Examining the crude fiber content of a supplement is normally the first place to estimate energy content. For example, a typical 20 percent range feed without any non-protein nitrogen contains approximately the energy (TDN) levels (below) where fiber levels are varied. Many supplements contain processed plant by-products such as wheat middlings, soy hulls, dehydrated alfalfa, and corn gluten feed that contain substantial levels of crude fiber. However, these crude fiber sources are highly digestible by ruminant animals. Thus, these supplements are higher in energy than indicated by their fiber levels. Protein can also be used as a source of energy for cattle, but it is an expensive proposition. Use of high-energy by-products or grains is more economical if energy is lacking in the diet.
TDN levels
Fiber % 5 10 15 20 25
TDN % 72 68 62 55 46
