This is the first examination of the efficacy of AI in the context of a significant number of giant pandas. The data are compelling in that they illustrate a feasible strategy for producing living, healthy offspring when natural breeding fails. We have determined that AI is particularly valuable:
1. for female pandas that are not in strong oestrus;
2. when the pair is so aggressive that injury is likely;
3. when an animal is young and behaviourally inexperienced; or
4. for a genetically valuable sperm donor that is critically ill.
However, our evaluation also provides encouragement for the utility of AI with cooled or frozen semen to help meet one of the highest priorities of ex situ programmes, achieving a self-sustaining population through genetic management (see Chapter 21). Since maintaining adequate gene diversity requires either moving animals between breeding facilities or transporting germ plasm, there are some significant advantages for the latter approach. Certainly, it is less stressful on the giant panda (and probably the keeper) as well as less costly to transport sperm than the living individual. However, the movement of germ plasm is also attractive for bureaucratic reasons, especially since giant pandas are the property of competing federal agencies in China. Thus, shipping plastic straws containing sperm causes fewer concerns than moving living, successful breeders.
In the context of assisted breeding, we suggest that there are two high priorities for future study.
Continue testing and improving artificial insemination efficiency with fresh and thawed spermatozoa
In Chapter 7, we reviewed those biological areas in basic gamete function that require more investigation, including in sperm cryobiology. However, more effort also needs to be directed at the practical application of the technology, especially identifying the optimal day for AI. Whether there is a single 'ideal' day (or time) or if multiple days are required is critical information for minimising the number of anaesthesia episodes and avoiding wastage of precious spermatozoa. For example, our initial analyses here seemed to suggest that pregnancy success was higher if sperm were deposited on the day coincident with declining excretory oestrogen concentrations. However, solid comparative data are required, including a more systematic and detailed correlation of ideal AI time with behaviours and vaginal cytology. Identifying the best day for AI would be possible by inseminating a female on each day of oestrus with sperm from a different male and then determining parentage using already established molecular techniques (see Chapter 10). Likewise, to conserve germ plasm, we need to know the minimum number of spermatozoa necessary to achieve successful conception. Although the giant panda produces mega-numbers of spermatozoa, understanding how many are needed in a typical AI will allow more efficient use (or long-term storage) of germ cells.
Developing genome banking strategies and resources to facilitate genetic management
Because we now know that cryopreserved sperm and AI can result in a high incidence of pregnancy success (of about 50%) in the giant panda, it is time to use transported semen more seriously to meet genetic management goals. However, the prerequisite step toward the wide scale use of frozen semen is the establishment of a formal GRB. The advantages of such banks have been described in detail (Wildt, 1997; Wildt et al., 1997). In addition to providing germ plasm to avoid the stress and cost of transporting living animals, a GRB:
1. helps ensure that more animals are successful breeders (through AI);
2. allows sperm to be used over generations rather than the lifetime of the male;
3. saves space in that fewer males need to be maintained at a breeding site;
4. preserves existing gene diversity from unforeseen catastrophes, e.g. disease epidemic or fire.
However, any effective GRB is only as good as a written protocol that is adhered to by all the institutions interested in sharing germ plasm. In previous literature, such practices have been referred to as a GRB Action Plan (Wildt, 1997), a document that details the justification for such an effort as well as information on:
1. genetic and population management goals;
2. accessibility of existing animals for banking;
3. amounts of spermatozoa to cryopreserve from targeted males;
4. technical aspects, including standard methods for sperm collection, evaluation, frozen storage, thawing and AI;
Within each of these is a host of issues that range from detailed record-keeping to ensuring security of the repository to the source of funds for maintaining the bank and using the stored materials. Many required practices are simply common sense, such as making sure that frozen samples are stored in at least two sites (two liquid nitrogen tanks in separate buildings or even different institutional facilities). In general, it has also been agreed that, to be effective and worthwhile, all holders of giant pandas must benefit. Therefore, a top priority is ensuring that sperm be shared on the basis of collective decision-making by managers who are adhering to genetic and demographic targets. Ballou et al, in Chapter 21, describe a scenario being explored by the Chinese that would also involve a 'global management' plan - one where frozen semen would be shipped between giant panda facilities throughout the world. Thus, a high priority is to begin to implement this plan on a practical scale, using stored giant panda sperm (when necessary) to maintain gene diversity and to continue to help grow the population.
Finally, we also see a future where giant pandas in nature, all of which are producing surplus germ plasm, become an important component of a GRB. The opportunistic banking of wild, occasionally captured males would provide yet more insurance for saving those truly wild genes while creating a resource for the occasional infusion of genetic variation into the ex situ population.
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