tenance. Energy above that used for maintenance is
available for reproduction, lactation, and growth.
Energy is the nutrient that most often needs to be supplemented in diets for Virginia cows. Energy requirements
for cattle and energy content of feeds are expressed in
several different ways - Total digestible nutrients
(TDN), metabolizable energy (ME), and net energy
(NE). For beef cows, TDN is the most commonly used
system. Net energy is more accurate than TDN because
it accounts for some losses due to metabolism, and it is
sub-divided into maintenance energy and energy used
for growth and lactation. Net energy is usually used for
growing cattle and some special cow rations.