Factors affecting the success of surgical and nonsurgical equine embryo transfer

Nonsurgical embryo recovery was attempted from light-horse and draft mares. Embryo recovery rates were not affected (P>.05) by technician or stallion but were lower (P<.05) from draft mares (44%) than light-horse mares (67%). Sham transfer of embryos on day 8 post-ovulation did not (P>.05) increase the number of mares returning to estrus by 22 days post-ovulation. Method of embryo transfer greatly affected pregnancy rates. Embryos transferred surgically during March–June resulted in 0 of 12 pregnancies versus 13 of 25 pregnancies obtained during July–September, This strongly suggests a seasonal influence on pregnancy rates. Technician influenced (P<.05) the success of nonsurgical transfer (46.2% vs. 7.7%). In addition, protection of the insemination rod with a sheath (guarded method) appeared to provide some advantage over an unguarded method of nonsurgical transfer (54% vs. 23%). Lastly, a preliminary experiment was conducted to evaluate transfer of embryos via flank incision. Four of 5 embryos transferred by this method resulted in a pregnancy at 50 days post estrus.