by L.'t Mannetje
Food production in some tropical regions has risen dramatically during the last two decades as a result of the green revolution, which consisted of intensified production with increased inputs, such as, fertilisers, improved cultivars and crop protection. The tropical pasture revolution, hailed in the 1960's, has also resulted in an increased potential for producing livestock products. However, production improvements have been less obvious than in the crop sector. This can be attributed to many factors, notably:
there is both a greater need and market for staple foods, such as rice, and cash crops than for food of animal origin,
livestock production is usually carried out in drier areas and on poorer soils, and
in many countries animal products are regarded as luxury rather than staple food items.
AVAILABLE TECHNOLOGY AND ITS APPLICATION
Tropical pasture technology aims at improving animal production through the judicious use of inputs according to the prevailing economic and social conditions effecting the production system.
Forage production can be improved by establishing a) grass pastures requiring fertilization with NPK, b) grass-legume mixtures, c) or oversowing legumes into existing pastures, d) monocultures of legumes (protein banks) and e) fodder crops. The use of fertilisers on legume based pastures would consist primarily of Phosphorus (P) and rarely Potassium (K) plus trace elements. For intensive production systems on poor soils, fertilization would materially increase both the yield and persistence of pastures and would provide a good return on investments. Grasses are, however, more difficult to establish and are less persistent without fertiliser (particularly N) than legumes, although some legumes will not persist on poor soils without P and trace element supplementation. However, in many situations fertilization is not practical because of the low return from animal products, in such cases legumes such as Stylosanthes species can introduced which will produce even under low fertility. How the forage will be utilized (grazing or cut-and-carry) is also important. With grazing nutrients are returned, albeit very unevenly, but this is rarely the case with cut-and-carry systems where the nutrients are removed along with the forage and dung (and urine) is used for other purposes (fuel or manure). Repeatedly cutting forages rapidly depletes soil fertility and fertilization is necessary to sustain production.
Forage production is not dependent on pastures and forage crops alone and crop residues can make an important contribution in integrated crop/forage production systems. Two examples of the latter are the integration of livestock under tree crops (Reynolds, 1988) and alley farming (Sumberg and Atta-Krah, 1988).
The most appropriate method of pasture improvement depends on the intensity and the objectives of the production system. Dairy production for the liquid milk market, with assured income and high requirements for quality feed, can justify more intensive production methods than say beef production in remote regions which rely on uncertain markets for low quality beef. The dairy farmer is more likely to base production on intensive, fertilized grasses or grass/legume mixtures; whereas the beef producer might consider, if anything, oversowing legumes into native pastures without fertilisation.
Numerous selected grass and legume varieties have become available since the 1960's for all tropical and subtropical regions with the exception of the semi-arid and arid zones (Henzell and 't Mannetje, 1980; 't Mannetje, 1984). Appendix 1 lists the main grasses and legumes for different climatic zones as defined by Troll (1966):
tropical rainy climates with 12 to 9.5 humid months (Zone V1)
tropical humid-summer climates with 9.5 to 7 humid months (V2)
wet and dry tropical climates with 7 to 4.5 humid months (V3)
permanently humid climates with hot summers and maximum rainfall in the summer (IV7)
climates with 9 to 6 humid summer months and dry winters (IV4)
The main requirements of forage species are that they are adapted to the prevailing climatic and soil conditions, tolerant of grazing, disease and pest resistant, free of harmful constituents (non-toxic) and tolerant of low fertility. It is not possible to find species to which all these requirements apply, however, management can make up for species' shortcomings. For example, legumes which have a low grazing tolerance could be replaced by those that do posses it or grazed intermittently. Another example is the mimosine content of Leucaena leucocephala, which need not be a problem to animal health so long as the animal's diet does not exceed 30 % of the diet for more than six months. Alternatively, it is also possible to infuse the rumen of susceptible animals with micro-flora which can break down the toxic derivative of mimosine (DHP) (Jones and Metgarrity, 1986). Not all species need to be tolerant to low fertility because fertilizers can be used in certain production systems.
THE APPLICATION OF PASTURE TECHNOLOGY
The decision to improve pastures in existing farm systems is governed by the following conditions:
the need for improved animal production
the value and marketability of animal products
the motivation of farmers
land tenure, and
the availability of resources
The need for improved animal production.
Animal proteins are an important component in the human diet and in most developing countries there is a need for both more and better quality food. Ruminants are able to produce food, especially proteins, from land which would otherwise be of little use for food production.
When comparing the distribution of people, farm animals and the production of meat and milk between temperate (mostly developed) and tropical (mostly developing) countries, it is clear that tropical countries lag behind (Table 1). Although far more animals are kept in the tropics, the production of meat and milk is only 36% and 18%, respectively, of the total world production. This is due to inadequate nutrition, health care and management of the animals. Therefore, if animal production is to be increased, not only for meat and milk, but also for draught purposes and manure, then the feed supply must be improved. Since forages and crop residues are the primary feed sources, it is evident that both production and quality of forage needs to be increased.
An increasing demand for forages will also result from a) the increase in the demand for food as human populations continue to expand, and b) increasing purchasing power which leads to a greater propensity to buy animal products.
The need for pasture improvement can be shown by the low levels of animal production in both developed and underdeveloped tropical regions. This will be illustrated by examples from northern Australia and Africa.
Table 1. Distribution of farm animals, people, production of meat and milk (source FAO Yearbooks)
|% in developed countries||% in developing countries|
Northern Australia: In northern Australia with its sub-tropical to tropical climate, large scale beef ranching is practised on unimproved native pastures. In the Northern Territory the average property size is 2500 km2, the stocking rate is 6–8 beef animals per km2 and the main emphasis is on breeding. Branding (weaning) percentages range between 40–60%, offtake ranges between 22–26% for animals aged between 3 to 4.5 years old and with dressed carcass weights between 225–360 kg. Most of the meat produced is exported as manufacturing beef ('t Mannetje, 1982).
By oversowing a legume into native pasture, or by establishing grass-legume pastures, substantial improvements in animal production can be obtained. Edye and Gillard (1985) reported that by oversowing Stylosanthes hamata cv. Verano into the native pasture along with the use of phosphate fertilizer, the carrying capacity could be increased up to ten-fold and cattle fattened in about half the time when compared with native pastures.
In an experiment at the Narayen Research Station in south-east Queensland three herds of breeding cows were used to measure beef production on unimproved native pasture at a stocking rate of 0.17 cows/ha and sown grass-legume pasture with superphosphate at stocking rates of 0.50 and 0.68 cows/ha over a period of ten years (Coates and 't Mannetje 1990). A summary of the results is given in Table 2.
On both treatments conception and calving rates were high, but the long term average calving percentage of 70–75% for commercial beef production in the region on native pastures is also considerably higher than the Queensland state average (c. 60 %). All production parameters on sown pasture were higher than on native pasture. The results are most strikingly presented in terms of production per ha. Sown pasture produced 4.5 times more weight of calves per ha than native pasture and they were 20 % heavier.
Africa: In Africa most livestock are kept by smallholders for numerous reasons, the most important being milk and manure production, although traction and beef production may be locally important. Also throughout Africa cattle act as capital reserves and offer security of income or survival. Animal husbandry practices differ greatly between traditionally kept herds and commercial ranching, with corresponding differences in production, which can largely be attributed to disease control and animal husbandry (Table 3). Birth weight and liveweight gains in indigenous cattle are low for both production systems, but particularly for traditional systems where the sale of animals for beef is not the primary objective.
Table 2. Mean conception and calving rates, average daily gain of calves, weaning weight (7 months of age), weight of calf per cow mated and weight of calf per ha on unimproved native pasture and sown grass-legume pasture in south-east Queensland.
|Native pasture||Grass-legume pasture|
|Conception rate||84 %||90 %|
|calving rate||79 %||82 %|
|Average daily gain calves||0.78 kg||0.92 kg|
|Weaning weight||200 kg||241 kg|
|Weight of calf/cow mated||155 kg||199 kg|
|Weight of calf/ha||26 kg||118 kg|
The value and marketability of animal products
Nomadic herdsmen and small farmers in Africa are usually subsistence producers with limited access to markets. It is unlikely that these producers will have the necessary inputs required for pasture improvement.
Large scale producers are by definition dependent on a market for their produce. Price in the local, national and international markets will be determined by supply and demand. Local demand will, in turn, depend on consumers' incomes, therefore, in most developing countries producer prices for animal products tend to be low and there is little incentive to invest in pasture improvement.
Table 3. Calving rates, birth, weaning and live weights of different breeds and production systems in Africa (Brumby and Trail 1986).
|Weight (kg)||4 yrs|
The motivation of farmers
An important consideration of a producer contemplating pasture improvement is the cost and the expected return on investment. Costs are high and it depends on the financial situation of the farm whether it would be attractive to apply the technology. Although, eventually, a high return may be achieved, during the first few years after pasture improvement there will be a negative cash flow (Wicksteed, 1986). Not all farmers are in a position to carry this and credit facilities are not always available. There is also a risk involved that the improvement may fail, or that beef prices will decrease.
D.B. Coates (pers. comm.) listed as the main reasons for the present interest in pasture development based on legumes in Queensland (Gramshaw and Walker 1988) as:
Land tenure can be a severe limiting factor to pasture improvement. If the producer does not have security of tenure then it is unlikely that he will be inclined to invest money into long-term pasture improvement. Most grazing lands in Africa are open to common grazing by privately owned herds. This system works well with low human population pressures and therefore low animal numbers in a region. However, as human and animal population increase so does the pressure on the land and, since individuals are not responsible for the control of the grazing or for the maintenance of the land, everybody tries to maximise their return from the communal resource. This leads to severe overgrazing, low productivity and danger of soil erosion. When land is owned or leased by the producer, there is the possibility of matching stocking rates with the carrying capacities in order to maintain and improve grazing and to replenish fertility. The chance of achieving a sustainable production system is less with communal than with privately owned grazing land.
The availability of resources and knowledge.
Before pasture improvement can be undertaken, there has to be an infrastructure for the distribution of inputs, such as, seed and fertilizers. In many regions there is no seed production or a seed trade. Pasture improvement is further constrained by the lack of finance and of knowledge by the farmers and the extension service. It is therefore necessary to promote the extension of pasture improvement practices, to encourage the development of seed production and to educate bankers on the possibilities of pasture improvement.
OPPORTUNITIES FOR FORAGE PRODUCTION IMPROVEMENT IN DIFFERENT LIVESTOCK SYSTEMS
Forage production systems.
Based on a classification of Perkins et al. (1986) for Indonesia and modified by 't Mannetje and Jones (1989) for south-east Asia; a number of distinct forage production systems can be distinguished on a global scale (Table 4).
Extensive permanent grasslands are unimproved native pastures (rangelands), which receive no inputs such as irrigation or fertilizer. On privately owned or controlled land, management consists of controlled grazing, burning and the control of trees and shrubs. Whereas communally grazing, which includes the savannas in Africa as well as road/canal sides and open forests, there are no forms of control and there is frequently overgrazing.
Semi-intensive forage production systems have inputs, such as, fertilizer and weeding also irrigation (primarily applied to the main cash crop) which also benefits associated forage production.
Intensive forage production systems have inputs applied for the sole purpose of forage production.
The ability to improve forage production is a function of climate, soils and the production system. Water and nutrients are physical prerequisites. Under natural conditions improved forage production is possible where rainfall is in excess of 650 mm/yr with a dry period not exceeding six months. In drier regions irrigation can be used. The existing production system, particularly the type of land tenure, also determines whether forage production can be improved and the type of inputs that can be realised.
Livestock production systems.
Livestock production takes place in three main systems:
Pastoralism: The main feature of this system is that the producers are entirely dependent on livestock for all their needs, there is no supplementary food crop production. There are three contrasting systems within pastoralism, viz. nomadism, ranching and commercial dairying.
Nomadism: is the way of life of indigenous peoples in arid and semi-arid regions who have no permanent place of settlement and move with all their livestock and possessions in search of water and forage. Regions in which nomadism is practised are characterised by an environment where the primary productivity which is so low that people cannot avail themselves of their feed requirements within a day's reach of a permanent settlement. The animals provide blood, milk, meat and income from the sale of surplus stock. The main source of animal feed is derived from extensive, unimproved, communally grazed grasslands. Post-harvest nomads are allowed to graze their animals on stubbles to consume crop residues and weeds and to deposit manure. However, nowadays, most crop farmers own livestock themselves and nomads are becoming less welcome. There are no real means to improve the feed base since the land is in communal resource.
Ranching: In Australia, Africa and South America ranching is undertaken in the sub-humid, semi-arid and arid regions to produce beef and wool. Properties are often large (1,000 ha to thousands of km2), particularly in semi-arid and arid regions and may carry from 500 to several (20–50) thousand cattle or sheep and are usually either on long term leases or freehold. Production is extensive, with low inputs and corresponding low productivity both per animal and per unit area. The main feed supply are extensive unimproved native grasslands. However, ranching has the potential for sustained use of such grazing lands plus the opportunity to improve part of it by either establishing grass-legume pastures, by oversowing with a legume or by establishing a protein or fodder bank. The area for improved forage production will usually be small compared to the total area of the property and a judicious management system is necessary to optimise animal production and to increase the sustainability of the production system (Rickert and Winter, 1980; Coates and 't Mannetje, 1990). The extensive unimproved grassland can be used as the basic forage resource, with supplementation from small improved areas of grass-legume mixtures, protein banks or fodder crops for special classes of livestock (breeders, steers for fattening) at times of nutritional stress. Larger areas of legumeoversown grasslands can be used to either increase the overall carrying capacity or to reduce the area of land required for the existing herd (Edye and Gillard, 1985).
The reasons for improving forage production are to supplement the basic forage resource with more and/or better quality feed for various purposes, which include:
to reduce mortalities which occur during dry times and where extra feed from improved pastures, protein banks or fodder crops can be used either for the whole herd to provide (near) maintenance rations or for a nucleus of animals to ensure continuation of the herd;
to increase the conception and calving rates where an increasing plane of nutrition leading up to conception can increase fertility and reduce calving intervals;
to keep the herd on a smaller area of land during the whole year, or part of the year (by oversowing part of the area) in order to reduce mustering costs; and
to fatten younger stock on improved pasture or on feed from fodder crops or protein banks.
Table 4. Forage production systems used in different livestock production systems.
|FORAGE PRODUCTION SYSTEM||M||G||G||P||V|
|EXTENSIVE PERMANENT GRASSLAND|
|SEMI-INTENSIVE PERMANENT FORAGES|
understorey tree crops
forage from shade trees
forage in alley cropping
edges of crop fields
|SEMI-INTENSIVE ANNUAL FORAGES|
after harvest crop
|INTENSIVE PERMANENT FORAGES|
|INTENSIVE SHORT-TERM FORAGES|
Commercial milk production: is practised in regions of better rainfall and with access to markets, mostly near to urban centres. In humid regions dairy farms use improved pastures consisting of tropical species whilst in subtropical regions winter pastures consisting of irrigated temperate species may be appropriate (Stillman et al., 1984). On tropical pastures milk production never exceeds 15 kg milk/cow/day without the use of concentrates and usually it is less than 10 kg; whilst on unimproved grasslands production is very low (3–5 kg milk/cow/day) (Stobbs and Thompson, 1975).
Livestock-crop systems: In regions with better rainfall, instead of nomadism people obtain their livelihood from a combination of livestock rearing and cropping. In these transhumance or seminomadic systems people have permanent settlements with some food cropping on better soils and a few animals for susistence, but with the main herd being moved to distant grazing lands in search of water and forage and returning to the settlements in the wet season. The main feed is obtained from extensive communally grazed grasslands yet there are opportunities to establish protein banks and fodder crops on privately owned crop land which also supply crop residues.
Crop-livestock systems: These occur in regions with relatively high rainfall or a reliable wet season. The main activity is crop production although there may also be a high domestic livestock population. In the humid tropics rice and, in drier regions, other cereals such as millet, sorghum or maize are the main food crops. Because of high human population densities there is often a land shortage and farms are usually small therefore crop production is intensive. Animals (cattle and buffaloes) are needed for draught power, extra income, food and dung which may be used as either a fertiliser or fuel. The forage for the animals is obtained from waste land, road sides or canal banks. In some countries (e.g. Malaysia) there are publicly owned grazing reserves or areas of abandoned crop land, often covered in weed grasses such as Imperata cylindrica, are used as grazing lands (as in The Philippines and Indonesia). In west Africa grazing land is often fallow crop land.
Tree crop plantations offer great opportunities for the production of forage, particularly under mature coconuts and newly planted oilpalm before the canopy is completely closed (Reynolds, 1988). In Indonesia coffee plants are shaded by Leucaena leucocephala and pruned branches provide fuelwood and leaves for animal feed. Similarly, alley farming also offers opportunities for livestock feed production (Sumberg and Atta-Krah, 1988). Crop residues are important as forage and crop by-products are available as concentrate feed.
There are few other opportunities for improving forage production because of the lack of land, however, leguminous trees and shrubs can be used as living fences or as single trees in back yards. Depending on the need for land for food or cash crops and the price of livestock products, it may be profitable to grow fodder crops.
Table 4 shows which forage production systems can be used in the different livestock systems. This indicates clearly that commercial dairying and crop-livestock systems have the greatest range of forage production systems at their disposal and that nomadism has the least options.
In each production system there is a basic resource which provides the bulk of the forage. In nomadic and ranching systems, as well as in livestock-crop systems, the unimproved extensive grasslands, which are too poor for cropping, provide the basic forage although yields are low. There is no point in fertilising native vegetation since the response will not repay the cost of the fertiliser (Henzell and 't Mannetje, 1980). On the other hand, there is little export of nutrients from extensively grazed pastures and management must aim at sustainability through controlled grazing, burning and control of woody weeds. Extensive grasslands are, however, the last major land resource in many regions of the world and with increasing population pressure these grasslands are being converted into marginal crop lands - such areas are liable to nutrient exhaustion and erosion. Controlled land use will remain an impossibility whilst there are communal rights of access because it is not in any individual's interest to reduce his use on the land if others continue or even increased their usage. The only solutions are controlled use and management of the grazing lands either instigated by the community using it or by government and population growth control.
Low cost forage improvement technology based on legumes with minimal fertiliser input is available. However, in developing countries serious constraints include communal land use, the low value of animal products and the lack of knowledge and resources, including finance. Integrated systems of crop and forage production and integrated use of forage production systems need to be further developed. The extensive unimproved grasslands (rangelands) are a precious resource which is under pressure of overuse and conversion to crop land.
Appendix 1. Selected grasses and legumes for pasture improvement in four climatic regions as defined by Troll (1966) ('t Mannetje and Jones 1989)
|GRASSES||V1 & V2||V3||IV7||IV4|
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