12 INDUCTION OF OVARIAN ACTIVITY IN THE MANED WOLF (CHRYSOCYON BRACHYURUS) USING A GnRH-AGONIST

Abstract

Induction of ovarian activity and ovulation is a valuable tool for the genetic management of ex situ populations of wildlife. Deslorelin, a gonadotropin releasing hormone (GnRH)-agonist, has been used earlier to induce oestrus in the grey wolf (Canis lupus). The objective of the present study was to determine the efficacy of Deslorelin (2.1 mg, Ovuplant^®, Peptech Animal Health, Australia) for manipulating ovarian activity of the maned wolf, a species speculated to be an induced ovulator. Eight female (4–12 years old) maned wolves were (i) paired with a male (n = 3) or (ii) housed alone (n = 5). Of the 8 females, 1 (1 in a pair and 1 singleton) were implanted with Deslorelin under the vulvar mucosa for 12 days. The remaining 6 received implants in the subcutaneous layer of the ear for 7 days. Fresh fecal samples were collected 5 to 7 days/week for 1 month before Deslorelin treatment through 6 weeks after implant withdrawal. Reproductive steroid metabolites were extracted from the fecal samples and quantified using a validated enzyme immunoassay. Baseline progestagen concentrations for each individual were calculated by an iterative process, whereby high values exceeding the mean plus one standard deviation were excluded. Comparisons of oestrogen and progestagen concentrations among pre-, peri-, and post-Deslorelin implant periods were performed using analysis of variance. Site and duration of the GnRH agonist treatment had no effect (P > 0.05) on subsequent ovarian responses. In paired females, oestrogen metabolites reached the highest (P < 0.05) concentration during Deslorelin (i.e. peri-) treatment (441.7 ± 20.2 ng g^–1 of feces) compared to pre- (174.9 ± 16.7) and post- (177.8 ± 9.1) treatment. Progesterone metabolites rose (P < 0.05) above the baseline (indicative of ovulation) starting on Day 10 after the onset of Deslorelin implantation and remained elevated throughout the study (pre-, 11 645 ± 4798; peri-, 31 521 ± 6444; post-, 55 843 ± 2924 ng g^–1 of feces). In singleton females, oestrogen metabolites increased (P < 0.05) immediately after implantation (from pre-, 184.2 ± 45.3 to peri-, 334.2 ± 29.8 ng g^–1 of feces) and then declined (post-, 192.3 ± 12.4). Progestagen metabolites exhibited a similar pattern with a rise (P < 0.05) during Deslorelin treatment (from pre-, 3870 ± 1336 to peri-, 10 546 ± 880 ng g^–1 of feces) followed by a decline after implant withdrawal (post-, 6171 ± 366), indicating that ovulation did not occur. These results suggest that Deslorelin can induce ovarian activity in the maned wolf. However, administration of an ovulatory agent after Deslorelin treatment may be required in females managed in the absence of a male, further supporting the assertion that this species is an induced ovulator.