 By the early years of the century, milk was beginning to overtake cheese as the main dairy product, mainly to supply the large urban centres close to the county's borders.Milk production required more intensive farming practices; the introduction of tuberculin-tested milk in 1923 and the drive towards increased hygiene also led to changes, including the replacement of traditional shorthorn cattle with Ayrshires and later Friesians, and the gradual adoption of milking machines.Surplus milk production was a problem until the 1930s; it was a major concern of the local branch of the National Farmers Union, founded early in the century, until the creation of the Milk Marketing Board in 1933, which guaranteed a fair minimum price.