Variable duration of reproductive suppression in male coyotes (Canis latrans) treated with a high dose of the gonadotrophin-releasing hormone agonist deslorelin
Marjorie J. MacGregor A E , Cheryl S. Asa B C and Donal C. Skinner A D
+ Author Affiliations
- Author Affiliations
A Department of Zoology and Physiology, University of Wyoming, Department 3166, 1000 E. University Avenue, Laramie, WY 82070, USA.
B Research Department, Saint Louis Zoo, 1 Government Drive, St. Louis, MO 63110, USA.
C AZA Wildlife Contraception Center, Saint Louis Zoo, 1 Government Drive, St. Louis, MO, USA.
D Program in Neuroscience, University of Wyoming, University of Wyoming, Department 3166, 1000 E. University Avenue, Laramie, WY 82070, USA.
E Corresponding author. Email: marjiem@uwyo.edu
Reproduction, Fertility and Development 29(7) 1271-1279 https://doi.org/10.1071/RD15253
Submitted: 25 June 2015 Accepted: 31 March 2016 Published: 10 May 2016
Abstract
Effective and humane management strategies for coyotes (Canis latrans) remain elusive. We hypothesised that exposure to a high dose of a gonadotrophin-releasing hormone (GnRH) agonist would cause prolonged suppression of the reproductive axis. Two groups of male coyotes were administered 47 mg deslorelin in the form of either five 9.4-mg controlled-release Suprelorin (Peptech Animal Health, Macquarie Park NSW, Australia) implants (n = 3) or 10 4.7-mg implants (n = 5). In the first group, deslorelin suppressed plasma LH, testosterone and testes volume in two of three coyotes for three breeding seasons. In the second group, two of five deslorelin-treated coyotes had no sperm production after 1 year and plasma LH, FSH, testosterone and testes volume were suppressed. Although plasma gonadotropins and testosterone were suppressed in three treated coyotes in group two, testes volume and sperm production were evident. Because the duration of suppression differed among individual coyotes, we further hypothesised that a variation in deslorelin release underlay the variability. To test this, we analysed in vivo plasma profiles of deslorelin concentrations. These profiles suggested that deslorelin concentrations >100 pg mL–1 are required to maintain suppression in male coyotes. For field implementation, the development of an implant capable of releasing deslorelin for the life of the coyote is necessary.
Additional keywords: contraception, fertility, neuroendocrinology, testosterone, wildlife.
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