Assisted breeding technology for the conservation and propagation of Phascolarctos cinereus or how to make a koala pouch young
Johnston, SD, McGowan, MR & O’Callaghan, P 1999, Proceedings of the Postgraduate Committee in Veterinary Science, Sydney, pp. 199-217.
This report presents an overview of the scientific developments that have contributed to the early success of artificial insemination (AI) in the koala. In the AI process, there are three major hurdles to be overcome: (1) collecting, manipulating and preserving semen; (2) selecting a suitable time for insemination; and (3) depositing inseminate at a suitable site to increase the likelihood of conception. Johnston, McGowan and O’Callaghan share their insights regarding these challenges and present a rationale for the ex situ conservation of koalas via artificial breeding programs.
There are numerous methods for collecting semen from mammals. Previously, electroejaculation was the most commonly employed method for koalas due to its high success rate and tolerability to the animals. The reliability of the method is, however, challenged by the need to anaesthetise koalas, which is undesirable unless absolutely necessary, and observed differences between electroejaculation and natural semen samples. An alternative method, semen collection with an artificial vagina, overcomes these challenges. This procedure involves allowing a male to begin mating with a female after which the penis is redirected into an artificial vagina. The artificial vagina method is now preferred as it takes advantage of the natural mating behaviours of the koala and is far less invasive than electroejaculation. Unless being used immediately, semen samples must be preserved after collection. As cryopreservation has not yet proven to be suitable for maintaining the viability of koala spermatozoa, artificial breeding programs may be currently limited by the use of fresh or extended semen. To be successful, deposition of inseminate must occur at or prior to ovulation. As the luteal phase and subsequently ovulation is now known to be induced by the physical act of mating, the use of a ‘teaser’ male to commence or complete copulation with a female has proven to be effective for inducing ovulation prior to AI. Alternatively, ovulation can also be induced pharmaceutically. Given the complexity of the female reproductive anatomy in the koala, depositing semen can be challenging. Johnston et al. describe two methods of intra-urogenital insemination that have led to conception: AI using the Cook insemination catheter, and AI using an otoscope and “Tom-cat” catheter.
In the wild, koalas are threatened by several compounding factors including habitat loss, disease and predation. The authors emphasise that the most sensible strategy for preserving this threatened species is to protect its habitat. In the absence of policies or programs that suffice to conserve free-ranging koala populations in situ, however, ex situ approaches such as artificial breeding programs in captivity can help to reinforce and potentially re-establish wild koala populations. Additionally, developing artificial breeding technologies for koalas has the benefits of improving understanding of the species’ reproductive biology, creating alternatives to the transportation of live koalas for introducing genetic material to populations, overcoming infertility as an obstacle to reproduction, and informing similar programs for other species.
Summarised by Joanna Horsfall
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