Effects of low-protein diets on growth performance and carcass yield of growing White Pekin ducks

A dose-response experiment with 6 analyzed dietary crude protein (CP) levels (13.54, 14.37, 14.71, 16.04, 16.61, and 17.22%) was conducted to investigate the effects of low-protein diets on growth performance and carcass yield of growing White Pekin ducks from 14 to 35 d of age. All diets were formulated to contain a similar dietary energy level and the standardized ileal digestible amino acid profile including lysine, methionine, threonine, tryptophan, arginine, isoleucine, valine, and glycine. A total of 288 14-day-old male White Pekin ducks were divided into 6 experimental treatments and each treatment contained 8 replicate pens of 6 birds. Ducks were raised in wire-floor pens from 14 to 35 d of age. At 35 d of age, the weight gain, feed intake, feed/gain, and the yield of carcass, breast meat, leg meat, and abdominal fat of ducks from each pen were measured. As dietary CP decreased from 17.22 to 13.54%, weight gain and feed intake were not affected (P > 0.05) but feed/gain increased when dietary CP decreased to 13.54% (P < 0.05). On the other hand, the yield of carcass, leg meat, and breast meat was not influenced by reducing dietary CP (P > 0.05) but the abdominal fat increased when dietary CP was 13.54% (P < 0.05). Based on broken-line regression, the 14.81 and 14.94% were the minimum dietary CP to keep the feed/gain and abdominal fat similar to the ducks fed with 17.22% CP diets, respectively. In summary, with crystalline amino acid supplementation based on a similar standardized ileal digestible amino acid profile, it was possible to formulate the low-protein diets containing about 15% CP for Pekin ducks without adverse effects on their growth performance and carcass yield.