A classification of livestock production systems

H. Steinfeld and J. Mäki-Hokkonen

H. Steinfeld is Senior Officer (Programme, Policy & Planning) and J. Mäki-Hokkonen is Senior Officer (Livestock Production Systems), Animal Production and Health Division, FAO, Rome, Italy.

Definition of systems Description of systems Conclusions Bibliography

The objective of this article is to describe a classification of the world's livestock systems based on a recent study carried out by the Animal Production and Health Division (AGA) of FAO. The systems classification aims at:

· Delineating and defining elements of a classification of livestock production systems.

· Quantitatively and qualitatively describing each livestock production system in terms of feed and livestock resources livestock commodities produced; production technology; product use and livestock functions; area covered; geographic locations; and human populations supported.

· Providing insights into the importance of livestock systems across world regions and agro-ecological zones and related trends in order to provide orientation to decision-makers involved in livestock development.

The results form a valuable basis for priority setting in AGA's new programme of work, which will be based on a systems approach starting from the 1996-97 biennium. They were originally used as the basis for the environmental impact assessment of an FAO-coordinated global multidonor study on interactions between livestock production systems and the environment. The results are useful in a general discussion of livestock development. Full statistics and descriptions are contained in the forthcoming FAO publication World livestock production systems.

The classification covers the following animal species: cattle, buffalo, sheep, goat, pig and chicken. In geographic terms, systems are grouped according to the following regions: sub-Saharan Africa (SSA); Asia; Central and South America (CSA); West Asia and North Africa (WANA); Organisation for Economic Co-operation and Development (OECD) member countries, excluding Turkey, which was included in WANA; eastern Europe and Commonwealth of Independent States (CIS); and other developed countries (Israel and South Africa). The study covers 150 countries, comprising over 98 percent of the world production of the commodities concerned.

Livestock production systems are considered to be a subset of farming systems. A review of the literature (Ruthenberg, 1980; Jahnke, 1982; FAO, 1980; De Boer, 1992; FAO, 1994) revealed that most farming systems classifications are not backed by quantitative criteria, which would enable cases to be clearly allocated to one class. These classifications are closer to typologies. No attempts at developing a classification of world livestock systems by using quantitative statistical methodologies (cluster analysis and related methodologies) could be located in the literature. This probably relates to the lack of appropriate data sets for such approaches on a global scale.

Using data from the FAO Information System for Agricultural Statistics (AGROSTAT), commodities or items were sequentially allocated to specific cells with defined attributes. At the first stage, national totals were assigned to one or more of the agro-ecological zones (AEZs) of the country in question using decision rules. For land-based production systems, for example, that is the proportion of arable land in each AEZ, and for landless production systems, the prorating factor became the population in each AEZ, in relative terms. The world's land surface was classified into ten AEZs.

The next stage was the overlay with classification criteria defining the attributes of the farming system, such as mixed versus grazing or mixed rain-fed versus mixed irrigated. This classification was based on decision rules related to the share of arable land as compared to grazing land and to the share of irrigated versus non-irrigated arable land.

Data for each item were then aggregated across specified AEZs to arrive at climatically broader and less numerous systems, for example, humid + subhumid tropics and subtropics. Data on different dimensions of a livestock production system were extracted from the item-oriented spreadsheets to produce system-descriptive spreadsheets.

Given the intrinsic weakness of the procedure of allocation to systems, in the case of large countries with diverse ecologies, subnational statistics were consulted to allocate the data manually to a production system for the major countries: China and India in Asia; Nigeria, the Sudan and Ethiopia in sub-Saharan Africa; and Brazil, Mexico and the United States in the Americas.

Definition of systems

Solely livestock production systems (L)

Livestock systems in which more than 90 percent of dry matter fed to animals comes from rangelands, pastures, annual forages and purchased feeds and less than 10 percent of the total value of production comes from non-livestock farming activities.

Landless livestock production systems (LL). Subset of the solely livestock production systems in which less than 10 percent of the dry matter fed to animals is farm-produced and in which annual average stocking rates are above ten livestock units (LU) per hectare of agricultural land.

Grassland-based systems (LG). Subset of solely livestock production systems in which more than 10 percent of the dry matter fed to animals is farm-produced and in which annual average stocking rates are less than ten LU per hectare of agricultural land.

Mixed-farming systems (M)

Livestock systems in which more than 10 percent of the dry matter fed to animals comes from crop by-products or stubble or more than 10 percent of the total value of production comes from non-livestock farming activities.

Rain-fed mixed-farming systems (MR). A subset of the mixed systems in which more than 90 percent of the value of non-livestock farm production comes from rain-fed land use.

Irrigated mixed-farming systems (MI). A subset of the mixed systems in which more than 10 percent of the value of non-livestock farm production comes from irrigated land use.

Description of systems

This section provides a summary of each system, with quantitative estimates of the magnitude of the resources involved in each system defined, together with the major outputs and a set of productivity indices. This information is supplemented by a brief description of the main features of each system as well as the development paths along which these systems are evolving.

Landless livestock production systems (LL)

Asia is already contributing some 20 percent and eastern Europe 15 percent, with the latter recently in sharp decline.

Landless monogastric production system (LLM). This system is defined by the use of monogastric species, mainly chickens and pigs, where feed is introduced from outside the farm, thus separating decisions concerning feed use from those of feed production, and particularly of manure utilization on fields to produce feed and/or cash crops. This system is therefore open in terms of nutrient flow.

Landless monogastric systems are found predominantly in OECD member countries with 52 percent of the total landless pork production and 58 percent of the landless poultry production globally. In the case of pig production, Asia is second, with 31 percent of the world total. For poultry, Central and South America follow, with 15 percent. To a large extent, this geographic distribution is determined by markets and consumption patterns in addition to levels of urbanization.

In Southeast and eastern Asia, this system is especially important. As much as 96 percent of the total pig-meat production in Asia occurs in China, Viet Nam and Indonesia. China, Thailand and Malaysia produce 84 percent of poultry meat. This is associated with fast economic growth and urbanization. The demand for monogastric meat is expected to grow from two- to fivefold between 1987 and 2006 from a base of 31 million tonnes, and a three- to tenfold increase is expected in the demand for eggs from 9 million tonnes (Devendra, 1995). The prerequisites for development into large-scale vertically integrated production include the use of appropriate breeds and strains, feed quantity and quality, housing and disease control, as well as assured markets both at home and abroad. Landless poultry and pig production systems account for the majority of the output in developed countries and their share is rapidly increasing in developing countries given their high supply elasticity in the short term.

The system is typically competing with traditional land-based production systems for shares in the urban markets. It must be kept in mind that poultry and pork are close substitutes for beef and mutton, thus also interacting with the ruminant systems. In a broader sense, the demand for cereals d by these systems is also competing for land resources with land-based ruminant systems.

Landless ruminant production system (LLR). This production system is defined by the use of ruminant species, principally cattle, where feed is mainly introduced from outside the farm system. Landless ruminant production systems are highly concentrated in only a few regions of the world. In the case of cattle, they are almost exclusively found in eastern Europe and the CIS and in a few OECD member countries. Landless sheep production systems are only found in western Asia and northern Africa.

Typical cases are large-scale feedlots in the United States and in eastern Europe and the CIS, and veal production in parts of the KU. Intensive dairy operations in the same regions are more land-based because of the need to feed palatable fodder, which cannot be transported economically over long distances. In Asia, the intensive ruminant systems are typically found in buffalo and dairy cattle production units/colonies in India and Pakistan.

The LLR system is based almost exclusively on high-producing, specialized breeds and their crosses, which, nevertheless, have not been bred specifically for performance under "landless" conditions. With regard to milk production, the Holstein-Friesian breed is clearly the most important, and for beef production, English breeds predominate in the United States, while the large European dual-purpose breeds provide animals for fattening. The abundance of rangeland in the United States has led to the specialized production of calves from beef breeds for feedlot operations, while under European conditions these animals are a joint product together with milk, mainly from mixed systems.

The LLR system is highly capital-intensive, leading to substantial economies of scale. It is also feed-intensive and labour-extensive. Key efficiency parameters are daily weight gains and feed conversion, basically reflecting the efficient use of capital invested in infrastructure or in the form of lean animals and feeds. Weight gains are usually in the range of 1 to 1.5 kg per day, and feed conversion rates are about 8 to 10 kg of grains per kilogram of weight gain.

This system is closely linked to land-based systems that normally provide the young stock for landless systems. This constitutes an important difference from landless monogastric systems, in which replacement stock is produced within the same vertically integrated system.

Driven by population growth, the landless ruminant system is expected to continue to grow slowly in North America and southern Asia. On the other hand, it is expected to decline in the EU as production becomes more extensive in response to policies reducing agricultural support. In eastern Europe and the CIS, its importance is also declining and ruminant production in that part of the world is shifting to land-based and smaller-scale systems.

A growing market for grain-fed beef exists in Japan and the newly industrialized countries of Asia. The growth rate of this market will depend mainly on the evolution of the international price of cereals and the increased per caput incomes. This market will in part be supplied domestically and through imports from the United States, Canada, Australia and possibly South America.

Grassland-based livestock production systems (LG)

Central and South America and the developed countries dominate the picture in terms of meat production, together accounting for more than three-quarters of the world's production.

Temperate zones and tropical highlands grassland-based system (LGT). In these areas, the grazing system is constrained by low temperatures. In the temperate zones, there are one or two months of mean temperatures, corrected to sea level, to below 5°C, whereas in the tropical highlands daily mean temperatures during the growing period are in the range of 5° to 20°C.

Locations in the tropical highlands comprise parts of the highlands of South America and eastern Africa, and in temperate zones they include southern Australia, New Zealand and parts of the United States, China and Mongolia.

Typical cases are Mongolia's steppe system, New Zealand's dairy and sheep enterprises, dairy systems close to Bogota, Colombia, and the South American camelid and sheep grazing systems in the altiplano of Peru and Bolivia. Extensive grazing systems are also found in parts of northwestern Pakistan involving sheep for mutton and wool (Nawaz, Naqui and Jadoon, 1986) and transhumant sheep on degraded high-altitude pasture in Nepal (Pradhan, 1987). Further cases are reported for Chinese merino wool sheep on communal grazing in Jilin Province and sheep ranching on grass-clover pastures of intensive animal production enterprises in the state of Oregon in the United States (Nawaz and Meyer, 1992).

The regions in which the LGT system predominates have a combined human population of 190 million, which represents only 3.5 percent of the world total, and almost half of this population lives in Asia. In OECD member countries, far fewer people (14 million or 1.7 percent) use the LGT system, but they control more land and cattle per inhabitant than in the other regions.

Under the LGT system, product use varies widely, ranging from export-oriented New Zealand farmers, to South American farmers mainly producing for the domestic market, to Asian and African smallholders concerned with local markets and their own subsistence.

Market forces and environmental concerns are curbing the potential for intensification of this system. As a result, their global market share is declining vis-à-vis that of other production systems.

Since the LGT system is found mostly in marginal areas, its production potential in global terms is relatively low. In developing countries it tends to form a subsistence basis for certain groups of the population and its future role is seen more in providing employment for these groups than in making a major contribution to output and economic development. In developed countries, frequently with production surpluses, the production from these systems is declining in relation to other values and uses assigned to these land resources, such as recreational value, value as a wildlife and biological diversity reserve and the contribution to water conservation.

Humid and subhumid tropics and subtropics grassland-based system (LGH). The LGH system is defined as a grazing system found in regions with more than 180 days of growing period. It tends to be concentrated more in the subhumid zone, particularly in regions where access to markets or, for agronomic reasons, crop production is limited. By definition, only very limited cropping is considered for subsistence.

The LGH system is found mostly in the tropical and subtropical lowlands of South America: in the llanos of Colombia and Venezuela as well as in the cerrados of Brazil. Dual-purpose milk-beef systems in the Mexican lowlands and estancias in Argentina are also typical cases of this system. In the African setting, many of the potentially suitable land resources are not used as a result of trypanosomiasis constraining livestock production. Outside Latin America, this system is important only in Australia because of its ample land resources in relation to its population.

Worldwide, the LGH system comprises about 190 million head of cattle, an important proportion of which are of the zebu breeds. In the subhumid and humid regions, cattle are clearly the dominant species, and in very high rainfall areas, such as the Amazon River delta and some parts of Queensland, Australia, buffaloes are also ranched. African hair sheep and dwarf goats are usually kept for local consumption only. In the subtropics, wool sheep are an important component of the system, for example, in Argentina, Uruguay, South Africa and Australia.

The LGH system produces approximately 6 million tonnes of beef and veal and 11 million tonnes of cow milk worldwide. By far the most important geographic region is Central and South America. The system is predominantly market-oriented.

Globally, 6 percent of the world's population (330 million people) lives in areas where the LGH production system predominates. Its importance in terms of sustaining the livelihood of rural populations is expected to decline as interaction with crop cultivation turns it into a mixed system. In rain-forest regions, efforts are being made to incorporate perennial tree crops, frequently into silvo-pastoral systems. In the savannahs, this system is being converted into a mixed-farming system by including annual crops, such as maize, soybeans and sorghum.

Improvements in road infrastructure and new technologies to allow the establishment of pastures with commercially worthwhile nurse crops are making the ley farming systems, involving rotations of crops and pasture, a potentially attractive pathway into mixed-farming systems (Thomas et al., 1992).

Arid and semi-arid tropics and subtropics grassland-based system (LGA). The LGA system is defined as a land-based system in tropical and subtropical regions with a growing period of less than 180 days, and where grazing ruminants is the dominant form of land use.

This system is found under two contrasting socioeconomic frameworks: in sub-Saharan Africa and the Near East and North Africa regions, where it constitutes a traditional way of subsistence for an important part of the population, and in Australia, parts of western United States and southern Africa, where private enterprises utilize publicly or privately owned range resources for ranching purposes.

While in western Asia, northern Africa and sub-Saharan Africa, the LGA system is important for the livelihood of large sectors of the rural population, in developed countries it is extremely labour-extensive.

In sub-Saharan Africa, agropastoralism is the most important interface between livestock production and other agricultural production. In other regions these systems are interrelated with other livestock production systems that have access to better-quality feed and are closer to markets. In low-income countries without an export market, incentives to produce quality beef are weak. This, in turn, limits the attractiveness of livestock production stratification.

Globally, new roles are emerging for these rangelands, besides that of producing ruminant animal products. In developing countries, the pressure to expand crop production is increasing population pressure on the remaining rangelands. In developed countries, the utilization of these rangelands for animal production has often been subsidized through very low prices for grazing permits and public investments in irrigation.

Rain-fed mixed-farming systems (MR)

Sub-Saharan Africa, West Asia and North Africa, and Central and South America are relatively unimportant in terms of meat production, whereas developed countries and Asia together contribute about 70 percent of the total meat production from mixed-farming systems.

Temperate zones and tropical highlands rain-fed system (MRT). This system is defined as a combination of rain-fed crop and livestock farming in temperate or tropical highland areas, in which crops contribute at least 10 percent of the value of total farm output.

The MRT system is found in two contrasting agro-ecozones of the world: it is the dominant system in most of North America, Europe and northeastern Asia, basically covering large strips of land north of the 30° northern latitude parallel, and it is found in the tropical highlands of eastern Africa (Ethiopia, Kenya, Uganda, Burundi, Rwanda) and in the Andean region of Latin America (Ecuador, Mexico).

The main common feature of these two regions is that low temperatures during all or part of the year limit and determine vegetation that is quite distinct from that found in tropical environments (e.g. C3 versus C4 grasses).

In the course of the development process, production technology in temperate locations evolved to higher specialization, more use of external inputs and more open systems. This has resulted in increasing negative externalities of these systems for the environment.

In most tropical MRT systems, production is less intensive, with livestock performing a series of functions in mixed systems: a continuous flow of cash income; means to concentrate nutrients for crops through manure; fuel; animal traction; a cash reserve for emergencies; and as a buffer to risks in crop production.

Globally, the MRT system is the most important source of animal products, providing 39 percent of the beef and veal production, 24 percent of the mutton production and 63 percent of the cow milk produced.

In developed countries, growing environmental concern, reduced protection of domestic production and increased international trade have led to a stagnation or even a reduction in output levels. In eastern Europe and the CIS, mixed systems will replace inefficient large-scale landless systems as these economies open up to the markets.

In Asia, this system has the potential for increased production and better use of feeds for intensified ruminant production, associated with reallocation of land-use patterns at the farm level.

In the highlands of sub-Saharan Africa and Latin America, production increases must come from a further intensification of crop-livestock land-use systems. The highlands should favour small-scale mechanization because of the high population density, continuous cultivation and relatively heavy soils.

Humid and subhumid tropics and subtropics rain-fed system (MRH). In the humid and subhumid regions of the tropics and subtropics, livestock production is based on mixed-farming systems. Given the range of socioeconomic conditions and soils and climates involved, this livestock system is very heterogeneous in its composition. It is found in all tropical regions of the world, mainly in developing countries. Parts of the southern United States are the only significantly developed regions included in this system. Typical cases are smallholder rice-buffalo systems in Southeast Asia or soybean-maize-pasture large-scale commercial operations in the Brazilian cerrados.

This system includes regions with especially difficult climatic conditions for livestock (high temperatures and high humidity). Adaptation of highly productive temperate breeds to these challenges has been notably poor. In many parts of Africa, trypanosomiasis constitutes an additional constraint to these systems. Particularly in African and Asian smallholder systems the local breeds are still widely used. In Latin America, Bos taurus cattle, sheep and goats were introduced some four centuries ago. Bos indicus cattle were introduced a few decades ago and have now replaced the earlier introduced cattle breeds in tropical areas.

In the African and Asian MRH system, the multiple roles of livestock have prevailed, particularly animal traction and manure. In Central and South America, this system caters to large domestic markets and, particularly in the case of Brazil, it is also linked to export markets. Under smallholder conditions, milk tends to be a more important output than meat.

The MRH system applies to approximately 14 percent of the global population. This ratio is particularly high in sub-Saharan Africa, where 41 percent of the region's population is associated with the system, and in Central and South America, where it is 35 percent.

The system is replacing grazing systems in Africa and Latin America. In Africa, the process is mainly driven by population growth, and, in Central and South America, by economic development and technological innovations.

The main challenge in sub-Saharan Africa is finding ways to increase productivity. It is generally acknowledged that the biological potentials of mixed systems will be the key to productivity increases, and the expectation is that purchased feed inputs will be replaced by nutrients cycled within the system. In Asia, increased crop production - and hence feed availability is an important way of intensifying and maximizing animal productivity, however, the prospects for increasing cultivation area are limited.

In Latin America, low population density, a high degree of urbanization and relatively high per caput incomes have resulted in farming systems that are generally more oriented towards livestock production. In the tropical rain-forest regions, high resource-consuming systems were established, in some cases driven by policies and in other cases by poverty. Many of the policies that promoted wasteful utilization of these resources have been stopped in the process of structural adjustment.

Arid and semi-arid tropics and subtropics rain-fed system (MRA). The MRA system is a mixed-farming system in tropical and subtropical regions with a vegetation growth period of less than 180 days. The main restriction of this system is the low primary productivity of the land resulting from low rainfall. The more severe the constraint, the less important crops become in the system and the more livestock take over as a primary income and subsistence source.

This system is important in the West Asia and North Africa region in parts of the Sahel (Burkina Faso, Nigeria), in large parts of India and in northeastern Thailand and eastern Indonesia, and less important in Central and South America. Given the low intensity of the system and the multiple purposes of livestock, the introduction of improved breeds has been limited. Globally, 11 percent of cattle and 14 percent of sheep and goats are found in this system. Small ruminants are particularly important in West Asia and North Africa under the MRA system.

As is the case in other largely smallholder systems, livestock have a range of simultaneous roles in this system, including animal traction, production of manure and use as a cash reserve, in addition to the production of meat and milk. Fuelwood is often scarce as a result of deforestation and range degradation, leading to the ever-increasing role of animals as providers of manure for fuel, in addition to means of transport.

While this system supports larger populations than any other grazing system, only 10 percent of the world's population is related to this system. Fifty-one percent of the population involved is in Asia, mainly India, and 24 percent is in the West Asia and North Africa region.

There is close interaction with the LGA system. With increasing population pressure, the LGA system tends to evolve into mixed systems, mainly MRA, because of the greater caloric efficiency of cropping vis-à-vis ruminant production when land becomes scarce.

The outlook for this system is relatively similar to that for the LGA system. The resource base puts a clear ceiling on agricultural intensification. Low and variable response to inputs makes their use financially risky. Population growth in this setting is contributing to the overexploitation of the natural resource base, as traditional property rights cannot cope with the growing demands. Alternative development strategies and the reduction of population pressure on the resource base are key elements for the sustainable development of these regions.

Irrigated mixed-farming systems

Temperate zones and tropical highlands mixed system (MIT). This system belongs to the group of land-based mixed systems of temperate and tropical highland regions. It is found particularly in the Mediterranean region (Portugal, Italy, Greece, Albania, Bulgaria) and in the Far East (the Democratic People's Republic of Korea, the Republic of Korea, Japan and parts of China), where plant growth is limited both by low temperatures in the cold season and reduced moisture availability during the vegetation period. The system's importance in tropical highlands is negligible.

Meat, milk and wool, the main outputs of this system, are mainly produced for the market. Manure is an issue only where animals are stabled, at least for certain periods of the day or the year.

About 10 percent of the global population lives in regions where this system is dominant. A large share belongs to developed countries with relatively high income levels and where agricultural trade is important.

This system is clearly associated with very intensive agriculture in temperate regions with a high population density. With the outcome of the General Agreement on Tariffs and Trade (GATT) negotiations, it can be expected that these systems will be less and less viable, having to compete with more efficient rain-fed systems producing the same commodities.

The expansion of international trade, and particularly the incorporation of southern European countries into the KU, has led to an increase in intensive production systems for off-season vegetables and fruits on the best irrigated land. The integration with livestock has been reduced, with ruminant grazing systems declining in absolute terms and being concentrated on the marginal sites.

Humid and subhumid tropics and subtropics mixed system (MIH). This is a mixed system in tropical and subtropical regions with growing seasons of more than 180 days, and in which the irrigation of crops is significant.

The MIH system is particularly important in Asia. High population densities require intensive crop production, and the irrigation of rice makes it possible to obtain more than two crops per year, even under conditions of very seasonal rainfall, substantially reducing yield variability as compared with the yield of upland rice or other rain-fed crops. In the past, animal production has been closely linked to the animal traction issue.

MIH systems throughout the world produce 13 million tonnes of pork (18 percent of global production), more than any other land-based tropical system. Among the tropical and subtropical systems, the MIH system is the one related to the largest population group, 990 million people, 97 percent of which are in Asia. Increasing labour productivity and relative affluence of farmers in this system are reflected in the more frequent use of tractors for cultivation. Manure is recycled on the fields. Ducks do well in this environment, as do pigs and poultry, which thrive on abundant crop residues. In addition, since large ruminants, such as buffaloes and, to a lesser extent, cattle, have little association with draught and transport, their output will be increased milk and meat for the market. Animals and intensive crop production in this ecological zone are an illustration of a successful and sustainable agricultural production system (Devendra, 1995).

Competition for urban markets for livestock products is the main form of interaction with the landless monogastric system, both domestically and globally, through international trade.

Arid and semi-arid tropics and subtropics mixed system (MIA). This is a mixed system of arid and semiarid regions, in which irrigation makes year-round intensive crop production feasible. It is found in the Near East, South Asia, North Africa, western United States and Mexico.

Typical cases are alfalfa/maize-based intensive dairy systems in California, Israel and Mexico; small-scale buffalo milk production in Pakistan; and animal traction-based cash-crop production in Egypt and Afghanistan. Cattle and buffaloes for milk and animal traction are the main ruminant resources, although sheep and goats are important where marginal rangelands are available in addition to irrigated land. In the MIA system, pigs are kept only in the Far East; they are virtually non-existent in West Asia and North Africa, largely for cultural reasons (Islamic and Jewish religions). The main introduced breeds are dairy cattle to supply milk to large urban centres. Under good management conditions, intensive dairy schemes have been quite successful in hot but dry environments. Some of the world's highest lactation yields are achieved in the MIA system in Israel and California. The traditional smallholder MIA system in Asia relies heavily on buffaloes for milk production.

In the traditional MIA system, irrigated crop production is the main source of income, with livestock playing a very secondary role. This is generally reflected in rather extensive management of livestock enterprises. The MIA system is predominant in regions that are home to over 750 million people, two-thirds of them in Asia and one-third in West Asia and North Africa.

The main interaction with other systems occurs through the international market, particularly for milk and dairy products.

The MIA system makes an important contribution to food availability and employment in semi-arid and arid regions. Irrigation allows increased fodder production as a by-product or part of crop rotation, which reduces the feed deficit. The improved feed base and utilization promotes intensification and commercialization of livestock production, especially in areas with good market access.

Conclusions

Globally, mixed-farming systems contribute the largest share (53.9 percent) of total meat production, followed by landless systems (36.8 percent).

Land-based systems still provide a large share of the total livestock output: 88.5 percent of beef and veal, 61 percent of pork and 26 percent of poultry, representing 60 percent of the total of all three meats. Globally, pork is the most important meat source (72 million tonnes), followed by beef and veal (53 million tonnes) and poultry (43 million tonnes). Among land-based systems, specialized grazing systems only contribute 23.5 percent of the ruminant meat output and 7.9 percent of all milk output; the vast majority is provided by mixed systems. It is expected that the importance of mixed systems as suppliers of livestock products will continue to grow in the future.

The relative importance of different production systems and animal species varies markedly across the geographic regions of the world. Grazing systems are more important in Central and South America, with its low population density and relatively high degree of urbanization, and where cattle are the most important livestock species. Africa has vast livestock resources in semi-arid and arid regions, where small ruminants play an important role. More than 90 percent of the world stock of buffaloes is concentrated in Asia, and in the Far East pigs have become a very important source of red meat. Asia's livestock are mainly found in mixed systems.

The MRT system is by far the largest. Globally it represents 41 percent of the arable land, 21 percent of the cattle population, 18 percent of sheep and goat stocks and 37 percent of dairy cattle stocks. In terms of output, its importance is even greater.

In comparing livestock resource availability indices among systems, within systems and across countries, a very wide range becomes evident in terms of resource endowment per inhabitant. Developed countries tend to be substantially better endowed with land and livestock per inhabitant. Similarly, wide differences in production intensity can be observed.

Intensity levels of the world's livestock production systems seem to be converging, though starting from very different levels. On the one hand, the very intensive systems of developed countries are facing a series of environmental problems. Furthermore, intensity levels are frequently linked to price-support policies. Both declining price support and increasing environmental regulations are inducing lower levels of intensity in this part of the world.

In developing countries, on the other hand, population growth and the rising per caput income in many areas are increasing livestock product demand. Given the fact that horizontal expansion is no longer a viable option for most countries, incentives for intensification are growing. In meat production, the landless systems are by far the fastest growing, followed by mixed-farming systems, with only marginal growth rates for the grazing systems. On the contrary, the trend towards deintensification triggered by the removal of subsidies has led to higher growth rates of milk production from grazing systems compared with mixed-fanning systems.

The limitations of the study summarized in this paper are many. Statistical reports do not present information by production systems, but rather by commodities, resources, etc. This required that links, particularly with the land base, crops, etc., had to be made using simple decision rules on which the classification scheme presented here is based.

These problems were compounded since national data tend to mask very important differences within countries. To a certain extent, this problem was circumvented by obtaining subnational data for the major countries and allocating it to ecological zones.

Landless systems presented similar problems as they are not reported separately in most national statistics. Qualified informants were used for landless ruminant systems. A simple mathematical model linking landless pig and poultry production to urbanization and gross domestic product per caput was developed for monogastric systems. Clearly, these aspects merit refinement should better data become available.

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