Transport of bovine oocytes in maturation medium without a controlled gaseous atmosphere

Oocytes (n=1177) aspirated from 2 to 8mm follicles obtained from bovine slaughterhouse ovaries (11 replications) were randomly distributed in four treatments. Oocytes were matured for 24h with modified TCM-199 Earle salts, plus 25mM bicarbonate, 25 mM HEPES, rFSH-h, Estrus Cow Serum (ECS), and piruvate at 39ºC, in incubator with 5% CO2 and saturated humidity (Control Group, n=296) or exposed to a simulated transport for 6 (T6, n=286), 12 (T12, n=294) or 18h (T18, n=301) in maturation medium containing TCM + HEPES, in a 39ºC water bath, with the same components used in the Control Group, but with 1mM bicarbonate. At the conclusion of each transport period, oocytes were transferred to dishes with maturation medium to reach 24h in incubator, under the same conditions described for the Control group. Fertilization was accomplished during 18h, with the same temperature and gaseous atmosphere, in FERT-TALP plus heparin. The insemination dose was 1x106 spermatozoa/mL, sorted by swim-up. Presumptive zygotes were cultured in SOF medium + 5% ECS for 8 days, in incubator at 39ºC using gasified bags with 5% CO2, 5% O2 and 90% N2. Cleavage rates did not differ between treatments. Embryonic development rates at D7 were similar for Control (20.9%), T6 (19.2%) and T12 (21.4%) groups, with a reduction (P<0.05) for group T18 (12.3%) when compared to Control and T12 groups. At D9, there was a lower production of expanded plus hatched blastocysts in T18 (P<0.05), without difference (P>0.05) in hatched blastocyst rate. The average number of cells of hatched blastocysts was similar (P>0.05) in Control (136), T6 (125.5) and T12 (126.8) groups. These results indicate the possibility of transporting bovine oocytes in maturation medium containing TCM + HEPES, without controlled gaseous atmosphere environment, at 39ºC, for up to 12 hours. This technique offers a practical and efficient alternative for the transport of bovine oocytes for in vitro production of bovine embryos (IVP).

bovine oocytes; Hepes; OPU; IVP; transportation

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