Effects of an intravaginal GnRH analogue administration on rabbit reproductive parameters and welfare

On commercial farms, rabbit does are subjected to a reproductive rhythm that does not account for their welfare or physiology, leading to reduced longevity and consequently high annual replacement. The European Food Safety Authority (EFSA) recommends limited and infrequent use of hormone treatments, and suggests replacement with alternative methods that do not threaten animal welfare when possible. In the present study, we aimed to determine whether the GnRH analogue lecirelin acetate could be administered by inclusion in the seminal dose during insemination. Twenty 9-month-old does (Grigio del Monferrato, autochthonous Italian breed),each having two previous deliveries, were individually housed and divided into two groups at artificial insemination. The control group received 0.2 mL of intramuscular lecirelin (Dalmarelin, Fatro^®, Italy) prior to insemination. The intravaginal group was inseminated with a seminal dose that included 0.3 mL Dalmarelin. The experiment was performed for six consecutive reproductive cycles at 42-day intervals, and included a total of 120 inseminations. Prior to each insemination, the heterospermic pooled semen samples were assessed for sperm motility and morphology. Each ejaculate was divided into two samples, with and without lecirelin addition. Compared to the control group, the does with intravaginal Dalmarelin administration showed equal or greater sexual receptivity, which resulted in a higher fertility rate over increasing cycles. The seminal dose volume was very low, possibly explaining the better results in the intravaginal group, which received a similar amount of hormone (0.3 mL/doe) as the control group (0.2 mL/doe). The negative performance of the control group may have also been due to anti-GnRH formation, and the more stressful method of ovulation induction. The number of live-born kits did not significantly differ between groups. Progressive motility was significantly positively correlated with motility characteristics, including VAP, VSL, ALH, BCF, STR, and LIN. Overall, our present findings supported that the incorporation of GnRH in a seminal dose could be used for ovulation induction in rabbit does. Further studies should identify the optimal dose of GnRH for intravaginal administration, taking into account that the intravaginal absorption capacity is about 10 times smaller than the intramuscular absorption capacity.