Effect of asynchronous non-surgical transfer of porcine embryos on pregnancy rate and embryonic survival

Embryo survival was determined after non-surgical transfer to recipients wi th a variable synchrony of ovulation. Groups of 10 to 15 freshly weaned mul tiparous sows (donors and recipients) were checked and paired for time of o vulation, resulting in recipients ovulating from 24 h before to 36 h after the donors ('asynchrony' of -24 to +36 h). Embryos were collected from 34 d onors at 120 h (range 108-132 h) after ovulation and 16.6+/-2.4 morulae and blastocysts were transferred to 31 recipients. Pregnant recipients were sl aughtered on Day 35 (Day 0 = ovulation) to evaluate embryonic survival. Twe lve recipients were pregnant at Day 21 and five were still pregnant at Day 35. One recipient was excluded due to cystic ovaries. An asynchrony of +18 to +36 h resulted in 1/12 recipients pregnant at Day 21 and no pregnancies at Day 35, while an asynchrony of -24 to +12 h resulted in 11/18 recipients pregnant at Day 21 and five still pregnant at Day 35 (P < 0.05). The prese nce of greater than or equal to 6 morulae within a litter never resulted in pregnancies at Day 21 (0/9), while with <6 morulae, 12/21 recipients were pregnant at Day 21 (P < 0.05), irrespective of the degree of asynchrony. Th e results seem to indicate that only blastocysts should be transferred succ essfully by a non-surgical procedure at 108 to 132 h after ovulation. Recip ients should ovulate between 24 h before to 12 h after the donors. Transfer s to recipients ovulating 18 to 36 h after the donors appear to lend to ver y low pregnancy rates. However, these conclusions need to be confirmed in a study with more animals. (C) 2000 Elsevier Science B.V. All rights reserve d.