Leon Rasmussen, 88; Editor for Daily Racing Form

Leon Rasmussen, 88, a thoroughbred breeding theorist and the Daily Racing Form’s bloodstock editor for 37 years, died of cancer Friday in Los Feliz.

The Seattle-reared Rasmussen, who served as a navigator for an air transport service supplying troops in Europe during World War II, joined the Daily Racing Form staff after the war and began writing his “Bloodlines” column in 1950.

Rasmussen was known for popularizing the Dosage Index, a mathematical formula that gauges a thoroughbred’s speed and stamina through a study of the animal’s bloodlines. If the number is too high, the theory says, a horse can’t win the Kentucky Derby.

He also co-developed, with Dr. Rommy Faversham, an inbreeding theory that became known as the Rasmussen Factor. The theory says the source of a prize-winning steed’s speed and endurance is a superior female ancestor rather than a superior male ancestor.

Rasmussen, who retired from the Racing Form in 1987, also bred and raced horses.