UTILIZATION OF PASTURE AND FODDER SHRUBS IN THE NUTRITION OF SHEEP AND GOATS IN THE HUMID TROPICS OF WEST AFRICA

A.N. Atta-Krah and L. Reynolds
ILCA Humid Zone Programme, P.O. Box 5320
Ibadan, Nigeria

RESUME

Une alimentation pauvre et inadéquate est l'une des principales contraintes pour la production des petits ruminants sous les tropiques humides de l'Afrique de l'Ouest.

Dans cette zone les petits ruminants sont considérés comme une entreprise d'élevage mineure, recevant peu ou pas d'investissement en aliments, santé et logement. La contrainte alimentaire est vue, dans ce document comme étant la conséquence de plusieurs raisons, dont notamment: 1. l'intensification de l'agriculture qui diminue les ressources fourragères provenant des terres en jachère; 2. l'absence de ressources de haute valeur nutritive dans les pâturages naturels; 3. le surpâturage par surcharge des pâturages et des arbustes fourragers naturels; 4. le manque de ressources et d'intérêt pour la production fourragère destinée aux petits ruminants.

Les potentialités des pâturages naturels et artificiels, aussi bien que les arbres et arbustes fourragers pour l'amélioration de la production des petits ruminants par l'amélioration de l'alimentation (en quantité et en qualité) sont analysées. Le rôle particulier des arbres fourragers et leur importance dans une situation de ressources minimales est explicité.

Les pâturages artificiels de légumineuses et de graminées fourragères sont présentés comme non attractif au niveau des petits éleveurs, alors que des potentialités existent pour leur utilisation au niveau des élevages de moyenne et grande taille. Les espèces adaptées de légumineuses et de graminées pour de tels pâturages sont recensées.

La nécessité d'une évaluation économique complète, avant d'établir des recommandations finales sur les pâturages destinés aux petits ruminants, est mise en évidence. L'article préconise aussi la nécessité de démontrer la faisabilité des systèmes de production fourragère à travers la collaboration de la recherche, du développement et de l'encadrement.

SUMMARY

Poor and inadequate nutrition is one of the major constraints to small ruminant production in the humid tropics of West Africa. In this zone small ruminants are generally kept as a minor farm enterprise, receiving little or no investment in feed, health or housing. The nutrition constraint is viewed in this paper as due to a variety of reasons including: (i) intensification of crop agriculture which has led to diminishing feed resources from fallow lands; (ii) inadequate resources of high nutritive value in natural pasture; (iii) overgrazing/overlopping of natural pasture and fallow trees; and, (iv) lack of resources and interest in pasture production for small ruminants. The potential of natural and planted pasture, as well as of fodder trees/shrubs in improvement of small ruminant production through improved feed, in quality and quantity, is analysed. The special role of tree fodder and its relevance for the smallholder minimum-resource situation are stressed. Planted pasture with forage legumes and improved grasses is presented as unattractive under smallholder situations, though some potential exists for its use for medium/large scale production of small ruminants. Suitable grass and legume species for such pastures are listed. The need for a thorough economic assessment before making final recommendations on pasture for small ruminant production is stressed. The paper also advocates the need to demonstrate workability of pasture production systems through collaboration of research, development and extension.

INTRODUCTION

The humid region of West Africa, receiving over 1500 mm annual rainfall with a growing season in excess of 270 days, covers the coastal strip with lowland forest and derived savannah zones. The lowland forest contains farmland under cultivation and bush fallow. Coarse grasses invade these areas and natural clearings but grass cover is sparse or absent under the trees. The derived savannah belt is found adjacent to and to the north of the lowland forest. This area is subject to regular fires and tree cover has been reduced to low trees, shrubs and bushes. Fallow areas are covered by coarse grasses but a reduction in the frequency of burning on uncultivated land allows an invasion of woody species and reversion to forest. Pennisetum spp are typical of the forest zone grasses associated with secondary tree growth, merging with Hyparrhenia in the northern parts of the derived savannah (Rattray, 1960). These two belts - lowland forest and derived savannah - together constitute the humid zone of West Africa (HZWA) (Figure 1).

Livestock production in the HZWA has generally been limited by the disease, trypanosomiasis, transmitted by the tsetse fly, and most resident animals are indigenous trypanotolerant dwarf breeds. An estimated 14 million small ruminants are found in the zone (Table 1), managed as one of a number of minor farm enterprises. Small ruminants represent the dominant ruminant livestock species in the zone, and their production is mainly by smallholder farmers. The importance of these animals in the zone is shown by their widespread distribution in villages and farmer households, and in their use as a major animal protein source and means of investment and savings by farmers.

Numbers kept per household are usually low (2–5) and it is estimated that they contribute only about 5 percent of total farm income (Flinn, 1974). However, an overwhelming proportion of small ruminants in the humid zone are kept under such smallholder village conditions, with probably much less than 5 percent under commercial large-scale management. An improvement in the productivity of animals at the smallholder, village level, will therefore have a great impact on the overall production of small ruminants in the zone.

Figure 1. The humid zone of West and Central Africa

Scale 1:20,000,000

Source: Derived by C de Hsan from a map prepared by A Blair Rains.

Table 1. Small ruminant and human agricultural populations (in millions) in humid West Africa

^a Data in parentheses have been taken from ILCA (1979).

Source: Jahnke (1982).

Major constraints to production in the humid zone have been identified as disease, feed and management (ILCA 1979; Sempeho 1985). This paper analyses the potential of pastures and fodder trees (browse) as tools in the elimination of the feed constraint for improved small ruminant production in the humid tropics of West Africa.

Available feed resources for small ruminants in the zone

Tropical grasses mature rapidly, and crude protein levels can fall to as low as 2 percent in the dry season. Deep rooted browse trees, however, show less variation in protein level throughout the year, and browse is often the only source of green forage in the dry season.

Under smallholder management systems, feed resources available for small ruminants range from those obtained by scavenging around households to grazing and browsing on natural vegetation in natural pasture, fallow lands or along roadsides. Under confinement systems these same materials have to be collected by the farmer and fed to the animals. Household scraps such as cassava and plantain peels and maize chaff also provide a significant contribution to feed resources for smallholder sheep and goats.

So long as flock sizes are kept at present low levels and availability of browse and other fodder from fallows and natural pasture is maintained, there is not likely to be a major feed deficit for small ruminants. However, improvement in disease control is likely to result in an increasing flock size/farmer, and the growing human population is resulting in shorter fallows and diminishing grazing lands as cropping is intensified. It has been reported that as human population density increases, there is a decrease in farm size and crop yield/ha, but an increase in livestock numbers/farm (Lagemann, 1977). These situations, therefore, imply a potential major limitation in feed availability for small ruminants in the zone. The need to increase feed supply and quality through an improvement in the production and utilization of pasture and fodder shrubs is therefore obvious.

ROLE OF PASTURE AND BROWSE IN SMALLHOLDER SMALL RUMINANT PRODUCTION

(i) Natural pasture

In this article, the term “natural pasture” will be used to describe any uncultivated piece of land on which livestock have access to grazing or browsing. As the name implies pasture and fodder/browse trees and shrubs on such lands are not planted and in most cases are not managed.

Within the HZWA, natural pasture is of more relevance in the derived savannah belt than in the lowland forest areas. Agricultural land in the latter consists essentially of “crop land” and “fallow land”. The fallows are usually, and ideally, dominated by trees and shrubs and very little grazing is done, which would not be realistic on such lands. Farmers, however, cut foliage from browse trees in fallows for feeding to their livestock. In the more open derived savannah zone, natural pasture consists of a mixture of grasses - (notably Imperata cylindrica, Andropogon gayanus, Pennisetum spp. and Hyparrhenia spp.), low-growing trees and shrubs and bushes. Such vegetation constitutes the basic form of feed for all classes of ruminant livestock in the zone (Aken'Ova, 1985).

It has been observed that natural pasture species in tropical environments are of low quality causing very low production per animal per hectare (Henzell and Mannetje, 1980). This is mainly because of the low nutritive value of tropical grasses (Adu and Adamu, 1982) and also because such pastures receive no management attention. They are overgrazed in the dry season and undergrazed in the wet season, during which period they grow rapidly, become coarse and fibrous and decline in nutritive value. In the dry season crude protein levels could drop as low as 2 percent. Thus the carrying capacity of most natural pastures is very low, at best 300 kg/3 ha natural grassland (Williamson and Payne, 1965). They do, however, contribute immensely even if inefficiently in maintaining sheep/goats and other ruminants in the derived savannah zone.

(ii) Planted pasture

Pasture establishment and management, whether with grasses or forage legumes, involve some expenditure in the form of land, labour and other inputs. Matthewman (1977) concluded that the experimental work on planted pasture would be of limited applicability to the small farmer sector because of the capital requirements and problems of management. Most smallholder farmers are also not willing or able to make this investment for small ruminants because of the minor role they play in the production system. Crop agriculture is the dominant farm activity in the zone and receives priority attention and resources. Any strategy to improve fodder production in the zone should not impinge negatively on crop production or crop land unless a clear economic or social benefit can be demonstrated.

Economic studies on pasture production for small ruminants are not available in the literature, but some indications are available with large ruminants. Doppler (1980), in an economic analysis of several years research into beef production from pasture at Avetonou, Togo, stated that costs were too high for economic production from pasture. Ruthenberg (1974) also concluded that ranches for multiplication of N'dama from pastures sown with Stylosanthes were not economically viable. De Leeuw and Agishi (1978) in the sub-humid zone of Nigeria stated that for beef production, the most economic system was grazing on natural pasture with supplementation.

It is against this background that the authors of this paper consider the issue of pasture establishment for smallholder production of small ruminants as a very delicate one which requires a lot of caution. The practicality, relevance and feasibility of such a system is clearly in doubt. Given the existing farming system in the zone, it does appear that there is very little scope for integration of improved grasses and herbaceous forages for small ruminants within local cropping systems.

The potential, however, exists for feed production through the use of fodder trees and shrubs. Trees have generally been considered as an integral part of the traditional farming system (the bush fallow/shifting cultivation system) and therefore, selected fodder trees and shrubs could be easily integrated into these systems (Atta-Krah, Sumberg and Reynolds, 1986; Atta-Krah and Okali, 1986). Furthermore, the establishment and management of fodder trees requires much less effort, time, expertise and resources than that for herbaceous legumes and grasses. Fodder trees can be established in farm plots, along farm boundaries, and around household areas, with very little management, to produce forage for small ruminants. The multipurpose nature of most trees is an additional attraction for the small farmer as other benefits such as fruits, fuelwood, poles, shade, etc. may be obtained from fodder trees.

The potential of fodder trees (especially nitrogen fixing leguminous ones) in contributing to soil conservation and fertility maintenance offers an entry point for their incorporation and intensification in crop fields, leading to an improvement in crop production and in many cases, in small ruminant feed supply.

Traditionally, browse plays a very important role in feed supply for sheep and goats in the humid zone. Animals under confinement or tethering management often receive browse fodder lopped from fallow lands. Wahua and Oji (1987) listed 35 local browse plants which were used in feeding confined small ruminants in Rivers State of eastern Nigeria, while Orok and Duguma (1987) working in Cross River State of southeastern Nigeria also identified 44 browse species used by farmers in the area. Both authors stressed the important role played by browse and strongly advocated a production strategy for local browse and other fodder trees within the existing farming system.

Introduced fodder trees for small ruminant production in the humid zone

The Humid Zone Programme (HZP) of the International Livestock Centre for Africa (ILCA) has since 1980 been working on two leguminous fodder trees, leucaena (Leucaena leucocephala) and gliricidia (Gliricidia sepium) in the development of smallholder fodder production systems. Both species are very well adapted to humid and sub-humid tropical conditions and are capable of nitrogen fixation. They therefore have a potential for improving soil fertility and enhancing crop production. The foliage from the two trees is rich in protein and other elements (Table 2) and therefore, offers a cheap means of supplementing available feeds, especially in the dry season.

Leucaena is the more productive of the two, and it is also more palatable; however, it contains a toxic element, mimosine, in its tissue, which can be harmful to small ruminants if leucaena is fed over 50 percent of total intake for long continuous periods. Gliricidia has proved to be a worthy companion and alternative species to leucaena and can be fed in much larger quantities without toxicity problems. Both species are fast-growing and coppice effectively. In various production systems developed by ILCA these two leguminous forages have shown fodder yields ranging from 6–38 tons DM/ha/annum on non-acid soils in the humid zone. The growth and productivity of both species, however, decline on acid soils and in low rainfall (<1000 mm) areas.

Table 2. Chemical composition (%, DM basis) of the edible parts of Gliricidia and Leucaena

^* NFE = Nitrogen-free extract; ADF = Acid detergent fibre.

Source: Mani, 1984.

Other tree species of potential for fodder production in the zone include Cajanus cajan (pigeon pea), Flemingia conqesta (syn. F. macrophylla) and Calliandra calothyrsus. Systems based on these fodder trees need to be developed for smallholder intensive small ruminant production in the zone.

Production systems with fodder trees

A number of possibilities exist for the integration of fodder trees into smallholder farming systems. These trees could, as already indicated, be planted within crop fields or along farm boundaries. They could also be used for fencing around home compounds and sometimes as shade trees.

With leguminous fodder trees such as leucaena and gliricidia, a major entry point should be based on their soil improvement characteristic, as a means of linking crop and livestock production. Two production systems developed by the HZP of ILCA on this basis are described below.

Alley farming: Alley farming involves the planting of leguminous or other soil improving fodder trees in rows within arable crop farms. The concept is based on the alley cropping system (Kang, Wilson and Sipkens, 1981) developed at the International Institute of Tropical Agriculture (IITA) in which legume trees are integrated into cropping fields to maintain soil fertility and promote continuous cropping. Food crops are planted in the 4 m alleys between established tree rows, and the latter is managed to support crop production through the use of its nitrogen-rich foliage as fertilizer (green manure or mulch). In alley farming, the dominant requirement is for the tree species used to be of good fodder value, with a potential in enhancing sustainable crop production. Leguminous nitrogen-fixing fodder trees therefore have a special advantage in these systems - though non- legumes could also be used.

The establishment of an alley farm involves the seeding of leucaena and gliricidia (or other locally acceptable fodder trees) in alternate rows 4 m apart in farmers' crop fields. This planting is done in the first rainy season, either before or after food crops have been planted. Weed control is very essential in the first 3 months of growth as the trees, especially leucaena, compete poorly with weeds. Under normal circumstances on average fertility crop land, no fertilizer is required in the establishment, but on badly degraded land such as is due for fallow, application of NPK (15-14-15) fertilizer along tree rows at a rate of 60–80 g per m (equivalent to 150–200 kg fertilizer/ha) is beneficial (Reynolds, Atta-Krah and Francis, 1987). In areas where the tree species have not been previously grown, inoculation with appropriate Rhizobia prior to planting may be necessary for effective nodulation and nitrogen-fixation.

The trees should ideally receive a full year's growth prior to first cutting. An average height of 2.0 m should be attained by then. The cutting preceding planting of the arable crop should be total and uniform to avoid shading the planted crops, and cut foliage should be used almost entirely for soil fertility promotion either through mulching or incorporated into the soil. Subsequent regrowths can then be selectively and periodically harvested on a continuous basis for feeding small ruminants, or may be cut and used as additional fertilizer. Cutting management during cropping periods should be such as would prevent excessive shading of the accompanying arable crops.

Research at ILCA and IITA has shown the benefit to crop production of having these legume trees within cropping fields (Kang, Wilson and Sipkens, 1981; Kang, Grimme and Lawson, 1985; Atta-Krah, Sumberg and Reynolds, 1986). Foliage productivity from trees under alley farming management is in the range of 6–8 tons DM/ha annum, with 4–6 cuttings in a year, 25 percent of which can safely be used as animal feed. Table 3 shows foliage DM, nitrogen yield and crude protein contents of 4 tree species used in alley farming. Crop yields under alley farming with both leucaena and gliricidia have consistently been higher than without the trees (Kang, Wilson and Sipkens, 1981; Atta-Krah, Sumberg and Reynolds, 1986; ILCA, 1987). It has also been shown that where short grazed fallows (2 years) are rotated with cropping phases in alley farming, crop yields when such grazed plots return to cropping, are boosted compared to continuous alley cropping (Table 4). Such grazing under the trees within an alley farming framework is referred to as alley grazing (Sumberg, 1984; Atta-Krah, Sumberg and Reynolds, 1986). Even though the response to soil, crop and tree is all positive, animal management within the system under smallholder conditions remains problematic (Atta-Krah, Sumberg and Reynolds, 1986). The presence of the trees on farmers' fields and their continued productivity in the dry season are providing farmers in a number of villages in southwest Nigeria, where this technology is being tested (Atta-Krah, 1985; Atta-Krah and Francis, 1987) with a high quality supplement to the diet of sheep and goats.

The intensive feed garden: These are intensively cultivated plots of leguminous fodder trees and productive grasses. Unlike alley farms no food crops are planted in this system, as the space between tree rows is planted to grass (usually Panicum maximum or Pennisetum purpureum). When tree rows are spaced 4.0 m apart, there is a possibility of transforming a feed garden into an alley farm after a number of years of production. Productivity in an intensive feed garden depends on the ratio of grass to trees, and on the cutting management adopted. With trees spaced at 4 m apart and four rows of Panicum within alleys, a DM yield of over 20 tons/ha is obtainable (ILCA, 1987). A similar level of production is obtained with trees spaced at 2.5 m apart and 2 rows of grasses within alleys. This latter arrangement has a higher tree density and therefore a higher protein content in the total production. It however requires some more management attention than the former design.

Feed gardens can also be established with trees only for production of protein supplement to available traditional diets. In a management trial with leucaena in such a system, the most productive option was an interrow spacing of 0.5 m, with a cutting frequency of 12 weeks, yielding 38 tons DM/ha of foliage (Figure 2).

No figures are available on productivity of fodder trees as live fences, shade trees, etc. in the West African humid zone. Such usage is however common among small ruminant keepers and contributes significantly to feed supply for small ruminants. In Central America from where gliricidia originates, the species is commonly established as live fences, and loppings from such fences provide feed for small ruminants (Romero et al., 1987).

Table 3. Leaf biomass, nitrogen and crude protein yield of 4 alley farming tree species

^a Source: B.T. Kang - unpublished (from Kang and Reynolds 1986).
^b Crude protein (CP) content estimated as follows:

CP = Kjeldahl nitrogen × 6.25.

Table 4. Ear leaf nitrogen and grain yield of maize in conventional farming, continuous alley cropping and alley farming after a 2-year grazed fallow with leucaena (Atta-Krah, unpublished data).

^a Values in parentheses are yield expressed as percentage of yield under conventional cropping.

Figure 2: Effect of cutting frequency and inter-row spacing on fodder dry-matter yield of leucaena under intensive cultivation, Ibadan, 1986.

Figure 3: Dry matter intake, adult sheep July 1986 - January 1987

Animal response to supplementation with legume tree fodder

Effect of leucaena/gliricidia supplementation: Given the existing farming system in HZWA, supplementation strategies will appear to be the most appropriate way of increasing smallholder small ruminant production. This view is also expressed by van Eys et al. (1986) for small ruminant production in south and southeast Asia. Results from a nutrition study at ILCA (ILCA, 1983; Reynolds and Adediran, 1987) in which different levels of supplementation of leguminous browse (1:1 ratio of leucaena and gliricidia) were fed to sheep on ad lib. Panicum basal diet showed (Figure 3) that increasing levels of supplementation led to:

1. a decrease in intake of Panicum;

2. an increase in intake of both leucaena and gliricidia, reflecting amounts offered; and,

3. an overall increase in total DM intake.

Similar results have been presented by Ademosun, Jansen and van Houtert (1985) using leucaena and gliricidia in separate trials as supplements to Panicum hay. The same authors also reported a linear relationship in the amount of legume fed with dry matter intake and digestible dry matter.

In another ILCA on-station trial to determine the effects of supplementation on lamb growth rates and survival, and on long-term animal productivity, leucaena and gliricidia were offered to dams in the last 2 months of pregnancy and 3 months of lactation (Reynolds and Adediran, 1987). Increasing levels of supplementation resulted in significant increases in growth rate of lambs (Table 5) and in survival to 24 weeks (Table 6). A regression analysis of this data showed that each 100 g of browse DM consumed daily raises the productivity index by 1.41 kg lamb weaned/dam/year (Reynolds - personal communication). Similar improvements in animal productivity from browse supplementation have been made by Ademosun, Jansen and van Houtert (1985).

POTENTIAL ROLE OF PASTURE IN INTENSIVE/COMMERCIAL SMALL RUMINANT PRODUCTION

While it is strongly felt that the issue of pasture establishment is irrelevant and impracticable for smallholder small ruminant production in the humid zone, there can be a role for pastures in medium and large-scale production. With the effective control of PPR, and other diseases, mortalities fall and animal numbers, even at the smallholder level, are bound to rise. There is going to be an increasing drive towards intensification and commercialization of small ruminant production. Such is already being evidenced in southern Nigeria, where a survey of small ruminant stocks per household gave a range of 1–120 for goats and 1–100 for sheep (Orok and Duguma, 1987; Wahua and Oji, 1987). Orok and Duguma also reported encountering a single farmer with over 1 000 goats.

Table 5. Supplementary feeding with Leucaena and Gliricidia on growth rate of lambs

Values within a column with the same letter are significantly different.

P<0.05 af; P<0.01 bdegjl; b<0.001 chik

* Between 8 weeks prepartum and 12 weeks postpartum

+ Between weaning at 12 weeks postpartum and 24 weeks.

Table 6. Effect of browse supplementation on the survival rates to weaning * and 24 weeks of lambs.

* Weaning at 12 weeks of age
+ Dietary treatment as shown in Table 5

Source: Reynolds and Adediran, 1987.

For large-scale production of small ruminants some investment in pasture establishment is necessary. This view is shared by Mathewman (1977), who remarked that “intensification of production would involve a change to a system based on high inputs of time, labour and capital and would require a re-orientation of ideas towards livestock”.

Leguminous fodder trees such as leucaena and gliricidia could form the basis of pasture and fodder production systems for HZWA, with forage legumes (herbaceous) and grasses providing the bulk feed required. The legume fodder trees will provide the much-needed dry season supplement, as well as assist in the maintenance of soil fertility in grass pastures. They will also help reduce the total cost of pasture production and make pasture establishment more economically feasible.

A considerable number of studies on pasture development in the humid zone was carried out in the 1960s and 1970s and reviews published (Crowder and Chheda, 1977, 1982; Matthewman 1977; ILCA, 1979). These have provided relevant information on pasture development in the humid zone.

Pasture species to use

1. Grasses

Work on the genetic improvement of suitable grasses has been confined mainly to Panicum maximum, (guinea grass), Pennisetum purpureum (elephant grass), Cynodon spp. and Abdropogon spp. (Crowder and Chheda, 1977). In addition to these grasses, McIlroy (1962) mentioned Digitaria decumbens, Brachiaria mutica and Axonopus compressus as being suitable for the lowland forest region.

Productivity

Dry matter percentage of most grasses in West Africa do not vary widely up to 6–8 weeks of growth and range from 15–20 percent for tall growing fodder grasses such as guinea grass and elephant grass, and 25–30 percent for pasture species such as star grass (Crowder and Chheda, 1982).

The productivity of grasses depends very much on the fertility status of the soils and on availability and use of nitrogen fertilizers. In general, yields of grasses are low in unfertilized plots (Table 7) but can be increased dramatically by application of adequate fertilizers (Adegbola, 1964). It has also been established that a wide range of variation on productivity exists both between and within species. A collection of Pennisetum purpureum varieties from southern Nigeria gave DM yields of between 8–12 t/ha annum under low fertility conditions, and crude protein from 10–17 percent (Chheda, 1971). C. dactylon vars coursii and elegans, C. aethiopicus and C. nlemfuensis vars robustas and nlemfuensis showed a high degree of pasture potential with several ecotypes yielding over 15 t DM/ha annum (Chheda, 1974). In 1968, Cynodon strain IB 8 which is a selection of C. nlemfuensis var nlemfuensis was released for general cultivation. This strain is easy to establish vegetatively, is drought tolerant, greatly superior to existing Cynodon cultivars in productivity and responds well to fertilizer application. With adequate fertilization and good management DM yields of 15–20 t/ha/annum are common under humid/derived savannah conditions, compared with yields of 3–4 t/ha/annum for local Cynodon cultivars (Matthewman, 1977).

Table 7. Dry matter production of unfertilized selected grass species at Agege, Western Nigeria, 1959–61.

Source: Adapted from Adegbola, 1964.

Pasture legumes

Pasture legumes have received relatively less attention in the humid zone than have grasses. Work at Moor Plantation (Ibadan) in 1960 showed that four pasture legumes Centrosema pubescens (Centro), Stylosanthes gracilis (Stylo), Pueraria phaseoloides and Calopogonium mucunoides are all well adapted to conditions in the humid zone (Ahlgren et al., 1959; McIlroy, 1962; Adegbola, 1964). Yields realized from these legumes in unfertilized plots at Ibadan are given in Table 8.

Results of pasture legume experiments in Nigeria have shown the superiority of Stylosanthes gracilis over the three other legumes in terms of dry season productivity (Adegbola, 1964). This legume therefore has a great potential for providing an all season feed for sheep, goats and other ruminants (Ademosun, 1970).

A preliminary evaluation of forage legume carried out at the humid zone programme of the International Livestock Centre for Africa at Ibadan, Nigeria, also confirmed the productivity of these legumes. Other promising legumes emerging from this evaluation were: Centrosema pascianum, Lablab purpureus cv. Jhonsi, Desmodium turtuosum, Desmodium cinereum, Calopogonium caeruleum and Desmanthus virgatus.

Table 8. Dry matter production of selected forage legumes at Agege, Western Nigeria, 1959–61.

Source: Adapted from Adegbola, 1964.

Grass/legume mixtures

A combination of forage grasses and legumes have the potential for producing energy and protein required for optimum growth of small ruminants. In the production system, the presence of the legumes enhances the production capacity of the grasses, through the latter's ability to fix nitrogen, which the grasses share. A number of trials carried out in the humid zone have shown the suitability of combinations of various tropical grasses including P. purpureum, P. maximum and Cynodon spp. with a legume such as Centrosema (Ahlgren et al., 1959; Borget, 1969; Evans, 1961; McIlroy, 1962). At Ibadan short grass-legume mixtures (e.g. Cynodon, with Centrosema or Stylosanthes) have provided about 15 t DM/ha annum while tall growing grasses (P. maximum, P. purpureum) in legume (Centro, Stylo) mixtures yielded 25 t DM/ha annum (Olubajo and Oyenuga, 1971). Olubajo (1974) further reports that at Ibadan, a sown pasture of Cynodon nlemfuensis var robusta and C. pubescens was generally superior in productivity and digestibility to four other mixtures of Cynodon nlemfuensis, Centrosema pubescens, Digitaria decumbens, Chloris gayana and S. gracilis. The Cynodon/Centrosema pasture was reported to have yielded over 30 t DM/ha annum when rotationally grazed at various stocking rates over 8 years.

Grass-legume mixture may be ideal for ruminant production but grazing/cutting management is critical in maintaining the optimum balance of the grass and legume components, and carrying capacity will vary widely between wet and dry seasons. The economics and financial viability of such pastures will determine their suitability for small ruminant production.

Establishment and management of sown pastures

This subject has been extensively reviewed by Crowder and Chheda (1982) and also by Matthewman (1977). The essential points in these reviews are as follows:

Seedbed preparation

Successful establishment of most fodder and pasture species is directly related to the extent of tillering prior to sowing (Rains, 1963). In most cases, ploughing, harrowing and soil firming processes are required to ensure soil and seed contact for effective germination, seedling emergence and development. These requirements are less critical for vegetatively propagated species than for the seed-sown ones.

Sowing or transplanting

Most pasture legumes are established from seed while the grasses are usually vegetatively propagated. Seed propagation of forage grasses is problematic, because of difficulties in seed production and maintenance of viability under tropical conditions. Seeds of herbage grasses and legumes are usually broadcast, though semi-decumbent and spreading types (e.g. Brachiaria spp., Cenchrus spp. and Chloris spp.) can be sown in rows generally spaced l m apart. Vegetatively propagated grasses such as Panicum maximum, Cynodon spp., Pennisetum purpureum, Digitaria decumbens, Andropogon gayanus and Brachiaria spp. are usually transplanted by hand into rows 1.0 m apart, with intra-row spacing ranging from 0.50 to 1.0 m.

Sowing at the beginning of the major rainy season is desirable, but this usually conflicts with labour demand for other agricultural activities, e.g. planting food crops. Establishment during this period may also be hindered by serious weed problems and also by run-off and erosion which may bury or wash off forage seeds. It is advisable to delay planting until after the first heavy rains, or until the end of the short dry season where a bimodal pattern prevails (Ahlgren et al., 1959).

Information on seed rate, depth of sowing and seed treatment depends very much on seed characteristics (size, viability, dormancy, etc.) of the various species. Seed rates generally range from 10 kg/ha to more than 40 kg/ha for grasses and from 5 kg/ha to 15 kg/ha for legumes (Adegbola, 1965; Ahlgren et al., 1959; Rains, 1963). The optimum depth of sowing of most grasses lies between 1–3 cm. Large seeded legumes such as Centrosema, Clitoria and Leucaena could emerge even from 4 cm depth, but small seed types such as stylo, glycine, peuro, calopo and Desmodium spp must not be placed deeper than 2.5 cm (Crowder and Chheda, 1982).

Some form of scarification is usually required for most tropical legumes to improve germinability. Hot-water, acid and mechanical means of scarification are the three most common means employed.

Cutting management

The frequency at which herbage is cut from pasture legumes and grasses has a big influence on total productivity of the pasture species as well as on its survival and sustainability. According to Crowder and Chheda (1982), an extended period between cuttings has the following results: an increase in the percentage contents of dry matter, crude fibre, lignin, and cell wall; an increase and then a decrease in total dry matter production and nitrogen-free extract; a decrease in leaf/stem ratio, percentages of crude protein, mineral constituents, ash and soluble carbohydrates; an increase and then a decrease in the amount of nitrogen uptake by the plant and nitrogen recovery; and a rapid decline in animal intake and in digestibility.

In a trial comparing four cutting frequencies (6, 8, 10, 12 weeks) on productivity of leucaena (ILCA, 1987), both total and fodder dry matter yields were found to be positively correlated to cutting interval, in all inter-row spacings tested (Figure 2). To frequent cutting reduces total forage yields, depletes carbohydrate reserves, causes a decline in root development and adversely affects regrowth potential (Akinola et al., 1971; Rains, 1963). The loss in nutritive value over extended periods of cutting is greater in grasses than in the legumes. More nutritious forage is obtained with reduced cutting intervals, thus an optimal harvest period must be chosen for a balance between quality and yield (Borget, 1969; Chheda and Akinola, 1971a, 1971b). A 4–6 week cutting cycle has been found to be ideal for most tropical grasses during the wet season. Cutting frequencies in the dry season are strongly controlled by the extent of dryness and the growth rate during this period. An 8–12 week cutting cycle is also found to be suitable for leucaena and gliricidia.

Fertilizer use

Fodder and forage crops can usually be established without fertilizers, but continuous cropping and removal of residues reduces soil fertility (Matthewman, 1977). Fertilizer use has been reported to have a remarkable effect on the productivity of pastures (Borget, 1969; Adegbola, Onayinka and Eweje, 1968; Rains, 1963). However, the economics of their use in pastures, especially for smallholder sheep and goat production is yet to be amply demonstrated.

With adequate fertilization yields can be considerably increased. While nitrogen inputs are essential for grasses, phosphorous is the most important nutrient in the successful establishment and maintenance of forage legumes. In addition to its effect on DM yield P often increases nodulation and hence increases N or crude protein content and P concentration or uptake by the plant (Haque and Tothill, 1987). Adegbola (1964) recommended 100–200 kg P₂O₅/ha and 50–100 kg N/ha in three instalments applied after 10 days regrowth, as being sufficient for establishment and early growth of legume and grass pastures. Adegbola, Onayinka and Eweje (1968) used a level of 100 kg N/ha for natural grassland (predominantly A. gayanus) and obtained more than 100 percent increase over unfertilized plots in the derived savannah zone. Some more specific reports on the effect of fertilizer use on pasture productivity are reviewed by Crowder and Chheda (1982).

A combination of grasses and legumes (both herbaceous and woody) can be managed such that a portion of the legume tree foliage is applied to the soil as mulch/green manure, to maintain fertility and reduce requirement for N fertilizer thereby reducing input costs. The efficiency of such a system and its effect on dry matter productivity and quality of forage needs to be explored.

Improvement of natural pastures

The low livestock returns on natural pastures can be said to be due to (i) low numbers of high quality species; (ii) lack of management; and (iii) indiscriminate burning during the dry season. Natural pasture can potentially be improved through fertilization, introduction of legume trees and proper management to avoid overgrazing. Where natural pasture is on communal land the incentive and modalities for making such improvements may not exist. Where individual ownership is possible, farmers may fence off a portion of such land, and improve it by fertilization for enhanced grass growth and also by introducing suitable legume trees within the pasture. Experience has shown that the introduction of legumes into natural pastures may not succeed if not coupled with limited phosphate fertilization (Agishi and de Leeuw, 1985). Such plots of improved natural pasture may serve as fodder banks for animals during the dry season.

By far the biggest institutional obstacle to improvement of natural pasture is land tenure regulations which makes natural pasture “open to all” in many countries. The requirement for fencing, the cost of which can be prohibitive and out of reach of most small ruminant keepers, represents the major financial obstacle to improvement of natural pasture. These two obstacles make the prospect of natural pasture improvement by livestock farmers indeed slim.

SUMMARY AND CONCLUSION

Small ruminant production in the humid zone is currently an under-exploited resource. A great potential exists for increased production and productivity if the major constraint of health and nutrition are removed. The nutrition constraint can be removed through and improvement in the production, management and utilization of feed resources for small ruminants.

Fodder trees and browse play a special role in this development. As an important component in the diet, they supply protein especially in systems involving low quality fibrous feeds. Their soil improvement characteristic and multiple-use efficiency make them most suitable for integration into smallholder production systems, and they make a valuable contribution to feed supply throughout the year. The production and wider utilization of these forages both at farm level and at medium/large scale level merits high priority.

Improved pasture development (herbaceous legumes and grasses) has limited relevance to the small farmer situation in the humid zone, but such could be developed for medium/large scale production of small ruminants. Grass species with potential for the zone include Panicum maximum, Pennisetum purpureum, Cynodon spp. and Andropogon spp. Promising legume forages for the zone include Stylosanthes guyanensis (gracilis) Centrosema pubescens, Calopogonium mucunoides and Puereria phaseoloides. Other legumes such as Centrosema macrocarpum, Lablab purpureus, Calopogonium caeruleum and Desmanthus virgotus are also important. A three-species pasture system involving legume trees, forage legumes and grasses is advocated for medium/large scale production in the humid zone.

Natural pastures are of much less relevance in the humid zone, though they exist at the northern boundary of the zone (i.e. derived savannah belt). Their improvement, though technically and biologically possible, is faced with serious socio-cultural, institutional (such as land tenure) and economic constraints, which make them unrealistic and impracticable for smallholder producers.

Efforts should be made at establishing a feed budget for the zone, to match availability of feed throughout the year with livestock (small ruminant) demands. To even out the seasonal feed supply there is need for increased attention on preservation and conservation of feed in times of plenty, such as in the wet season for utilization in dry seasons. This should apply to both pasture forages and tree fodder.

Efforts should also be made, through collaboration of research, development and extension, to demonstrate the workability, practicality and economic viability of intensive or commercial medium/large scale production of small ruminants in the humid zone. Until some concrete evidence is made available, through such a process, the issue of improved production of small ruminants in the humid zone will continue to be a “flying potential” which never lands. It is in the best interest of the region that this potential is made to touch ground in the very near future. Research organizations, both international and national, development agencies and extension services all have a role to play in this task.

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