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
Southdown Motor Services 1950s and 1960s that Southdown purchased many of the vehicle types most commonly associated with the company, notably the Leyland Titan PD3 'Queen Mary' vehicles. Southdown did not take any deliveries of rear engined double deck vehicles until 1970 when it purchased a batch of Daimler Fleetlines with Northern Counties bodywork similar to that on later PD3s for Brighton & Hove and a number of Bristol VRTs with Eastern Coach Works (ECW) bodies painted in green and cream livery. A further batch of Fleetlines with ECW bodywork was delivered in 1972. In 1964, Southdown moved into new headquarters in Freshfield