Report of working group A
Report of working group B
Report of working group C
Feeding cassava to ruminants
Scenario A-Cassava surplus
1. The circumstances
In the circumstances of surplus cassava production, both cassava and its byproducts can be used for animal feeding. Research confirmed the biological feasibility of using cassava and its by-products for feeding ruminants. The economics of this depends upon prevailing market prices.
Small ruminants: Cassava and its by-products can be fed to small ruminants provided adequate roughage is available. The energy from cassava will improve digestibility of dry matter and nitrogen.
Beefcattle: The economics of using cassava tuberous roots in beef cattle rations requires further study. Cattle in sub-Saharan Africa are usually free ranging, and their major areas do not overlap with cassava producing areas. Cassava tuberous roots and/or peels could provide complementary energy to a low cost N source such as poultry manure for cattle concentrate. Research is needed to investigate this further. Short-term wilting (3-4 hours) of cassava leaves gives toxic levels of HCN, but 48-hour wilting is safe. Cassava leaves contain 20 percent protein and could be an important source of nitrogen.
Dairy cattle: In smallholder dairy units in Tanzania, cassava tuberous roots with dried Leucaena and a mineral supplement support levels of milk production of 10-12 liters per day in crossbred Freisian cows on natural grazing and twice-daily milking. Research is needed on other combinations of cassava and legume forages that can be produced on-farm and are suitable for smallholder and commercial dairy units.
Cassava varieties that produce high leaf yields and fewer tubers exist and are frequently used as vegetable for human consumption. These varieties could be investigated as a forage protein source. The effects of leaf harvesting on the tuber yields of high yielding cassava varieties, the timing of leaf harvesting, and its effect on HCN levels in the tubers should be studied. The economics of labor for leaf harvesting, and the possibility of direct grazing on mature plants before lifting the tubers should be studied. Little information is available on the feeding value of cassava stems, but the group believed that this would be a low priority research area.
When a surplus of cassava exists, the overriding consideration for its use in livestock feed will be the relative prices of animal products, cassava, protein supplements, and competing energy sources.
2. Target groups
For the use of cassava for ruminant feeding, three main target groups were identified. The groups are:
a. Farmers with access to limited resources (small-scale);
b. Farmers with better access to resources (medium/large-scale); and
c. Small-scale feed processors.
The other groups considered were traders with short-term livestock holdings, and large-scale feed processors.
Traders may purchase feed packages. Large-scale producers have not been responsive to changes in technologies that would permit the use of cassava for ruminants. Ruminant feed accounts for only about 5 percent of commercial feed production. Small-scale feed processors are likely to be more receptive to change.
The differentiation between small-, medium-, and large-scale producers was discussed, but an Africa-wide definition was difficult to formulate. The general descriptions of "subsistence" and "commercial" were taken as acceptable working terms.
3. Research strategy
The major research focus would be the development of feeding systems using cassava with home-grown N-rich forages for subsistence farmers, and other low cost N sources (poultry manure, urea) for commercial farmers. Small-scale feed processors would also rely on low-cost N sources (locally available) to mix with the cassava. Rapid fermentation of cassava in livestock rumen is best utilized in combination with an NPN source (urea) or forage legumes that can be consumed before cassava. This might be practicable if cattle grazed a legume pasture, and then received a cassava concentrate on return to the kraal. Adequate on-station and on-farm testing are needed before new packages are extended to farmers. With dairy cattle, the long-term effects on reproduction should also be tested. Research into small-scale processing of cassava should be encouraged.
4. Prioritization and formulation
Cattle, sheep and goats can utilize tubers, leaves, peels and other processing byproducts. The priority given will depend upon the relative importance of the various animal species in a given environment. Kenya and Tanzania may prefer to use tubers for dairy cattle, while in southwestern Nigeria, where few cattle are found, cassava may be fed to small ruminants.
Energy feeds are important for draft animals, but cassava producing areas do not overlap with draft use. Therefore, if cassava is to be used as a feed source, it will be in the form of processed concentrate.
5. Economic and social implications
Use of cassava for animal feed will raise demand, and hence stabilize prices when surplus cassava is produced. The market structures and pricing policies should be in place to cope with increased production of animal products. Eventually, increased production of animal products will raise family income, but initially, more family labor will be required. This may come from the women and children in the farming families. With increased income, hiring of labor may be possible. Cooperative grouping of producers and processors may also emerge.
Scenario B-Cassava insufficiency
1. The circumstances
In the circumstances of insufficient cassava production, by-products (peel, leaves, other processing by-products) can be used for animal feed. However, because of infrastructural inadequacies there may be localized areas of cassava surplus, although there may be a deficit throughout the African continent.
2. Target group
The target group to use the cassava by-products will now be predominantly small farmers. Very little cassava or cassava by-products will reach the small farmer from processors for animal feed.
3. Research strategy
There is a need for industrial users of cassava to examine the uses of, and animal responses to cassava by-products. The economics of using fibrous byproducts should be studied.
4. Prioritization and formulation
Cattle, sheep and goats will feed on leaves, peels and other processing byproducts.
5. Economic and social implication
The use of cassava by-products will provide additional income to the farmer.
Feeding cassava to nonruminants
1. Current knowledge and application
There is abundant literature to indicate that cassava and its by-products in the fresh and dried forms can be fed to different classes of livestock. For monogastrics, tubers can be fed at levels of 20-40 percent. The mayor constraints of cassava product utilization are its (a) low protein, (b) high cyanide content, (c) dustiness, and (d) microbial contamination due to high moisture content.
Supplementation of cassava diets with soybean meal is recommended. Where practicable, fishmeal supplementation should be adopted to meet the lysine and methionine requirements in such rations. Processing techniques have also been developed to reduce the cyanide contents of cassava to low levels. In this regard, a level of 100 ppm total HCN should not be exceeded in cassava products for animal feeding. Pelletizing is recommended to reduce the dustiness of feed in large scale feedmilling. Vegetable or animal fat or molasses can be used to reduce dustiness and boost energy content of the rations. Materials should be dried to as low as 12 percent moisture content to reduce the incidence of microbial growth. Introduction of other contaminants during drying should be avoided. The adoption of these recommendations should be guided by their economic implications.
2. Research gaps and future actions
While there are several methods for cyanide determination, there is the need to adopt a uniform analytical technique so that results from different areas can be compared. There is also need to develop a rapid, simple and cheap technique for cyanide determination on farm sites. In this regard, it was noted that the picrate test, though rapid, does not guarantee the estimation of total HCN in the cassava material.
There is the need to study the present forms in which cassava is processed and fed to livestock particularly on farm sites in different regions of Africa. Researchers should also intensify on-farm research and interaction with cassava/livestock farmers. This will form the basis for the development of cassava processing and utilization programs that will be evolved from existing on-farm practices.
Due to the scarcity of fishmeal in many African countries, it is necessary to explore the utilization of other animal by-products that can be used to supplement for lysine and methionine in cassava-based rations.
3. With cassava surpluses
In African countries where there is surplus in cassava production over that required for human consumption, the surplus can be used in industry or livestock feeding, or exported. In addition to feeding fresh or ensiled cassava and its by-products to pigs, the possibility of feeding wet material to poultry has been demonstrated in some countries. Adoption of such a feeding system can contribute significantly to the expansion of smallscale poultry units in different regions of Africa.
4. General comments
It is recognized that the adoption of any of the recommended processing and utilization techniques will be primarily dictated by economic implications. It is envisaged that even where there is a deficit in cassava supply, techniques can be developed and adopted for the utilization of cassava leaves, stems and peels with favorable economic returns to the farmers. It is necessary to encourage cassava farmers to integrate livestock production into their farming systems such that the by-products of cassava can be used for livestock feeding, while the manure from such stock can be utilized for production of vegetables and other crops. This practice will enhance the economic efficiency of such farming systems.
Finally, it should be recognized that it is socially and economically advantageous to encourage the utilization of cassava in animal feeding, because experiences have confirmed that increase in production of cassava leads to a glut in the cassava market. The price instability that prevails discourages the expansion of cassava cultivation and utilization. The diversion of such excess cassava for animal feeds will guarantee price stability of cassava, and encourage sustained cassava production.
Processing technology of cassava to animal feed
1. Examination of technologies
The group examined different aspects of processing of cassava into animal feed. The objectives of processing are to:
a. Extend the shelf life of the crop for safe storage,
b. Make for easy handling and marketing,
c. Improve on the palatability of the cassava-based diet, and
d. Maximize the natural components and reduce the toxic ones.
In attempting to achieve these objectives, the differences and similarities were highlighted among the various cassava processing technologies of the countries represented (Nigeria, Liberia, Togo and Uganda). The links were established between cassava type (high or low cyanide content) and complexity of processing and type of animal to which the feed was directed. Generally speaking, pigs were found to be the least problematic in terms of cassava variety and processed form while poultry animals presented the most specific feed requirement category. Many different sequences and combinations of the cassava processing plant were explored. It was decided that the emphasis would be on small farmers as our primary target groups, commercial farmers and feed processors would later evolve. The unit operations in these processes included chipping, grating, shredding, fermenting, drying and packaging. The fermentation step is included to reduce the cyanide content to levels below 100 ppm. This step is optional depending on the cyanide content of the raw material used. In addition, the production of single-cell protein was also considered and though this is not economically sensible at the farm level, more work needs to be done on improving the economic feasibility on a large scale.
2. Research needs
The group observed that there were certain areas where research needs to be conducted in order to optimize the efficiencies of cassava processing methods.
Composition changes: There is the need to monitor the changes in nutritive and toxic composition of the plant through the unit operations of the above processes and in particular the cyanide levels.
Cyanide determination: is a need to develop simple, cheap and effective on-farm techniques.
The use of cassava leaves and stems is not very common in countries represented despite its abundance and high protein content. It was therefore suggested that research be done on the scientific and socioeconomic constraints which have hindered their utilization.
There is a pressing need to define and categorize the different varieties of cassava plant in terms of their cyanide content and their ecological and geographical locations, to facilitate the appropriate processing technologies.
There is also the need to design and fabricate equipment for use at the local level with the following characteristics: (a) simplicity, (b) affordability, (c) utility, and (d) adaptability to both existing food technology equipment and local environmental constraints.
This feature of adaptability should acknowledge the need to utilize other farm byproducts with cassava for animal feed purposes. The importance of drying was emphasized in order to achieve the stated objectives. Work has been done by the Postharvest Unit of IITA in this area-in terms of optimum crop size (3 x 7mm), and loading capacity (5kg/m²) on concrete form which can reduce moisture content from 60 70 percent to 13-14 percent in a day during the dry season. But there is a need for more research to test this technology under various environmental conditions.
The socioeconomic implications of the above were also considered. It was observed that there is a need to:
a. Describe and analyze existing socioeconomic patterns in cassava producing and consuming areas,
b. Focus on possible innovative individuals or groups who may readily accept and use new technologies,
c. Identify existing and possible marketing channels from producer to consumer in terms of economic viability in various national settings, and
d. Be aware of the dangers of disrupting existing regional farming systems and ensuring that processing and marketing innovations would rather improve and facilitate the utilization of available resources for the benefit of all socioeconomic groups.
In order to achieve all of these it would appear necessary to establish a cassava network for the African subregion. This network would hold annual meetings and regularly publish a newsletter to review the state of cassava production, utilization and processing in Africa.
