]William Regan was born in Joplin, Missouri, in 1884. He received a BS in Agriculture in 1912 and an MS in Dairy Production in 1949, from the University of Missouri. He was an Instructor at his alma mater and then an Associate Professor and Head of the Department of Dairying at the University of Nevada between 1912 and 1917.
Bill Regan accepted an appointment as Head of the Dairy Department of the University of New Jersey. This tenure was interrupted by an interval of war service in 1918.
In 1922 he came to the University of California where he continued his work on the first large-scale inbreeding experiment with dairy cattle. This project uncovered ten hereditary defects of dairy cattle and their modes of inheritance. He also published data on effects of inbreeding on calf mortality, growth, fertility, milk production, and gestation.
Professor Regan initiated some of the earliest research on effects of temperature and humidity on the physiology of the dairy cow, including effects of these factors on composition of milk. Other research included studies on solids-not-fat content of milk, nutritive value of numerous dairy feeds, and causes and prevention of bloat. In cooperation with the Agricultural Engineering Division, he developed plans and specifications adopted as minimum standards for dairy buildings in California.
For many years the official milk testing programs in California were under the direction of Bill Regan. He was largely responsible for organization of the California Purebred Dairy Cattle Association.
Bill was a member of Phi Beta Kappa, Sigma Xi, Gamma Alpha, the American Dairy Science Association, the American Society of Animal Production, the American Genetic Association, and the New York Academy of Sciences.
Professor Regan was an able, dedicated teacher. Hundreds of students found him a sympathetic friend and were influenced by his character and ideals. His wife, Susan, served as UC Davis Dean of Women for many years. He retired from the University in 1951 and died on April 14, 1962 at his home in Davis.