LAUSR

Abstract A dose-response experiment was conducted to investigate the effects of feeding 6 starter diets containing the analyzed crude protein (CP) contents (168.6, 178.9, 184.2, 192.0, 195.8, and 203.3 g/kg) from d 1–19 on growth performance and carcass traits of starter Pekin ducks and the subsequent growth performance and carcass traits of ducks fed a common grower diet from d 20–35. The 480 one-d-old male White Pekin ducks were divided to 6 experimental treatments and each treatment had 8 replicate pens of 10 ducks. All starter experimental diets were formulated to contain similar dietary energy concentration and standardized ileal digestible amino acid contents. At d 19 and 35, the growth performance of each pen were determined and 2 ducks were randomly selected from each pen and harvested to evaluate carcass traits. During the starter period, as dietary CP decreased from 203.3 to 168.6 g/kg, the body weight, weight gain, and feed intake were not affected but feed/gain increased linearly ( P = 0.017). According to broken-line regression, the 196.8 g/kg was the minimum dietary CP requirement necessary to obtain the optimal feed/gain during the starter period. Moreover, the breast meat percentage of starter ducklings was not influenced by reducing dietary CP, but the leg meat percentage decreased linearly ( P = 0.024) and abdominal fat percentage increased linearly ( P = 0.018). During the grower period from d 20–35, the protein restriction during the starter phase had no negative effects on the subsequent growth performance from d 20–35 or carcass traits at d 35. It was concluded that reducing dietary CP had negative effects on the performance of starter ducks but the protein restriction during the starter phase had no adverse effects on the overall performance of grower Pekin ducks.