W. FERGUSON
Introduction
The fixed factors
The dynamic factors
Discussion
References
Subsequent papers in this section will deal with production performance. of trypanotolerant livestock. This review paper will therefore attempt to focus mainly on some of the wider issues which can be expected to bear heavily on the potential role of these animals in agricultural development.
Many of the major determinants are those which would influence the production attainment of any breed, trypanotolerant or otherwise. Paramount among these is the vegetative growth potential of the area in question.
As Jahnke (1974) concluded, the tsetse and trypanosomiasis problem must be viewed as a problem of land use. Few would argue with his assertion that the choice of economic policy for mitigating the impact of trypanosomiasis should vary according to the natural potential, the trypanosomiasis challenge and other characteristics of the area in question. It is therefore necessary at the outset to define the area in which production is envisaged and to examine its resource potential.
The next factor requiring clarification in determining potential for trypanotolerant livestock concerns the manner of utilization of the resource attributes. Farming systems in much of tsetse-infested Africa have entered the phase of rapid change. Being subject to so many technical, economic, social and political variables the precise rate at which changes in land-use practice will progress is difficult to predict for each of the thirty-eight tsetse-infested countries. However the direction of these changes can be discerned by recalling some of the key changes which have emerged in recent decades and some of the associated adjustments in research and development priorities which have resulted. Governments may influence the trends by ensuring the adequacy of price incentives and other supports, but it is the farmer who makes the ultimate decisions which shape the pattern of livestock development.
The factors which influence the potential of trypanotolerant livestock are divisible into two categories:
i) Those which tend to be relatively static or "fixed" over the medium-to-long term i.e. most of the biological factors such as climate, natural resource base and physiological attributes of breed; andii) those which are "dynamic" in that they may be subject to significant change over the short-to-medium term e.g. disease risk, management systems, production incentives, effectiveness of extension services, land tenurial adjustment and other socio-economic factors.
It is beyond the scope of this paper to examine all of these factors in detail. An attempt is made to concentrate on aspects which seem particularly relevant to the present stage of research on livestock productivity and trypanotolerance and ultimate development objectives,
Relevant resource attributes
It is assumed here that significant extension of trypanotolerant livestock beyond the areas of tsetse distribution is not currently envisaged.
Reference to the FAO Agro-Ecological Zones Project data (FAO, 1978) confirms that much of the land infested by tsetse (Fig. 1a) has, by African standards, relatively high agricultural potential. This is adequately confirmed by the positive correlation with suitability for growing cassava (Fig. 1b), sorghum (Fig. 1c) and maize (Fig. 1d) This is not to imply homogeneity of tsetse distribution or cropping potentials of course. As indicated by Jahnke (1974), detailed resource inventory and land-suitability classification would be necessary at a scale compatible with project planning. However, the aggregated information portrayed in the figures serves to illustrate that only three important tsetse areas are generally characterized by insufficient length of growing period for reliable rain-fed crop production. These are the Zambezi Valley, Somalia and the Okavango Delta in Botswana. Since they do not contain recognized populations of trypanotolerant livestock and are not encompassed in the ATLN as currently designed, they are not considered further here. This paper focusses mainly on the humid and sub-humid zones having a growing period in excess of 180 days and existing livestock populations identified as trypanotolerant.
Von Kaufmann (1986) and Bourn et al. (1986) have convincingly exposed as a fallacy the belief that the expansion of crop production involves a decline in ruminant livestock population in the higher rainfall areas. They have also indicated the high potential for both crop and livestock production in the sub-humid zone (180 to 270 days growing period). This zone, which occupies some 5 million km or 23% of Africa, has a lower population density than its neighbouring humid and semi-arid zones. Although subject to accelerating spontaneous colonization it still offers an important opportunity for timely and effective research and development contributions to agricultural and livestock production (von Kaufmann, 1986; Mohamed-Saleem 1986a).
Figure 1. Area of tsetse distribution and suitable agro-ecological zones for three major crops.
Fig. 1a
Fig. 1b
Fig. 1c
Fig. 1d
The relief, soils and vegetation of the sub-humid zone of West Africa have been the subject of review by ILCA (1979a). For purposes of indicating appropriate development directions it suffices to recall the following facts:
(a) it is the availability of nitrogen and not moisture which is the main factor limiting plant growth and animal nutrition in tropical grasslands with a growing season of 150 days or longer; and(b) pasture and forage legumes, with their well-known ability to convert atmospheric nitrogen into nitrates which can be used directly by other plants, can play a crucial role in achieving sustainable crop/livestock production systems.
Breed adaptation
Resistance to locally endemic diseases
By the middle of the present century the relative tolerance of N'Dama and West African Dwarf Shorthorn cattle to trypanosomiasis and the field indications that this was probably innate rather than acquired were well recognized, as was the need for fuller investigation of the nature and specificity of this aspect of breed adaptation (Stewart, 1937 and 1951; Mulligan, 1951).
Although at least one institutional zebu herd had been established under light Glossina palpalis challenge in the humid zone (Hill, 1956) this was not seen as a realistic basis for cattle development in tsetse areas. At this stage the choice was considered to lie between raising trypanotolerant cattle or having no resident cattle within the tsetse areas. A need for further comparative study of the N'Dama and West African Dwarf Shorthorn breeds was seen as a research priority. Since that time some progress has been made towards understanding the nature of trypanotolerance (Murray, see article 15 of these Proceedings). However the fact of superior innate and apparently highly heritable resistance within the N'Dama and West African Dwarf Shorthorn breeds has, for practical purposes, been well established (Hill and Esuroso, 1976; Murray and Trail, 1984; Roberts and Gray, 1973). In the case of small ruminants, general field observation confirms the capability of West African Dwarf breeds to develop a useful degree of tolerance to trypanosomiasis (ILCA, 1979b).
Although trypanotolerance may prove to be classifiable as a relatively fixed factor, it is necessary for purposes of livestock development planning to recognize that its economic significance can alter with time when other factors such as tsetse distribution, husbandry practices, livestock values and effectiveness of veterinary cover undergo change.
The evidence for resistance of trypanotolerant livestock to cutaneous streptothricosis (Coleman, 1967; Abu-Samra, 1980; ILCA 1979a) appears more substantial than that for resistance of these animals to helminth infections and tick-borne diseases (Ikede 1982); their very high susceptibility to rinderpest is well recognised particularly in the case of the West African Dwarf Shorthorn breed (Ferguson, 1967a).
The streptothricosis factor influences the potential of trypanotolerant livestock in much the same way as does trypanosomiasis. For the present it effectively precludes the use of temperate zone exotic breeds which might otherwise be introduced on a larger scale than the existing tentative trials for improving milk production by crossbreeding in Nigeria (Ibu et al., 1987) and elsewhere (Vargas and Mendoza, 1984). A difference has been the lack of effective prophylactic or curative chemotherapy for streptothricosis to date. However this could change in the short-to-medium term.
Since the advent of rinderpest tissue culture vaccine in the early 1960's, an effective protection which can be safely applied to the highly susceptible trypanotolerant breeds has been, technically speaking, available. Given the lessons learned during the resurgence of this disease in the early 1980's and the rehabilitation of vaccine production and increased attention to quality control which followed, there is justification for confidence that rinderpest will be held within the limits of acceptable risk.
Rinderpest tissue culture vaccine can be used to confer effective protection of sheep and goats against endemic peste des petite ruminants which is a major cause of mortality in West Africa, so that there is some reason for confidence that this risk can also be contained.
Heat tolerance and grazing behaviour
A useful degree of trypanotolerance is of course only one of the economically important components of adaptation of the so-called trypanotolerant breeds.
Their high heat tolerance may be partly attributable to their relatively small size and therefore larger surface area: body-weight ratio, particularly in the case of forest-zone-adapted strains of West African Dwarf Shorthorn. The latter have a higher susceptibility to direct solar radiation and therefore a higher level of shade dependence than have zebu cattle or N'Dama. This is evidenced by elevated rectal temperatures when deprived of shade (Ferguson, 1967b) and by pronounced shade-seeking behaviour during the hottest hours of the day. Coupled with marked path-forming behaviour which persists on improved pastures, this would indicate satisfactory adaptation to the rain forest environment rather than to the open savanna. It also might imply suitability for village herding, oil-palm intergrazing or stall feeding rather than for ranching in open treeless situations (Ferguson, 1966). West African Dwarf Shorthorn found in the more northerly latitudes of the Guinea savannas tend to have different coat characteristics and show more grazing activity during the hours of maximum solar radiation. This is in general agreement with the findings of Pagot (1974) who reported a positive correlation between cattle size and the surface area of respective climatograph for the area of breed distribution.
Cadot (1966) recorded a mean grazing time of 11 hours 5 minutes in the dry season and 9 hours 13 minutes in the rainy season for N'Dama cattle in Cote d'Ivoire and reported 57 minutes and 1 hour 32 minutes spent in the shade in the dry and wet seasons, respectively. Ferguson's (1966) study of West African Dwarf Shorthorn was conducted in the early dry season and showed that these animals, given continuous access to pasture, shade/shelter and water would graze for approximately 9 hours in 24 but might spend as long as 4 hours 30 minutes (1045-1545) resting or ruminating in the shade and might graze for about 3 hours during the night.
Although the N'Dama breed is subject to much variation in size and coat characteristics (Toure, 1976) it is not clear whether this is associated with differences in daytime grazing efficiency.
Production Performance
Meat
The meat production potential of trypanotolerant livestock is well established. By the middle of this century an earlier view that the small, indigenous breeds of cattle in West Africa were uneconomical or had deteriorated was already being refuted. Recognition of the beef production potential of the N'Dama breed had led, in Nigeria, to the establishment of one parastatal ranch and another regional multiplication and selection centre for this breed. A policy of upgrading indigenous village herds of West African Dwarf Shorthorn to N'Dama had become sufficiently advanced to generate concern for preservation of the breed. Several years of study of the West African Dwarf Shorthorn under village and investigation-centre conditions had confirmed its beef production potential and by 1958 a "reserve" area had been created for that breed in the southern half of Nigeria's present day Ondo state (ILCA, 1979a).
Table 1. Levels of production of selected breeds of African cattle, sheep and goats occurring in association with trypanosomiasis risk.
|
Species |
Breed |
Breeding female viability (%) |
Progeny per breeding female per year |
Progeny viability (%) |
Progeny weight at 5 mo (kg) |
Breeding female wt (kg) |
Productivity index1 |
|
Cattle
|
Zebu and Sanga |
98 |
0.81 |
89.0 |
189.02 |
371.0 |
4.1 |
|
N'Dama and W. African Shorthorn |
98 |
0.80 |
92.0 |
109.02 |
219.0 |
3.7 |
|
|
Sheep |
Dwarf W. African |
86 |
1.79 |
68.0 |
11.5 |
23.6 |
6.4 |
|
Goats
|
Small E. African |
95 |
1.18 |
70.0 |
10.5 |
30.2 |
2.9 |
|
Dwarf W. African |
88 |
2.24 |
77.2 |
7.5 |
21.3 |
6.9 |
1 The productivity index is the weight of progeny produced per 10 kg. of breeding female maintained per year.2 The progeny weight of cattle is at 12 months of age.
Source: Carles, A.B. (1981).
More recently data on the performance traits of trypanotolerant livestock in West and Central Africa have been extensively surveyed by ILCA (Trail and Wissocq, 1982) and FAO (1980). The production potential of large and small Trypanotolerant ruminants in different ecological zones and under different levels of management and trypanosomiasis risk is currently being studied by ILCA and ILRAD in collaboration with national research teams at 13 sites in 10 African countries. Table 1 summarizes some of the resultant data. Of particular note is the relatively high productivity of Dwarf African sheep and goats.
Milk
Trypanotolerant cattle are milked to provide for human consumption in several parts of West Africa, but it is generally acknowledged that they have low milk-production potential.
Starkey (1984) describes the N'Dama as a beef breed with very low milk production. He reports yields of around 70 to 100 kg per year where milking for human consumption is carried out and states that full lactation yields are considered to be about 500 to 600 kg. Toure (1976) reports that the N'Dama is not a good milker even when well fed and proposes crossing to improve their lactation.
The first FAO Expert Consultation on Research on Trypanotolerance and Breeding of Trypanotolerant Animals, held in 1976, reported that milk production of these animals is low and milk for human consumption only available at the expense of the calf. This group concluded that development of urban milk supplies would have to be based on high-yielding animals managed on an intensive basis, which would practically eliminate the risk of trypanosomiasis and thus make it possible to dispense with trypanotolerant breeds for this purpose. However milk production by smallholder farmers in tsetse areas and procurement of urban milk supplies are often quite separate issues.
Since milk production is likely to have a growing influence on a farmer's breed preferences, the evaluation of N'Dama milk-production potential being made by ILCA and ILRAD in collaboration with the ITC in the Gambia and that of the East African Zebu in Ethiopia and Kenya (ILCA, 1986a) deserves close attention and support.
Traction
The first FAO Consultation on Research on Trypanotolerance and Breeding of Trypanotolerant Animals (1976) expressed the view that Trypanotolerant cattle can be introduced into the agricultural system without much risk and without straining the technical competence of the smallholder farmers, but did not comment on their draught potential or compare it with that of zebu breeds. As Starkey (1984) reports, N'Dama cattle are often used for traction within their natural area of distribution and even the females of the breed are sometimes used successfully. Toure (1976) on the other hand dismisses Trypanotolerant cattle as being of limited usefulness because of their small size. Judging from the tendency of West African farmers to employ crossbred zebu x Trypanotolerant cattle for draught purposes wherever the tsetse challenge is light enough to permit this, his view is widely shared.
There is little doubt that the larger breeds will usually provide more draught force per animal unit than the smaller breeds. Lawrence (1987) who compared the draught qualities of American Brahmans and two Criollo breeds in Costa Rica found that the distance travelled, work done, speed and power all followed predictable trends whereby the values were greatest for the heavier Brahmans and least for the lighter of the two Criollo breeds. This is not to imply that small animals cannot be used successfully for draught. Farmers who wish to employ animal traction will make use of whichever competent animals are available locally and efficiency of operation will probably be determined at least as much by the design and quality of harness and equipment as by the breed of cattle used.
Disease risk
Disease risk is a dynamic factor in that it is subject to change which can be brought about by the following:
a) advances in veterinary research bringing new vaccines and drugs, better understanding of the epidemiology of animal diseases and improved control of parasite vectors;b) adoption of new production systems with consequent changes in environmental stress and inter-animal contact frequency; also changes in nutritional status;
c) demographic change which alters vector habitat (agricultural expansion; fuel wood removal);
d) socio-economic change such as alteration in animal values, efficiency of livestock production support services and government sect oral priorities, etc.
Change in disease risk may be relatively gradual, as in the advance or retreat of tsetse populations, or sudden as with the advent of rinderpest tissue-culture vaccine.
In considering the disease factor it is necessary to recognize the strategically important diseases which constitute the sequential barriers to progressive livestock development and to consider the reappraisals in breed preferences which may occur as each barrier is breached. Until the advent of a safe and effective rinderpest vaccine this disease constituted the primary threat to survival of trypanotolerant cattle. At the present juncture trypanosomiasis, closely followed by streptothricosis, constitute the main impediments to livestock production and investment at farm level. Effective control of these diseases will open up the possibility of using dual or triple purpose zebu breeds and possibly wider adoption of their crosses, throughout the humid and sub-humid zones. At this stage other formidable disease barriers, and in particular the tick-borne diseases, would still confront any initiative to move forward with introduction of temperate zone breeds except under closely monitored controls.
Trypanosomiasis
Thirty years ago tsetse control technology had reached the stage of large-scale, selective ground spraying of tsetse resting places within their dry-season retreat areas (MacLennan and Kirkby, 1958) but was still largely confined to the relatively dry Sudan zone. The strategy was to achieve eradication in areas which were or would become contiguous with adjacent fly-free barriers large enough to minimize risk of re-invasion. Since that time important advances in tsetse-control technology have occurred.
Newly developed tsetse-control techniques are based on low-to-nil environmental contamination risk and are attracting increasing donor agency interest and support. They include ultra-low volume spraying of insecticide, insecticide-impregnated screens and traps used with or without olfactory attractants and, more recently, deltamethrin-treated bait cattle (Hursey et al., in press; Thomson, 1985). The use of artificially reared and sterilised males has also been developed and used in integrated operations in limited areas (Lyndquist, 1987; Oladunmade et al., 1985) but has yet to be fully costed for comparison with alternative mopping-up methods.
Prospects for reducing tsetse challenge over wide areas and for involving community self-help in this have greatly improved with the development of effective lethal screens and traps and may improve further with the advent of economical and effective use of insecticide-treated bait cattle. As this technology is being refined, tsetse habitats are being progressively reduced in many areas as a result of agricultural expansion. This is particularly evident in the sub-humid zone of West Africa (Bourn et al., 1986). Consideration of the potential role of trypanotolerant livestock would therefore seem to call for study, and so far as possible, monitoring on a geographical basis, of the rate at which trypanosomiasis risk may be disappearing or coming within economically acceptable chemotherapy requirement levels. On this subject there appears to be, at first sight, some conflict of opinion in the published literature.
Jordan (1979) describes the rapidly accelerating disappearance of Glossina morsitans from vast areas of West Africa and attributes this mainly to expanding cultivation and tree removal. Putt et al. (1980), referring specifically to Nigeria, conclude that Glossina morsitans populations are in general declining. Bourn et al. (1986) referring to Nigeria's sub-humid zone, describe a general contraction of Glossina morsitans which they predict will lead to local extinction of this species and be followed by dwindling and ultimately the disappearance of the riverine species as the remaining riverine forest is progressively encroached on by cultivation, logging, palm-wine collection and fire. Murray and Gray (1984) on the other hand conclude that the net effect at the continental level of agricultural expansion and tsetse control has been small and that the problem of African animal trypanosomiasis is escalating and will continue to escalate over the next decade unless more active steps are taken to control the disease. Citing MacLennan (1980) they list significant tsetse advances in Nigeria, Cameroon, Botswana, Zimbabwe, Uganda, Tanzania, Sudan, Ethiopia, Eastern Senegal and Western Mali. The latter authority, who considers it necessary to take a perspective longer than 20 years, expresses the view that although population pressures can lead to changes in the Glossina species present, this will in many circumstances ensure the perpetuation of the trypanosomiasis problem except where specific measures are successfully applied to eliminate infestation and maintain tsetse-free areas.
The above conclusions are not necessarily at variance. Although generalizations by country are misleading, the facts which seem to emerge clearly are:
a) land which remains undeveloped after tsetse eradication is likely to be vulnerable to re-invasion; as in the Nigerian and Cameroon situations referred to by MacLennan (1980);b) land abandoned by farmers during periods of civil strife or for other reasons, will become vulnerable to invasion by tsetse if adjacent to an infected area as happened in Zimbabwe, Uganda and to some extent in Zambia and probably in Mozambique; and
c) tsetse infested land which is of good agricultural potential, is adjacent to areas of high population density and subject to spontaneous or organized colonization and intensification of cultivation, will become increasingly unsuitable for tsetse and therefore less hostile for trypanosomiasis-susceptible livestock (as is happening in the sub-humid zone of West Africa).
Streptothricosis
If trypanosomiasis risk did not exist in West Africa, streptothricosis would still militate heavily against zebu cattle in the wetter areas. It would also preclude the successful use of purebred exotics or their crosses with zebu cattle except under closely controlled husbandry conditions.
The promise offered by the live intradermal dermatophilosis vaccines has not been fulfilled to date and study is now made of the possible need to relate the antigenic composition of the vaccinal strains used to those predominating in the field in any particular region (Lloyd, 1984).
There is good evidence that effective tick control can reduce if not prevent the occurrence of this disease but, as pointed out by Ilemobade (1984), the regimentation necessary for tick control by dipping would be difficult to apply in West Africa and would probably be unwarranted. Both zebu and trypanotolerant breeds enjoy a high degree of resistance to endemic piroplasmosis and anaplasmosis. However the advent of pour-on acaricides (deltamethrin and flumethrin) opens new possibilities and the prospect of controlling streptothricosis by this method is now being examined. Morrow (1987) has reported the apparent disappearance of the clinical diseases from the island of St. Lucia following use of pour-on flumethrin.
Traditional Management
By the mid-1950's good progress had been made in research and on-station development of improved pastures. Large-scale expansion of commercial ranching was envisaged in national development plans. Village livestock on the other hand were for the most part free-roaming or confined overnight and herded in daytime. Production of forage on fallow land was a subject of technical discussion, but the reality seemed fraught with insurmountable problems of distance, time-budgeting and fragmentation of land holdings. Shifting cultivation with long bush fallows was universal. The management factors which predispose to occurrence of clinical trypanosomiasis in trypanotolerant breeds i.e. low plane of nutrition, overwork, intercurrent disease, change of environment, systematic reactions to certain vaccines etc., were well recognized thirty years ago (Littlewood, 1958). They were not of major concern in village herds. No strategies had yet evolved for intensifying management other than provision of confinement and herding to reduce the social conflicts resulting from crop damage by free-roaming livestock.
A comprehensive and competent review of current management of trypanotolerant livestock in West and Central Africa has been provided by Wissocq (1981). Insufficient reliable information existed to enable quantitative economic assessment of the importance of these animals in either the agropastoral, ranching or crop-farming sectors. However, as his review clearly indicates, their economic role in commercial terms, is lowest among the small farming communities in the high rainfall areas. A few of the salient factors which still influence the performance of trypanotolerant livestock in the high rainfall areas will be outlined briefly here.
Restriction of grazing opportunity
Mack et al. (1984), in the case of West African Dwarf goats, and Ferguson (1967), in the case of West African Dwarf Shorthorn cattle, observed that trypanotolerant livestock in village situations usually perform best when not managed at all. This information can be useful if it indicates where management improvements may be achieved within the framework of production priorities and resources of local livestock owners.
In many villages typical management systems still involve confinement or tethering on bare ground from dusk until around 9 a.m. thus providing only 9 hours or so of grazing time for animals that would spend several of these hours resting and ruminating in the shade under free-choice conditions. This restriction constitutes more of a problem when herdsmen are employees having only limited proprietary interest in performance other than milk yield. It is often a major factor responsible for poor condition and low performance of village herds. Rotational night grazing paddocks could, in theory, compensate for restriction of daytime grazing but they are costly to establish and maintain and consequently are seldom adequate in size or number.
Fragmentation of village grazing
In the rain forest environment particularly, village grazing tends to consist of small isolated areas of derived grassland resulting from land clearing around village schools, playing fields, churches etc., or where roadside verges have been clear felled and kept open. Unhusbanded herds utilize all corners of such secondary grassland effectively by dispersing widely during grazing. Herds which are kept intact by herdsman are restricted to the few grassed areas large enough to accommodate the entire herd at one time. This aggravates risk of overgrazing. Coupled with the effect of restricted grazing time, it can account for deterioration of both cattle and available pasture.
Pasture management
Lignification and protein dilution in rapidly growing, tall grasses during the rains is a frequent cause of poor nutritional status of trypanotolerant cattle in the high rainfall areas. It can occur alongside areas which are heavily overgrazed. If herding is inefficient or stocking density too light during the rains, grazing will be concentrated on limited areas while grass growth proceeds unchecked elsewhere. This can lead to a situation where animals are unable to consume sufficient dry matter to obtain nutritional requirements for maintenance and can be an important factor in increasing susceptibility of trypanotolerant breeds to trypanosomiasis. It was a prominent aspect (personal observation) of the poor standard of management alluded to, but not specified, by Godfrey et al. (1964) in their account of a high incidence of trypanosomiasis in a herd comprising trypanotolerant breeds.
Intensification Trend
As surely as shifting cultivation is giving way to more continuous cropping, so livestock management systems are becoming more static and more closely linked with crop farming in areas which have good crop production potential (FAO, 1984). The main factors associated with this trend over recent years can be summarized as follows.
1. Increase in population pressure which leads to:
(a) expansion of agricultural activity both within and outside the sub-humid zone (Putt et al., 1980);(b) reduction of fallow periods (Ruthenberg, 1980);
(c) accelerated removal of fuelwood;
(d) reduction of traditional grazing land (Powell, 1986);
(e) demographic shift, both spontaneous and assisted, into the higher rainfall tsetse areas (Ikede and Taiwo, 1985);
(f) a gradual disintegration of the ethnic division between herding and cropping, i.e. progressive transition from transhumant pastoralism to settled or semi-settled agropastoralism accompanied by increasing acquisition of cattle by indigenous crop farmers (Straw and Colville, 1950; Van Raay, 1975; Oxby, 1982; Waters-Bayer and Taylor-Powell, 1986);
(g) contraction of savanna tsetse habitat over large areas (Bourn et al., 1986);
(h) increased demand for livestock products;
(i) closer integration of crop and livestock production (FAO, 1984);
(j) increasing need for measures to sustain soil fertility, linked with increasing farmer need for improved cash flow to meet operational costs as land use becomes more intensive; and
(k) rehabilitation of vaccine production and veterinary diagnostic facilities throughout Africa and improvement in vaccine quality control. (FAO has targeted African self-sufficiency in production of vaccines against the major epidemic animal diseases, but not including trypanosomiasis or streptothricosis, by the year 2000).
2. Increase in allocation and improvement in delivery of external assistance for livestock production and farming systems research and development which is now yielding guidelines and direct assistance for improving the following:
(a) sustainability of soil fertility and thus of food crop production by interplanting food crops with leguminous tree crops (ILCA, 1986b, 1987);(b) supply of dry season animal feed and improvement in food crop yields by replacing bush fallows with forage legume leys in the sub-humid zone (Mohamed-Saleem, 1986b);
(c) efficiency of utilization of crop residues as animal feed; and
(d) consultation with and participation by farmers and livestock owners on farm livestock research (McIntire, 1985; Atta-Krah, 1985).
3. Reaffirmation by most African governments and donor agencies of the crucial role of the traditional sector in rehabilitation of African agriculture which should lead to:
(a) improved production incentives for crops, livestock and livestock products;(b) revival or initiation of farmer associations concerned with improving marketing and procurement of essential farming inputs, e.g. seeds, fertilisers, breeding stock, veterinary supplies; and
(c) improved delivery of such supports as credit, veterinary, extension, and where appropriate, artificial insemination services, possibly involving establishment of cost-recovery arrangements linked with (a) and (b) to help achieve sustainability of these services at an effective level.
The important meat production potential of trypanotolerant sheep and goats is clear. Most farmers own a few of these animals. They are capable of high productivity, already have wide distribution throughout the humid and sub-humid zones, involve less capital risk than cattle and can provide more regular income than small-scale beef production.
A major factor holding back development of sheep and goat production in the more humid areas has been the traditional association of these animals with homesteads rather than with farms. This separation from farming activities is now conceptual as well as geographical.
The programme being developed by ILCA in collaboration with IITA, Ibadan, is designed to promote small ruminant meat production in combination with legumes grown in alley cropping systems in small farms. If the participating farmers succeed in adjusting their allocation of labour and animal management practice to make optimal use of available feed supplies, then the prospect for progressive development of both breeding and fattening enterprises will have improved. In the event that trypanosomiasis risk eventually diminishes or disappears, these animals are likely to retain favour on the basis of general adaptation and highly competitive meat production performance vis-a-vis other breed alternatives in the high rainfall tropics.
It is the potential role for trypanotolerant cattle which may be subject to some uncertainty, being more likely to be influenced by changes in disease risk and farming practice. This is not to imply agreement with the view that trypanotolerant cattle are about to become obsolete. On the contrary they must continue to play an important and probably expanding role for many years to come. But the question should be asked "for how many years to come."
Trends in tsetse population density and distribution are area and time-specific and generalizations on a regional or even a national basis can be misleading. Until more precise monitoring of these trends becomes possible, judgement must be based on existing evidence. This indicates that Glossina morsitans may be retreating rapidly from extensive savanna areas, particularly in West Africa, but tsetse fly, and especially the riverine species, will be with us for very many years. Whether this will be associated with a sustained or an increased need for trypanotolerant cattle will depend in large measure on the comparative economics of the other options, i.e. on the relationship between breed productivity, market prices for cattle-derived products and cost of maintaining satisfactory control of trypanosomiasis without incurring serious increase in risk of generating drug resistance.
In some tsetse-infested countries the price incentive to improve crop and livestock production remains low and support services are seriously handicapped by lack of transportation and other essential inputs such as trypanocidal drugs and acaricides. It is where these circumstances coincide with light-to-medium challenge that trypanotolerant cattle will continue to have their most successful application.
As challenge increases beyond the limits of effectiveness of trypanotolerance, so dependence on chemotherapy and/or vector control increases and advantage over non-trypanotolerant breeds is, to some extent at least, eroded. At the other end of the scale, i.e. as trypanosomiasis risk diminishes, this comparative advantage again recedes until, in the absence of this risk, it becomes discountable in comparative breed evaluations. In the same way the advantage of resistance to streptothricosis could become heavily discountable, given the advent of an effective prophylactic agent and the right relationship between the cost of this and livestock values. For so long as effective control has to be based on widespread use of trypanocidal and/or insecticidal agents the danger of generating drug resistance must be addressed. However the present indications are that availability of effective tools for controlling streptothricosis and trypanosomiasis will become increasingly available over the next decade and that techniques for the integrated use of these will undergo significant development during that period.
The beef production potential of trypanotolerant cattle is well established but how this is to relate to ILCA's two priority groups, i.e. pastoralists and small farmers, is less clear.
The trend from extensive pastoralism to settled or semi-settled agro-pastoralism is already well-advanced and will continue. However the majority of this community will retain extensively managed breeding herds for so long as they have access to communal grazing land as a no-cost resource. Milk will remain high among their production priorities and the majority's preference for zebu breeds and their crosses is likely to persist.
With the exception of such countries as Guinea, The Gambia, Senegal and Sierra Leone, which have substantial and well distributed populations of N'Dama cattle, it is difficult to foresee the significant development of smallholder fattening schemes receiving regular supplies of trypanotolerant feeder animals on a continual basis. Trypanotolerant cattle resources are not sufficiently developed or organized for this to be established on a significant scale.
The N'Dama breed has proved to be well suited to beef ranching, but this type of enterprise, whether para-statal or private, has had a disappointing record in West Africa. Furthermore Trail and co-workers in East Africa have confirmed that with good management and an efficient trypanosomiasis monitoring programme, chemoprophylaxis can be highly effective in maintaining zebu beef cattle in areas of even high tsetse challenge (Trail et al., 1985). In this work they showed that the use of Samorin every 80 days on average in an area of high tsetse challenge enabled attainment of 35% superiority in herd productivity over that of the N'Dama breed reared in moderate-to-light challenge in West Africa.
The N'Dama breed seems particularly suited to ranching conditions in the relatively open derived savannas and the West African Dwarf Shorthorn to traditional level production in the more humid areas, according to Pagot (1974). Field experience has confirmed that both are eminently suited to grazing within plantations of, for example, oil palms which offer constant access to shade but enough light for successful pasture-legume establishment.
Pagot et al. (1975) in their review of the use of trypanotolerant breeds concluded that the slow pace of livestock production in the humid areas was as much due to lack of interest as to disease factors. It is doubtful whether this conclusion remains valid today, yet it is still not clear how transition from village traditional methods to more advanced management systems can best be achieved. As in the case of small ruminants in the high rainfall areas and in contrast to agro-pastoralists' herds in the savanna regions, they are still closely associated with the village environs and so far as possible, geographically separate from farming operations to which they are generally considered a threat rather than a complementary adjunct. Some exceptions exist in the form of draught oxen and of course the complementarity between pastoralists herds and fallow land is traditional in the sub-humid zone. However it is by no means clear how communally owned herds are to be further developed or incorporated into local farming systems. The prospect of continuing expansion of village herds on communal pastures is unattractive in the light of pan-African experience of the situation to which this leads.
It seems certain that land use in the sub-humid and humid zones must continue to intensify in the foreseeable future. The biological resource base will be able to support this trend within the zones which are currently tsetse infested for many years at least. As intensification proceeds, livestock are assuming a new importance and breed selection criteria must evolve in line with their changing role.
Current economic and socio-political indications are that most African governments are backing away from a policy of dependence on State or parastatal farms and refocussing priority on the traditional sector. It seems very likely that the requirement will be for multipurpose animals which can best fulfil, under the locally prevailing conditions, the functions which Jahnke (1982) has listed as follows:
(a) the output function (subsistence income and nutrition);
(b) the input function (crop inputs and farm integration);
(c) the asset and security function; and
(d) the social and cultural function.
As competition for land continues to increase and production systems to intensify, the input function of livestock will become more crucial but more heavily dependent on successful generation of- income for the purchase of seeds, fertiliser, fencing, veterinary treatment, etc. The sporadic income which smallholders could derive from widely spaced sales of live animals does not meet this requirement. Meat production from small ruminants would come closer to providing the necessary improvement in day-to-day cash flow but would be less effective for this purpose than production of marketable milk surplus even on a seasonal basis.
The catalytic role of milk sales in boosting smallholders' crop production has been eloquently expounded by Brumby (1983) and forms the basis for a proposed ILCA initiative to establish a milk production research network in West Africa (ILCA, 1986c).
Milk production will become more attractive to farmers when trypanosomiasis and streptothricosis are, like rinderpest, brought within the realm of acceptable risk. This could happen over large areas in the short-to-medium term, say 3 to 15 years. When it does it will reinforce the existing tendency to replace trypanotolerant purebreds with zebu crosses for milk and possibly draught. This could well be followed by an increasing demand for Jersey x trypanotolerant crossbreds for example. The production of these animals would justify the investment of additional labour and money in establishment, management and utilization of legume leys, fodder banks or forages from alley cropping and result in improved handling and utilization of crop residues and improved veterinary and other support services on a cost-recovery basis.
Whether development of milk production could be satisfactorily achieved with trypanotolerant purebreds in the short-to-medium term is highly improbable. However since pockets, at least, of tsetse are expected to persist into the foreseeable future, genetic improvement for milk production is likely to rely into the long term on a strategy of crossing trypanotolerant breeds in many areas.
Over the last decade, at the many international meetings which have been devoted to the subject of trypanotolerant livestock, it has become routine to express concern at the shortage in availability of these animals. This alleged shortage has become the subject of numerous proposals for costly projects to provide a solution in the form of more multiplication and selection centres for trypanotolerant breeds. However this shortage is theoretical until it is established that an unfulfilled demand really exists. The fact that senior technicians from tsetse-affected countries have subscribed to these proposals may be taken as adequate confirmation of their justification. On the other hand it could be argued that measurement of such demand has to involve farmers, since it is they who will ultimately decide whether multiplication or incorporation into their farming operations will materialise on a significant scale. A recent study of international supply and demand for trypanotolerant cattle (Straw and Hoste, 1987) focussed on expressed interests of some national institutions. This needs to be followed by an examination at farm-level of such demand and of the factors which determine this.
Since the role of trypanotolerant livestock in the agricultural development of the sub-humid and humid zones will ultimately be decided by the farmers and agropastoralists who now constitute ILCA's priority target groups, close monitoring of their evolving livestock production requirements and associated breed preferences is more essential than ever. More detailed study of the distribution of trypanotolerant livestock by sector and production objective is also needed to ensure continuing relevance of research and development assistance to adjustments in producers' priorities. Wissocq (1981) has provided a good baseline for further studies in this direction.
Since Wissocq drew attention in 1981 to the lack of factual information necessary for formulation of livestock production strategy in areas of tsetse challenge, ILCA's ATLN has made good progress towards correcting this deficiency. Being more comprehensive than its title implies, this research network assembles the technical information needed on non-trypanotolerant as well as trypanotolerant breeds under a range of management systems and degrees of trypanosomiasis risk. It is the only programme in Africa having the capability to provide the technical basis for selection from among the several key options available to the livestock producers or mixed-farmers in tsetse areas or to the governments charged with responsibility for delivering appropriate support.
ILCA's proposal to establish a milk-production research network in West Africa is timely in relation to the accelerating trend towards more intensive farming systems and need for improved cash flow on small farms. This proposed network should operate in very close collaboration with the ATLN in the tsetse-affected areas of West Africa and could share resources with this programme in the latter areas.
A better understanding of the genetics of trypanotolerance is required. This would facilitate policy decision-making in relation to crossbreeding for the improvement of milk production.
Current studies of milk-production potential of trypanotolerant and non-trypanotolerant cattle maintained under tsetse challenge and chemotherapy should, so far as possible, be extended to secure sufficient data for comparative economic evaluation of alternative systems operative under similar environmental conditions.
Long Term
A recent report on the genetic basis for trypanotolerance in N'Dama cattle (Soller and Beckman, 1987) offers the exciting prospect of achieving rapid introgression of desired traits from other breeds into the N'Dama, while retaining trypanotolerance or, conversely, the rapid introgression of trypanotolerance from the N'Dama to other breeds.
The aforementioned report shares the view that the N'Dama cannot fill all the agro-ecological niches in the tsetse-infested areas. It recognizes a need to develop trypanotolerant types having higher milk production and other types with larger body-size for use as draught animals. It also recognizes that genetic improvement by selection for these characters would be slow and proposes instead the mapping of the trypanotolerance loci of the N'Dama and the tagging of these with genetic markers so that they could be conveniently followed in breeding programmes. Their research proposals indicate that at the end of nine years there would be available, probably in The Gambia, the knowledge, organizational framework, trained technical manpower, laboratory and field facilities required for a major endeavour to increase the trypanotolerance and productivity of the N'Dama.
Assessment of the implications for development of this research proposal requires realistic appraisal of the technical, economic and institutional arrangements for implementing timely transference of trypanotolerance by this method to the scattered populations of nomadic and sedentary cattle within the millions of sq. km of tsetse-infested Africa. In this context it is difficult to derive optimism from the present status of the many artificial insemination programmes which have been initiated in Africa over the past twenty or so years.
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