An energy system is described in which, in both single-stomached and ruminant animals, the heat increment of feeding is considered to be linearly related to five measurable quantities. For both kinds of animals three of the quantities, with their heat increments in parentheses, are urinary N (wu; kJ/g), faecal organic matter (wd; kJ/g) and positive protein retention (wp; kJ/g). In ruminants the...
