where gases were expressed in L/d and Nur is urine nitrogen in g/d. Retained energy (RE) was calculated as the difference among MEI, HP and milk energy (Emilk ).
Energy associated with the oxidation of protein (OXP), carbohydrate (OXCHO) and fat (OXF) was calculated by the method
of Brouwer (1958) and Chwalibog et al. (1997) for ruminants: