by T.R. Preston
Technologies developed in the temperate countries for production of milk and beef as independent specialized systems are not appropriate to the needs of developing nations in the tropics.
Instead, a multi-purpose approach based on combined production of milk, beef, fuel and fertilizer in a single integrated unit could improve the level of nutrition of the population as a whole and contribute to savings of foreign exchange.
The objectives in developing animal production systems in the tropics embrace a number of factors. These can be listed as follows:
T.R. Preston is with the Centre for Livestock Research (Centro de Investigación y Experimentación Ganadera), Chetumal, Mexico.
This is a long list, but it is important to take account of all of these factors when planning a livestock development strategy. There have been too many examples of development which set out to satisfy only one or two of these objectives, with the result that the overall gain to the country concerned has often been minimal.
An example of unbalanced development is provided by Taiwan (China). In the past 15 years, livestock development has proceeded at a rapid rate to the point of self-sufficiency in pig and poultry products. Yet this self-sufficiency has only been brought about by a corresponding increase in imports of cereal grains and protein meals, from negligible quantities in 1962 to some 1 million tons of grain and 600 000 tons of soybean meal (worth about U.S.$ 300 million) in 1971. Livestock development in Trinidad and Tobago has had a similar history. As efforts were concentrated on the development of nonruminants at the expense of increasing imports of raw materials (mainly feeds), the net effect of the livestock development programme on the overall balance of payments was found to be close to zero (Cropper, 1974).
Because so many mistakes have been made in the past, it is all the more important to weigh the various alternatives before deciding on a blueprint for livestock development in the tropics. An integrated approach is needed because errors have frequently been made when development is pursued on a piecemeal basis. Even in 1976 it was still possible to read in reports from international agencies statements such as “This proposal refers only to beef production since the development of a milk industry was the subject of an independent study,” or “No plans are contemplated at this stage for the utilization of the male calves.” The latter example is drawn from an investment plan for setting up a large-scale milk production scheme in an African country.
Of course, the most fundamental question is: Why has livestock development been so retarded in the tropics, and why has it not kept pace with that in the temperate countries? Is it because the tropics are not really suitable for livestock, or are there more basic reasons underlying the apparent lack of progress in animal production in these regions?
This article attempts to show that the tropics, far from being unsuitable for livestock development, offer a potential for productivity per unit area and an economic viability which far surpass the present or even future prospects of the temperate countries. The thesis is that the retarded development of livestock in the tropics reflects not lack of potential, but simply the fact that the research inputs required to develop an appropriate technology for these areas have never been provided on an adequate scale. The emphasis is on the word “appropriate” because, as will be made clear in this article, the nature of the feeds, the type of cattle and the management systems all differ materially from those which have been developed in the temperate world.
The need for planning
The first step in working out an appropriate technology for livestock development in the tropics is planning. Decisions are required as to the most appropriate animal species, feed resources and management systems.
Choice of animal species. Of particular relevance, when it comes to selecting an animal species, is the fact that in most tropical regions there may be quantitative, and almost certainly qualitative, shortages in the human diet. Competition between animals and humans for the same basic nutrients then poses a problem in resource utilization that must be taken into account.
For planning purposes, domesticated animals can be divided into the two broad categories of ruminants and nonruminants. The latter have the same digestive system (and therefore similar nutrient requirements) as humans. The former possess an additional compartment in the stomach - the rumen - through which all solid foods pass, and where predigestion takes place by anaerobic fermentation. Because of this latter feature, the ruminant has the capacity to both degrade (digest) and use for synthetic purposes substances which are not usable by man. In this sense, they need not compete for available feed supplies. If they do compete, it is probably a result of bad planning and/or the application of “inappropriate” technology.
In marked contrast with the ruminant, pigs and poultry must nearly always compete with the human population for basic feed resources, especially cereal grains.
In nutritional terms, the special virtue of the synthesizing capacity of rumen microorganisms is their ability to transform inorganic ammonia nitrogen into microbial protein of excellent biological value - protein which subsequently becomes available to the host animal for formation of milk, meat and wool. The degrading properties of rumen microorganisms are used to advantage on feeds containing structural carbohydrates, chiefly cellulose and related compounds, for which the non-ruminant digestive system possesses no enzymes.
These two characteristics enable the ruminant to occupy a different ecological niche in comparison with the human; hence instead of competition, there can be true symbiosis between the two species. Thus, by transforming inorganic nitrogen and carbohydrate into animal protein (milk meat), the ruminant will enable humans to live adequately in conditions where otherwise they would suffer protein deficiency.
The disadvantage of making the ruminant depend on simple nitrogen sources such as ammonia is that this in turn exerts a certain constraint on its rate of production. The efficiency of anaerobic fermentation in the rumen is relatively low, since there is only partial oxidation of the energetic components (as far as the volatile fatty acids). One result of this is that the amount of microbial protein that can be synthesized is determined by the amount of fermentable carbohydrate that is consumed. The second factor is that even at maximum voluntary intake levels, the actual amount of carbohydrate available for fermentation is not sufficient to allow the production of all the microbial protein needed to sustain high levels of animal productivity.
The importance of these relationships is illustrated in the graph, which shows the overall amino acid requirements of ruminants (expressed as daily retention of nitrogen), according to their productive state. The contribution of microbial protein to these requirements (as indicated by the dotted line) approaches adequacy only for late growth, early and mid-pregnancy and mid- and late lactation. Both fast growth in young animals and early lactation represent critical points when considerable supplementation with performed protein will be required.
Glucose is another nutrient which may limit production rate and play a critical role when emphasis is on maximizing rumen function. The glucose needs of ruminants were once thought to be so small that they could be ignored. But it is now known that these requirements are sometimes very high, and that under certain feeding regimes (low protein/low starch diets) they are not easily met (Leng and Preston, 1976).
It appears that the pattern of glucose requirements is also related to productive rate and closely parallels the needs for amino acids (see graph). The significance of the relationship between productive rate and requirements for amino acids and glucose lies in the high cost of both of these nutrients and/or their precursors relative to the basal energy and non-protein nitrogen components of the diet. Moreover, sources of amino acids (mainly as preformed protein) are generally to be found in feeds which are usable by humans. Known glucose sources (chiefly starch) fall into the same category.
This means that the degree to which ruminants are non-competitive with humans for feed supplies will vary inversely with their productive rate. While it is to be expected that increasing knowledge of rumen function on low protein/low starch diets will eventually allow these constraints to be lifted, the solution in the short term will be to avoid the critical peaks in the production cycle when supplement needs are highest. Ways of achieving this through manipulation of the production system are discussed later.
Feed resources. If it is concluded that the ruminant is the preferred species for livestock development in the tropical world, then the feeds that are likely to be most appropriate will be those which are readily fermentable. They do not need to be rich in natural protein because of the ruminant's ability to utilize inorganic nitrogen.
These characteristics of “appropriate” feeds are of particular relevance in the tropics, because in these regions the crops which are highly productive and best adapted are those rich in fermentable carbohydrates, e.g. sugarcane, sweet potato, cassava and bananas.
Another important characteristic of feed crops for tropical regions is that they should be perennial. This is because the nature of the climate often makes annual cropping extremely hazardous in terms of seed bed preparation, sowing date and weed control. Annual crops are also much more prone to erosion. When these additional factors are taken into account, the virtues of sugarcane are particularly apparent, as it can be harvested from the same sowing for up to 10 years if necessary.
The final reckoning must be in terms of energy capture and utilization. The high energy cost of intensive temperate country agriculture has been highlighted by Blaxter (1974), with the final balance being negative, i.e. energy has to be introduced into the system to supplement that obtained by photosynthesis. An energy balance sheet has yet to be drawn up for a sugarcane feeding system. But what is clear is that this crop probably captures more solar energy per land area unit than any other; moreover, the possibilities for recovering fuel as biogas by fermentation of the undigested fractions will almost certainly result in the overall energy balance being positive.
So one answer to the question as to whether or not the tropics are appropriate for livestock production is that the potential of the sugarcane crop in the tropics far exceeds that of crops in temperate regions. The fact that this has been hitherto unrecognized reveals neglect of the concept of appropriate technology and how to develop it. Perhaps if there had been less emphasis on the transfer of inappropriate temperate country technology and more attention had been paid to research to develop the real resources of the tropics, livestock production in these regions would not be in its present backward state.
Pattern of requirements for amino acids and glucose in relation to phase of production 1
1 Amino acid requirements are expressed as N retained per unit digestible organic matter (Ørskov, 1970). Glucose requirements are expressed as the rate of synthesis of glucose per unit body weight (Leng, 1975).
Of course, it can be argued that all sugarcane is needed for sucrose production, and that this is a staple in the human diet. But, even leaving aside the nutritional significance (or otherwise) of sucrose in the human diet, direct competition will exist only where a sugar industry has already been established. However, even in such a situation, the mere by-products of sucrose extraction (molasses, cane tops, bagasse and filter mud) are enough to form the basis of a cattle industry. For example, Mauritius, which produces nearly one ton of sugar per inhabitant, plans to meet its milk and beef requirements from cattle fed sugarcane by-products (Preston, 1974).
The role of sugarcane per se as a cattle feed is in areas where there is no existing sugar industry. In the greater part of the humid tropics the possibilities for growing sugarcane are almost unlimited.
Management systems. It is commonly believed that there are only two ways of managing cattle: for milk production or for beef production. This belief is not only taught in animal husbandry textbooks, but it is generally claimed to be the most efficient way of supplying our needs for milk and beef. But it must be remembered that this philosophy of milk on the one hand and beef on the other reflects mainly experiences in the temperate regions of the world. It does not follow that today in the tropics (and perhaps even in temperate countries) such a separation and specialization is the most appropriate procedure.
One reason for re-examining this approach relates to the constraints on rate of production which arise if maximum reliance is put on rumen function, i.e. feeding cattle in a way that will not create competition with the human population.
A system of specialist milk production implies a lactation yield of 4 000 to 5 000 litres and the artificial rearing of the calf to permit maximum liquid milk sales. These are unlikely to be achieved under conditions where the diet is composed primarily of soluble carbohydrates and inorganic nitrogen. Thus specialist milk production is not an appropriate system for the tropics, unless the main items of feed are to be imported from the cereal-producing temperate countries. To accept that strategy, however, is to depart from the principal objective, namely the development of an appropriate technology based on the use of national resources. Superficially, this is the first indication that the tropics are not appropriate for efficient cattle production. Fortunately, however, this is only one side of the story. For beef is needed as well as milk, and the basis of a sound livestock strategy is to consider the two together.
Demand for beef and milk
The obvious starting point is the national requirement for beef and milk and the possibilities for export. Here it is necessary to differentiate between what might be consumed if purchasing power were not a limitation, and what is actually consumed by the population as a whole. For the purpose of this calculation, it is not necessary to estimate absolute figures, but rather the ratio between the two products. Also, as a general yardstick it is proposed to base this upon data from developed countries, on the assumption that this is what most developing countries aspire to when purchasing power is adequate. These theoretical demand figures are 50 kg carcass beef per year and half a litre (0.5 kg) of fresh milk equivalent daily.
The annual milk beef demand ratio represented by these consumption rates is 3.6:1. A specialized dairy cow (e.g. Friesian) giving 4 500 kg per lactation produces a calf which eventually ends up as beef, either as a culled female or a fattened bull or steer. Assuming the weight of carcass produced in either of these categories is 250 kg, the milk/beef production ratio is 18:1. Since the demand ratio is only 3.6:1, this means that if milk production is based on a specialist system, either beef must be imported to make up the deficit, or there should be a parallel specialist beef production industry.
The general policy in the developed countries has been to opt for the latter alternative. In countries such as the United States, Brazil, Argentina and Australia, such a policy may be acceptable because there are large areas of pasture land on which inexpensive ranching is feasible without recourse to supplementary feeding. In almost all other countries single-purpose beef production is a luxury operation which cannot be afforded.
Single-purpose Jersey cow and calf in Seychelles. Calf growth to weaning at 4 months was 800 g/day and lactation milk yield 1 700 kg.
Dual-purpose Creole cow and calf in Seychelles. Calf growth to weaning at 4 months was 1 kg/day and salable lactation milk yield was 1 600 kg.
The reasoning behind this argument is as follows: If the milk/beef demand ratio is 3.6:1 and the specialized dairy cow gives a production ratio of 18:1, then we need an additional four specialized beef cows for every dairy cow. But specialized beef cows, because of their low reproductive rate, are biologically and economically inefficient, particularly when there are no extensive grazing areas. Therefore, predicated on a philosophy of specialist milk and specialist beef, the greater the degree of self-sufficiency in both products, the less efficient the overall cattle industry becomes (since there are four inefficient beef cows for every efficient dairy cow), and the greater is the burden on the taxpayer in the end. As witness to this, the present government subsidy to the beef industry in the United Kingdom is almost $400 million. To achieve the desired milk/beef ratio without having to support an inefficient beef industry requires either the import of beef from countries which produce it more cheaply and which would be anxious to trade beef to pay for their own imports, or the restructuring of the cattle industry. For developing countries in the tropics with a rich agricultural potential, the latter course is more attractive.
Dual-purpose cattle. Such a restructuring involves the substitution of both specialized beef cattle and specialized dairy cattle by dual-purpose animals which produce milk and beef in accordance with demand. For a milk/beef demand ratio of 3.6:1, the specifications become a lactation yield of 1 500 kg in 300 days, and additional milk to suckle the calf throughout lactation to a weaning weight of 200 kg (at which point it can enter the fattening programme with minimal need for supplementary feeds).
In terms of milk alone, such a yield level may be viewed with derision by most cattle breeders as representing an unacceptable reversal of the technological clock. Nevertheless, there are a number of sound reasons why such a policy is particularly appropriate for the tropics, and for the developing countries in general:
Multi-purpose cattle. Cattle, in addition to producing milk and beef, can also help to alleviate the effects of the oil crisis.
When a forage crop such as sugarcane is consumed by cattle, some 40 percent in terms of dry weight is excreted as faeces and urine. This effluent contains undigested carbohydrate, the three mineral elements which make up standard fertilizers (nitrogen, phosphate and potash) and valuable trace elements.
If all of this effluent is collected and passed through a simple anaerobic fermenter, it is possible to produce biogas rich in methane that can be used as a source of fuel and, after suitable processing, of light and power. This process utilizes only part of the carbon, hydrogen and oxygen present in the effluent and leaves intact the mineral elements which can be recovered after the fermentation process and used for fertilizer.
Table 1 shows the fuel and fertilizer value of a 120-ton/ha crop of sugarcane after processing through cattle. At a power cost of $0.08/kwh, the fuel value is the equivalent of $1 835 (enough to supply the needs of three households), while the fertilizer recovery is equal to $544.
The economics of establishing and operating a multi-purpose cattle enterprise in the tropics using sugarcane as the basal feed resource are set out in Tables 2 and 3.
Table 1. Fuel and fertilizer value of a 120-ton/ha sugarcane crop1
|Output||Amount produced||Energy produced||Value|
|Biogas||23 276||32 290||41 835|
|Nitrogen||979 kg at $0.40/kg||392|
|Phosphate||145 kg at $0.52/kg||76|
|Potash||189 kg at $0.40/kg||76|
1 One cow unit (cow and weaner) eats 5.84 tons dry matter per year and excretes 2.34 tons of dry matter. A 120-ton/ha sugarcane crop feeds 7.06 cow units which excrete 16.5 tons of dry matter.
2 Biogas derived from manure containing 50 to 60% CH4
3 At 7 kwh/m3.
4 At power cost of $0.08/kwh.
In a multi-purpose cattle unit, each breeding cow gives 5 kg milk per day for a 300-day lactation and also rears her calf to a weaning weight of 210 kg. After weaning, the calf is fattened intensively at a growth rate of 0.85 kg daily to reach a slaughter weight of 400 kg at approximately 17 months of age. On a yearly basis we then have 365 mature cow days, 300 calf days and 210 fattening days.
The technical coefficients assumed to apply to this population are a 90 percent calving rate and an 80 percent weaning rate. The cost of establishing one hectare of sugarcane is estimated at $1 500 and it is assumed to have a productive life of five years. The price of a balanced 30 percent protein supplement is $250 per ton, urea is $150/ ton and minerals $100/ton. Milk sells ex-farm at $0.20 litre and beef at $0.80/ kg live weight. The value of the fertilizer elements in the effluent is estimated at $0.40/kg nitrogen, $0.52/kg phosphate and $0.40/kg potash. A unit of one breeding cow plus followers will produce 2.5 tons of dry matter as effluent per year, and from this is recovered 468 m3 of a mixture of methane/carbon dioxide with an overall fuel value equivalent to 3 270 kwh, valued at $0.08/kwh. All of the effluent is returned to the sugarcane (but in fact not all is required, and part could be used as fertilizer for vegetable crops).
Table 2. Technical coefficients for a multi-purpose cow unit (Holstein-zebu crosses) fed sugarcane
|Assumed calving rate||0.9|
|Assumed weaning rate||0.80|
|Salable milk||5 kg/day for 300 days|
|Calf growth to weaning||600 g/day|
|Weaning weight||200 kg|
|Growth from weaning to slaughter||850 g/day|
|Age at slaughter (400 kg)||17 months|
|Intakes and feed costs||Sugarcane||Urea||Protein supplement||Minerals|
|Calves to weaning||kg/day||8||0.08||0.3||0.03|
|Assumed total cost||U.S.$||26.29||145.00||4.40|
SOURCE: Centro Dominicano de Investigación Pecuaria con Caña de Azúcar, Dominican Republic.
The final economic analysis highlights the potential contribution to output made by all four products from the cattle enterprise. Obviously, the degree to which these potential outputs are converted into cash income and/ or personal benefits (particularly the fuel from effluent) will depend on the development of appropriate technology, supply of credit and marketing services.
But the intensity of production in terms of the limited land area needed to support one family, the almost certainly favourable overall energy balance and the minimum dependence on imports are all factors that make the concept relevant to the sociological and nutritional problems facing many developing countries.
Table 3. Costs and returns for multi-purpose cow units1
|Milk||1 350 litres at $0.20/litre||270||31|
|Beef||320 kg at $0.80/kg||256||30|
|Biogas||3 270 kwh at $0.08/kwh||262||30|
|Fertilizer||139 kg N|
21 kg P
27 kg K
|Land||0.14 ha2 at $240.00/ha||34|
|Cow||450 kg at $ 0.80/kg||360|
|Feed supplement (3 months)||58|
|Establishing sugarcane at $1 500/ha||210|
|Cane establishment depreciation3||43|
|Interest at 12%||103|
|Return to labour and management|
|Per cow unit||446|
|Per hectare||3 289|
NOTE: In the calculation on return to labour and management, the investments and inputs necessary for the production of biogas are not included.
1 Each unit includes 365 cow days, 300 calf days and 210 fattening days.
2 Assumes 120 tons cane/ha/yr.
3 Lasts 5 years.
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Cropper, J. 1974. Concentrate feeds for livestock in Trinidad and Tobago: an economic view of developments since 1960. In Proceedings of the Conference on Animal Feeds of Tropical and Subtropical Origin. London, Tropical Products Institute.
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