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Additional Protein Sources

The following section will discuss a few additional high-protein feedstuffs. A number of these feedstuffs are potential high-protein feeds for the future.

As discussed earlier, animal wastes may be fed as high-protein feeds. Animal wastes are defined as a mixture of animal excrements, either with or without bedding. AFCO has developed the following terms to categorize animal wastes: 1)dried poultry waste; 2)dried poultry litter; 3)dried ruminant waste; 4)dried swine waste; 5)undried processed animal waste product; and 6)processed animal waste derivative. AFCO has defined each term according to origin, processing, and minimum nutritional value. In the U.S., the use of animal wastes is regulated.

The following will describe the general nutritional value of animal wastes. Nitrogen is a major component of animal wastes. Nitrogen is present in both protein and nonprotein forms. The contents of crude fiber and ash are also high. The available energy is low. Vitamins synthesized in the lower GI tract will be present in the waste. In general, the nutritional value of poultry is the highest. Technically, ruminant waste does not qualify as a protein source. However, ruminant waste may be fed to ruminants. Nutritional value will vary by animal species of origin, diet of animal of origin, amount of bedding included in the waste, and processing method. Processing methods include dehydrating, ensiling either alone or combined with other feeds, and a number of other methods. Two potential concerns associated with feeding animal waste that must be addressed are contamination by microorganisms and excessive amounts of specific minerals such as copper.

Adequately processed animal wastes, included as part of a balanced ration, may be fed to a range of species with favorable performance results. However, as a result of their components, animal wastes are best suited for use in ruminants with lower nutrient requirements.

Plant extracts are a group of high protein feeds. Green, leafy plants, especially legumes, contain high quantities of crude protein. In addition, the protein is also of high quality. However, as a result of the relatively high fiber content of the plants, the nutrients are not efficiently used by nonherbivores. Therefore, processing of the plants to separate the components produces a feedstuff that can be used by a range of species. Processing includes removal of the juice from the plant matter, coagulation of the protein, and separation of the protein from other solubles. The separated protein fraction is referred to as leaf protein concentrates (LPC). Leaf protein concentrates may be fed wet or dried. The crude protein content of dried LPC is 40-70%. At this time, use of LPC as animal feeds is cost prohibitive.

Single-cell proteins (SCP) have the potential to develop into a significant high protein feedstuff. Presently, production of single-cell proteins is relatively expensive and therefore use as a feed is limited. One positive attribute is SCP production is a productive use of a wide range of by-products. Single-cell proteins are proteins originating from algae, yeast, bacteria, and fungi. In general, single-cell proteins are a good source of protein and various other components. The value of the SCP will vary depending on organism selected, quality of organism, growth conditions, and harvesting and processing methods. Algae are primitive plants, which range in size, shape, and environment. Algae may be fed either wet or dried. The common form of algae is dried, ground algae. The nutrient composition of algae varies. In general, algae are high in protein and low in fiber and energy. Algae may be fed to a range of species in limited amounts. Yeast is another SCP. Unlike algae, yeast has been available for a number of years. Yeast is available as dried, live, and irradiated products. The crude protein content of dried yeast is high. In addition, yeast is a good source of most of the B-complex vitamins and irradiated yeast is a good source of vitamin D. Bacterial single-cell proteins are among the newer products. A number of bacterial SCPs are available. The crude protein content is relatively high. Cost, palatability, digestibility, protein quality, and presence of toxic compounds are among the issues that must be overcome prior to extensive use of SCP as feeds.

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