Effects of dietary energy and lysine levels on growth performance and carcass yields of Pekin ducks from hatch to 21 days of age
A 2 × 6 factorial experiment, using 2 dietary apparent metabolizable energy (AME) levels (2,750 and 3,050 Kcal/kg) and 6 supplemental lysine (Lys) levels (0, 0.10, 0.20, 0.30, 0.40, and 0.50%), was conducted to study the effects of dietary energy and lysine levels on growth performance and carcass yields of Pekin ducks from hatch to 21 d of age. A total of 576 one-day-old male White Pekin ducks was randomly allotted to 12 dietary treatments, each containing 6 replicate pens with 8 birds per pen. At 21 d of age, body weight gain, feed intake, and feed/gain were measured, and then 2 ducks selected randomly from each pen were slaughtered to evaluate the yields of abdominal fat, breast meat, and leg meat. As a result, birds that were fed basal diets with no Lys supplementation showed growth depression, and significant positive effects of dietary Lys supplementation on body weight gain (P < 0.001), feed intake (P < 0.001), and feed/gain (P = 0.002) were observed as dietary Lys increased gradually among all the groups. In addition, increasing energy levels did not affect overall body weight gain (P > 0.05), but feed intake (P = 0.001) and feed/gain (P = 0.009) decreased significantly between the groups. Dietary Lys levels influenced the yields of breast (P < 0.001) and leg (P = 0.001) meat among all the groups, but dietary energy levels had a significant positive effect only on abdominal fat yield (P = 0.014). The interaction between dietary energy and Lys influenced body weight gain of ducks significantly (P = 0.004). According to the broken-line regression analysis, Lys requirements of Pekin ducks for weight gain at 2,750 and 3,050 Kcal of AME/kg were 0.94 and 0.98%, respectively. It suggested that Lys requirement was higher at 3,050 Kcal of AME/kg than at 2,750 Kcal of AME/kg. Dietary energy content determined feed intake of the ducks, and high-energy diets will require a higher amino acid concentration to compensate for a lower feed intake.