The purpose is to breed out a Jewish genetic weakness that produces mental retardation and Acromegaly, a rare bone disease. I found out about this program when a Conservative Rabbi learned of my Mensa-level IQ and sent half a dozen teenage Jewish girls to my apartment. He quit after I told him that I take an active part in raising my offspring as Spinozans. Da Cunha Islanders took advantage of a volcanic eruption to evacuate to England, where their girls and women were encuraged to conceive babies by English men to bring back to the Island after the volcano quieted down. It was done to breed out an eye disease that was decimating the Islanders.
Recent information says that it worked well.
Breeding slaves is universal. It can be found from ancient times to the breeding of kidnaped Blacks during the slavery days in North America and continues today in some undeveloped parts of the world. It has to be admitted that wifely approval wasn't all that reluctant in many cases. It also has to be said that having babies by their employer was considered an honor by many bond servants. The same attitudes and practices can be found among owners of Black slaves, but at a lower level because of the color bar.