The GnRH analogue Decapeptyl was able to induce ovulation in cyclic jennies

The aim of this study was to assess the ability of the GnRH analogue decapeptyl to induce ovulation of jennies in oestrus. Most of the northern hemisphere donkey breeds are faced with the risk of extinction (Camillo et al. J Equine Vet Sci 2018;65:44-49), thus donkey reproduction is considered an emerging branch of theriogenology and the management of induction of ovulation is a crucial point to set up preservation protocols (Carluccio et al. Theriogenology 2007;68:914-919; Camillo et al. Anim Reprod Sci 2014;151:56-60). In this study six Amiata jennies aged between 3 and 10 years, cyclic, in good general health and with a body condition score of ¾ were employed (Vall et al. in: Pearson, et al. Ed., 2003:93–102). For four consecutive cycles, jennies’ ovarian activity was routinely monitored; ultrasound examination was performed daily from the evidence of a follicle diameter ≥27 mm until ovulation. Upon reaching a follicular diameter ≥32±2 mm (hour 0), estrous jennies were treated alternatively with 100 mg Decapeptyl, sc, (DEC) or the equivalent volume of saline, sc, (CTRL) and examined ultrasonographically at hours 14, 24, 38, 42, 48, 62 and every 24 hours until ovulation. The experimental design was a 2 × 2 (with two replicates) Latin square. Induction of ovulation was considered successful if ovulation occurred between hours24 and 48 from treatment. An independent sample Student T Test and a Fisher Exact Test were performed to compare mean ovulation hour and ovulatory rates between DEC and CTRL groups, respectively. A forward stepwise multivariable logistic regression model based on the Wald statistics criterion of a P value smaller than 0.05 was used to establish significant predictors (group, jenny, and cycle number) for ovulation after treatment. Eleven/12 and 12/12 cycles resulted in ovulation for DEC and CTRL groups, respectively. Mean±SD ovulation time after treatment was 47.1±21.0 and 66.8±25.9 hours for DEC and CTRL respectively (P=0.059). Ovulation rates between 24h and 48h were 10/12 (83.3%) and 2/12 (16.7%) for DEC and CTRL respectively (P=0.003). Decapeptyl-treated jennies had a 25 times higher probability to ovulate between hours 24 and 48 than controls (P=0.003), while there were no jenny and cycle effects on the ovulatory rate. The results of this study show how Decapeptyl successfully induced ovulation in jennies, similarly to other GnRH analogs previously evaluated (Canisso et al. Vet Clin North Am Equine Pract 2019;35:607-642). Acknowledgments: The authors are grateful to Ente Terre Regionali Toscane for funding and for providing the jennies.