|Sustaining the Future: Economic, Social, and Environmental Change in Sub-Saharan Africa (UNU, 1996, 365 pages)|
|Part 3: Environment and resource management|
|Agricultural development in the age of sustainability: Livestock production|
When considering ecological stability and increased animal protein production from domestic animal species, the two main natural factors of production are:
· the animals - in this case the ruminants but, to a lesser extent, the monogastrics;
· the land and climatic conditions.
Other factors of production are credit facilities, marketing, and the socio-economic status of the herd owners. These factors do not have a direct effect on environmental degradation, whereas the cultural practices in the husbandry system do.
The animal species: Contribution and spatial distribution
Among domestic animals, the ruminants - for example, cattle, sheep, and goats - form the largest number and are of paramount social and economic importance in tropical Africa. There are several reasons why ruminants should be given special attention when considering ecological change in Sub-Saharan Africa.
First, they supply the bulk of livestock products. The ever-increasing demand for these products owing to increased human population and better health education justifies greater attention to animal production if the continent is to avoid a huge animal protein deficit.
Secondly, because of the large population of ruminants and their dependence mainly on global grazing, large areas, especially in West and East Africa, are in danger of irreversible soil degradation and desertification. Ruminants, though not the sole factor in these ecological disasters, contribute through overgrazing and subsequent soil compaction and wind erosion. Their survival is based on genotype adaptability to the fragile environment and the vagaries of climatic conditions.
Cattle and a few other large ruminants constitute 83 per cent of food animals and produce over 45 per cent of meat products and over 90 per cent of available domestic milk supply. Sheep and goats (medium-large stock), on the other hand, constitute 15 per cent of the total number of food animals and contribute about 35 per cent of meat, as well as fibre. As of 1990, 187.8 million cattle, 205.0 million sheep, 173.9 million goats, and 13.6 million pigs were estimated to be in Africa (FAO 1991: 191 and 194). Of these, approximately 178.6 million cattle, 162.4 million sheep, 157.8 million goats, and 13.5 million pigs were in Sub-Saharan Africa. Sub-Saharan livestock produced 6.7 million metric tons of meat (slaughter weight), 14 million metric tons of milk, and 0.9 million metric tons of hens' eggs (FAO 1991: 199-226).
However, there is a higher elasticity of demand than of supply. In West Africa alone, a deficit of 2-4 million tons of meat and 6.5-9.0 million tons of dairy products is envisaged by the year 2000 (McDowell and DeHaan 1986). Table 12.1 shows the distribution of some animal species in Africa compared with world estimates These animals are not evenly distributed across the African continent. As shown in table 12.2, for the West African region, the semiarid zones contain the largest number of ruminant species (16. TLU1) compared with the arid (10.8 TLU), sub-humid (6.2 TLU), and humid zones (4.3 TLU) (Jahnke 1982; McDowell and DeHaan 1986). In terms of stocking density (table 12.3), the arid zone has a low livestock per unit area (2.7 TLU/km2) compared with the semiarid zone (11.1 TLU/km2). Thus the semi-arid areas have more animals per km2 but this is possible because of higher land productivity The highest number of ruminants is found in this zone in West Africa Although the sub-humid and humid zones have greater forage potential, the climate and prevalence of typanosomes limit the use of these two zones for raising ruminant livestock, hence the very low numbers per unit area (2.2 TLU/km2) in the humid zone.
Table 12.1 Livestock numbers in Sub-Saharan Africa, West Africa, and the world, 1990
|World (m. head)||1,279.3||1,190.5||557.0||856.7|
|Sub-Saharan Africa (m. head)||178.6||162.4||157.8||13.5|
|% of world||14.0||13.6||28.3||1.6|
|West Africa (m. head)||42.8||42.2||59 5||6.4|
|% of SS Africa||24.0||26.0||37.7||47.4|
Source: FAO (1991).
Table 12.2 Human and livestock distribution in western Africa, 1979
|Area (km2 million)||4.0||1.5||1.6||1.9||9.0|
|Agricultural population (m.)||6.9||36.1||16.1||31.1||90.2|
|Cattle (m. head)||9.0||21.6||6.2||3.8||40.6|
|Sheep (m. head)||13.2||10.1||6.7||6.0||36.0|
|Goats (m. head)||14.8||19.2||11.8||8.7||54.5|
Source: Adapted from Jahnke (1982) by McDowell and DeHaan (1986).
TLU, Tropical Livestock Unit = 250 kg livestock body weight.
Table 12.3 Livestock densities in various ecological zones of West Africa
|Agricultural population density (n/km2)||1.7||24.0||10.1||16.4|
|TLU per agricultural capita||2.5||0.5||0.4||0.1|
Source: McDowell and DeHaan (1986).
TLU, Tropical Livestock Unit = 250 kg livestock body weight.
The role of monogastric food animals - poultry and swine in particular - in increased animal production potential in Sub-Saharan Africa cannot be underestimated. These animals compete with human beings for available grain, especially maize and sorghum, which are the staple food of the African peoples. However, these species can have greater meat and egg turnover in a relatively short time. Although they are intensively raised on restricted land areas, their contribution to environmental problems can be great. Air pollution owing to odour from pig and poultry houses can be a nuisance to nearby inhabitants. Sustainability of productive capacity of these animals is more easily accomplished, especially with modern trends in housing and feed technologies. Recycling of manure by spreading it on arable cropland ensures increased crop production at reasonable cost as well as environmental conservation.
The land resource, climate, and production systems
Large areas of African soils are said to be fragile and are classified as of low productive capacity in many countries within the continent. Most of the available land for agricultural production is located within fragile and ecologically sensitive regions, e.g. tropical rain forest, arid savannas, and the drought-prone Sahel, where a large proportion of the cultivated area is not compatible with sustainable agriculture. Land-use systems are usually based on incomplete knowledge of the status of the land resources of the various areas (Anande-Kur 1992). These factors must be borne in mind because knowledge and information about the land resources of a given ecosystem for a particular production - arable or livestock - are essential, as can be seen when related to the stocking density and effect on the environment.
For the purpose of this paper, I am more concerned with the ecological and agro-climatic zones in Sub-Saharan Africa as they relate to livestock enterprises and to the sustainability of all production systems.
The ecological zone classification is based on the number of growing days, i.e. days with rainfall. Thus the arid zone has 0-90 days of rainfall, the semi-arid zone has 90-180 days, the sub-humid zone has 180-270 days, and the humid zone has rainfall for over 270 days annually (McDowell and DeHaan 1986). It is the agro-ecological zones that determine both crop and livestock production in a given zone. The intensity, frequency, and distribution of rainfall influence biomass production in a given area, and hence are a determinant factor in the carrying capacity of the land for the purpose of raising livestock. In general, the majority of ruminants in Sub-Saharan Africa are raised on range-land where feed resources are mostly naturally growing grasses and legumes but with occasional supplementation with leaves of shrubs and trees. The husbandry systems are either nomadic, semi-nomadic, or settled. Stock owners with large herds often practice full pastoralism, while those who are agro-pastoralists often have small herds and are sedentary or settled. The global grazing habit of a large number of domestic ruminants has a detrimental effect on the environment, especially as the stocking density can be very high in marginal grazing areas (table 12.3). Because of the high stocking density and fewer watering points in these zones, erosion due to constant trampling around water points can be an added detrimental effect of overgrazing.
The effect of seasonality on ruminant livestock production is also very important. In the mid wet season, forage biomass is higher in quality and quantity, with crude protein up to 9 per cent in most of the native grasses. Natural grasses and legumes are rich and highly digestible at this period. As the dry season sets in, the protein level drops and the roughage quantity increases. There is an increase in lignin content and voluntary intake decreases. This is a poor feed resource, resulting in weight loss and decreased fertility and milk yield for up to 4-5 months of the year. The severity and duration of low-quality feed differ from one country to the other within the region. To worsen the ecology and its available food resources further, there is widespread annual burning of native grasslands, thereby drastically reducing the amount of forage on offer. Indeed, it has been observed that a combination of these factors - low-quality roughage and bush burning, which reduce the biomass available in quantity and quality - could lead to weight losses ranging from 300 to 400 g per head per day for cattle (Zemmelink 1974) and up to 15 per cent of body weight in sheep (Otchere et al. 1977).
In the arid zone, nomadism and transhumant systems of livestock production prevail. In these systems, high mobility for global grazing habit is the most efficient adaptation to the erratic rainfall. Migration from one area to another in search of good quality and quantity of feed and water is the rule. Transhumant or semi-nomadic systems have a home base, although they too are very mobile, with the majority of animals and the family away for several months and only 2-6 lactating cows left at the base to provide milk for sale and for the utilization of the aged parents left behind. Feed from crop residue provides the main energy source during and shortly after harvesting periods.
In all the zones, the main constraints on feed resources are the destruction of perennial tree cover for firewood, bush fires caused by hunters and livestock rearers, and overgrazing. These man-made constraints often lead to serious degradation of the range resources and in some cases to an irreversible process of desertification, especially in the Sahel zone. The sub-humid zone (SHZ) has a high potential for ruminant production because of the high rainfall and vast land area for forage production. In Nigeria, the SHZ contains only 19.59 per cent of the total national livestock units (Otchere and Nuru 1988). This low percentage of TLU in the Nigerian SHZ is attributed partly to tse-tse infestation and high humidity.