R.T. Wilson, L. Reynolds and T. Armbruster
International Livestock Centre for Africa
P.O. Box 5689 Addis Ababa Ethiopia
Relativement peu de recherches ont été entreprises jusqu'ici sur la gestion des systèmes de production des petits ruminants dans les zones humides africaines. Néanmoins, il y a un intérêt évident à améliorer la productivité de ces animaux qui représentent encore un secteur trop souvent négligé. Il est également évident que les recherches devront être entreprises par des institutions aux niveaux national, régional et international ainsi que par les universités.
Les résultats existants ont déjà servi à créer le besoin d'approfondir les recherches afin d'en ressortir des informations supplémentaires et à affirmer la volonté d'intensifier les efforts concernant la gestion des troupeaux de petits ruminants. Une analyse perspective de certains résultats suggère que le domaine le plus critique (c'est-à-dire où les améliorations sont le plus nécessaire) est celui des mortalités dont il faut essayer de freiner le taux. L'approche la plus évidente est celle du renforcement des mesures de contrôle sanitaire comme part exemple le contrôle de la PPR. L'amélioration des techniques d'alimentation aura également un effet dépressif sur la susceptibilité aux maladies et donc sur la mortalité.
Des variations du taux de croissance per se ne semblent avoir qu'un impact limité sur les rendements. le second facteur le plus influent sur l'ensemble des facteurs économiques est le taux de reproduction. Celui-ci sera vraisemblablement amélioré, dans une phase initiale tout au moins, par l'amélioration des techniques de gestion.
Relatively little research has so far been undertaken on management in small ruminant production systems in the African humid zones. There is, nonetheless, an evident interest in improving productivity from this previously neglected sector. This is evident from research currently being carried out by universities and national, regional and international research bodies.
Existing results have served to lay the foundation for additional and more intensified efforts to be made in the field of small ruminant management research. Sensitivity analysis of some of these results (Upton, 1984) suggests that the most critical area (i.e. where improvements are most needed) is that of reducing mortalities. The most obvious approach is through veterinary control measures such as the control of PPR. Improved nutrition might also, however, have an impact on disease susceptibility and therefore on mortality. Variation in growth rate per se seems to have a relatively small impact on returns. The second most influential factor on overall economic performance appears to be the reproductive rate. This is most likely to be improved, initially at least, by improved management.
The West African humid zone has traditionally depended on areas to the north to meet its demand for animal protein. Trypanosomiasis has generally limited livestock production and most small ruminants in the zone are indigenous trypanosomiasis-tolerant dwarf breeds. Dwarf sheep and goats are the most common ruminant species, with an estimated 14 million dwarf goats and sheep within the zone in 1984 (Table 1).
Table 1: Small ruminant and human agricultural populations (in millions) in humid West Africa
|COUNTRY||Small Ruminants||Human agricultural population||Small ruminant human population ratio|
|Nigeria||5 621||3 476||9 097||11 955||0.76|
|Ghana||1 200||990||2 190||4 347||0.50|
|Côte d'Ivoire||816||874||1 690||1 555||1.09|
|Sierra Leone||59||20||79||1 601||0.05|
|TOTAL||8 010||5 669||13 679||22 063||0.62|
Source: Adapted from FAO, 1985
While such census data are only crude estimates, small ruminants would appear to be a major underexploited food and capital resource in the humid zone. They are raised almost exclusively for meat but also provide a flexible financial reserve for the rural population and play important social and cultural roles. There have been few systematic attempts by farmers or development agencies to increase small ruminant production, and small ruminants have, until recently, rarely been mentioned in any detail in descriptions of farming systems in the area.
All the available evidence suggests that goats and sheep are owned by a large proportion of the rural population in the humid zone. Small ruminants are also owned by individual men and women rather than by domestic units or kin groups. The majority of rural owners are male farmers engaged in food and tree crop production or women involved in food processing or marketing. Both groups of owners have relatively limited skills in livestock husbandry.
Sheep and goat production throughout much of the zone is one of several minor farm enterprises that add a measure of diversity to the overall farm economy. Livestock are not generally integrated with crop production; few forage crops are grown, and manure is not generally returned to cultivated plots.
The nature of small ruminant production varies from extensive, low-input scavenging to more intensive cut-and-carry feeding of confined animals and commercial grazing of sheep flocks. Although there has been no systematic study of production systems on a zonal basis, it is probable that the majority of animals are kept in free-roaming flocks which may or may not be tethered during the cropping season. Owners of free-roaming animals do not generally provide special feed, housing or veterinary care and there is no control of reproduction. The major investment is in acquiring new stock but caretaking of animals is commonly practised, thereby greatly reducing the initial cash investment. The potential complementarity between smallstock husbandry and other farm activities is evident in the combination of food processing and goat rearing common among women in many rural areas.
Small ruminants are an important item of trade within humid West Africa. Demand and consumption patterns for sheep and goats differ but the importation of animals from the arid north indicates a vast potential market in the humid zone for locally produced animals. The marketing of sheep reaches a peak at Muslim religious holidays, whilst goats are used for all ceremonies throughout the year, such as births, deaths, marriages and festivals. Demand for goats is therefore consistently high. There is a clear price premium for male sheep during the festival period, and some early purchasing for fattening and re-sale takes place.
Under traditional management, sheep appear to yield a higher output and rate of return than goats. Goats are more prolific but sheep are bigger, heavier and have lower mortalities, in addition to fetching a higher price (Upton, 1984). Small-scale sheep production is a somewhat more specialized enterprise than goat rearing, demanding greater management inputs in exchange for higher returns. This specialization, often involving older men with more available time, is a direct response to market forces and illustrates one potential development path for small ruminants in the zone. The commercial sheep flocks currently found in Côte d'Ivoire and Ghana are a further example of this type of specialized development.
Most research with West African Dwarf goats and sheep has taken place on experimental stations, often under the auspices of university departments of animal science and veterinary medicine. Much of this work has recently been reviewed by Ademosun et al (1983) and Berger (1983). These studies give some indication of the biological potential and of potential productivity under certain “improved” management practices but there is now also a considerable body of published and unpublished data on traditional and improved traditional management. The authors of this paper consider that improving husbandry practices in the traditional sector could considerably increase output from that sector. Relatively little work has been done on this, however, and subsequent section of this paper will concentrate on management in the reproduction, nutrition and health fields through the medium of a number of case studies.
Field studies of reproductive performance have been undertaken in Nigeria and in Côte d'Ivoire as well as elsewhere.
Under the traditional conditions in south-west Nigeria the average litter size in goats was 1.50 kids and the kidding interval was 259 days. This gave an annual reproductive rate (ARR) (litter size x 365/kidding interval) of 2.1 kids per breeding female per year. For sheep in the same environment the average litter size was 1.23 lambs and the lambing interval was 322 days: this gave an annual reproductive rate of 1.4 lambs per ewe (Mack, 1983). In this system there was no control of the reproductive processes and does and ewes were mated for the first time when they achieved puberty (first parturition at about 430 days) and produced young all the year round.
In Côte d'Ivoire, data were obtained from three different systems of sheep management which were otherwise operating under very similar ecological conditions. These systems were: uncontrolled traditional breeding management; traditional management with some control of breeding which involved seasonal mating (élevage encadré-lutte groupée); and a ranching system.
In the completely open traditional system age at first lambing was 413 days, in the controlled traditional system it was 480 days and in the ranching system it was 494 days.
Intervals between parturitions (Figure 1) were shortest in the open traditional system (230 ± 53.6 days) and were longer in both the controlled traditional (275 ± 75.6 days) and ranching (267 ± 107.5 days) systems. There were no apparent differences in litter sizes between the three systems, the number of lambs born in each at each parturition being 1.18, 1.23 and 1.15. There were significant differences in the annual reproductive rate between the systems. In the open traditional system the ARR was 1.97 lambs per ewe per year, in the controlled system it was 1.56 and on the ranch it was 1.76.
Figure 1: Distribution of parturition intervals in sheep under three systems of management in Côte d'Ivoire
Within each major system (traditional and ranching) the sources of variation which may have acted on both the lambing interval and the litter size were analysed. There were some differences evident between the two systems, particularly for the two sources over which management could be expected to exert some control. There was a strong (P < 0.01) seasonal effect on lambing interval in the traditional system but not in the ranch system and there were no effects on this trait of the age of the ewe in either system. Similarly, there was an effect of season (P < 0.05) on litter size in the traditional system but not in the ranching system. In both systems, the age of the ewe very strongly (P < 0.01) influenced the litter size with the number of lambs born at each parturition being greater in ewes in the middle-age groups of three to four years.
The combined effects of parturition interval and litter size on ARR did not produce any significant differences due to season in either the traditional (although results were apparently better in the open than in the controlled one) or the ranching system. There were significant differences in this trait, however, due to the age of the ewe with, once again, older ewes producing more young per year.
Although these are only preliminary data, the evidence from these humid zone studies seems to be in general agreement with those found in other ecological zones of Africa (Wilson & Durkin, 1983 and 1987). In the absence of management measures which include factors other than a simple control of breeding (e.g. improved nutritional status at conception), there appear to be few if any advantages to be gained from the practice of controlling the reproductive process. Keeping more middle-aged ewes than young or very old ewes in the flock may improve reproductive performance to a limited extent but it is possible that greater advantages will accrue from concentrating on nutritional and health measures in the early stages of a management improvement programme.
Nutritional constraints in the humid zone are sometimes considered to be less severe than in other ecological zones of Africa. Whilst quantity might often be adequate, the quality of food on offer is often poor. In many systems there is little attempt to overcome these deficiencies but the potential complementarity between smallstock husbandry and other farm activities is evident in the combination of food processing and goat rearing common among women in many rural areas. Household wastes, combined with cassava peels or other crop by-products of small-scale commercial food processing, are important feed resources available to livestock owners having no direct access to land or to fodder crops. Indeed, this kind of feed supplementation is one of the few discernable management inputs in the free-roaming production system. Individual ownership of a relatively limited number of animals could make this an attractive and efficient combination of enterprises.
The major feed resource in extensive systems is, however, uncultivated browse and grasses. Goats in particular are able to select the most nutritious plants and parts of plants, obtaining a reasonably balanced diet throughout the year. It is rare to see extensively raised goats in poor condition unless carrying capacity is exceeded. Farmers may assist by lopping branches that would otherwise be out of the reach of livestock and by providing water to animals at night.
Use must also be made of whatever crop residues are available. Crop residues left in the field will help to maintain soil structure through the provision of organic matter. Is it more beneficial to incorporate residues into the soil or to return manure from livestock as a by-product of crop-residue feeding? The feeding value of a particular residue will be related to the overall feed situation. Where there is a shortage of forage, a residue of low nutritional value will assume a greater importance than when adequate feed is available. Under the latter conditions, quality rather than quantity becomes the major factor.
As human population density rises, the importance of crop-residue feeding increases relative to uncultivated forage. Livestock can have free access to arable fields after harvest in addition to whatever natural forage is available. Animals grazing maize stover always waste part of the feed by knocking it over. Contamination with soil, urine and faeces occurs, and the resultant mixture is unpalatable. A bimodal rainfall pattern limits access to first-season crop residues in situ because cultivation for the second crop closely follows the first harvest. Storage of first-harvest maize is difficult in the absence of drying facilities, so it is often picked green. The remaining stems and leaves can be fed to animals. Farmers can carry forage to the animals each day during harvest, to feed in the pen at night. Any wastes can be composted to fertilize vegetable gardens or can be returned to the fields. Access to fields after the second harvest is less restricted and labour is more readily available for collection and transportation of residues to animal pens.
In many areas, maintenance of soil fertility depends on the inclusion of fallow periods in the farming system. Regrowth during these periods can be made available to animals. Alley farming - growing rows of leguminous trees such as Leucaena leucocephala and Gliricidia sepium with food crops between the rows - provides mulch and browse to the advantage of both crops (Table 2) and livestock (Table 3). The leguminous trees provide high quality, cut-and-carry feed for confined animals. The trees are managed for maximum forage availability in the dry season. In addition, mulch nitrogen helps to maintain soil fertility and reduces the need for a fallow period, so that a larger proportion of land can remain under cultivation. The resultant crop residues are important feed resources during the dry season. The cut-and-carry system of feeding a portion of the tree foliage to small ruminants is highly flexible and can be used with both free-roaming and confined animals. Depending on the availability and quality of other fodder resources, a range of browse feeding strategies can be developed. Browse may be fed as a protein supplement or as a sole feed and it can be fed all the year or solely during the dry season. The effect of browse supplementation to a basal Panicum maximum and cassava peel diet, when offered to adult sheep in the last two months of pregnancy and for a three month lactation period, on productivity index, measured as kg lamb weaned/ewe/year is shown in Figure 2.
Table 2: The effect of alley farming on the yield of maize cobs in southern Nigeria
|Maize yield (t/ha)|
1 st season
|1st season||2nd season||1st season||2nd season|
|Continuous cropping (control)||2.19||2.55||1.16||2.49||1.09|
|Continuous alley cropping||2.54||3.75||1.45||2.83||2.00|
Note: 1) Values in parentheses indicate yields as proportions of control yields.
Source: Attah-Krah, Sumberg & Reynolds, 1986.
Table 3: The effects of supplementary leucaena and gliricidia, with ad libitum Panicum maximum, on the productivity of West African Dwarf sheep (means ± S.E.)
|Parturition interval |
|Survival to 90 days||0.65||0.65||0.82|
|Birth weight (kg)||1.80||1.52||1.72|
|Daily liveweight gain to 90 days (g)||64.4||73.4||83.8|
Note: 1) Productivity index = kg lamb weaned/year.
Source: Reynolds & Adeoye, 1985.
Figure 2: Effects on productivity index of humid zone sheep of provision of a browse supplement
In order to give sufficient benefit to the crop and to ensure that nutrients are returned to the soil, the results of crop yield studies indicate that approximately 75 percent of the available tree foliage should be applied to the soil as mulch. An annual tree foliage yield of 4 t DM/ha would then give 1 t DM/ha of feed. This amount would be sufficient to support approximately 14 adult animals/ha when used as a year-round supplement (25 percent of daily feed intake), or 4 animals/ha when used as a sole feed.
The management of browse trees within the alley farming context must take into account the requirements of the crop for nutrients and light, as well as the seasonality of demand for fodder. Year-round browse feeding, for example, will require a tree management strategy different from simple dry season supplementation.
Where there is only a limited amount of supplement available, preferential feeding to animals in late pregnancy and lactation, or perhaps to growing weaners, is advisable. This will ensure that animals under the greatest nutritional stress will benefit. In intensive systems, the provision of extra rations prior to mating (steaming-up) has been demonstrated to increase litter size, particularly when breeding females are in poor to moderate body condition initially. Steaming-up would be difficult to implement in extensive systems with open breeding but it could be used where animals are confined.
HEALTH AND MORTALITY
Mortalities from disease are high, particularly among goats. Peste des petits ruminants (PPR), a rinderpest-related viral disease, is perhaps the most important cause of mortality, and can drastically reduce the numbers of animals in the flocks. Small ruminant production therefore entails a considerable degree of uncertainty. Other diseases often mentioned as important causes of mortality include the pneumonia complex and gastro-intestinal parasites. Studies of diseases under village conditions are rare, however, and with some exceptions it is currently impossible to determine the actual importance of these as causes of mortality. There is still considerable discussion concerning the importance of PPR in different countries in the zone, and the efficacy of available control measures (ILCA, 1983).
Mortality in goats is usually higher than in sheep, at least in the period before weaning. In south-west Nigeria mortalities in goats to 150 days of age were 23 percent of all young born, whilst losses in sheep were 16 percent (Wilson et al, 1984 and 1985). Losses are, however, known to be as high as 40 percent at weaning.
Health interventions are an area which can have a beneficial impact on productivity. In Côte d'Ivoire the mortality rate to 150 days averaged 29.3 percent for sheep under traditional management whilst under controlled management this was was only 16.7 percent and it was at a similar rate of 15.7 percent in the ranching system. After weaning, mortalities continued at a high level in the uncontrolled traditional system such that by one year of age 48.1 percent of animals born had already died. In the controlled system the death rate at one year was only 28 percent (Figure 3).
Figure 3: Mortality rates in traditional and improved traditional systems of sheep production in Côte d'Ivoire
There are good possibilities for reducing mortality via a relatively simple intervention package. In the Nigerian humid zone, for example, a veterinary package comprising vaccination against PPR and a regular dipping programme to control external parasites has been tested. This has had the effect of significantly increasing the survival rate from 0.67 for animals not benefitting from the package to 0.86 percent for those which did benefit from it (Figure 4). The main effect of these measures was to reduce mortality in the most stressful period during the rains. At 1983 prices the added value of weaned kids was the equivalent to US$ 4.64 per breeding female (Mack, 1983).
Figure 4: Survival rates of goats with and without a veterinary intervention package in south-west Nigeria
Reducing the number of deaths resulting from the husbandry factor offers one of the best prospects for improving productivity but is perhaps one of the most difficult problems to resolve. The factors leading to reduced losses for individual owners need to be identified and then extended to all owners operating within the same production system. Analytical and diagnostic work on this aspect of mortality is in its infancy, but more attention to dams and young at the time of birth and during the first week of life would obviously pay considerable dividends.
Environmental factors influencing mortality include some of those already discussed under the section on reproduction. In addition to system, season and dam age, they would include the sex of the young and the type of birth. The “flock” effect considered to result, at least in part, from individual management abilities, as has just been mentioned, is also an important variable influencing the death rate. Other factors include predation by wild animals (which can also be considered as a husbandry factor). A decrease in the death rate could obviously be achieved within, and perhaps between, countries by attempting to transfer comparative advantages from one system to another and by controlling the season of breeding. In some systems, advantages may also accrue from selecting for birth type or manipulating flock structures so that most breeding females are in the middle age groups.
This paper has been compiled from various earlier sources, mostly produced by our colleagues in ILCA. Sources are acknowledged in the reference list but we take this further opportunity of thanking those colleagues for allowing us the use of their material.
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Attah-Krah, A.N., Sumberg, J.E. and Reynolds, L. (1986). Leguminous fodder trees in the farming system - An overview of research at the Humid Zone Programme of ILCA in south-western Nigeria. In: Proceedings of the workshop on the potential of forage legumes in farming systems of sub-Saharan Africa. ILCA: Addis Ababa (in press).
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Wilson, R.T., Traore, A., Peacock, C.P., Mack, S. and Agyemang, K. (1985). Early mortality of lambs in African traditional livestock production systems. Vet. Res. Commun. 9: 295–301.