Embryo culture techniques were used to maintain the viability of swine embryos during shipment from the United States to England. Embryos recovered surgically from Chester White and Hampshire sows and gilts were shipped to England, then transferred to Large White gilts. Estrus was synchronized between donors and recipients by including allyl trenbolone in the daily feed for 18 and 17 consecutive days, respectively. Daily dose of allyl trenbolone was 15 mg for recipients and either 15 or 20 mg for donors. Donors were mated or artifically inseminated one to three times during estrus. During shipment, embryos were cultured in groups of six to ten in polystyrene tubes (12 × 75 mm) containing 2 ml of a modified Krebs-Ringer bicarbonate medium. The gas phase was 90% nitrogen, 5% oxygen, and 5% carbon dioxide. Culture temperature was maintained at 35 C with a temperature-controlled box, and shipment was by commerical airline. Embryos were inserted into recipient uteri 20.5 to 27 hr after recovery. In total, 227 eggs were transferred to 12 recipients, resulting in the birth of seven litters totaling 58 pigs.

Embryos were surgically recovered 63 times from 13 purebred donor sows for an average of 4.8 times per donor. Recoveries were completed at three or six week intervals. An average of 15.6 transferable embryos were collected per surgery. Based on these limited observations it would appear that multiple surgical embryo recoveries may be completed on a specific donor at three and/or six week intervals without impairing future production.

A major threat to swine enterprises is the possible introduction of disease when new breeding animals are purchased and introduced. So, methods of introducing new genetic material while minimizing the potential for introducing disease are needed. Transfer of embryos from a donor sow in another herd or country would minimize disease risks. Already used to introduce new breeding stock into Specific Pathogen Free herds and other closed herds, embryos now are placed in the recipient gilt’s or sow1s uterus within a few hours after their recovery from the donor. That method prevents export and limits application of swine embryo transfer in this country, so we evaluated the feasibility of using an in vitro culture system to store embryos between donor sows and recipient females.; Swine Day, Manhattan, KS, November 8, 1979