Energy requirements of young female cattle. 5. Energy intake and energy expenditure

From 6 experiments dealing with the development of young female cattle, partly from calf to calving, 660 metabolism periods were evaluated as to energy intake, live weight gain (LWG) and energy expenditure. Growth intensity was deliberately regulated through energy intake. In the experiment with the highest growth rate the average LWG was greater than 850 g/animal and day and in the experiment with the lowest growth rate at about 550 g/animal and day. Energy expenditure increased from 15 MJ net energy fatcattle/kg LWG at a live weight of 50 kg to 50-80 MJ NEFcattle/kg LWG in clear dependence on growth intensity. Comparative examinations of energy intake and energy requirement, estimated with equations forming the basis of recommendations for the energy supply of young female cattle in the framework of the GDR system of feed evaluation, lead to the conclusion that a new concept of identifying the energy requirement of young female cattle has to be developed.