Duck Raising
"Pekin Duck is almost the only breed kept by American commercial duck farmers who make a specialty of producing 'green' ducks… Green ducks are duckling which are grown rapidly and marketed at from 9 to 13 weeks of age, when they weigh about 4 ˝ to 6 pound apiece… Long brooder houses heated by hot-water-pipe systems are used… When the ducklings are about 6 weeks old and well feathered they are transferred to inexpensive fattening sheds along the water… About 300 ducks are placed in each fattening yard, which is about 100 by 150 feet and extends into the water about 50 feet. Here the ducks have a chance to swim and to clean their plumage…"

U.S. Dept. of Agriculture, Farmers' Bulletin No 697, titled Duck Raising, Issued December 1919