Assisted reproductive technologies in captive rhinoceroses

Abstract

Survival of the five remaining rhinoceros species is threatened. Four of the five species are in managed collections, but captive populations are not self‐sustaining and low reproductive rates make population growth slow. Slow population growth, coupled with behavioural incompatibilities, acyclicity, low genetic diversity, and disease susceptibility, creates the need for assisted reproductive technologies (ARTs) to maintain genetic diversity while bolstering population numbers. Both published and unpublished data are included in this review of ARTs, to facilitate understanding consistencies and variations between and within each rhinoceros species. Progress has been made to address species‐specific characteristics of reproductive physiology in rhinoceroses. This review outlines the ARTs that have been performed and identifies areas in need of research. In vivo technologies have resulted in live calves by artificial insemination, created genetic reservoirs through semen collection, and provided new avenues of gamete retrieval via ovum pickup. In vitro technologies have enabled genetic rescue post mortem and support early stage embryo production through oocyte maturation and fertilisation. As conservation efforts focus on rhinoceroses, improvement of existing techniques and development of new technologies will allow for a broader application of successful rhinoceros ARTs.

Increasing the Yield and Cryosurvival of Spermatozoa from Rhinoceros Ejaculates Using the Enzyme Papain

“…Consequently, this enabled the cryopreservation of an additional 3.5 billion cells on average per male. To the best of our knowledge, when both fractions are combined, this amount exceeds what has previously been reported (2.8 ± 0.8 × 10 9 ) for high quality spermatozoa collected from the southern white rhinoceros via electroejaculation [10,17]. It is also higher than that recorded for the black (200 × 10 6 spm [13]) and Sumatran (2.5 × 10 9 [39]) rhinoceros.…”

“…Following the adaptation of equine protocols, motilities post-thaw increased to 55% [ 6 , 7 , 8 , 9 ], siring the first calf with frozen sperm in 2008 [ 6 ]. Since this time, work has continued to try to improve the success of cryopreservation protocols for all rhino species, improving the quality and quantity of spermatozoa post-thaw [ 10 ]. Consequently, extensive development of freezing extenders with different cryoprotectants and freezing rates has determined that freezing rhinoceros spermatozoa in ButoCrio ® supplemented with glycerol and methylformamide above liquid nitrogen vapour can yield a post-thaw sperm motility of 75.6 ± 3.9% [ 11 ].…”

The Comparison of Semen Collection in Electroejaculation, Rectal Massage and Combination of Both Methods in the Critically Endangered Malayan Pangolin, Manis javanica

“…The semen kinetics (total motility, progressive motility and mass motility) in pangolins are good, though faced with the challenge of the minute volume of semen yield, the ejaculates can further be extended using a semen extender. There is high potential in using ART in pangolins with the current semen quality, as attempts in ART with even lower semen parameters were found to be successful for in wildlife [ 41 ]. Artificial insemination is yet to be performed in pangolins; however, successful captive breeding in pangolins suggests that the animals fare well in captivity, and captive breeding is possible [ 21 ].…”

Ethical Analysis of the Application of Assisted Reproduction Technologies in Biodiversity Conservation and the Case of White Rhinoceros (Ceratotherium simum) Ovum Pick-Up Procedures

“…In human medicine, ARTs are usually defined as those procedures or treatments in which both the male and female gametes or embryos are manipulated in vitro to achieve pregnancy ( 14 ). In contrast, in veterinary medicine, the catalog of ART is normally broader, including, for instance, artificial insemination ( 15 – 21 ), cloning via somatic cell nuclear transfer ( 3 , 22 – 25 ), and gamete production from induced pluripotent stem cells ( 3 , 5 ). Following this broader use, the term ART will hereinafter be applied to any procedure involving, in one or more of its stages, the manipulation of reproductive cycles, gametes, or embryos with the final aim of producing a new individual.…”