Micromanipulation of equine embryos to produce monozygotic twins

Abstract

Summary The uteri of Welsh Pony donor mares were flushed non surgically late on Day 5 after ovulation (at 18.00 h or midnight) or on Day 6 (between 06.00 h and 12.00 h) to recover morulae or early blastocysts. Twenty‐six embryos were recovered from 63 flushing attempts (41 per cent). To investigate the effects of in vitro culture and micromanipulation on the development of the acellular equine blastocyst capsule, intact and manipulated embryos were cultured for varying times before being fixed and stained for histological examination. The capsule developed normally on two non‐manipulated morulae and one blastocyst cultured for 12 to 48 h. However, no development or redevelopment of the capsule occurred during 48 to 96 h in culture of the 18 demi‐embryos which resulted from the bisection of two morulae and seven blastocysts. The remaining 14 embryos were also bisected and the demi‐embryos transferred surgically to synchronised recipient mares within 4 h. All eight pregnancies which developed, including two sets of monozygotic twins, originated from bisected morulae. No pregnancies developed following transfer of bisected blastocysts.