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Embryo transfer in pigs normally involves surgery. In connection with the development of nonsurgical or endoscopic transfer techniques, it is important to know whether the uterine site to which embryos are transferred has an effect on the success rate. In the present investigation, prepubertal donor gilts were treated with 1,500 IU of PMSG and, 72 h later, with 500 IU of hCG. Gilts were artificially inseminated 24 and 36 h after hCG injection. Embryos at the expanded blastocyst stage were collected from donor gilts. Recipient gilts were treated synchronous with the donors, using 1,000 IU of PMSG followed, 72 h later, with 500 IU of hCG. After a maximum of 3 h in vitro, embryos (n = 15 to 20, mean = 17.3) were transferred surgically to the middle of the uterine horn, to the caudal quarter of the uterine horn, or to the uterine body. Recipients were slaughtered between 28 and 34 d after transfer. The pregnancy rate of the recipients was low when the embryos were deposited in the uterine body (12%), compared with the middle (88%) or the caudal quarter of the uterine horn (81%) (P < .01). The corresponding average number of viable fetuses per pregnant recipient was 8.2 in the uterine body, 5.6 in the middle, and 4.5 in the caudal quarter. Average survival rate of embryos after transfer to the middle of the uterine horn was 41% vs 29 and 3% after transfer to the caudal quarter or the uterine body, respectively (P < .01). Hence, the uterine body seems to be an unsuitable site for embryo transfer in pigs. These results may explain the unsatisfactory results achieved with nonsurgical embryo transfer in the past.

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Prepubertal gilts were treated with 1,500 iu equine chorionic gonadotrophin, followed 72 hours later by 500 iu human chorionic gonadotrophin (hCG), and inseminated 36 and 48 hours later. Embryos were collected at slaughter 168 hours after the hCG treatment. Blastocysts classified as 'good' or 'fair' were transferred to synchronised recipients, either by conventional surgical means or by a 'semi-endoscopic' approach, and the recipients were slaughtered four weeks later. Of 238 donor gilts, 98.4 per cent had responded with a mean (se) 23.5 (1.0) ovulations and 19.1 (1.0) ova or embryos, of which 47 per cent were considered morphologically intact and transferable. The large proportion of non-transferable embryos was not associated with the age or weight of the gilts, the season or with their housing conditions. Conventional surgical transfer of 15 to 20 (mean 17.4) blastocysts to synchronised recipients yielded 88 percent (14 of 16) pregnancies with between seven and 14 (mean 8.2) viable fetuses, and an embryo survival rate of 47 per cent in the pregnant recipients and 41 per cent in all the recipients. The corresponding data for the semi-endoscopic transfers were 16 to 20 (mean 17.7) blastocysts transferred, 47 per cent (eight of 17) pregnancies, four to 12 (mean 7.3) viable fetuses per pregnant recipient and an embryo survival rate of 41 per cent in the pregnant recipients and 19 per cent in all the recipients. Significantly fewer of these recipients became pregnant and a significantly smaller proportion of the embryos survived (P<0.05).