Physiological and Endocrine Factors Contributing to Acyclicity in the Captive Female African Elephant (Loxodonta africana)

Currently, the captive African elephant population in North America is not self-sustaining. An increase in acyclicity has been documented among post-pubertal females of all ages. Due to ethical issues and cost, importation of new animals is not feasible at this time; therefore, it is imperative that all post-pubertal females within zoological facilities be reproductively viable. The main objectives of these projects were to assess the reproductive status of the captive population and to identify contributing factors to acyclicity. In addition, prevention and treatment protocols were to be designed to promote reproductive proficiency in all reproductive-age females to avert the population collapse that has been predicted.;Experiment 1 A written survey assessed reproductive status of female Asian and African elephants in AZA/SSP facilities in 2008, and data were compared to surveys conducted in 2002 and 2005. Results showed ovarian acyclicity rates across the surveys remained unchanged for Asian (13.3, 10.9 and 11.1%) and African (22.1, 31.2 and 30.5%) elephants, respectively (P\u3e0.05), but were higher overall for African compared to Asian elephants (P0.05). In summary, incidence of ovarian cycle problems continues to predominantly affect African elephants. Although percentages of acyclicity did not increase between 2005 and 2008, 42.2% Asian and 30.2% African females were no longer being hormonally monitored; thus, reproductive cycle abnormalities could be worse than current data suggest.;Experiment 2 This paper described anti-Mullerian hormone (AMH) secretion in Asian and African elephants of different age groups and reproductive status. We concluded that circulating AMH concentrations in elephants were similar between species and not affected by reproductive status; however, concentrations were significantly higher in males than females, and were elevated in younger animals. The diagnostic value of AMH to assess fertility status of individual elephants remains to be determined.;Experiment 3 Currently, reproductive age (11-35 years old) female African elephants (Loxodonta africana) in U.S. zoos are experiencing high rates of ovarian cycle problems (\u3e40%) and low reproductive success. Previously, one-third of acyclic females exhibited hyperprolactinemia, a likely cause of ovarian dysfunction. This follow-up study examined the current state of hyperprolactinemia in African elephants and found the incidence has increased significantly to 71%. Of most concern was that over two-thirds of acyclic females now are hyperprolactinemic, a dramatic increase from the one-third observed 7 years earlier. Furthermore, females of reproductive age constituted 45% of elephants with hyperprolactinemia. Until the cause of this problem is identified and/or a treatment is developed, reproductive rates will remain suboptimal and the population non-sustaining.;Experiment 4 Perturbations in serum prolactin concentration have been identified as a common symptom among captive acyclic African elephants. In the human, hyperprolactinemia and prolactin deficiencies are significant causes of amenorrhea. Pituitary prolactin is held under constant inhibition by a hypothalamic derived neurotransmitter, dopamine; thus, regulation via exogenous treatment with antagonists or agonists has been successful in reinitiating normal ovarian cycles. Oral administrations of Cabergoline (dopamine agonist; n=4) and domperidone (dopamine antagonist; n=4) were studied as possible treatments for hyperprolactinemia or prolactin deficiency, respectively. Prolactin synthesis can be regulated with either a dopamine agonist or antagonist resulting in a decrease or increase in serum prolactin concentration, respectively. Although serum progestagen concentration increased in response to Cabergoline treatment, whether estrous cyclicity sufficient for successful breeding was reinitiated could not be determined. (Abstract shortened by UMI.)