Animals, management and sample preparations
The male Korean native ducklings (KND, n = 45) and commercial meat-type ducklings (Grimaud, n = 45) were received on the day of hatch from a local hatchery (breeder flocks at 45 and 40 wk of age each), individually weighed and randomly assigned into three replicate pens, respectively. Fifteen ducks were housed on rice husks in floor pens of same size (2.0×1.5 m) and provided 23/1 light/dark cycle throughout the experimental period. The pens contained rice husks to a depth of 10 cm. The ducklings were initially reared at 33°C; the room temperature was gradually decreased by 4°C weekly until a final temperature of 22°C was reached. The room temperature was automatically controlled using whole brooding heaters. They were fed same experimental diets during 56 d and 42 d, respectively to obtain similar slaughter weights