Survival of sheep x goat hybrid inner cell masses after injection into ovine embryos

Modified blastocyst injection techniques were used to inject immunosurgically isolated sheep x goat hybrid inner cell masses (ICM) into ovine blastocysts, with subsequent transfer of composite embryos to ovine recipients. Hybrid embryos were collected from does artificially inseminated with Barbados ram semen. A total of 13 live and 2 aborted offspring resulted from the 34 composite embryos transferred to recipient ewes (38% embryo survival). Of the 15 offspring, 4 exhibited phenotypic hybridism and 2 (13%) of these were determined to be hybrid <-> sheep chimeras by karyotype, serum protein and isoenzyme analyses, and fiber identification. Each of the 4 was produced by an injection procedure that involved damage of the ovine host ICM. One additional offspring was unusual in appearance, but the presence of hybrid cells was not proven. Similarly, caprine ICM were immunosurgically isolated and injected into ovine blastocysts that were then transferred to ovine recipients. Of the 13 composite embryos transferred, 12 offspring were produced (92% embryo survival). Eleven were overt goat <-> sheep chimeras and, of these, 7 were also blood chimeras. The hybrid ICM was shown to be capable of contributing to normal embryonic and fetal development after injection into an ovine blastocyst but may be less likely to be incorporated with the ovine host ICM than is the caprine ICM.