Thermal properties of rhinoceros ovum pick-up probes: possible effects of temperature shock on oocyte maturation potential.

Background: The implementation of assisted reproductive techniques and use of in vitro embryo production has highlighted their potential in attempts to prevent the extinction of the northern white rhinoceros (Ceratotherium simum cottoni). However, in vitro embryo production has proved challenging. Transrectal ovum pick-up (OPU), while done successfully with custom-made aspiration probes (AP), may expose oocytes to detrimental temperature shock.

Objective: This study compares the temperature regulation properties between two AP, made from different materials and used during OPU in southern white rhinoceros (C. s. simum).

Methods: The initial PVC plastic AP, produced using a computer numerical control machine, was compared to a modified aluminium AP. A rhinoceros model was constructed using a 210 L water container fitted with heating elements and a water pump. Water was warmed to 37.5-38.5 ℃ to simulate rhinoceros body temperature. The AP was equilibrated to room temperature (22 ℃; simulating summer) or in a walk-in fridge (4 ℃; simulating winter) overnight. Temperature loggers were placed inside and on the outside of the AP.

Results: The aluminium AP equilibrated to the model water temperature within 15 minutes of submersion in the model, while the temperature of the PVC AP remained significantly lower during the three-hour period. The inside of the PVC AP remained significantly colder compared to outside during both winter and summer (33.23 ± 4.28 ℃ vs. 36.51 ± 2.13 ℃ and 36.04 ± 1.69 ℃ vs. 37.22 ± 0.92 ℃, respectively). There was no significant difference between the inside temperature of the aluminium AP compared to the outside temperature during both the winter and summer simulations (36.75 ± 0.49 ℃ vs. 37.83 ± 0.40 ℃ and 37.86 ± 0.16 ℃ vs. 38.04 ± 0.11 ℃, respectively).

Conclusion: This research highlights the importance of using material with good thermal properties during assisted reproductive procedures. It also contributes to further advancement during the establishment of a successful in vitro embryo production protocol for rhinoceros in South Africa.