Non-surgical transfer of 4',6'-diamidino-2-phenylindole-stained equine embryos

Abstract

4',6'-diamidino-2-phenylindole (DAPI) is a fluorescent dye that binds only to the DNA of dead blastomeres of an embryo. The use of DAPI for assessing viabilities of equine Day 6 to 7 embryos was studied. The pregnancy and normal development of the embryo until 20 days after transfer (day of pregnancy termination) was used as an indicator of embryonic viability. Eleven embryos were stained with DAPI at room temperature for 15 min. They were then exposed to UV light to visualize staining, and cultured for 2 h before non-surgical transfer to recipient mares. Eight control embryos were cultured for 2 h before transfer to recipient mares. The recipient mares were scanned for pregnancies every other day starting 6 days after transfer. Twenty days after the transfer the pregnant recipient mares received luprostiol to induce abortion of the foetus. The pregnancy rate 6 days after transfer was 82% in the treatment group, and 75% in the control group (P>0.05). One DAPI-stained embryo resorbed and was no longer visible 12 days after transfer. However, this particular recipient mare had a uterine inflammation as shown by examination in the oestrus following embryo transfer. Although the number of embryos is insufficient to demonstrate lack of treatment effect, the high pregnancy rates following DAPI staining should encourage further studies on this subject.;