Numerous mammalian taxa exhibit reproductive delays, pauses in reproduction that occur between mating and fertilization, between fertilization and implantation of the embryo, or after an embryo has implanted. Of the 27 mammalian orders, 9 are known to exhibit reproductive delays, including Diptrotodontia, Dasyuromorphia, Eulipotyphyta, Cingulata, Carnivora, Rodentia, Chiroptera, Lagomorpha and ...

Although the mechanisms under which sex ratio is controlled in nature remain unknown, researchers have attempted to treat sperm in an effort to predetermine the sex of the offspring. The methods of sperm separation that have been repeatedly reported to isolate fractions rich in X- or Y-chromosome bearing sperm are serum albumin gradient swim-up and flow cytometry. However, the ability of the se...

background: embryo transfer (et) has traditionally been performed two days after oocyte retrieval. delaying transfer from day two to day three or four would allow for further development of the embryo might therefore optimize the selection of viable and best quality embryos for transfer and may be closer to the physiological time of the entry into the uterus than transfer on day two and might h...