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. |
