Effects of deslorelin implants on reproduction in the common brushtail possum (Trichosurus vulpecula)
Jutta Eymann A , Catherine A. Herbert A D , Brian P. Thomson B , Tim E. Trigg C , Desmond W. Cooper A D and Douglas C. Eckery B E FA Department of Biological Sciences, Macquarie University, North Ryde, NSW 2109, Australia.
B AgResearch, Wallaceville Animal Research Centre, Upper Hutt, New Zealand.
C Peptech Animal Health Pty Ltd, Macquarie Park, NSW 2113, Australia.
D Present address: School of Biological, Earth and Environmental Sciences, The University of New South Wales, Kensington, NSW 2052, Australia.
E Present address: School of Biological Sciences, Victoria University of Wellington, P. O. Box 600, Wellington, New Zealand.
F Corresponding author. Email: doug.eckery@vuw.ac.nz
Reproduction, Fertility and Development 19(8) 899-909 https://doi.org/10.1071/RD07046
Submitted: 9 March 2007 Accepted: 2 August 2007 Published: 11 September 2007
Abstract
The present study investigated the effects of slow-release implants containing the gonadotrophin-releasing hormone (GnRH) agonist deslorelin on reproduction in the common brushtail possum (Trichosurus vulpecula). Captive female brushtail possums were assigned to control (placebo implant), low dose (4.7 mg deslorelin) or high dose (9.4 mg deslorelin) groups; males were assigned to control or high dose (9.4 mg deslorelin) groups. The acute effects of deslorelin treatment at the level of the pituitary gland were similar between the two sexes, where a transient rise in luteinising hormone concentration was induced over the first 24 h. In females, this was associated with the disruption of the normal oestrous cycle and mating within 2–10 days in some treated individuals, but no young were subsequently detected. By 3 weeks after treatment, treated females became anoestrus and remained infertile for at least one breeding season. The effects of treatment were reversible in a subset of females that had their implants removed, although the time taken to produce offspring was variable. Paradoxically, male brushtail possums remained fertile during chronic deslorelin exposure. Despite significant declines in basal follicle-stimulating hormone and testosterone concentrations, as well as an inability to respond to a GnRH challenge, treated males sired as many offspring as control males and there was no evidence of testicular regression. In conclusion, there is potential to control reproduction in female brushtail possums by using chronic GnRH agonist treatment.
Additional keywords: contraception, endocrinology, fertility control, progesterone, vaginal cell cytology.
Acknowledgements
The authors thank Michael Beaumont, Jolene Hay and Kirsty Simpson for taking care of the animals in the present study and assistance with their handling, Dr Janet Crawford and Brigitta Mester for help with hormone assays, Margaret Wilkinson, Cameron Wood and Mark Ridgwell of Royal North Shore Hospital (Sydney, NSW, Australia) for assistance with the testosterone assay, Dr Marie Herberstein for statistical advice and Peptech Animal Health Pty Ltd for the supply of deslorelin implants. Funding was provided by the New Zealand Foundation for Research, Science and Technology. J. Eymann was the recipient of an international Macquarie University Research Scholarship and the Higher Degree Research Fund.
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