Abstract
The absence of fertility problems in male dogs after a single treatment with deslorelin acetate (Suprelorin(®)) is well acknowledged. However, reports on the application of deslorelin in the bitch and information concerning fertility after implant treatment are still limited. In this retrospective study, data concerning induced and spontaneous oestruses of 39 bitches from 17 breeds, treated with deslorelin acetate implants (4.7 mg Suprelorin(®), Virbac, France), were retrieved to assess post-treatment fertility (ovulation rate, pregnancy rate and litter size). Animals were grouped according to treatment characteristics: group 1 (Gr1) - females submitted to oestrus induction, showing natural oestruses afterwards (n = 19); group 2 (Gr2) - females re-implanted with 4.7 mg deslorelin acetate to re-induce oestrus, showing subsequent spontaneous post-implant oestruses (n = 7); and group 3 (Gr3) - females submitted to a 4.7 mg deslorelin acetate implant for oestrus suppression, evaluated at subsequent spontaneous post-implant oestruses (n = 13). Comparison of fertility traits between induced and post-treatment spontaneous oestruses in Gr1 and Gr2 (short treatments), or between spontaneous oestruses after long-treatment schedules (Gr 3) revealed a slightly better performance in spontaneous cycles compared with induced cycles: ovulation rate post-treatment was 97.1%, 94.1% and 94.4% and the pregnancy rate post-treatment was 91.2%, 88.9% and 84.6% for groups 1, 2 and 3, respectively. Nevertheless, fertility in induced and post-treatment oestruses was considered normal. Moreover, the individual litter size did not differ within groups between induced and spontaneous cycles. From these findings, we concluded that treatment with 4.7 mg deslorelin implants did not compromise the bitches' fertility in subsequent oestruses.
Highlights
The search for a practical and successful method of oestrus control in the bitch has been a frequent research topic in the past 25 years (Thun et al.1977; Wright 1980; Shille et al 1989; Kutzler 2005; De Gier et al 2008; Kutzler et al.2009)
When considering the total of oestruses, no significant differences were found on the overall ovulation rate between groups (respectively 92.5% (49/53), 92.3% (24/26) and 94.4% (17/18) in Group 1 (Gr1), Group 2 (Gr2) and
Non-ovulatory situations encompassed ovarian cysts and anovulation. The latter occurred both in induced (n=3, in Gr1, being two in Boxer females and one in an English Bulldog) and spontaneous oestrus (n=3; these were found in a 4 year old White Swiss Shepherd in Gr1, in a 4 year old German Shepherd, in Gr2; and in a 6.1 year old Estrela Mountain Dog, in Group 3 (Gr3))
Summary
The search for a practical and successful method of oestrus control (induction or suppression) in the bitch has been a frequent research topic in the past 25 years (Thun et al.1977; Wright 1980; Shille et al 1989; Kutzler 2005; De Gier et al 2008; Kutzler et al.2009). There has been an upsurge of publications describing the use of slow gonadotropin-releasing hormone (GnRH) agonist releasing implants in several species (Johnson et al 2002; Padula and MacMillan 2005), predominantly in dogs (Volkmann et al 2006; Kutzler et al 2009; Fontaine et al 2011). The use of a slow release GnRH implant, containing 4.7mg of deslorelin acetate (Suprelorin®, Virbac, France) in adult bitches has been described (Fontaine et al 2011; Walter et al 2011). Deslorelin implants act by suppressing the pituitary-gonadal axis (Trigg et al 2001) in a dual phase mechanism: the implant initially stimulates the pituitary axis (flare-up effect), releasing both follicle-stimulating hormone (FSH) and luteinizing hormone (LH) and subsequently activates a complex network of transduction pathways resulting in a down-regulation of the GnRH receptors through the inhibition of mRNA coding for the β-subunits of the gonadotropins LH and FSH (Navarro and Schober 2012).
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