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Most wild donkey breeds are on the verge of extinction, such as the Asian wild donkey (Equus hemionus) or the African wild donkey (Equus asinus africanus), mentioned in the Red List of the International Union for Conservation of Nature (IUCN). Many breeds of domestic donkeys in the world are threatened. In France, of the seven breeds of donkeys, five are in the process of extinction with less than 100 females breeding in 2015 (23 Bourbonnaises donkeys, 34 Grand Noir du Berry donkeys, 40 Norman Norman donkeys, 43 Provence donkeys, 88 Cotentin donkeys) and two are in danger of extinction with less than 300 females breeding in 2015 (136 Pyrenees donkeys, 296 Poitou baudets).
The preservation of this genetic heritage is therefore urgent, and involves in particular the cryopreservation of sperm, oocytes and embryos. The cryopreservation of oocytes requires their collection from live females. The production of embryos requires their production in large numbers from a few females, which is not possible in vivo since these animals produce only one embryo per 26-day cycle. This large number of oocytes can be produced in vitro but requires the collection of oocytes from live females. This collection is therefore an essential step for the conservation of the female heritage.
The staff of the UEPAO1 equine platform at INRA succeeded in developing for the first time a technique for collecting oocytes from live donkeys by transvaginal follicular puncture under ultrasound, in agreement with the Val de Loire Animal Experiments Ethics Committee. A total of 92 oocytes were collected during 22 punctures, an average of 4.2 oocytes per donkey. Then, researchers from unit PRC1 adapted an in vitro maturation technique for mare oocytes to donkey oocytes, making it possible to study for the first time the chronology of donkey oocyte maturation. It has been observed that it is possible to obtain 44% of oocytes from mature donkeys after 34 hours of in vitro culture.
This work has therefore made it possible to develop a technique for in vivo collection of donkey oocytes by follicular puncture under ultrasound and to ensure their maturation in vitro: two crucial steps in the conservation of the genetic heritage of species undergoing extinction. Work is currently ongoing on the development of an in vitro fertilization technique to obtain embryos suitable for freezing or transfer to a recipient female for gestation.