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Millfeed Protein Sources

Millfeed protein sources are plant-based high protein feedstuffs. Millfeed protein feeds are high-protein by-products from the milling of cereal grains. Milling by-products originate from wet and dry milling of cereal grains. The minimum crude protein content, on a dry-matter basis, for millfeed protein feeds is 20%. Corn-based protein feeds are fed in the largest quantity and therefore the discussion will focus on the corn-based protein feeds. The major corn-based high protein feeds include corn gluten meal, gluten feed, fermented extractives or solubles, and germ meal.

Figure 6.13 illustrates the basic steps in the wet milling of corn including the origin of by-products.

The primary milling by-product used as a protein feedstuff is corn gluten meal.

Figure 6.14 illustrates corn gluten meal.

Corn gluten meal is available at either approximately 41 or 60% crude protein on an as-fed basis. Corn gluten meal is a good source of methionine. The next corn milling by-product is gluten feed. Gluten feed is approximately 23% crude protein on an as-fed basis. The crude fiber content in gluten feed is higher than the fiber content in gluten meal. For cattle, corn gluten meal and feed are sources of energy, fiber, and by-pass protein. Fermented corn extractives or corn solubles are 21-23% crude protein as-fed. The water content of fermented corn extractives is approximately 50%. Germ meal is the final major high protein milling by-product feedstuff. Germ meal has the best amino acid profile compared to the other high protein milling by-product feeds.

In general, the nutritional value of the protein is similar to the parent grain. Similar to the parent grain, the by-products are low in lysine and tryptophan. However, high protein milling by-products contain a higher amount of sulfur containing amino acids such as methionine.

The feeding recommendations for high protein milling by-products vary by feed and by species. Gluten meal is fed to all livestock species. In contrast, typically, gluten feed is not fed to monogastrics. Solubles find limited use in dry feeds.

Similar sorghum-based products are also available in lesser amounts and include grain sorghum gluten feed, gluten meal, and germ cake or germ meal. In addition, germ meals are high-protein by-product feeds originating from the milling of cereal grains for flour.

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