The culture of sheep embryos in either a bicarbonate-buffered medium or a phosphate-buffered medium enriched with serum

Totals of 66 Day-3 and 72 Day-5 (estrus = Day 0) sheep embryos were cultured for 3 days in test-tubes containing either 1 ml synthetic oviduct fluid (SOF) or enriched phosphate-buffered saline (EPBS) equilibrated with a gas phase of 5% CO₂, 5% O₂, 90% N₂. Thirty-four Day-3 and 36 Day-5 embryos were cultured in 2 ml EPBS under liquid paraffin and exposed to air. After culture the embryos were examined for stage of cleavage and either fixed and stained or transferred to suitable recipient animals.Day-3 embryos cultured in SOF developed more readily than those in EPBS or EPBS under paraffin and were more viable in recipient animals (15 surviving of 29 transferred vs 2 of 29 and 1 of 28, respectively). The development of Day-5 embryos varied between years with SOF being superior in 1976 but with no differences between media in 1977. The Day-5 embryos cultured in SOF were more viable than those in the two EPBS systems (15 surviving of 24 transferred vs 16 of 54).