Assessment of canine oocyte viability after transportation and storage under different conditions

To improve assisted reproductive technologies in the domestic dog, different transport treatments were evaluated for their ability to maintain viability of canine oocytes, as assessed by esterase activity 8 h after storage or after 48 h of in vitro maturation (IVM) culture. In Experiment 1, ovaries were transported within reproductive tracts or were excised and stored at either 20 or 37 °C in phosphate buffered saline. Oocytes collected from reproductive tracts transported at 37 °C had the greatest viability after storage (P < 0.05). However, after IVM there were no significant differences among any of the four storage conditions in oocyte viability or meiotic resumption (P = 0.05). In Experiment 2, isolated oocytes were transported in either TCM-199 with Hankʹs salts and Hepes buffer or in TL-Hepes at either 20 or 37 °C, or in maturation medium equilibrated with 5% CO2 at 37 °C. In Experiment 2, oocytes transported in Hepes buffered media at 37 °C had greater viability rates after storage than did those transported in these same media at 20 °C or in sodium bicarbonate buffered medium at 37 °C (P < 0.001). After IVM, oocytes transported in the 37 °C treatment groups had greater viability rates than did those transported at 20 °C (P < 0.01). Overall, isolated oocytes transported at 37 °C had greater rates of meiotic resumption than did those transported at 20 °C (P < 0.05). Taken together, these data indicate that canine oocytes exhibited sensitivity to lesser temperatures and maintained greater rates of viability during transport at 37 °C. Isolated oocytes maintained greater viability than oocytes transported in situ. Hepes buffered media increased viability rates for isolated oocytes transported at 37 °C compared to a similar medium buffered with sodium bicarbonate.