Piglets born after non-surgical deep intrauterine transfer of vitrified blastocysts in gilts

The aims of this study were: (1) to evaluate the effect of the number of previous estrus of recipient gilts on effectiveness of intrauterine insertion of a flexible catheter designed for non-surgical deep intrauterine catheterization during diestrus in pigs; and (2) to determine the farrowing rate and the litter size after non-surgical deep intrauterine embryo transfer (ET) of porcine blastocysts vitrified by the open pulled straw (OPS) method. In experiment 1, 27 large white hyperprolific gilts (LWh) with 2–6 previous estrus were used. Intrauterine insertions of the flexible catheter were carried out at day 5.5–6 of the estrous cycle (D0 = onset of estrus). During insertions, no or only moderate reactions were observed in 88.9% of gilts and was not related (P > 0.05) to the number of estrus prior to the insertion periods. The number of the estrus had a significant effect (P < 0.05) on the difficulties found during the procedure. In the 100% of gilts with two estrus (N = 6) it was not possible to insert the flexible catheter through the cervix. In gilts with three or more estrus, it was possible to pass the cervix and to progress along a uterine horn in 80.9% of the cases. In 86.7% of the gilts, the tip of the flexible catheter achieved the second or third quarter of the uterine horn. In experiment 2, following non-surgical deep intrauterine transfer of 20 vitrified/warmed blastocysts, 9 Meishan recipients (42.9%) farrowed an average of 5.4 ± 0.8 piglets (range 3–9) of which 0.6 ± 0.3 piglets (range 0–2) were born dead. In conclusion, this study shows that it is possible to obtain birth of piglets following non-surgical deep intrauterine embryo transfer (ET) of vitrified/warmed blastocysts. Non-surgical deep intrauterine ET and OPS vitrification methods are promising procedures to be used together for the introduction of new genetic material in a farm.