The role of altered uterine-embryo synchrony on conceptus growth in the pig

This study was conducted to determine whether inducing an embryo-uterine as ynchrony during the preimplantation period would alter fetal and(or) placen tal size at term. Yorkshire gilts (n = 24) were checked twice daily for est rus and bred to a Yorkshire boar 24 h after the first exhibition of estrus. Embryos (1 to 4 cells) were flushed from the oviducts of each donor gilt o n d 2.5 of gestation and transferred in equal numbers to the oviducts of a recipient gilt on d 1.5, 2.5, or 3.5 of the estrous cycle. Gilts were slaug htered on d 112 of gestation (calculated on the age of the conceptus) and f etal and placental weight, placental surface area, and implantation site le ngths were determined. Although litter sizes were similar (9.1 +/- 0.9), co nceptuses transferred to d 3.5 recipients became heavier fetuses (1.44 +/- 0.05 vs 1.23 +/- 0.04 kg, P < 0.001), with larger placental surface areas ( 1,793 <plus/minus> 60 vs 1,459 +/- 43 cm(2), P < 0.01), and longer implanta tion sites (32.1 +/- 1.5 vs 24.9 +/- 0.6 cm, P < 0.001) than those transfer red to recipients on d 2.5. These data demonstrate that oviductal transfer of embryos into a reproductive tract that is more advanced by as little as 24 h can result in alterations in placental growth and function during gest ation.