Two trials were carried out to investigate the optimal nutrients level of metabolizable energy (ME ) and crude protein (CP) in feeds for Shelduck.The first trial was determined for three periods from the age of 1 day to 7 weeks (0-2 weeks, 3-4 weeks, 5-7weeks) to estimate the suitable nutrients level of ME and CP with the best performance and feed efficiency in Shelduck. Four hundred and fifty ducks were divided into nine equal groups and fed on the diets with different ME (12.92 KJ/kg、 12.19 KJ/kg、 11.49KJ...