Piglet production by non-surgical transfer of vitrified embryos, transported to commercial swine farms and warmed on site.

We investigated the feasibility of piglet production by non-surgical embryo transfer (Ns-ET) of vitrified porcine blastocysts and expanded blastocysts transported to commercial farms and warmed on site (V/T/W embryos). Ns-ET was performed by depositing 11-20 vitrified and warmed embryos at a proximal site within the uterus via a catheter. In Experiment 1, the effect of donor-recipient estrous cycle asynchrony on the efficiency of Ns-ET of vitrified and ordinary warmed embryos was investigated at the experimental facility. With a 1-day delay recipients relative to that of donor, the farrowing rate was 50.0% and the survival rate to term was 21.1%. In Experiment 2, Ns-ET using recipients with a 1-day delay and vitrified embryos after one-step warming and dilution was evaluated at the experimental facility. Although the resulting farrowing rate was 42.9%, the survival rate was 6.4%. In Experiment 3, Ns-ET was conducted using V/T/W embryos at four commercial farms, where piglets derived from them were produced. When artificial insemination was conducted prior to Ns-ET, the farrowing and survival rates obtained using V/T/W embryos were 75.0%, and 21.3%, respectively. These results show that Ns-ET of V/T/W embryos using this protocol would be feasible for piglet production at farms.

Non-surgical transfer of vitrified porcine embryos using a catheter designed for a proximal site of the uterus.

This study aimed to compare the efficiency of non-surgical embryo transfer (ET) using a newly developed catheter, which enables transferring embryos into a proximal site of the uterus (mostly uterine body), and surgical ET of vitrified porcine embryos. In Experiment 1, the catheter was inserted into 12 gilts, with each half of the group allocated to skilled or novice operators. The time required for insertion into the uterus did not differ between skilled and novice operators (4 min 9 s and 4 min 6 s, respectively). In Experiment 2, 12 gilts were used as recipients for non-surgical and surgical ET with vitrified embryos (n = 6, each). There was no significant difference in the rate of piglet production based on the number of transferred embryos between surgical and non-surgical ET (25.8% vs. 15.4%, p = .098). The results suggest that non-surgical ET catheter allowed for easy insertion and transfer of embryos without special training. Although the catheter is effective for deposition of embryos into the proximal site of uterus, the efficiency of piglet production is not enhanced compared with surgical ET. The ET method using this catheter, being labor-saving and less-invasive, may contribute to the improvement of ET in pigs.

Effect of volume of non-surgical embryo transfer medium on ability of porcine embryos to survive to term.

Non-surgical embryo transfer is a promising method for improving efficiency in the pork industry and also for biotechnology applications, such as in vitro embryo production, transgenesis and cloning. Several groups have reported successful piglet production using an artificial insemination catheter or flexible catheter designed for this procedure; however, the efficiency of the technique is still low. The critical points that need to be addressed in order to improve this procedure are (1) the embryo deposition site and (2) volume of transfer medium associated with the embryos; however, the latter has not yet been examined systematically. In the present study, we evaluated the effect of the volume of non-surgical embryo transfer medium on the ability of porcine embryos to survive to term by using a recently produced flexible catheter. The catheter consists of a guide and an injector. Blastocysts 200-230 mum in diameter were collected from donor gilts and transferred to recipient gilts. The time required for the completion of embryo transfer using this catheter was 14.6 +/- 3.9 min. The tip of the injector was determined by laparotomy to be located in a uterine horn 20-30 cm anterior from the branching point of the uterus body. We transferred 17.0-17.3 embryos with different volumes of medium (1.6, 3.2 and 10 ml) into each of 5, 4 and 4 recipients, respectively, and pregnancy was confirmed in 4, 3 and 1 of these recipients, respectively. Three recipients in the 1.6 ml group farrowed a total of 19 piglets (4, 5 and 10 piglets, respectively). These results suggest that successful non-surgical embryo transfer is affected by the volume of transfer medium.