An Earlier Uterine Environment Favors the <i>In Vivo</i> Development of Fresh Pig Morulae and Blastocysts Transferred by a Nonsurgical Deep-uterine Method

Abstract

This study aimed to evaluate the effect of recipient-donor estrous cycle synchrony on recipient reproductive performance after nonsurgical deep-uterine (NsDU) embryo transfer (ET). The transfers (N=132) were conducted in recipients sows that started estrus 24 h before (–24 h; N=9) or 0 h (synchronous; N=31), 24 h (+24 h; N=74) or 48 h (+48 h; N=18) after the donors. A total of 30 day 5 morulae or day 6 blastocysts (day 0=onset of estrus) were transferred per recipient. The highest farrowing rates (FRs) were achieved when estrus appeared in recipients 24 h later than that in the donors (81.1%), regardless of the embryonic stage used for the transfers. The FR notably decreased (P<0.05) when recipients were –24 h asynchronous (0%), synchronous (61.3%) or +48 h asynchronous (50%) relative to the donors. No differences in litter size (LS) and piglet birth weights were observed among the synchronous and +24 h or +48 h asynchronous groups. While a +24 h asynchronous recipient was suitable for transfers performed with either morulae (FR, 74.3%; LS, 9.2 ± 0.6 piglets) or blastocysts (FR, 84.6%; LS, 9.8 ± 0.6 piglets), a + 48 h asynchronous recipient was adequate for blastocysts (FR, 87.5%; LS, 10.4 ± 0.7 piglets) but not for morulae (FR, 30.0%; LS, 7.3 ± 2.3 piglets). In conclusion, this study confirms the effectiveness of the NsDU-ET technology and shows that porcine embryos tolerate better a less advanced uterine environment if they are nonsurgically transferred deep into the uterine horn.

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.…”

“…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.…”

Recent advances toward the practical application of embryo transfer in pigs

“…During the first attempt at NsDU-ET using fresh embryos, an acceptable reproductive performance of the recipients was achieved [4]. With improvements in the procedure, the results were greatly enhanced [5,6], even when fresh embryos cultured for 24 hours were used [7].…”