2005). Livestock provide traction for plowing, transportation of produce and processing of produce plus manure for soil fertility and use crop residues as feeds. Farmers who use animal draft power for cropping operations improved the quality and timeliness of farming operations, have increased crop yields and incomes and cultivated more land (Wilson, 2003). Livestock contribute to the environment and its conservation through the provision of manure which can assist in sustainable nutrient cycling and in improving soil structure and fertility. It has been argued, however, that livestock merely transfer nutrients from the range and concentrate them in cropping areas and this could be detrimental to the range (De Leeuw et al., 1995).

In addition to the environmental and cropping advantages discussed above, livestock contribute to reduction in hunger as food sources (meat, milk and eggs). The cropbased livestock systems provide a least-cost, labor-efficient way of increasing these outputs (Devendra et al., 2005).

Landless systems. These are defined as systems in which less than ten percent of the dry matter consumed by livestock is produced on the farm (Sere and Steinfeld, 1996) and the systems are further divided into ruminant and monogastric systems or rural and urban systems. The ruminant systems are often based on zero grazing with the increase use of purchased forages or hired land with forage or leguminous trees to harvest leaves (Devendra et al., 2005) or grazing limited to roadsides. Small ruminants (especially sheep in Ethiopia and Nigeria) predominate in these systems although dairy production is practiced in Lesotho, Kenya and Ethiopia. The monogastric systems in SSA are mainly poultry systems, unlike in South Asia where pigs are the major livestock. Urban and periurban livestock production systems involve pigs, poultry, dairy cattle and, where by-laws permit, feedlot fattening. The scale and intensity of production are determined by market opportunities, food preferences and availability of space.

The productivity of these commercial enterprises is high (Sere and Steinfeld, 1996; Delgado et al., 1999; Spencer et al., 2004; Devendra et al., 2005), but their land area is limited. Though current and projected productivity levels lag behind world averages (FAOSTAT, 2005), there is potential to increase productivity per animal unit in SSA through improved genetic resources and disease management and eradication, including gene-based technologies (Makkar and Viljoen, 2005).

 On the downside are the potential environmental and human health hazards posed by these urban and periurban systems (UNDP, 1996; Delgado et al., 1999; Devendra et al., 2005), especially where laws and by-laws regulating livestock production are weak or nonexistent. This presents an opportunity for AKST to provide policy options and goods and services to avert the risks posed by these systems.

2.2.3 Trends in productivity, processing, marketing and value addition
Livestock in SSA are kept for multiple purposes and their products can be classified into immediate, intermediate and indeterminate (Wilson et al., 2005). The immediate prod-

ucts include meat, milk, eggs, fiber, hides, skins and feathers while intermediate products are draft power and manure (as fertilizer and as fuel). The are intangible values attributed to livestock, based on indeterminate products, which include hedging against crop failure (risk reduction), serving as an investment portfolio, sociocultural and religious roles, as well as sport and recreation functions.

Livestock and wildlife are important to SSA country economies. For example, the livestock subsector is responsible for over 30% of the agricultural gross domestic product (GDP) and more than 50% of agricultural labor. The wildlife sector, on the other hand, is worth US$7 million with an annual growth rate of 5% (Wambwa, 2003). The productivity of SSA livestock in terms of immediate products is low in comparison to world averages and projected to remain so for the next 20 or so years (Table 2-1) unless there are major technological and policy interventions. Beef production is 20 times less while milk production is about 40 times less than world averages and pig and poultry products do not fare any better.

The protein consumption from livestock in SSA has remained low, with an average of 9 kg meat and 23 kg milk per person per year, compared to the developed countries, with an average of 76 kg and 145 kg respectively (Delgado et al., 1999). In some SSA countries the proportion of wild meat in total protein supplies can be high thus complementing livestock protein, however, wildlife consumption is often unrecorded and therefore underestimated (Asibey and Child, 1990).

 The increase in population and urbanization, however, has resulted in an increased demand for livestock products (Delgado et al., 1999; ILRI, 2001; Owen, 2005). The huge production deficit is currently met through imports of animal products (FAOSTAT, 2003; ILRI, 2003; Owen, 2005). Interventions in animal breeding and genetics, nutrition and health and policy options for management of grazing and land tenure systems are needed to increase productivity levels in SSA, so as to take advantage of income potentials from the increased demand for livestock products.

 In SSA edible livestock products are generally marketed in an unprocessed form. Milk is a perishable product and needs to be processed within a few hours from milking to prolong shelf life and marketability. Several traditional and modern processes exist for the processing of milk (Brumby and Gryseels, 1985). Most of the milk produced in SSA is marketed raw or with minimum rudimentary processing within the community. Meat is often sold fresh and there are very few canning and other processing plants outside of Southern Africa. The market for live animals is quite large, especially during religious festivities. This lack of value-addition provides a potential for AKST to contribute to increased income earnings and hunger reduction through technologies and systems that increase processing of these livestock products for increased shelf life, ease of transportation and diversification of products on sale to consumers and ultimately, wealth creation.

2.2.4 Livestock and wildlife pests and diseases
Pests and the diseases they transmit are major constraints to the development of livestock and wildlife industries in SSA (Bengis et al., 2002). Hence one step toward develop-