plantation. In Proc. 7th Ann. Conf. Malays. Soc. Anim. Prod., Port Dickson, Malaysia, p. 199-205.
Nitis, I.M. 1986. Production systems based on tree cropping. In Proc. IDRC/SR-CRSP Workshop on Small Ruminant Production Systems in South and South East Asia, Bogor, Indonesia, p. 101 117. Ottawa, IDRC.
Parawan, O.O. & Ovalo, M.B. 1987. Integration of small ruminants with coconuts in the Philippines. In Devendra, C., ed. Small ruminant production systems in South and Southeast Asia. Proc. of a workshop, Bogor, Indonesia, 6-10 October 1986, p. 269-279. Ottawa, IDRC.
Pillai, K.R., Thiagarajan, S. & Samuel, C. 1985. Wee-d control by sheep grazing under plantation tree crop. In Proc. 9th Ann. Conf. Malays. Soc. Anim. Prod ., Serdang, Malaysia, p. 43-52.
Rajaguru, A.S.B. 1987. Integration of crops and small ruminants in Sri Lanka. In Devendra, C., ed. Small ruminant production systems in South and Southeast Asia. Proc. of a Workshop, Bogor, Indonesia, 6-10 October 1986.
Rika, I.K. 1983. Pengaruh pengembalaan kombing (pada berbagai "stocking rate") dibawah pokok kelapa. Bull. Fapet UNUD, No. 123/83.
Tan, K.L. 1987. On-farm research in Malaysia - illustration of economic analysis. In Proc. Winrock Int./IDRC Workshop on On-Farm Animal Research Extension and Its Economic Analysis, p. 86-90.
Tan, K.M. & Abraham, P.D. 1980.-Livestock production on rubber plantations. First Asian-Australasian Anim. Sci. Congr., Serdang, Malaysia.
Timon, V.M. 1986. Small ruminant production in the developing countries, p. 226-232. FAO Animal Production and Health Paper No. 58. Rome.
Velayuthan, A. & Choo, Y.L. 1986. Sheep farming - another tool for weed control under oil palm/rubber plantations by using a cheaper management technique. The Planter, 62: 319-332.
Wan Mohamed, W.E. 1987. Integration of small ruminants with rubber and oil palm cultivation in Malaysia. In Devendra, C., ed. Small ruminant production systems in South and Southeast Asia. Proc. of a Workshop, Bogor, Indonesia, 6-10 October 1986, p. 239-256. Ottawa, IDRC.
Wan Mansur, W.S. & Tan, K.M. 1982. Viability of-sheep rearing under rubber. In Jainudeen, M.R. & Omar, A.R., eds. Animal production and health in the tropics, p. 333-335. Malaysia, University Pertanian.
