EFFECT OF B-MERCAPTOETHANOL ON THE VIABILITY OF IVM IVF/IVC BOVINE EMBRYOS DURING LONG-DISTANCE TRANSPORTATION IN PLASTIC STRAWS/

Experiments were conducted to assess the effect of B-mercaptoethanol ( beta-ME) on the quality and viability of bovine blastocysts derived fr om in-vitro culture (IVC) of in-vitro matured and fertilized (IVM-IVF) oocytes during their transport between 2 distant places. Follicular o ocytes were collected from ovaries obtained at a slaughterhouse and we re cultured for 20 to 21 h in modified TCM-199. The IVM oocytes were f ertilized in vitro with frozen-thawed spermatozoa. Fertilized oocytes were cultured for 7 d, and embryos that developed to the blastocyst st age were used for the experiments. The blastocysts, packed in straws w ith transportation medium that consisted of modified TCM-199 with HEPE S equilibrated in air and supplemented with 20 % calf serum and 0, 10, 50, 100 or 150 mu M beta-ME, were transported at 37 degrees C from To kyo to Sapporo by air (18.3 h). The quality of blastocysts was assesse d and ranked as excellent (A), good (B), fail (C) or poor (D) after tr ansportation. The percentages of blastocysts ranked as A or B were sig nificantly higher (P<0.05) when the embryos were transported in beta-M E supplemented medium (80 to 100%) than when transported without beta- ME (54%). Blastocysts ranked as A or B after transportation in medium with or without 150 mu M beta-ME were nonsurgically transferred to syn chronous recipients; 60 d after embryo transfer, 21/36 and 19/35 cows, respectively, were diagnosed as pregnant by palpation per rectum. The se results indicate that beta-ME maintains the quality of bovine blast ocysts in plastic straws for several hours without control of CO2 and that the concentration of beta-ME used in this experiment is not detri mental to the blastocysts.