Abstract: This experiment was conducted to investigate the effects of dietary methionine (Met) and metabolizable energy (ME) levels on growth performance, carcass characteristics, and plasma biochemical parameters of Pekin ducks from 15 to 42 days of age, and to determine the ME requirements of Pekin ducks at different dietary Met levels. A 2×6 two-way completely randomized experimental design was used, and 576 male Pekin ducks, with similar weight[(545.9±3.3) g] at 15 days of age, were randomly divided into 12 groups with 8 replicates per group and 6 ducks per replicate. The present experiment was set with 2 Met levels (0.30%, 0.50%) and 6 dietary ME levels (10.47, 11.10,11.72, 12.35, 12.98, and 13.61 MJ·kg^-1). The experiment was lasted for 28 days. The results were showed as follows:1) As dietary ME levels increased, the average body weight at 42 days of age and the average daily weight gain of Pekin ducks from 15 to 42 days of age were significantly increased (P<0.05), average daily feed intake and feed to gain ratio decreased significantly (P<0.05). 2) As dietary ME levels increased, the percentage of breast meat and leg meat were decreased significantly (P<0.05), the percentage of eviscerated carcass, abdominal fat, and subcutaneous fat were significantly increased (P<0.05). 3) With the increasing dietary ME levels, the plasma total cholesterol and high density lipoprotein cholesterol contents of Pekin ducks at 42 days of age were significantly decreased (P<0.05), while the free fatty acid content was significantly increased (P<0.05), and the albumin content had a tendency to decrease (P=0.053). Dietary Met supplementation significantly increased plasma albumin and reduced free fatty acid contents (P<0.05), and there exists a significant interaction effect between dietary ME and Met levels on plasma total cholesterol and high density lipoprotein cholesterol contents (P<0.05). 4) Based on the linear broken line model, the ME requirements to meet the optimal average daily weight gain of Pekin ducks were 12.46 and 12.85 MJ·kg^-1 at dietary 0.30% and 0.50% Met levels, respectively. The t test showed that the ME requirements of Pekin ducks at dietary 0.50% Met level tended to be greater than those at 0.30% Met level (0.10<P<0.05). Taken together, increasing dietary energy level can improve the growth performance of Pekin ducks, and dietary Met level could affect dietary ME requirement of Pekin ducks.

Key words: Pekin duck, metabolizable energy, methionine, growth performance, carcass characteristics, biochemical parameters, metabolizable energy requirement