Cramming. The duck used in Peking duck is Peking duck, which is a high-quality carnivorous duck that is fattened using fill-feeding methods. Peking ducks are ducks that have been bred through long-term careful feeding and continuous development of superior breeds. They originated from the cramming method of raising ducks that was recorded in the Northern and Southern Dynasties. The ducks bred by this method have white fur, tender meat, large bodies and thin skin, and are called Peking ducks.