By-products link crop and livestock production

In much of the developing world animals and crops are raised through separate enterprises and often seem to compete for the same limited resource, namely land. The problem has recently been aggravated as growing human populations cultivate more land and reduce the available grazing area. Larger populations also need more livestock, adding further to the pressure on the land. Poor nutrition and lack of feed are major constraints to livestock output. They result in lowered yields of milk, meat, power and fibre and render animals susceptible to disease. Increased feed supplies and better nutrition are thus priorities in animal production. Animal numbers must also be matched to the feed resources available and all possible feed sources should be efficiently used to improve production. The ideal is that livestock and crops in agricultural systems should complement each other as much as possible. The crop subsystem can provide energy and protein feeds for animals while the animal subsystem provides power and fertilizer for crops, and possibly power and light for people through biodigesters producing gas. Integration of crops and livestock increases output at the lowest economic and environmental costs. Practices which integrate livestock and crop farming include grazing sedentary livestock on stubbles after the harvest, nomadic migration onto cropped areas for feed and water in nominal exchange for manure, and feeding the products of small-scale processing to backyard animals. Also, many crop residues and by-products and agroindustrial by-products are already fed to livestock. Much of this is done on an ad hoc or traditional basis and neither crop nor animal production are optimized. Obstacles to integration Several problems can arise from attempts at integration. In Sudan, mechanized crop schemes refuse access to nomads because of allegations that manure from their cattle carries noxious weed seeds. In other regions fields are burned after harvest and in this and other ways potential feeds are wasted. Some potential feeds become sources of pollution as, for example, effluents from sisal processing; others are not utilized because they are toxic or poorly digestible in the raw state and require some processing. Despite such difficulties the advantages from increased use of crop products as feed and closer integration of animals with arable and plantation crops generally outweigh the disadvantages. Much recent work in basic, applied and adaptive research in the biological and socio-economic sciences has been directed at overcoming the limitations of crops as feed and of possible conflicts between major subsystems. One scientific objective has been to design and extend technologies for use at farmer level without the need for large machinery or financial inputs. Multiple uses for crop residues The use of sugar cane by-products illustrates the possibilities for using crops for feed. Cane areas are largely unavailable to livestock but they can still contribute to livestock production. Major sugar cane products for animal feeds are molasses (which is also used to produce industrial alcohol), bagasse (which also provides fuel for the factory) and green tops. Molasses is difficult to handle when liquid but rolling ball feeders have been designed and are widely used. Molasses is often fed in blocks which also contain urea, thus providing both energy and protein. Blocks using straw or cereal brans as fillers and binding agents can now be easily made at village or household level. Unpalatable and indigestible crop components can be converted into animal feed through a variety of biological (e.g. microbial digestion), chemical (alkali) or physical (crushing) treatments, all of which help break down cellulose to a more palatable state. Although some are only possible on an industrial scale others have been adapted to farm use. The peels and leaves of many tuber and root crops have always been used as feed in the humid tropics. Protein supplements composed of the residues of the oil-producing crops, such as coconut, oil palm, groundnuts and cotton, have long been exported from developing to developed countries where they are used to boost livestock production. The time has now come to make better use of these products in their countries of origin. Some plant products not previously considered as feed (often known as nonconventional feed stuffs) can also be converted to animal protein for eventual human use. Citrus pulp and peel and banana products are used as feed in many areas, including the Caribbean. In North Africa the pulp and stones of dates and olives are increasingly used as feed. Brewery and distillery byproducts, whether at industrial or village level, can also be valuable feeds. In Senegal livestock are fed crop residues and byproducts under sheds with a manure pit attached; these 'compost pens' result in higher dry season milk production, stronger traction animals and quality organic manure to go back to the land. More complex integration systems utilize poultry manure and fish waste. It is encouraging that there is now interest in improving the integration of livestock and crop production, but efforts must continue and the results already achieved must now be made more widely available through training and extension campaigns.In much of the developing world animals and crops are raised through separate enterprises and often seem to compete for the same limited resource, namely land. The problem has recently been aggravated as growing human populations cultivate more land..