The present invention provides a new and improved sperm stimulating additive comprising a certain amount of inorganic pyrophosphate (PPi). Addition of PPi in the media for human/animal in vitro fertilization (IVF) improves fertilization rate addition of PPi in the semen extender for farm animal artificial insemination (AI) may improve pregnancy rates furthermore, mammalian oocytes matured in vitro in a medium including PPi attain improved fertilization and developmental potential, while embryos cultured in medium supplemented with PPi have improved development to blastocyst.
