Three years after starting its ambitious programme to save the northern white rhino from extinction through advanced assisted reproduction technologies, the BioRescue consortium draws a positive interim conclusion: Following the 10^thevent of harvesting immature egg cells (oocytes) in the northern white rhino female Fatu, the international team produced 5 additional embryos – bringing the total to 22 sired by two bulls. This nourishes the hope to eventually succeed in producing new offspring and give a keystone grazer of Central Africa a new future. At the same time, the consortium places the highest value on respecting the life and welfare of the individual animals involved. Regular veterinary and ethical assessments of oocyte collection procedures show that Fatu handles the procedures well and shows no signs of detrimental health effects. BioRescue is supported by the German Federal Ministry of Education and Research (BMBF).

The 10^th oocyte collection in northern white rhinos (NWR) was performed by a team of scientists and conservationists from the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW), Ol Pejeta Conservancy, Safari Park Dvůr Králové, Kenya Wildlife Service (KWS) & Wildlife Research and Training Institute (WRTI) on July 28, 2022, at Ol Pejeta Conservancy in Kenya. The BioRescue team was able to collect 23 oocytes from Fatu, the younger of the two remaining NWR females. Oocyte collections from Najin, Fatu’s mother, were ceased in 2021 following an in-depth ethical risk assessment. The oocytes were immediately air-lifted to the Avantea laboratory in Cremona, Italy. Following maturation, 7 of the oocytes were fertilized using cryopreserved, thawed semen from the deceased NWR male Angalifu. Eventually, 5 embryos of Fatu were successfully produced and cryopreserved in liquid nitrogen.

This collection followed on from the 9^th oocyte collection held at the same location and by the same team on April 24^th. Out of 16 collected oocytes, 3 embryos were produced in the Avantea laboratory, again using the semen of Angalifu. Successful results of both procedures raised the total number of NWR embryos produced to 22 – all of them from female Fatu, with half of them sired by the deceased male Suni who was born in Safari Park Dvůr Králové, Czech Republic, and the other half sired by Angalifu who lived in San Diego Zoo Safari Park, USA.

Once the protocol to transfer the embryos to surrogate southern white rhino (SWR) female recipients is optimized, the embryos will be the foundation of a new NWR population, eventually destined to step back into their ecological role as keystone grazers in Central Africa.

To set up suitable conditions for a successful embryo transfer, the team has been carefully following the interactions of the sterilized SWR bull Owuan, who serves as the oestrus detector, with the possible surrogate females that share an enclosure with him. Once the conditions allow it, the BioRescue team will attempt to conduct an embryo transfer – first with SWR embryos to demonstrate that the whole procedure works properly before the team uses the extremely valuable NWR embryos. The team is currently considering whether adding more SWR females to the program might increase the chance of achieving the first successful embryo transfer.