Most of us are still using the total digestible nutrient (TDN) system for formulating ruminant rations, evaluating feedstuffs and estimating animal response to different rations. The TDN system has served a useful purpose and will continue to be useful. However, it has definite limitations and drawbacks.
"Net Energy - A New Measure for Evaluating Feeds and Rations for Beef Cattle,"
Iowa Farm Science: Vol. 20
, Article 3.
Available at: https://lib.dr.iastate.edu/farmscience/vol20/iss12/3