Equine and Bovine Oocyte Maturation in a Novel Medium Without CO2 Gas Phase

OoTrap: enhancing oocyte collection and maturation with a field-deployable fluidic device

Assisted reproductive technologies (ART) are pivotal for contemporary reproductive medicine and species conservation. However, the manual handling required in these processes introduces stress that can compromise oocyte and embryo quality. This study introduces OoTrap, a novel fluidic device designed to streamline ART workflows by facilitating the capture and maturation of oocytes in a compact unit. The device also reintroduces mechanical forces similar to those in the in vivo environment, which are often missing in conventional systems. OoTrap operates in both static and perfusion-based modes, offering flexibility and optimal conditions for oocyte maturation. Notably, OoTrap achieved higher in vitro maturation (IVM) rates under perfusion, produced oocytes with fewer chromosomal abnormalities, and maintained spindle morphology integrity. The incorporation of a heating system and a 3D-printed syringe pump enabled IVM outside the incubator, making OoTrap suitable for field applications. The results highlight the potential of OoTrap to enhance ART outcomes by reducing manual handling, providing a controlled microenvironment, and offering a practical solution for field-based ART applications.

Overnight holding aids in selection of developmentally competent equine oocytes

The demand for equine in vitro produced embryos has increased over the last decade. The aim of this study was to compare the effects of an extended IVM or a prolonged period before fertilization, including holding time, on equine immature oocyte developmental competence. Oocytes, collected from abattoir-derived ovaries, were divided into 4 groups: H0/24 (n = 165) 0 h holding + standard 24-26 h IVM; H8/36 (n = 160) 8 h holding + 36 h IVM; H20/24 (n = 187) 20 h holding + 24 h IVM; H0/44 (n = 164) 0 h holding + 44 h IVM. Oocytes matured to MII were fertilized by intracytoplasmic sperm injection (ICSI) and cultured for 10 days. The oocyte degeneration rate was higher (P < 0.05) for H20/24 than the other groups (H0/24 38.2 %, H8/36 43.1 %, H20/24 54.5 %, H0/44 32.9 %). Cleavage was higher (P < 0.05) in H20/24 (70 %) compared to H0/24 (45 %) and H8/36 (54 %) but not to H0/44 (63 %). No differences among groups were observed in the number of blastocysts per oocyte. Injected oocytes that reached the blastocysts stage were higher (P < 0.05) for H20/24 (20 %) than H0/24 (7 %) and H0/44 (7 %) but not H8/36 (12 %). For cleaved oocytes, a higher blastocyst rate (P < 0.05) was observed for H20/24 (28 %) than H0/44 (11 %), while H0/24 (15 %) and H8/36 (21 %) were not different from any group (P > 0.05). Timing of blastocyst development was not different among groups. Overnight holding of equine immature oocytes followed by a standard IVM interval may induce a pre-selection of the most competent oocytes thereby improving cleavage and embryo development rates after ICSI.

Pregnancy obtained in a late gestational mare by in vitro embryo production

Recently, the demand for invitro embryo production in the horse has increased worldwide. Most clinical transvaginal ultrasound-guided ovum pick-up (OPU) procedures are performed in non-pregnant donor mares, and few experimental studies have described invitro embryo production from oocytes of pregnant donors 21-150 days in gestation. This report discusses OPU, follicular growth and invitro embryo production in a pregnant mare during late gestation.