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Small-ruminant feeding systems for small-scale farmers in humid West Africa

O. B Smith

International Development Research Centre (IDRC)
Regional Office for West and Central Africa
BP 11007, CD Annexe, Dakar, Senegal

ABSTRACT

Although not fully integrated into the crop-farming systems which constitute the major agricultural activity in humid West Africa, small ruminants play important economic, cultural and social roles. Of particular interest is their use as a means of storing wealth in times of agricultural plenty, to provide cash reserves for emergencies and to guarantee a degree of food security in times of crop failure. If small ruminants are to continue to play these roles, in addition to improving the protein nutrition of the population, constraints on productivity must be alleviated. One of the major constraints is inadequate and fluctuating feed supply. It is suggested that this results from poor feed management and utilisation, rather than from absolute shortages.

The major feed resources available are natural pastures, browses and crop residues and byproducts. The availability and quality of these resources vary, but evidence is presented to show that when they are properly selected and combined according to their nutritional characteristics, adequate and productive diets could be provided all year round, for sustainable small-ruminant production and productivity. A number of proven feed combinations targeted towards particular seasons and ecosystems are suggested. Future research activities required to identify additional feeding systems are highlighted.

RESUME

Systèmes d'alimentation destinés aux petits producteurs d'ovins et de caprins dans la zone humide d'Afrique de l'Ouest

Bien qu'ils ne soient pas encore pleinement intégrés dans la production végétale, la principale activité agricole de l'Afrique de l'Ouest les petits ruminants occupent une place économique et socio-culturelle importante dans cette région. Plus particulièrement, ils constituent en période d'abondance, une forme d'accumulation richesses. Celles-ci procurent des recettes monétaires permettant de faire face aux situations d'urgence et d'éviter le pire en cas de mauvaises récoltes. Cela dit, seul un accroissement durable de la productivité de ces animaux leur permettra de continuer à remplir ces fonctions tout en contribuant à améliorer l'alimentation protéique des populations. Les principaux obstacles à l'amélioration de cette productivité sont l'insuffisance et les fluctuations des ressources alimentaires du bétail. Ces problèmes semblent dus, non pas à des pénuries réelles, mais d'une mauvaise gestion alliée d'une mauvaise utilisation des ressources alimentaires disponibles.

Celles-ci sont constituées de foin de pâturages naturels, de fourrages ligneux, de résidus de récoltes et de sous-produits agricoles de diverses qualités produits en quantités variables. Cette étude montre que des choix rationnels et des combinaisons tenant dament compte des caractéristiques nutritionnelles de ces divers aliments pourraient permettre d'offrir aux petits ruminants, d'un bout à l'autre de l'année, des rations propres d'assurer chez ces animaux une productivité et une production soutenues. Un certain nombre de combinaisons satisfaisantes ont été proposées selon les saisons et les écosystèmes. Enfin, des axes de recherches futures ont été suggérés en vue de l'identification d'autres systèmes d'alimentation appropriés.

INTRODUCTION

Humid West Africa is made up of two distinct belts - the lowland, coastal rain forest and, to the north, the derived savannah belt. Together, they cover a total land area of 707 000 km², stretching from the lower third of Nigeria to Guinea. According to Jahnke (1982), annual rainfall in this zone is well over 1500 mm, and the crop growing season could be 270 days or more. The coastal lowland forest area contains cultivated farm land and bush fallow which, together with natural clearings, are often invaded by coarse grasses (Pennisetum spp). These grasses are sparse or absent under the forest trees that are abundant in this belt but sparse in the savannah belt, where regular fires have reduced tree cover to low trees, shrubs and bushes. Fallow areas in the savannah are also covered by coarse grasses, predominantly Hyparrhenia spp (Atta-Krah and Reynolds, 1989).

Small ruminants are the dominant livestock species in the zone, with an estimated population of about 14 million (Table 1). The dominant breed of both sheep and goats is the West African Dwarf. These animals are raised exclusively for meat, serve as cash reserves for emergencies and guarantee a degree of food security in times of crop failure. They therefore play an important social and cultural role for the households and communities that keep them. Small-ruminant flock sizes in these communities are small, about two to six animals per household, with goats out-numbering sheep. But large numbers of households keep small ruminants: figures reported in the literature range from a low of 23 to a high of 70% of rural households. A large proportion of these animals are owned and managed by women.

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

Country

Populations (thousands)

Ratios

Goats

Sheep

Total small ruminants

Agricultural humans

Goats:sheep

Small ruminants per agricultural human

Côte d'Ivoire

816

874

1 690

1 555

0.93

1.08

Ghana

1200

990

2 190

4 347

1.21

0.50

Guinea

79

86

165

1 104

0.92

0.15

Liberia

190

190

380

1 268

1.00

0.30

Nigeria

5621

3476

9 097

11 955

1.62

0.76

Sierra Leone

59

20

79

1 601

2.95

0.05

Togo

45

33

78

233

1.36

0.33

Total

8010

5669

13 679

22 063

1.41 a

0.62 a

a Means

Source: Jahnke (1982)

PRODUCTION SYSTEMS

Small-ruminant production is just one of several farm activities undertaken in humid West Africa. Household food needs are met from cereals (maize, sorghum), root crops (cassava, yam, sweet potato) and food legumes (cowpeas) which are grown in a bush fallow rotation. Cash needs are met by income from cultivation of tree crops (cocoa, oil palm, rubber) and fruits (pawpaw, orange, plantain and banana). Small ruminants and other livestock are rarely integrated with crop production, and account for a small portion of household expenditures, but nevertheless make an important contribution to the total economy. This lack of crop-livestock integration means that crop residues and byproducts are not systematically and strategically used for livestock feeding, and the potential of animal waste to improve soil fertility and conservation is not fully exploited.

Perhaps the most common small-scale small-ruminant production system is that described as the traditional system - a low-input extensive or subsistence system, based on free grazing of roadside and bush forages complemented with kitchen wastes (peels of tubers and fruits, cereal brans) and crop residues (cereal stovers). Another common system of production is the intensive cut-and-carry feeding of tethered or confined animals, found in densely populated areas where almost all available land is devoted to cultivation, such as Eastern Nigeria and Benin Republic. In such densely populated areas, small ruminants are tethered or confined to protect crops and are therefore hand-fed, albeit with the same feed resources as in the free-roaming system.

Although the two systems are reasonably efficient in terms of the objectives and resources of the small-scale farmer (von Kaufman and Francis, 1989), there is room for improvement if major constraints facing the producers can be alleviated. Identified constraints include a high incidence of disease and pests, inadequate and fluctuating feed supply, poor husbandry and a lack of effective extension services (Ademosun, 1988; Atta-Krah and Reynolds, 1989; von Kaufman and Francis, 1989). This paper mainly addresses the problem of inadequate and fluctuating feed supply, particularly highlighting ways of alleviating this constraint through a judicious exploitation of the potential complementarily of the available feed resources.

AVAILABLE FEED RESOURCES

Feed resources available to smallholder production systems are natural pastures, browses, crop residues and kitchen wastes.

Natural pastures

Natural pastures grow on uncultivated land to which animals have access for grazing. They are found along roadsides and on fallow lands in the coastal forest belt of humid West Africa. They assume more important proportions in the open derived savannah. According to Atta-Krah and Reynolds (1989), natural pastures consist of a mixture of grasses such as Imperata cylindrica, Andropogon gayanus, Pennisetum spp and Hyparrhenia spp. These grasses grow rapidly during the wet season, becoming fibrous and coarse, and are undergrazed because of the large amounts that become rapidly available. Their quality declines further during the dry season when they become standing hay and are subject to overgrazing.

A review of published nutrient contents of these grasses shows that during the period of rapid growth (wet season) they contain, on average, about 25% dry matter, made up of 10% crude protein, 6% ash and a fibre content of 32% crude fibre or 43% acid detergent fibre (ADF). As the dry season advances and conditions become harsh, their nutritional quality declines to the extent that crude protein could fall to as low as 2%. Ash values decline to about 3-4% as a result of translocation to the root system, while fibre content increases in response to the process of lignification, sometimes to up to 50% crude fibre or 60% ADF.

In other words, these grasses cannot meet the nutrient requirements of small ruminants for most the year. Even during the rains they can only satisfy maintenance requirements. In vitro and in vivo studies carried out to evaluate these grasses have confirmed this conclusion.

In a recent study in which rumen degradability in sheep, goats and cattle was used as a screening technique to evaluate the potential nutritive value of various feed resources, Smith et al (1989) concluded, on the basis of 48-hour dry-matter degradability in sheep and goats, that because of high cell wall contents during the dry season, the quality of grass forages such as Pennisetum and Andropogon spp may be too low to sustain the animals. Supplementation with browse or crop residues was recommended.

Table 2. Intake and utilisation tropical grasses by goats

Feed

Dry matter (g/kg0.75)

Digestibility (%)

Digestible dry-matter intake (g/kg0.75) a

Offered

Consumed

Panicum maximum (well fertilised, 6 weeks old)

75

54.9

75.8

41.6

P. maximum (hay)

77

43

45

19.4

Cynodon nlemfuensis

87.5

40.6

43.2

17.5

C. nlemfuensis (hay)

131.5

39.9

46.6

18.6

a NRC (1981) maintenance requirement for goats is 27 g digestible organic matter intake/kg0.75 per day, le, about 30 g digestible dry matter intake/kg0.75 per day, assuming 10% ash

Source: Ademosun et al (1988)

Data from Ademosun et al (1988), summarised in Table 2, confirm the suggestion that unless well fertilised, and harvested young, tropical grasses alone cannot supply small ruminants with the nutrients required for a reasonable production level. The production of high quality forages requires inputs and management know-how not yet available to the small-ruminant producers within the farming system described above. Other readily available feed resources must therefore be used to complement the forages. Fodder trees and shrubs (browses) can apparently fulfil this role.

Browses

Browses, in the form of fodder trees and shrubs, form an integral part of farming systems in humid West Africa (Atta-Krah et al, 1986). As their establishment and management require little effort, labour, time, technical know-how or resources, it should be easy to promote and intensify their use as animal feed. The multipurpose nature of browses as fuel wood, shade, food (fruits), poles, etc. as well as their potential to improve soil fertility and conservation, are added incentives.

In terms of utilisation as animal feed, browses currently play an important, albeit non-strategic, role, as animals under confinement often receive one type or another of browse, from fallow lands or around homesteads. Efficient utilisation in a complementary way with grass forages and crop residues is what needs to be worked out through research, in order to exploit their potential nutritive value.

Data in the literature demonstrate the potential complementarily between browses and grass forages. The nutrient contents of some common browses, shown in Table 3, indicate that, on average, browses contain more crude protein and organic matter, but less fibre, than tropical grasses, and should, therefore, increase nutrient supply to the animal when combined with the poorer quality forage. Rumen degradability studies by Smith et al (1989) and others (Minor and Hovell, 1979; Kabaija, 1985) show that many browses degrade fairly well and rapidly (Table 3), supplying much needed soluble carbohydrates and fermentable nitrogen to the rumen, thus enhancing forage breakdown. Many of these browses contain high levels of essential elements such as calcium, sodium and sulphur, as well as critical microelements such as iron and zinc (Kabaija and Smith, 1989; Devendra, 1990), which have been shown to be deficient or borderline for productive purposes in many tropical grasses (Olubajo, 1974; Kabaija and Smith, 1987). Moreover, most of the browses remain green all year round and, if properly managed, continue to provide substantial amounts of foliage even during the dry season. Browses, therefore, complement grasses both quantitatively and qualitatively. Several feeding and growth trials have confirmed the potential of browses to enhance forage utilisation and improve performance.

In long-term studies designed to evaluate the effects of browse supplementation on the productivity of sheep (Reynolds and Adediran, 1987) and goats (Reynolds, 1989), pregnant ewes and does maintained on a basal diet of Panicum maximum were supplemented with graded levels of a 1:1 (w/w) mixture of Gliricidia sepium and Leucaena leucocephala over two reproductive cycles. Browse supplementation increased growth rate to weaning of both kids and lambs by 45%. When the effect of direct supplementation to the kids and lambs was examined, browse supplementation doubled growth rate from birth to six months in both species. It was also observed that browse supplementation increased overall daily dry-matter intake by the dams during the final two months of pregnancy and four months of lactation A productivity index calculated as weight of offspring weaned/dam per year increased by 0.64 kg in goats, and 1.41 kg in sheep.

Table 3. Nutrient contents and rumen degradabilities of some common browses

Browse

Dry matter (%)

% Dry matter

Dry-matter digestibility (%)

Half life (hours)

Crude protein

Acid detergent fibre

Crude fibre

Ash

Dry matter

Nitrogen

Bamboo leaves

27.3

21.0

47.9

28.2

11.0

36.6

-

-

Cassava leaves

23.8

23.0

29.8

17.4

3.5

84.3

13.1

20.5

Gliricidia leaves

23.5

28.4

29.4

20.7

9.7

75.7

12.0

7.9

Leucaena leaves

24.0

30.0

33.8

31.7

8.8

70.0

23.2

21.2

Sources: Minor and Hovell (1979); Kabaija (1985); Ademosun et al (1988); Smith et al (1989)

Recently, Ademosun et al (1988) reported that in a series of feeding trials with goats, results from preliminary experiments suggested that tropical grasses alone could not provide stall-fed goats with the nutrients required for reasonable production levels. Therefore, in subsequent trials they evaluated the effect of supplementing these grasses with two common browses, Gliricidia and Leucaena. The results, summarised in Table 4, demonstrate the potentials of these browses to improve the utilisation of poor quality forages. Follow-up studies were designed to investigate the potential of these browses as sole feeds, a feeding system that could be particularly valuable during the dry season when there is an acute shortage of conventional forages. Table 5 summarises some of the results obtained.

All of these studies suggest that the use of browses, such as Gliricidia and Leucaena, either as supplements to tropical forages or as sole feeds, is a viable feeding system in humid West Africa. The spectre of dihydroxypyridone (DHP) toxicity in the case of Leucaena should not be a deterrent, as evidence exists that rations containing up to 50% by weight of Leucaena constitute no hazards to sheep and goats (Ademosun, et al 1988).

Crops residues and kitchen wastes

As indicated above, an important component of the farming system in humid West Africa is the cultivation of various crops - food crops (maize, sorghum, cassava, plantain) or tree crops (cocoa, oil palm, rubber). Many of these crops undergo primary processing, either at the homesteads or farmsteads, thus producing a substantial amount of crop residues. Unlike browses, which tend to have medium to high nutritional values and hence complement poor quality forages, the nutritional value of crop residues could vary from high to low levels, similar to those of poor quality forages.

Table 4. Complementarity of tropical forages and browses

Feed combination

Intake (g/kg0.75 per day)

Dry matter

Digestible dry matter

Panicum maximum hay ad libitum

43.1

19.4

Panicum maximum hay ad libitum plus


10 g Gliricidia/kg0.75

51.1

23.5


20 g Gliricidia/kg0.75

58.7

30.0


30 g Gliricidia/kg0.75

69.1

37.9

Panicum maximum hay ad libitum

48.3

22.9

Panicum maximum hay ad libitum plus


10 g Leucaena/kg0.75

50.8

20.2


20 g Leucaena/kg0.75

66.1

34.4


30 g Leucaena/kg0.75

68.4

32.6

Source: Adapted from Ademosun et al (1988)

Table 5. Leucaena and Gliricidia as sole feed for goats

Feed combination

Intake (g/kg0.75 per day)

Proportion consumed (%, dry-matter basis)

Total dry matter

Digestible dry matter

Growth rate (g/day)

% of optimum growth rate

Panicum maximum (hay)

100

43.1

19.5



Gliricidia sepium

100

66.7

37.9

23.3

39

Gliricidia sepium plus

65

70.9

42.3

36.0

60

Leucaena leucocephala

35





Gliricidia sepium plus

36





Leucaena leucocephala plus

31

70.1

49.6

43.5

73

Cassava

33





Panicum maximum plus

20

77

55

60

100

Concentrate

80





Source: Adapted from Ademosun et al (1988)

Many crop residues are low in protein, are highly fibrous and, therefore, low in fermentable carbohydrates. Such feeds fail to maintain an efficient rumen ecosystem for their own degradation and/or that of equally poor forages. Theoretically, but also from practical observations, it has been suggested that the characteristics of a maintenance diet for adult ruminants are a crude-protein level of 6-7%, a dry-matter intake of about 1.7% of body weight and a dry-matter digestibility of 50-55% (Devendra, 1985). Table 6 shows that many crop residues rarely meet these requirements. Such residues may require upgrading by chemical, physical or biological treatments to improve their value and usefulness. Such treatments may, however, not be economically suitable for small-scale small-ruminant production systems in humid West Africa.

Whereas crop residues (cereal straws, stovers) may not be suitable as supplements to poor quality forages, they could be used as basal feeds, supplemented with better quality feed materials such as browses. Evidence exists in the literature (Table 7) that a feeding system consisting of fibrous crop residues supplemented with browses is a viable one.

Table 6. Voluntary dry matter intake and digestibility of selected crop residues

Crop residue

Crude protein (%)

Intake as % of body weight

Dry-matter digestibility (%)

Sources

Sheep

Goats

Sheep

Goats

Maize stover

4.0

-

0.7

-

53

1

Sorghum stover

4.0

-

2.0

-

57

1

Rice straw

4.2

1.4

1.9

47

48

2

Cocoa pods

5.0

-

-

20

-

3

Sources: 1. Alhassan et al (1984); 2. McManus et al (1972); 3. Smith and Adegbola (1982)

Table 7. Performance of goats fed on crop residues supplemented with browses

Basal diet

Dry-matter intake (g/kg0.75 per day)

Growth rate (g/day)

Corn stover

78.5

56.3

Sorghum stover

74.8

55.0

Sugar-cane tops

67.3

50.0

a All three diets supplemented with groundnut haulms, cassava tops and Leucaena leaves

Source: Soedomo-Reksohadiprodjo (1985)

Other crop residues could, nevertheless, be used as supplements in feeding systems based on poor quality forages, because of their fairly high nutritive values. Such residues as roots and tuber peels, cereal brans and grain legume brans supply a fairly high amount of much needed soluble carbohydrate and fermentable nitrogen to the rumen. The potential feeding value of this category of crop residues is demonstrated in Table 8.

Table 8. The value of sun-dried peels as supplements to poor quality tropical forage for sheep

Diet a

Dry-matter intake (kg/day)

Weight gains (g/day)

Dry-matter digestibility (%)

70% Pennisetum purpureum

0.87

45.2

50.7

35% Pennisetum purpureum plus 35% Cassava peels

136

106.7

79.0

70% Cassava peels

1.06

227.1

88.1

a Au diets supplemented with cottonseed cake

Source: Fomunyam and Meffeja (1987)

In other words, in order to maximise the feed value of crop residues in humid West Africa, researchers need to investigate this nutritive-value-based dichotomy, and classify these materials into potential supplements to forages or browses, and potential basal feeds that require supplementation with browses. Table 9 shows such a classification for some crop residues available in the forest belt of humid West Africa. The classification based on crude-protein and fibre (ADF or NDF) contents and in-situ degradability will facilitate the formulation of feeding systems that maximise the use of available feed resources.

Table 9. Nutritional role of common crop residues in humid West Africa

Crop residue classification

% DM

Crude fibre

Acid detergent fibre

Crude protein

In situ degradability (% DM)

Basal feeds

Rice straw

20-45

45-55

2-9

30-34

Cocoa pods

20-45

55-59

2-8

38-40

Sugar-cane tops

28-34

43

5-8

10-20

Sorghum stovers

31-35

45-50

3-6

25-30

Corn stovers

28-46

46-50

2-8

50-65

Supplements

Cassava peels

10-22

15-18

3-7

70-75

Yam peels

5-8

10-12

5-8

75-80

Sweet potato peels

-

15-18

6-10

80-90

Cowpea husk

40-45

38-40

6-10

70-75

Maize bran

-

8-10

15-20

75-80

RECOMMENDATIONS

From the foregoing, it is clear, that a number of feasible feeding strategies exist. In order to exploit available resources, the choice must be guided by season, number of animals to be fed, available resources and ecological zone. The suggested systems shown in Table 10 have been guided by these factors as well as by research results discussed above. The list of suggested feeding systems in Table 10 is by no means exhaustive, and many more could be added as a result of current and future research results. Some of the pressing future research needs which have high potential pay-offs include:

· characterisation through nutritional studies of the role of various crop residues and kitchen wastes as supplements or basal feeds within particular feeding systems

· nutritional evaluation of local browse species. The advantages of promising local species over introduced species such as Leucaena in terms of farmer adoption, are obvious

· integration of small ruminants into the alley farming concept, particularly working out the proportion of foliage to be recycled directly as mulch, or indirectly through animal faeces, in order to ensure sustainability

· development of small-scale producer-targeted technology for making forage silages. Such technology would involve no more machinery than a hand-run chopper and no additives other than forages, crop residues or browses rich in fermentable carbohydrates and nitrogen

· integration of small ruminants into tree-crop production

· adaptation of the fodder bank concept to small-ruminant production.

Table 10. Suggested feeding systems for small ruminants in humid West Africa

Feeding system

Target belt

Target season

Forage based

Forage plus browse

Forest, Savannah

Wet

Forage plus browse plus crop residues

Forest, Savannah

Wet

Forage plus highly fermentable crop residues

Forest, Savannah

Wet

Browse based

Browse alone

Forest, Savannah

Dry

Browse plus fermentable crop residues

Forest, Savannah

Dry

Crop-residue based

Fibrous crop residues plus browse

Forest, Savannah

Dry

Fibrous plus fermentable crop residues

Forest, Savannah

Dry

Novel systems

Under-tree crop grazing plus supplement

Forest

Wet

Alley farm foliage plus crop residue

Forest

Dry

Fodder banks

Savannah

Dry

CONCLUSIONS

Efforts to alleviate current constraints of inadequate and fluctuating feed supply to small ruminants in humid West Africa should be directed primarily toward a proper knowledge of the nutritional characteristics of various feed resources available in order to fully exploit the natural complementarily that exists between them. Current feed management and utilisation practices also need to be examined critically, in order to identify those that maximally exploit the nutritional potential of the feed resources.

For example, farmers keeping small ruminants in the forest belt of humid West Africa feed crop residues and kitchen wastes such as cassava peels, maize bran and cowpea husks to their animals first thing in the morning, before turning the them out to graze fibrous grasses all day. Results of rumen degradability studies suggest that this system should be the other way round, with the rapidly degraded peels, brans and husks fed late in the afternoon and at night, to better synchronise the release of the energy and nitrogen they contain with those of the less rapidly degraded grasses. This thesis needs to be verified on-farm.

The abundant, lush and nutritive roadside and fallow land grasses during the rains are currently underutilised. This resource needs to be preserved as silage for dry-season feeding. The challenge to researchers is to develop an ensiling technology harmonious with the resources of the small-scale producers.

Feed constraints currently limiting small ruminant production and productivity in humid West Africa are, to a large extent, due to a non-strategic utilisation and combination of available feed resources, to develop production feeding systems, rather than absolute quantitative and qualitative shortages.

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