The Biomedical Survey gave us access to significant numbers of giant pandas that, in turn, allowed a substantial increase in our understanding of male reproductive biology. We now know that:
1. giant pandas held ex situ generally produce high numbers of motile, structurally normal spermatozoa during the breeding season;
2. sperm quality is similar between individuals that were born in nature versus captivity as well in males of proven fertility versus nonbreeders;
3. males as young as 5.5 years old produce sperm although the quality is not as good as that of older counterparts;
4. there is a hypoplastic testicular anomaly of unknown etiology in a giant panda subpopulation;
5. rapid freezing rates are optimum for sperm cryopreservation;
6. giant panda sperm subjected to freeze-thawing exhibit good motility, morphology and functionality in vitro.
Although much has been learned, there are high research priorities for the future, especially linking new knowledge in male and female physiology with behaviour and management to enhance natural or assisted-breeding success. The highest priority is to optimise the practical use of frozen-thawed sperm to meet the genetic management goals identified by the managers of the ex situ population (see Chapter 21). It is evident that physiological infertility in male giant pandas is uncommon, and that sperm are robust and comparatively resistant in vitro to the stresses of cryopreservation. So, even though preliminary positive data are available (see Chapter 20), there is a need to conduct systematic studies of AI with thawed sperm, especially to identify the optimal numbers of sperm and timing of deposition in the oestrual female. Once it is determined that cryopreserved sperm can consistently result in pregnancies, many of the political and logistical concerns associated with moving animals between breeding centres become moot. Rather, it will be possible simply to transport semen from the most desirable male to the facility holding the most genetically compatible mate. Associated with this priority will be an eventual need to prove the ability to collect and freeze sperm from free-living males, another strategy for infusing new genes into the ex situ population while leaving wild pandas in nature. All of these priorities also are related to an ability to develop genome resource banks (see Chapter 20), organised stores of biomaterials, especially sperm, that will allow meeting genetic management goals. Developing these repositories and sharing the best technologies and the banked biomaterials will require high levels of cooperation.
There is also a need for more fundamental studies of male reproductive biology. One high priority issue is male seasonality: does the adult giant panda produce viable sperm of similar quality throughout the year, or is it highly seasonal like its female conspecific? A seasonal pattern in spermatogenesis has practical implications, as it will limit the times of the year when semen can be collected for cryobanking. In contrast, if males produce sperm throughout the year, then it will be possible to collect and freeze sperm during the nonbreeding season, potentially increasing the total amounts of genetic material that can be stored and shared. Secondly, although we now have some information on the age-related onset of sperm production, there is a need to identify the earliest onset of male fertility. For example, can 5- or 6-year-old males be used for breeding or AI? Finally, there is a need to fully understand the testicular hypoplasia/atrophy anomaly identified during the Biomedical Survey. If indeed this malformation has genetic origins, then it will be necessary to eliminate affected or carrier animals from the breeding population.
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