Problems associated with commercial embryo transfer in swine include difficulties in the selection of suitable recipients, reduced pregnancy rates, reduced reproductive efficiency and reduced acceptance by the commercial swine industry. Transplantation of distinguishable embryos into mated recipients may simplify recipient preparation, improve reproductive efficiency and increase both the acceptance and efficiency of commercial embryo transfer in swine. Embryos were obtained by techniques commonly utilized for commercial embryo transfer services. Mated recipients were selected within the regular breeding scheme of a commercial pig complex for stages 2-3 days younger than the usual synchronized uterine endometrium of unmated recipients. Reduced numbers of day 6-7 porcine embryos (blastocysts) were transplanted into day 4 mated recipients following procedures utilized for commercial embryo transfer in swine. When following this protocol it is possible that the more developed embryos synthesize estrogen first, thus advancing the secretory patterns of the uterus, resulting in improvement of the efficiency of the offspring produced per embryos transferred.
