rarely developed to blastocysts and, therefore, were not
used for ET.
Embryos for transfer were placed in Syngro holding
medium and loaded into 0.25-mL ET straws (Bioniche).
Embryos used for transfer (approximately 7.5 days after
onset of fertilization) were quality one or two blastocysts
[11], expanded blastocysts or, rarely, early hatching, or
hatched blastocysts. Embryos were placed into 0.25-mL
straws for transportation (approximately 1 hour), and the
straws were loaded into ET guns at the farms. The ET guns
were covered with a plastic chemise and then put into gun
warmers (EM Tools Inc., Rusk, TX, USA) at 38 C. Embryos
were transferred into recipients assigned to treatments by
a predetermined random selection method.