The effect of Stilbestrol implants on fertility in adult male guinea pigs.

July 6, 1955, two adult guinea pig males each was implanted with 24 milligrams of stilbestrol. A young female that previously had given birth to a litter was placed in the cage with these males, but for some time they showed no interest in the female. One male died during the latter part of the summer but the other male remained in the colony until February 29, 1956. The female was kept in the cage with the implanted male and she gave birth to a litter about February 1, 1956. The average gestation length in the guinea pig is 68 days so the implanted male must have recovered from the effect of the stilbestrol and sired this litter by about November 24, 1955, approximately 4% months after the implant was administered. This indicates that adult guinea pig males can recover sufficiently from large dosages of stilbestrol to sire progeny