Complications Associated With Long-Term Contraception of a Mixed Species Group of Artiodactyls
Abstract
Melengestrol acetate (MGA) has been used as an oral contraceptive agent in hoofed mammals at the Wildlife Conservation Society’s Bronx Zoo since 1991.2 It has been used in a total of 11 species at WCS facilities. It is milled into a pelleted hoofstock feed at the rate of 0.00015% and fed at a rate to deliver 1–2 mg of MGA per individual animal per day. A mixed species herd of barasingha (Cervus duvauceli), axis deer (Axis axis), and blackbuck (Antilopa cervicapra) are housed and exhibited together at the Bronx Zoo. They are generally managed as a single herd unit rather than as individuals, typically with multiple males of each species present at a given time. Challenges and complications associated with long-term contraception in this herd of animals include failure of contraception due to competition for medicated feed; dystocias in primiparous females that matured while being fed medicated feed; mummified fetuses; prolonged interbirth intervals; endometrial hyperplasia; and mucometra. Barasingha, a large seasonally breeding cervid, have taken the longest periods of time to return to near pre-treatment fecundity levels. They are also the only of the three species to have had mummified fetuses and mucometria requiring surgical intervention. Axis deer and blackbuck will show signs of estrus within 2 days of discontinuing delivery of MGA and have a significant return to fertility at that time. Overall, the incidence of adverse effects associated with MGA administration has been low compared to the numbers of artiodactyls it has been fed to at WCS over the past 15 years.1,2
Acknowledgments
This project was conducted under INAD 6016.
Literature Cited
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2. Raphael BL, Kalk P, Thomas P, Doherty J, Cook R. The use of melengestrol acetate for contraception in hoofed animals. Zoo Biol. 2003;22:455–463.