Monitoring and controlling aspiration fluid temperature during ovum pick-up in southern white rhinoceros (Ceratotherium simum simum)

Abstract

Assisted reproductive technologies need to be developed to assist in the battle against the extinction of endangered and threatened species. Temperature control during oocyte recovery and transportation is essential for ensuring in vitro embryo development. In this study, we examined the temperature pathway of oocyte aspiration fluid during ovum pick-up (OPU) in the southern white rhino (Ceratotherium simum simum) in South Africa, and its role in oocyte maturation success. The large aspiration instrument used was made from PVC plastic. As a poor heat conductor, it needed to be pre-heated for several hours before the OPU procedure commenced to avoid cooling of the oocytes. Fewer temperature fluctuations were recorded when oocytes were transported in a portable transport heating/cooling incubator than in an Equitainer. A greater number of oocytes were harvested per aspirated follicle during the suggested predominant breeding season (November – April), after adjusting for the duration of the OPU procedure. Oocytes harvested from rhino cows given a warm-water enema prior to the OPU procedure were 2.31 times more likely to mature in vitro than those harvested from cows receiving a cold-water enema, after adjusting for the individual effect of the rhino and the negative effect of follicular wave stimulation on the oocyte maturation success. This study indicates that to ensure the successful maturation of oocytes in southern white rhino, oocyte hypothermia during aspiration and transportation is a major concern. The results and conclusions of this study may inform future research with respect to temperature control of oocytes during recovery and transportation for other endangered wildlife species.