Lamb Birth Weight is Affected by Culture System Utilized during in Vitro Pre-Elongation Development of Ovine Embryos

Abstract

It has previously been reported that ovine embryos cultured in Synthetic Oviduct Fluid medium supplemented with 20% human serum (SOF+HS) develop into lambs with a high birth weight. We have investigated this phenomenon by culturing ovine zygotes in SOF+HS or a serum-free version of Synthetic Oviduct Fluid with BSA and amino acids (SOFaaBSA) in place of serum. Zygotes were either obtained from superovulated and naturally mated ewes or produced in vitro. Embryos were subsequently transferred to synchronized recipient ewes (n = 63). An additional group of ewes (n = 16) served as flock fertility and lambing controls. Development of zygotes to stages suitable for transfer (i.e., good to excellent compact morulae or blastocysts) was not affected by medium (SOFaaBSA = 53 +/- 5% vs. SOF+HS = 59 +/- 5%) but was affected by source (in vivo-derived = 74 +/- 5% vs. in vitro-derived = 35 +/- 5%, p < 0.001). Embryos incubated in SOF+HS were morphologically different from those incubated in SOFaaBSA, having abundant lipid droplets. Pregnancy rate (65%) and embryo survival (48%) of recipients determined by ultrasonography on approximately Day 60 of pregnancy did not differ between medium treatments or source of embryo. Mean weight of lambs from embryos cultured in SOF+HS (4.2 +/- 0.2 kg) was significantly heavier than that of controls (3.4 +/- 0.2 kg, p < 0.01) or of lambs from embryos cultured in SOFaaBSA (3.5 +/- 0.2 kg, p < 0.05). Furthermore, mean gestation length was longer in recipients receiving embryos incubated in SOF+HS (147 +/- 1 days) than in SOFaaBSA (145 +/- 1 day, p < 0.05). Reasons for this birth weight and gestation length difference are unclear, but our data suggest that different culture conditions can produce embryos with differing morphology, apparent chemical composition, and rate of development, resulting in lambs with differing gestation length and birth weight.

Delipidating in vitro-produced bovine zygotes: Effect on further development and consequences for freezability

“…The composition of culture medium and particularly the presence of serum, has a marked influence on morphology and cytoplasmic appearance of in vitro-produced embryos that look dark. Under close examination, these blastocysts have numerous "granules" in the trophectoderm cells (12,37). Pollard and Leibo (31) noticed that a difference in the zona pellucida to enzymatic digestion between in rive and in vitro produced embryos could modify their permeability to water and cryoprotective agents.…”

Regulation of sheep oocyte maturation using cAMP modulators

“…Discrepancies between IVM and in-vivo matured oocytes in embryo yield and pregnancy outcomes have been reported consistently across mammalian species [13][14][15][16]. The ovine oocyte is no different in this respect, with one report citing blastocyst rates of 35 and 75% for in vitro-and in vivo-matured oocytes, respectively [16].…”

“…The ovine oocyte is no different in this respect, with one report citing blastocyst rates of 35 and 75% for in vitro-and in vivo-matured oocytes, respectively [16]. When the oocyte is mechanically removed from the follicular environment, meiotic resumption occurs spontaneously [17].…”

The Epigenetics of Adult (Somatic) Stem Cells

“…In fact, a growing body of evidence documents that culture of bovine and ovine embryos to the blastocyst stage prior to embryo transfer results in higher incidences of fetal and perinatal loss. [115][116][117] In the bovine, these abnormalities are not observed if the embryos are first transferred to the oviducts of sheep and then transferred at the blastocyst stage to the reproductive tracts of recipient heifers. 115 Thus, the abnormalities are likely attributable to embryo culture.…”