title: Effect of variation in embryo stage on the establishment of pregnancy, and embryo survival and growth in ewes with two embryos.
abstract: Embryos at different stages of development were transferred to recipient ewes on Day 6 to investigate the effect of variation in stage of development on embryo survival and growth. Three groups of ewes received 2 embryos that were at the same stage of development, Day 4, Day 6 or Day 8. A fourth group received 1 Day-4 and 1 Day-8 embryo. At autopsy on recipient Day 34 there were no significant differences in embryo survival (Day 4, 34%; Day 6, 50%; Day 8, 46%; and Day 4 and 8, 48%). Fetuses developing from Day-8 embryos were heavier than others (Day 4, 1.10 +/- 0.06 g; Day 6, 1.15 +/- 0.06 g; Day 8, 1.41 +/- 0.08 g; P less than 0.05). In Group 4 neither survival nor growth of embryos was significantly affected by the presence of an embryo at a different stage of development. The ability of the uterus to stimulate development of a relatively retarded embryo is confirmed. Apparently the uterus has less effect in slowing the development of advanced embryos.
authors.affiliation: AFRC Institute of Animal Physiology and Genetics Research, Edinburgh Research Station, Roslin, Midlothian, U.K.
authors.forename: I
authors.initials: I
authors.lastname: Wilmut
authors.forename: C J
authors.initials: CJ
authors.lastname: Ashworth
authors.forename: A J
authors.initials: AJ
authors.lastname: Springbett
authors.forename: D I
authors.initials: DI
authors.lastname: Sales
mesh_terms: D000818:Animals; D004624:Embryo Transfer; D004622:Embryo, Mammalian / Q000502:physiology*; D005314:Embryonic and Fetal Development; D005260:Female; D005313:Fetal Death / Q000209:etiology*; D011247:Pregnancy; D012756:Sheep; D014427:Twins; D014599:Uterus / Q000502:physiology