[Embryo transfer in swine in relation to a gene transfer program].

The production of the recommended embryonic stage for microinjection of foreign DNA into pronuclei needs a precisely timed preparation of donor pigs. For oestrus induction 1250 IU of PMSG is used at a body weight of 60 kg to 90 kg. To induce ovulation 750 IU of HCG are injected 3 days later. After two inseminations eggs are collected by surgical flush of the oviducts and centrifuged for 3 min at 15,000 g for visualization of the pronuclei. After DNA-microinjection the embryos are transferred to 12 h asynchronous recipients. About 50% of the collected eggs could be used for our experiments. The number and quality of the recovered eggs was related to the body weight of the donors. An in vivo culture system in the non-ligated pig oviduct was established in order to measure the effects of the distinct steps in microinjection on embryo survival. The survival rate of untreated zygotes was 52%. After centrifugation the rate was reduced to 38% and after microinjection to 12%. Pregnancy rate after 98 transfers was 37% and an average of 3.9 piglets were born per litter.