S.K. Hahn
Animal scientists, agronomists and feedmill managers have exchanged views and two international centers, ILCA and IITA, have shared their knowledge and experiences at this workshop on production and utilization of cassava as livestock feed, which was held in the interest of national agricultural research systems and industrialists engaged in the production of animal feeds in Africa.
Cassava is one of the most important staple food crops grown in tropical Africa. Because of its efficient production of cheap food energy, year-round availability, tolerance to extreme ecological stress conditions, and suitability to present farming and food systems in Africa, it plays a major role in efforts to alleviate the African food crisis.
Traditionally, cassava tuberous roots are a major source of carbohydrates in human diets and are processed by various methods into numerous products utilized in diverse ways according to local customs and preferences. In some cultures, the leaves are also consumed as a favorite green vegetable. Many traditional foods processed from the roots and leaves of cassava thus constitute the mayor part of a family's daily food. However, cassava is frequently denigrated because its roots have a low protein content. But unlike the roots that are essentially carbohydrate, cassava leaves are a good source of protein and vitamins which can provide a valuable supplement to the predominantly starchy diets and feed. Cassava leaves are rich in protein, calcium, iron, and vitamins, comparing favorably with other green vegetables generally regarded as good protein sources. However, while the vitamin content of the leaves is high, the processing techniques used can lead to huge losses. Boiling of the leaves especially may reduce vitamin C substantially.
Cassava contains the cyanogenic glucosides, linamarin and lotaustralin. After tissue damage, these are hydrolyzed by the endogenous enzyme linamarase to the corresponding cyanohydrins. Further hydrolysis to hydrogen cyanide is responsible for the chronic toxicity associated with inadequately processed cassava products. Therefore, processing procedures must seek to reduce the cyanide in cassava before use. Various processing methods have been used to reduce cyanide quite effectively. For example, grating, sun-drying, boiling and fermenting can reduce cyanide considerably. Aerobic fermenting methods which are commonly used in many parts of Africa also increase the protein content of the final product by introducing molds to cassava tuberous roots.
In collaboration with national programs, IITA has developed high yielding, stable cassava lines, and many national cassava improvement programs in Africa have released improved cassava varieties resulting from IITA's work. Higher productivity is therefore expected from these improved varieties and production technologies. As a result, a surplus is anticipated that could lower the farm prices of cassava products. This has led to a growing interest among government authorities and researchers in Africa on the improvement of processing and utilization of cassava and development of new or alternative uses and products.
Research strategies in national and international research institutes have focused mostly on preharvest activities. However, the future of cassava depends largely upon the development of improved processing technologies and of improved products that can meet the changing needs of urban people and on its suitability for alternative uses such as animal feeds and as industrial raw materials.
The limited supply of raw materials for the livestock feed industry has resulted in a continuous increase in the cost of production, causing a phenomenal rise in the unit cost of livestock products. Thus, these products have become too expensive for the majority of the population.
The principal-future market for cassava is as livestock feed. Cassava has long been recognized by researchers in Africa as an appropriate animal feed and it has been used as an important and cheap feed in many European countries. Both roots and leaves are usable as livestock feed. Cassava offers tremendous potentials as a cheap source of feed energy for livestock, provided it is well-balanced with other nutrients. There is a great deal of current interest in the supplemental feeding of livestock with cassava in Africa.
Traditionally, cassava is fed to sheep and goats in the tropics and it can constitute 20-40 percent of compound livestock feeds, especially in poultry and pigs, with considerable reduction in production costs. However, there is a need to increase available knowledge of technology of utilization of cassava as livestock feed.
I believe that one limiting factor in using cassava as livestock feed is the lack of awareness about its potential and relevant technologies.
The objectives of this workshop are, therefore, to:
1. Collate information on traditional African processing technologies with emphasis on cassava as a livestock feed,2. Review the marketing and economics of cassava by-products,
3. Recommend strategies for future research and development on the processing and utilization of cassava as a livestock feed, and 4. Disseminate up-to-date information on cassava.
On behalf of the organizing committee, I would like to express sincere appreciation to the International Development Research Centre (IDRC) of Canada, particularly Dr Kategile, for sponsoring this important Joint workshop.
