Effects of varying levels of dietary protein on the performance and production cost of white Pekin ducklings

Nitrogen requirement for maintenance in Yangzhou goslings

1. Experiments were conducted to determine the nitrogen (N) requirement for maintenance (N(m)) in Yangzhou goslings. 2. At 56 d old, 18 birds were divided into three equal groups and fed on diets with equal metabolisable energy (ME) and different contents of crude protein (CP; low, medium and high) in an N balance test. N(m) was estimated from the relationship between N output (N(E)) and N intake (N(I)). Following the above N balance test, 16 goslings at the same age were used in a N balance test with an N-free diet. The birds were divided into 4 equal groups and offered an N-free diet at intakes of 90, 70, 50 and 0 g per d, respectively. 3. The estimated N(m) was 240 mg/kg BW(0.75) per d in the N balance test. The result from the N-free diet trial gave a value of 244 mg/kg BW(0.75) per d, confirming the result of the N balance test. The lower intake of N-free diet resulted in more N(E), suggesting that protein catabolism may occur in the body of birds to meet N(m) when dietary N(I) was very low. 4. It was concluded that the N(m) of Yangzhou goslings was about 240 mg/kg BW(0.75).