In a paper published in the journal “Reproduction” in October 2023, the team evaluated ovum pick-up (OPU) and in-vitro fertilisation (IVF) procedures and showed that aART in white rhinos is safe for the donor females and can reliably yield viable embryos. This scientific paper now received the prize for best research published in the journal in 2023, awarded by the Society for Reproduction and Fertility. BioRescue furthermore announces the production of five additional embryos from northern white rhino Fatu in the second half of 2024, adding to the outcome of five years of work since the first OPU in 2019.
The prize was awarded to the whole group of authors and it was accepted by Dr Susanne Holtze and Prof Dr Thomas Hildebrandt from the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) on behalf of all the authors at a ceremony held in Liverpool on January 8, 2025. BioRescue’s aART procedures described in the paper comprise hormonal ovarian stimulation, ovum pick-up (OPU), in-vitro oocyte maturation and in-vitro fertilisation (IVF), embryo culture and cryopreservation. The team of authors around Hildebrandt, Holtze, Dr Frank Göritz, (all Leibniz-IZW), Dr Silvia Colleoni, and Prof Cesare Galli (both Avantea Srl.) evaluated 65 of these sets of procedures conducted from 2015 to 2022 in both northern and southern white rhinos. The evaluation showed not only that aART proved to be a reliable way for successful production of white rhino embryos and that it is safe for the donor females with no negative health effects, but also that regular OPUs benefited the reproductive health of nulliparous female rhinos of advanced age by improving their ovarian function, increasing follicle numbers and instigating the regression of pathological structures such as ovarian cysts. For more information, please consult the BioRescue press release from October 2023.
The recognition of the achievements of the BioRescue team comes at a moment when the team summarizes 5 years of its work with northern white rhinos (NWR). The first OPU in females Fatu and Najin was conducted in August 2019, with the two first NWR embryos produced in September 2019. Since the start of the project, 35 NWR embryos were generated in total, resulting from 18 OPUs in Fatu conducted until October 2024. On average, the team managed to achieve approximately 2 embryos per procedure (on average 1.94, to be precise). While there were oocyte collections that resulted in no embryo, there were also unusually successful procedures – the largest number of embryos produced after a single oocyte collection was five. For production of embryos, semen of the two deceased males Suni and Angalifu (both died in 2014) was used.
In the second half of 2024, the BioRescue team was able to produce five new embryos in total. Three embryos were generated in July following OPU in June 2024 and two further embryos were produced as the result of OPU in October 2024. This indicates that Fatu sustains her good reproductive health. This is a good result after a transient decline in OPU success following an infectious incident at the end of 2023. An ancient bovine ‘mummy’-born Clostridia infection resurfaced caused by heavy rains in Kenya and hit the rhinos at Ol Pejeta. Therefore, planned procedures had to be postponed. As Fatu had already been hormonally stimulated when the unforeseen bacteria outbreak occurred, the team employed hormonal treatment to avoid ovarian hyperstimulation syndrome. This drug administration temporarily decreased follicle numbers and oocyte quality in early 2024, but the good news is that Fatu’s health and welfare, which are regularly assessed before and after every procedure, continue to be very good and have not been affected by the repeated procedures.
In addition to the production of embryos, the BioRescue team also mastered the subsequent step in the IVF programme – the successful transfer of a rhino embryo into a surrogate mother. A southern white rhino embryo produced in-vitro was transferred into a southern white rhino surrogate mother at the Ol Pejeta Conservancy in Kenya in September 2023. The BioRescue team later confirmed a pregnancy of 70 days with a well-developed 6.4 cm long male embryo. For more information, please consult the BioRescue press release from January 2024.
The successful embryo transfer followed by a pregnancy – a world’s first in rhinoceroses – are proof of concept and allow the BioRescue team to safely move to the transfer of NWR embryos – a milestone in the mission of saving the northern white rhino from extinction. The team is hopeful to achieve the first pregnancy from a successful transfer of NWR embryos in the foreseeable future.
