Southdown sheep no longer economical and smaller flocks averaged only 135 ewes apiece. The use of artificial fertilizers had gained ground, and the combine-drill, which sowed grain seeds and fertilizer together, rendered close-folding by sheep unnecessary. Gradually surrendering to basic arable farming changes, the Southdown became largely a grassland breed. During the interwar years, the United Kingdom was known for farm animal breeding, and pedigreed Southdowns were still being exported to most parts of the world, especially New Zealand. In 1937, the number of exported Southdowns reached 459 head. During the Great Depression, a severe and prolonged fall in the prices of
Breed registry animal's "papers". Registration papers may consist of a simple certificate or a listing of ancestors in the animal's background, sometimes with a chart showing the lineage. There are breed registries and breed clubs for several species of animal, such as dogs, horses, cows and cats. The US "Association of Zoos and Aquariums" (AZA) also maintains stud books for captive species on display ranging from aardvarks to zebras. Kennel clubs always maintain registries, either directly or through affiliated dog breed clubs. Some multi-breed clubs also maintain registries, as do non-affiliated breed clubs, and there are a few registries that are maintained