Effectiveness of Gamete Preservation in Roe Deer (<em>Capreolus capreolus</em>) by Determination of Collected Post Mortem Oocyte and Semen Parameters and In Vitro Fertilization

The aim was to evaluate the effectiveness of semen cryopreservation and oocyte vitrification in roe deer as a potential method of gamete preservation for endangered deer species. Sperm was isolated from the cauda epididymis (N=14). The motility parameters (CASA) and morphology of fresh semen (FS) and frozen&ndash;thawed semen (TS) were compared. A hyaluronic binding assay (HBA) was used in FS to distinguish between mature spermatozoa that express hyaluronan re-ceptors on their plasma membrane and immature ones that lack these receptors, and the mito-chondrial membrane potential in TS was determined (flow cytometry). The HBA showed a via-bility rate of 61.9% in FS. Oocytes (N=8) underwent a viability test (MTT) and vitrification and fresh oocytes (FOs; N=8) were fertilized with TS and embryos were cultured until the blastocyst stage. The number of isolated oocytes, cumulus&ndash;oocyte complexes (COCs), cleaved embryos and expanded blastocysts was evaluated. Higher percentages of morphological parameters (acro-some, head, midpiece, and tail shape) were observed in FS compared to TS, whereas the motility and progressive movement were greater in TS (P &le; 0.001). The viability was 50.5% and the mito-chondrial membrane potential was 40.6% in TS. In total, 311 oocytes were collected and from 150 COCs, 125 blastocysts developed. The oocyte viability after vitrification in thawed oocytes was 81%. The morphology, motility, progressive movement, difference in viability in FS and TS and high viability of fresh and vitrified oocytes indicate that an effective freezing protocol has been established that has potential for implementation in other deer species.