Regular ovum pick-up (OPU) – the retrieval of immature egg cells (oocytes) from ovaries — has benefited the reproductive health of individual female rhinos from whom the eggs are being harvested by improving ovarian function, increasing follicle numbers and instigating the regression of pathological structures such as ovarian cysts.

The BioRescue project that has been working on the Advanced Assisted Reproduction (aART) in white rhinos at Ol Pejeta, Kenya, has shown that over time, the number of oocytes collected per procedure, oocyte retrieval rate, and the success rate of producing embryos have all significantly increased.
In findings published in Reproduction journal, scientists attributed the improvements to technical optimisations, improved team performance, and repeated OPUs on donor reproductive health.

Read: ‘In Vitro’: Life viewed from inside a bottle

Reducing extinction threat

This may have just bumped up the chances of the nearly extinct northern white rhinoceros.

The team has been analysing success rates in relation to OPU and IVF with 20 southern rhinos, as well as Fatu and her mother Najin who are the last two northern white rhinos alive in the world today. This duo lives under constant protection from poachers in Kenya’s Ol Pejeta Conservancy.

The scientists noted clear indications of health benefits for rhinos exposed to OPUs. The procedures seemed to be vanquishing Fatu’s ovarian cyst.

“There was no sign of detrimental effects or risks even in the northern white rhino female Fatu after ten procedures performed at three-month intervals,” said the scientists in a press release.

In-vitro fertilisation (IVF) success greatly depends on the age of the oocyte donor. A study conducted on a group of female white rhinos revealed that when the donor was older than 24 years, no oocytes were retrieved in approximately half of the ovarian pick-up procedures (OPUs).

Read: Only 3 northern white rhinos left in the world

On the other hand, when the donors were 24 years or younger, only six percent of OPUs resulted in no oocytes. Additionally, the research team was unable to produce embryos at the blastocyst stage suitable for cryopreservation from individuals older than 24 years.

These findings are significant as most rhino species and subspecies face difficulties in natural reproduction and are at risk of extinction. Advancements in aART technologies such as OPU and IVF offer promising approaches to their conservation.

“This indicates that the IVF success of Fatu, who is 23 years old, may soon decline. However, it is worth noting that factors such as optimal nutrition, physical exercise, the Kenyan climate, semi-wild husbandry, and possibly subspecies-related factors could potentially prolong this period,” the team led by Prof Thomas Hildebrandt, Dr Frank Göritz, Dr Susanne Holtze (from the Leibniz-IZW), Dr Silvia Colleoni and Prof Cesare Galli suggested.

Additionally, the team said removal of ovarian cysts in two southern white rhinos during OPU procedures, has increased follicle numbers. Ovarian follicles are small fluid-filled sacs in the female’s ovaries each containing eggs for fertilisation.