The Impact of Veterinary Medicine on Breeding Success in Non-Domestic Species
Thomas B. Hildebrandt, DVM
Management of wild animals in captivity has a history of more than two thousand years (Rookmaaker, 1998). Captive management has improved dramatically since then. Better housing facilities, nutrition, husbandry, and especially improved medical care within modern zoos and regional and global management programs such as EEP / SSP / CBSG are attributable for the successful establishment of self-sustaining captive populations. The classic tasks of veterinary medicine in established breeding programs of non-domestic species are as follows:
general health monitoring such as disease prevention and treatment, diet, etc.
determination of basic reproductive parameters such as onset of puberty, cycling pattern, seasonality
assessment of the reproductive soundness
treatment of reproductive disorders
pregnancy detection and monitoring
birth and perinatal management
Despite this long history of animal management and accumulated knowledge of wild animal husbandry, reproduction remains limited or absent in many captive endangered species. Captive populations of charismatic species such as the Asian and African elephant, white, Sumatran and Indian rhinoceros and most aquatic species are not self-sustaining. International regulations such as the Convention on International Trade in Endangered Species of wild Fauna and Flora (CITES) and an increased critical public opinion make it difficult to continue with the classic form of zoo management with frequent replacement of losses by new individuals caught in the wild. As a result, zoo managers are confronted with a rapidly aging captive populations in these species. For example for the captive African elephant population in North-America, basic demographic models predicted that seventy-five percent of the female population will be post-reproductive in just fifteen years (Wiese, 2000). In the Sumatran rhino and the northern white rhino (Hermes et al. 2002, Roth, 2002) the situation is even more serious with only one reproducing pair left in captivity. "Management to extinction" is a term which describes the negative final scenario if there will be not a dramatic change in the quality and efficiency of captive breeding programs in these species. Key words: non-domestic species, assisted reproduction, contraception, conservation.
Veterinary scientists in cooperation with wildlife biologists can have an important impact on enhancing the propagation of highly endangered species by introducing assisted reproduction technologies (ART) to breeding programs (Hildebrandt et al., 2002a, b). Based on the advances made in the livestock industry, these technologies can be used to preserve or even expand genetic diversity of captive populations. However, the reproductive anatomy and physiology of different species are so complex and divergent that the direct use of results derived from domestic model species or the application of established technologies in husbandry and human reproduction medicine are of limited value for effective assisted reproduction protocols in many of these species (Lasley and Shideler, 1993, Loskutoff, 1998, Hildebrandt et al., 2000). For example, there are 20 orders of mammalia with over 3500 species. Knowledge of the reproductive anatomy and physiology are likely to be of particular importance for successful assisted breeding programs in endangered species. A basic understanding of reproductive parameters is necessary not only for effective captive breeding programs, but is also needed, for example, to establish minimum viable population sizes used in managing free-ranging populations.
Detailed knowledge of reproductive processes also constitutes the basis for a successful assessment of reproductive status and clinical condition, monitoring of sexual maturation, characterization of the ovarian cycle and gestation. Despite the controversy surrounding the potential cloning discussions of the Tasmanian tiger and the mammoth, basic techniques such as artificial insemination, sperm cryo-preservation or sexual cycle manipulation are not yet established for the majority of endangered species. Therefore, veterinarians must tailor ART to the needs of non-domestic species in order to ensure successful propagation in wild and captive populations. The new relevant tasks are as follows:
sexual cycle manipulation such as induction of ovulation, superovulation
gamete and embryo recovery such as electro-ejaculation, ovum-pick-up, embryo flushing
semen sex sorting
long-term storage of gametes/embryos/gonads for instance by cryo-preservation or freeze-drying (frozen zoo)
artificial insemination (AI)
in-vitro-maturation and fertilization
oocyte / embryo transfer
The development of these new techniques will facilitate the potential for gamete / embryo transfers from the wild into captive breeding programs, and even vice versa. Although enhancing reproductive rates through ART is particularly attractive for veterinarians, controlling reproduction through contraception is also an important field of the new discipline conservation medicine. The improvement of animal husbandry and wildlife conservation has enhanced the breeding success of several species, thus creating self-sustaining populations. Consequently, the limited carrying capacity in zoos and shrinking wildlife habitats, respectively, mandates the application of appropriate means of contraception. Reversible contraception is important as a method to aid in the establishment of genetically variable captive populations within the constraints of the limited area available to captive populations (Seal et al., 1976). Other forms of contraception including irreversible surgical once can also be applied. Choosing amongst different forms of contraception includes the biochemical design of contraceptive compounds and the appropriate mode and frequency of application, which in turn requires a detailed knowledge of the reproductive physiology of a particular species. Contraception is often most successful when applied to female animals, where it requires information on such parameters as duration of sexual cycle, time and mode of ovulation, implantation, and pregnancy. Contraception not only prevents the production of surplus animals, it is also critical for suitable genetic management and for maintaining natural social groups (Asa, 2002).
Veterinarians are not only responsible for classic tasks such as health monitoring; in populations of non-domestic species they play an increasingly important role in the development, modification and application of ART to non-domestic species. The ability to integrate these new propagation tools into existing conservation programs will have a key impact on their success.
1. American Zoo and Aquarium Association Elephant Special Survival Plan (AZA Elephant SSP®, 1997).
2. Asa C (2002): Integrating reproductive management into wildlife conservation programs. Proc Int Symp Physiol Ethol Wild and Zoo Anim, Erkner; 29.10.-3.10.2002, p 3.
3. European Association of Zoos and Aquariums Elephant Studbook (EAZA Elephant Studbook, 1999).
4. Hermes R, Schwarzenberger F, Walzer C, Göritz F., Tomasova K, Patton ML, Hildebrandt TB (2002): Fertility evaluation of the captive female northern white rhinoceros population (Ceratotherium simum cottoni). Proc Int Symp Physiol Ethol Wild and Zoo Anim, Erkner; 29.10.-3.10.2002, p 138.
5. Hildebrandt TB, Hermes R, Jewgenow K, Göritz F (2000): Ultrasonography as an important tool for the development and application of reproductive technologies in non-domestic species. Theriogenology, 53, 73-84.
6. Hildebrandt, TB, Göritz, F, Hermes, R, Fritsch, G (2002a): Ultrasonographic techniques applied to non-domestic species BMUS Bulletin 10(2), 1-6
7. Hildebrandt, TB, Hermes R, Göritz F (2002b): Novel design to facilitate assisted reproduction in nondomestic animals. Proc 2nd Int Symp on ART, Pp 219-223.
8. Lasley BL, Shideler S (1993): Methods for assessing reproduction in nondomestic species. Fowler ME (ed) Zoo and wildlife animal medicine. Current Therapy 3. Philadelphia: WB Saunders Company, 597-604.
9. Loskutoff NM (1998): Biology, technology and strategy of genetic resource banking in conservation programs for wildlife. Proc 50th ICAR Gametes: Development and Function; Pp 275-286.
10. Rookmaaker, LC (1998): The Rhinoceros in Captivity, a list of 2439 rhinoceroses kept from Roman times to 1994. SPB Academic Publishing bv, P.O. Box 97747, 2509 GC, The Hague, Netherlands.
11. Roth T (2002): The role of reproductive science and technology in achieving the birth of the first Sumatran rhino calf produced in captivity in 112 years. Proc Association of American Zoo Veterinarians Annual meeting, 5.10.-10.10., Pp 210-212.
12. Seal US, Barton R, Mather L, Grayx CW (1976): Hormonal contraception in captive female lions (Panthera leo). J Zoo Anim Med;7:1-17.
13. Wiese, RJ (2000): Asian elephants are not self-sustaining in North America. Zoo Biol; 19: 347-367.