Clinical Evaluation of Deslorelin to Induce Oestrus, Ovulation and Pregnancy in the Bitch
Author's address (for correspondence): A von Heimendahl, Veterinary Reproduction Services, 27 High Street Longstanton, Cambridge CB24 3B, UK. E-mail: firstname.lastname@example.org
The aim of this study was to evaluate the practical use of Deslorelin in a clinical setting to induce oestrus and ovulation and to assess pregnancy rates. Sixteen anoestrus bitches that were brought into the clinic were implanted subcutaneously in the ventral abdomen with Deslorelin. Implants were removed after ovulation was assumed to have occurred. All bitches came into oestrus and 13 ovulated. 11 of 16 bitches became pregnant (68.8%) and all continued to term. Average litter size was 7.6 puppies. On average, the implant was in place for 13.8 days.
Compared to other species, timing of oestrus and manipulation of cyclical activity are limited in the canine. Given the length and unpredictability of the anoestrus period, induction of oestrus is of particular interest to be able to plan matings and time whelpings. Many different preparations and methods have been investigated to induce oestrus in the bitch, with gonadotrophin-releasing hormone (GnRH) agonists showing very promising results. Gonadotrophin-releasing hormone agonists act in a two-step mechanism, firstly acting on the pituitary gland to increase LH and FSH production with an accompanying increase in sex hormone concentrations. Secondly, after sustained release, GnRH leads to pituitary desensitization and a dramatic decrease in LH and FSH production. Recently, deslorelin, a GnRH implant, has been used for chemical sterilization in the dog and also used experimentally with varied results for oestrus induction in the bitch. Deslorelin has been shown to reliably induce oestrus (Fontaine and Fontbonne 2010) and also ovulation (Walter et al. 2011) in the bitch. Pregnancy rates following deslorelin implants have varied between studies (Volkmann et al. 2006a; Fontaine et al. 2011). Most of these studies are performed using experimental groups of bitches, and the methods are varied, so the results of deslorelin use in a clinical setting have not been reported.
The aim of this study is to evaluate induction of oestrus and assess ovulation and pregnancy rates after implantation with deslorelin in a clinical setting.
Materials and Methods
The study used 16 late anoestrus bitches (at least 160 days since previous oestrus) that had come to the clinic for various reasons such as long anoestrus period (more than 10 months) or to time mating and whelping for convenience of the owner or for unsuccessful pregnancies after previous breedings. The bitches were of different breeds, ages and reproductive history. Deslorelin (Suprelorin®4.7 mg; Virbac, Carros-Cedex, France) was implanted on Day 0 subcutaneously in the ventral abdomen close to the umbilicus. Onset of oestrus was noted. Time of ovulation was determined by serum progesterone levels, and ovulation was assumed if a progesterone concentration >15 nm was found. Venous blood samples for progesterone levels were not taken every other day as have been described in previous studies (Walter et al. 2011) because of the clinical nature of the trial. When progesterone concentration was >15 nm, the deslorelin implant was removed. It was easy to find and locate by palpation. To remove the implant, a small amount of local anaesthetic was infused sub-dermally and the skin over the implant was incised with a scalpel blade. No sedation was required. The clinician had limited influence on breeding regime, and bitches were mated 1–4 days after ovulation to unknown dogs according to owner's preference.
Bitches did not exhibit any pain or discomfort when inserting or removing the implant. All implanted bitches came into oestrus, on average 4.5 days after implantation. Ovulation was detected in 13 bitches (81.3%) which occurred on average 9.2 days after onset of detected oestrus (range 4–16 days). 11 of 16 bitches became pregnant (68.8%) and all continued to term and whelped (Table 1). Average litter size was 7.6 puppies. Implants were removed on average 13.8 days after insertion.
Table 1. Number of bitches that came into oestrus, ovulated and became pregnant
|Oestrus (n = 16)||100||4.5||1–10|
|Ovulation (n = 13)||81.3||9.2||4–16|
|Pregnancy rate (n = 11)||68.8|| || |
Using the method described earlier, deslorelin was safe and reliable to induce oestrus in the bitch. It has been demonstrated that prolonged GnRH agonist use leads to pituitary desensitization (Junaidi et al. 2007) which results in luteal failure and pregnancy loss. Previous studies (Kutzler et al. 2002) removed the implant when progesterone levels start to rise around the time of the LH peak in an attempt to avoid luteal failure. Given the clinical nature of this trial, the involvement of the breeder time of ovulation was tested for as it had a practical implication for the mating. Also knowing that ovulation had occurred might have a positive effect on pregnancy rates. Therefore, the implant was removed after ovulation. Previous studies have achieved pregnancy rates of 72% (18/25 that ovulated) using the same methods in a clinical setting (Fontaine et al. 2011). The results in this study, 84.6% (11/13 bitches that ovulated), demonstrate that high pregnancy rates can be achieved when the implant is removed after ovulation. The acceptable litter sizes that were achieved after induction of oestrus with deslorelin indicate that oocyte quality was similar to that of a natural oestrus. It has been suggested that this could be in response to the stimulation of follicular recruitment by the GnRH agonist (Fontaine et al. 2011) but more work is required to investigate this further.
Deslorelin has been associated with some suppression of serum progesterone concentrations during the second half of the luteal phase (Volkmann et al. 2006b), and luteal failure has been possibly identified as a cause for failure in pregnancy. However, the influence of possible luteal failure in this study cannot be evaluated because progesterone levels were not routinely recorded during gestation. Despite no progesterone supplementation, there were no pregnancy failures.
Included in this study was one bitch that was implanted twice, first to induce an early oestrus to prevent an anticipated oestrus and then again 23 weeks later to have a litter. She whelped seven puppies. This could suggest that deslorelin can be used successively to induce fertile oestrus.
However, despite an 84.6% pregnancy rate in the bitches that ovulated, 18.7% of bitches that were implanted failed to ovulate. This anovulation rate is similar between other studies, and further work is required to investigate this. This should be taken into consideration when discussing the use of deslorelin with clients.
This study adds additional clinical cases to previously published work (Fontaine et al. 2011) and confirms that deslorelin can be safely and reliably used in a clinical setting to induce oestrus and pregnancy in the bitch.
Conflicts of interest
None of the authors have any conflicts of interest to declare.