Nonsurgical deep uterine transfer of vitrified, in vivo-derived, porcine embryos is as effective as the default surgical approach

Abstract

Surgical procedures are prevalent in porcine embryo transfer (ET) programs, where the use of vitrified embryos is quasi non-existent. This study compared the effectiveness of surgical vs nonsurgical deep uterine (NsDU) ET using vitrified, in vivo-derived embryos (morulae and blastocysts) on the reproductive performance and welfare of the recipients. The recipient sows (n = 122) were randomly assigned to one of the following groups: surgical ET with 30 vitrified-warmed embryos (S-30 group, control); NsDU-ET with 30 vitrified-warmed embryos (NsDU-30 group) and NsDU-ET with 40 vitrified-warmed embryos (NsDU-40 group). Regardless of embryo stage, the NsDU-ET with 40 embryos presented similar rates of farrowing (72.7%) and litter size (9.9 ± 2.1 piglets) as the customary surgical procedure (75.0% and 9.6 ± 2.7 piglets). Numbers of ET-embryos appeared relevant, since the NsDU-ET with 30 embryos resulted in a decrease (P < 0.05) in farrowing rates (38.9%) and litter sizes (5.7 ± 2.4 piglets). In conclusion, we demonstrate for the first time that farrowing rate and litter size following a NsDU-ET procedure increase in function of a larger number of transferred vitrified embryos, with fertility equalizing that obtained with the invasive surgical approach. The results open new possibilities for the widespread use of non-invasive ET in pigs.

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

“…These data, together with the excellent fertility results following NsDU-ET [2][3][4][5][6], suggest that the insertion of the catheter does not cause significant damage to the cervix and/or uterine horn. The results of the present study parallel earlier studies and reinforce the suggestion that NsDU-ET is a non-invasive and welfare-preserving technology.…”

“…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.…”

“…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].…”

Factors of importance when selecting sows as embryo donors

“…Donor sows were subjected to mid-ventral laparotomy on day 6 of the estrous cycle (day 0: onset of estrus). Surgeries and embryo recovery were performed as described previously (Martinez et al, 2015). After exposure of the genital tract, ovarian corpus luteum, and the presence and number of follicular cysts (ovarian structures filled with a transparent liquid, without ovulation signs, and with a diameter >2 cm at the moment of laparotomy) were counted in each donor sow.…”

“…In addition, primiparous sows have a longer WEI than multiparous sows (Clark et al, 1986;Koketsu and Dial, 1997), which has been associated with differences in length of estrus and timing of ovulation (Soede and Kemp, 1997). Despite the fact that differences between primiparous and multiparous sows may have important consequences for the schedule of ET protocols, primiparous or multiparous sows have been -throughout available literature -arbitrarily selected as donors without a proper screening of the effect of parity on the number and quality of embryos collected at days 5 to 6 after insemination (Brüssow et al, 2000;Beebe et al, 2011;Martinez et al, 2015).…”