Efficacy of Histoprep® gradient for isolating ovine epididymal sperm

Low developmental competence and high tolerance to thermal stress of ovine oocytes in the warm compared with the cold season

Heat stress can potentially affect most aspects of reproduction in mammals. To our knowledge, no studies have ever been conducted for evaluating the influences of hot season on the developmental competence of ewe oocytes. In the present study, for the first time, we evaluated the effects of season (winter or summer), in vitro thermal stress, and their interaction on the ewe oocytes harvested from slaughterhouse ovaries. Cumulus-oocyte complexes (COCs) were either incubated at 39 °C for the entire length of IVM period or first incubated at 41 °C for 12 h and then at 39 °C. Evaluated endpoints included the ratios of total aspirated COCs/ovary and good-quality COCs/ovary, the apoptosis (Annexin V staining) and nuclear maturation of oocytes after 24-h IVM, and the developmental competence of oocytes after IVF. Our results showed that the number of aspirated oocytes per ovary was similar in both seasons, but the winter ovaries yielded significantly more oocytes with acceptable morphology in winter than in summer (2.1 ± 0.14 vs. 1.5 ± 0.09, P < 0.05). There was a significant interaction between season and thermal stress on the apoptosis, some nuclear maturation parameters, and blastocyst development of oocytes (P < 0.05). Although the winter oocytes were more developmentally competent than the summer oocytes, the winter oocytes were more sensitive to the thermal stress than summer oocytes. In conclusion, the developmental competence of ovine oocytes was lower in summer than in winter. However, it seemed that summer oocytes were more resistant to the in vitro thermal stress during IVM period compared with winter oocytes.

In vitro and in vivo fertilization potential of cryopreserved spermatozoa from bull epididymides stored for up to 30 hours at ambient temperature (18 °C-20 °C)

The aims of this study were to compare the viability and in vivo and in vitro fertilization potential post-thaw sperm collected at different times postorchiectomy from bull epididymides (EP) at 18 °C to 20 °C, with those of semen collected by electroejaculation (EJ) from the same bulls. Semen samples were collected by EJ from 10 Zebu bulls and cryopreserved. A week later 20 epididymides from these bulls were obtained by orchiectomy and randomly divided into five groups (G) to be maintained at ambient temperature for 6, 12, 18, 24, and 30 hours before sperm recovery by retrograde flow. The sperm were cryopreserved, and post-thaw parameters were determined by both computer-assisted sperm analysis and morphologic analysis. In vitro fertilization of oocytes was performed to assess the cleavage rate, blastocyst rate, total number of cells, and hatching rate of embryos. The G30 sperm samples were also used for fixed time artificial insemination (FTAI) of Zebu heifers (n = 10). The results of post-thaw sperm viability showed that total and progressive motility and plasma membrane integrity were lower in sperm in which cryopreservation was delayed for 30 hours, showing a negative correlation of these parameters with delay before cryopreservation. In all groups, it was possible to obtain viable embryos, and embryos from G6 samples had more cells than the other groups. The greatest embryo production rates were observed in G6, G12 and G18 (27.2 to 32.2%) and it was significantly lower in G24 and G30 samples. For EJ, many individual variations were observed in embryo production potential between bulls. G30 samples, with only 5.2% of post-thaw progressive motility, were able to fertilize and produced a pregnancy. To the authors' knowledge, this is the first time in vitro embryos up to 8 days of development and a pregnancy after FTAI have been produced with sperm from bull epididymides that had been stored at 18 °C to 20 °C for up to 30 hours.