Success of embryo transfer of hybrid embryos in Old World camelids: A first study

This is the first study to test the embryo transfer (ET) of hybrid embryos in Old World camelids and produces a live calf from a dromedary recipient. Hybrid embryos were collected from 7 dromedary and 10 Bactrian donors, with or without ovarian super-stimulation, and transferred to dromedary recipients. Pregnancy diagnosis was conducted on Day 10 post-ET by using the progesterone-ELISA test and trans-rectal ultrasonography at 1 and 2 months of gestation. The date of abortion, stillbirth, or normal calving for each pregnant recipient was recorded. Without ovarian super-stimulation, two and one recipients were pregnant at 10 days post-ET, from ♂ Bactrian X ♀ dromedary and ♂ dromedary X ♀ Bactrian, respectively. While at 2 months of gestation, only one recipient was diagnosed pregnant from ♂ Bactrian X ♀ dromedary. Response to ovarian super-stimulation was successful in all 4 of the tested dromedary donors and in 8 out of 10 Bactrian donors. Additionally, 4 super-stimulated Bactrian donors (40%) showed failure of ovulation. The number of super-stimulated developed follicles and recovered embryos was higher in dromedary donors compared to Bactrian donors. Ten and two recipients were diagnosed pregnant at 10 days post-ET for ♂ Bactrian X ♀ dromedary and ♂ dromedary X ♀ Bactrian, respectively. At 2 months of gestation, the number of pregnant recipients from ♂ Bactrian X ♀ dromedary was reduced to eight, while the two pregnant recipients from ♂ dromedary X ♀ Bactrian remained pregnant. Total early pregnancy loss at 2 months gestation for all transferred hybrid embryos, obtained with or without ovarian super-stimulation, was 4/15 (26.6%). One healthy male calf was born from a recipient, with a total gestation period of 383 days, that received an embryo from a Bactrian male and a dromedary donor. Stillbirth was observed in six cases after 10.5-12 months of gestation and three cases aborted between 7 and 9 months of gestation due to trypanosomiasis. In conclusion, ET of hybrid embryos in Old World camelids is successful. However, further studies are required to improve the outcome of this technology to be used for meat and milk production in camels.