Successful Non-Surgical Deep Uterine Transfer of Porcine Morulae after 24 Hour Culture in a Chemically Defined Medium

Abstract

Excellent fertility and prolificacy have been reported after non-surgical deep uterine transfers of fresh in vivo-derived porcine embryos. Unfortunately, when this technology is used with vitrified embryos, the reproductive performance of recipients is low. For this reason and because the embryos must be stored until they are transferred to the recipient farms, we evaluated the potential application of non-surgical deep uterine transfers with in vivo-derived morulae cultured for 24 h in liquid stage. In Experiment 1, two temperatures (25°C and 37°C) and two media (one fully defined and one semi-defined) were assessed. Morulae cultured in culture medium supplemented with bovine serum albumin and fetal calf serum at 38.5°C in 5% CO2 in air were used as controls. Irrespective of medium, the embryo viability after 24 h of culture was negatively affected (P<0.05) at 25°C but not at 37°C compared with the controls. Embryo development was delayed in all experimental groups compared with the control group (P<0.001). Most of the embryos (95.7%) cultured at 37°C achieved the full or expanded blastocyst stage, and unlike the controls, none of them hatched at the end of culture. In Experiment 2, 785 morulae were cultured in the defined medium at 37°C for 24 h, and the resulting blastocysts were transferred to the recipients (n = 24). Uncultured embryos collected at the blastocyst stage (n = 750) were directly transferred to the recipients and used as controls (n = 25). No differences in farrowing rates (91.7% and 92.0%) or litter sizes (9.0±0.6 and 9.4±0.8) were observed between the groups. This study demonstrated, for the first time, that high reproductive performance can be achieved after non-surgical deep uterine transfers with short-term cultured morulae in a defined medium, which opens new possibilities for the sanitary, safe national and international trade of porcine embryos and the commercial use of embryo transfer in pigs.

Factors of importance when selecting sows as embryo donors

“…Unlike in sows Martinez et al, 2014), superovulation treatments in prepubertal gilts and synchronized mature gilts yield high proportions (25% to 50%) of unfertilized oocytes and degenerated embryos (Guthrie et al, 1974;Holt and Schlieper, 1991;Wallenhorst and Holtz, 2002;Ziecik et al, 2005), which makes the use of this these females as embryo donors inadvisable. We had only selected multiparous sows due to their high accessibility on-farm and because they usually have farrowing rates and litter sizes higher than those in primiparous sows.…”

Surgical embryo collection but not nonsurgical embryo transfer compromises postintervention prolificacy in sows

“…A volume of 30 mL of protein-free embryo recovery medium, consisting of Tyrode's lactate (TL)-HEPES-polyvinyl alcohol (PVA) (TL-PVA; [11]) with small modifications [4], was introduced into the uterine horn from the tip of the uterine horn using a 60 mL syringe connected to a blunt needle. The flushing medium was forced through the glass cannula into a 50 mL sterile tube by manual massage of the uterus.…”

“…All NsDU-ETs were performed in weaned recipients that started estrus 0 or 24 h after the donors using a previously described method [2][3][4]. Briefly, six hours prior to ET, each recipient received a single intramuscular injection of a long-acting amoxicillin suspension (Clamoxyl LA ® ) at a dosage of 15 mg/kg body weight.…”

“…With the recent development of non-surgical deep uterine (NsDU)-ET technology, the commercial use of ET in pigs is now possible. The NsDU-ET technique is a reliable procedure that yields good fertility levels when coupled to fresh embryos [1][2][3] or stored embryos, either short-term [4] or long-term [5].…”

“…Several factors affecting the success of the NsDU-ET procedure, including superovulation of the donors, synchrony between donors and recipients, use of fresh, short-term or long-term stored embryos, number of embryos transferred per recipient and the recipient's parity, have all been recently assessed [2][3][4][5][6]. However, other factors not directly related to the success of ET have to be quantified to properly estimate the final costs of porcine ET, a most relevant factor for the successful establishment of 3 commercial ET programs.…”