The aims of the present study were to evaluate the effect of cooling of the dromedary camel embryos on the pregnancy and pregnancy loss rates, and to investigate the factors which might affect the outcomes of the transfer of cooled embryos. After the donors (n = 56) had been super-ovulated and mated, they were flushed at Day 8 or 9 post-mating. Of 487 collected embryos, 110 were refrigerated at 4°C for up to 5 days in holding medium (HM), flushing medium supplemented with 10% fetal calf serum (FM + FCS) or TCM199 supplemented with 50% FCS and HEPES (TCM + FCS + HEPES). Both fresh (n = 377) and cooled embryos were transferred individually into synchronized recipients. Pregnancy diagnoses were carried out at Days 18–19, 30 and 60 post-mating of the donors. Transferring of fresh embryos into the recipients resulted in significantly higher pregnancy rates at Days 18–19 (53.1% vs. 38.2%, P < 0.01), Day 30 (46.4% vs. 31.8%, P < 0.01) and Day 60 (42.4% vs. 26.4%, P < 0.005) compared with those of cooled embryos, respectively. Pregnancy rates after transferring cooled embryos progressively decreased with the prolongation of the storage period. A significant difference in the pregnancy rate (56% vs. 13%, respectively, P < 0.05) was recorded only at Days 18–19 between cooled embryos held for one day and those held for 5 days. The pregnancy rates at Days 18–19, Day 30 and Day 60 were non-significantly higher when TCM + HEPES and FCS medium used for cooling of embryos compared to those of FM + FCS or HM medium. Cooling of spherical embryos resulted in significantly higher pregnancy rates at Days 30 (45.6% vs. 17.0%, respectively, P < 0.005) and 60 (42.1 vs. 9.4%, respectively, P < 0.005) and a significantly lower pregnancy loss rate (11.1% vs. 66.6%, respectively, P < 0.005) compared to those resulting from cooling of folded embryos. Neither the size of embryo nor the day of flushing had a significant effect on the pregnancy and pregnancy loss rates after the transfer of cooled embryos.
In conclusion, pregnancy could be obtained after the transfer of camel embryos refrigerated for up to 5 days. In addition, higher pregnancy rates could be obtained if only spherical embryos were selected for cooling.
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