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Introduction to Supplemental Protein Sources

Protein nutrition is an important component of animal nutrition. Modules VI and VII will primarily focus on supplemental protein sources.

As the other dietary feedstuffs typically do not fulfill the crude protein requirements, the addition of supplemental protein sources is required for most species and classes of animals. The one exception may be mature animals at maintenance.

The first factor to consider when assessing the nutritional value of a protein supplement is the protein quantity. Crude protein is most commonly used to quantify protein. The National Research Council (NRC) defines a protein supplement as a feed containing a minimum of 20% crude protein on a dry-matter basis. As with high-energy feedstuffs, protein supplements are classified as concentrates. Concentrates are feeds high in nitrogen-free extract and total digestible nutrients and low in crude fiber. Concentrates may be high or low in protein content. The second factor is the quality of the protein. Factors contributing to protein quality were discussed earlier in Module II and include factors such as availability and profile of amino acids. The third factor is the presence of contaminants. As with other feedstuffs, deleterious factors present in the feedstuff should be assessed.

Of the plant-based protein supplements, the higher protein supplements include oilseed meals. In general, crude protein content is at least 40%. Lower protein supplements include grain legumes and various milling by-products. In general, their crude protein content is 20-30% crude protein. In general, the protein’s digestibility and biological value are lower. Finally, these protein sources also contain a higher fiber content and a lower energy content.

As with the high-energy feedstuffs and the roughages, the supplemental protein sources will be divided into two modules. The first module will primarily focus on plant-based protein feedstuffs and the second module will discuss animal-based, miscellaneous, and non-protein nitrogen feedstuffs.

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