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Overview Because conventional feedstuffs are often expensive, livestock producers have regularly been forced to seek less costly alternatives. By-products from food and beverage processing bran, middlings, tankage, oil meals, brewers and distillers grains- represent one such class of alternatives. Some of these wastes have been used extensively as feeds, and their use has resulted in more economical livestock production. But many other potentially valuable feed sources, some of which have substantial nutri- tional value and are available inexpensively and in large quantities, have been underutilized. These products include food processing wastes, such as vegetable and fruit processing residues; dairy whey and tannery by- products; wastes from industrial processing and from municipalities; forest products and pulp and papermill residues; crop residues; aquatic plants; and animal waste (excrete). There are, of course, alternative uses for some of these substances. Forest products may be used for fuel or as soil conditioners. Crop residues left in the fields are generally plowed under. Animal wastes are typically used as fertilizer, although in at least some instances the costs of hauling and spreading them are greater than the value of the plant nutrients they provide. Such uses of these materials may be economically feasible, but their use as feedstuffs will usually be more economical. Many products have no other uses. These underutilized materials (in this report, "underutilized" materials mean those that have substantial potential value as feedstuffs but that are now used only to a limited extent) frequently present problems for disposal.
2 Overview Dumping them in landfills, applying them to the land, or incinerating them is usually not feasible; in some instances it is impossible. Concen- trated animal enterprises, such as feedlots, are generally located in places where areas available for land application of wastes are limited. Because these enterprises are often near municipalities, lakes, or streams, they also present potential air and water pollution problems. Similar difficulties are encountered in disposing of food and forest product processing wastes. Air pollution regulations of the Environmental Protection Agency and of other federal, state, and local monitoring agencies generally preclude incineration, and at any rate, materials containing high moisture levels are difficult to burn. The increased use of these wastes as feedstuffs would help keep such problems of disposal and pollution to a minimum. The extent to which these substances will be used depends on a number of factors among them availability, the attractiveness of competing al- ternative uses (as fuel, for instance), and the ease with which they may be used. But the most significant factors are the cost, based on nutritional value, of the processed products relative to conventional feedstuffs and their safety for both animals and humans. Available data indicate that animal performance is generally related to nutritional value, and the nutritional value of these substances varies greatly (see Appendix Tables). Classes of underutilized substances have the fol- lowing general characteristics: · Food processing wastes. The generally high water content and per- ishability of food processing wastes require that they be used shortly after processing. Animal processing wastes are usually high in protein; plant processing wastes are usually low. The high water content of the wastes makes processing and storing difficult and expensive, although ensiling with low-moisture materials may be feasible. · Industrial nonfood processing wastes. These wastes usually have high moisture content. Some, such as fermentation residues from the production of antibiotics, can be used directly, with minimum processing. Others, such as acids, alcohols, aldehydes, and esters, can be used for single-cell protein production. The possible presence of toxic organic chemicals and heavy metals represents a major obstacle to their use. o Forest residues. Carbohydrates from whole-wood residues are gen- erally resistant to ruminal cellulolytic microbes. Some chemical and phys- ical treatments are effective to a limited extent: Generally, hardwoods are more responsive to treatment than softwoods. Wood residues are, how- ever, usually low in protein. Some residues from the pulp and paper industries are partially delignified and are thus potentially good sources of feed for ruminants.
Overview 3 · Animal wastes. These wastes are low to fair in energy value, fair to high in crude protein, and high in minerals. The high fiber and frequently high levels of nonprotein nitrogen make them best suited for use by ruminants. Because the wastes may potentially contain pathogenic micro- organisms, processing is needed. One method that appears especially feasible is ensiling with other ingredients. Quality or taste of animal products is not adversely affected by the feeding of animal wastes. · Crop residues. These wastes are usually low in protein and low to fair in energy value. The energy value can be improved by certain pro- cesses; treatment with alkali or ammonia appears the most promising. · Aquatic plants. Plants vary in nutritional value. Algae are high in protein and low in fiber; water hyacinths are high in fiber, indicating limited energy value, and lower in protein than algae. Satisfactory animal performance has been achieved by including these plants in animal diets. Their location and their high water content, however, present problems in harvesting and processing. The safety of underutilized materials for use as foodstuffs must also be considered. They may contain pathogenic organisms or be contaminated with pesticides, drugs, heavy metals, or other substances toxic to livestock. Data are limited concerning chemical residues in milk and eggs from animals consuming feeds with significant levels of these residues. In meat- producing animals, appropriate withdrawal periods have been effective in preventing harmful residues in edible tissues. Sufficient data are available to ensure that many substances are effective and safe for target animals and that the resulting animal products will not compromise human health. Further research is needed, however, to ensure that feeding of some sub- stances is safe and to satisfy the requirements of the U.S. Food and Drug Administration and other agencies regulating their use.