Reuben Mapletoft was born on Little Pipestone Ranch near Fort Pitt, Saskatchewan. His father, Edgar Mapletoft was among the earliest importers of Simmental cattle in Canada. Reuben received his DVM from the University of Guelph before interning at the University of Saskatchewan in 1967-1968—the first student to intern at the college. In 1970 he accepted a position in Reproduction at the Veterinary School at Onderstepoort in Pretoria, South Africa, where he worked for three years. He went on to obtain his MS (1975) and PhD (1977) at the University of Wisconsin, and returned to the WCVM as a professor in the Department of Clinical Studies. He became the Head of the Department of Herd Medicine and Theriogeneology in 1998, and in 2002 he became a consultant to the pharmaceutical industry (Bioniche).