Fundamental aspects of ovum transfer in cattle.

Although it may ultimately be possible to fertilise ovarian follicular oocytes in vitro, superovulation and insemination are currently the only practical method for obtaining a supply of fertilised ova. It is likely that this will remain true for sometime to come. Pregnant mares serum gonadotrophin (PMSG) is almost universally used for inducing superovulation, and response to it has recently been more reliably achieved by using, in addition, prostaglandin F2alpha to induce oestrus in superovulated donors. The recovery of fertilised ova from donors depends on the expected site of the ova within the genital tract, but both surgical and non-surgical methods involve suspending the ova in a stream of fluid which is collected into glass cups and examined microscopically. A variety of in vivo and in vitro environmental conditions affect the success of transfer of fertilised ova. These include the healthy state of the recovered ovum, the storage medium, the method and length of storage, the age of the ovum and the synchronisation of oestrus of donor and recipient.