Apparent metabolizable energy requirement of feed-restricted White Pekin duck breeder pullets

Abstract

A dose–response experiment with 5 dietary apparent metabolizable energy (AME) levels (10.00, 10.62, 11.24, 11.87, and 12.49 MJ AME/kg) was conducted to estimate the AME requirement of White Pekin duck breeder pullets from 8 to 24 weeks of age. A total of 240 8-week-old female White Pekin duck breeder pullets were assigned to 5 experimental treatments, and each treatment was replicated 6 times with 8 birds per replicate. The ducks were reared in raised wire-floor pens from 8 to 24 weeks of age. All duck pullets were restricted-fed by limiting feed intake, and the feed intake increased gradually as age increased. At 24 weeks of age, the body weight, weight gain and feed/gain of each treatment were measured, and the relative weight of abdominal fat, skin and fat, and ovary of pullets and the contents of luteinizing hormone, follicle-stimulating hormone, and estradiol in plasma were also determined. As the dietary energy level increased from 10.00 to 12.49MJ AME/kg, the 24-week-old body weight and weight gain increased linearly or quadratically (P < 0.05) and the feed/gain decreased linearly or quadratically (P < 0.05). The absolute or relative weight of abdominal fat and skin and fat of the duck pullets also showed a linear increasing response to increasing dietary energy (P < 0.05). The duck pullets fed with high dietary energy levels had a higher absolute or relative weight of ovary than the birds fed with low dietary energy (P < 0.05) and this was accompanied by linearly or quadratically increasing plasma follicle-stimulating hormone and estradiol as dietary energy increased (P < 0.05). According to broken-line regression, the AME requirements for feed/gain and relative weight of skin and fat were 12.40, and 11.92 MJ/kg, respectively, and low AME requirements should be considered to control body weight and fat before laying age.