Search for a command to run...
Artificial insemination represents a fundamental tool in contemporary rabbit production but continues to depend largely on the administration of exogenous GnRH analogues to trigger ovulation, raising concerns related to animal welfare and long-term sustainability. This study combined a comparative histological analysis of the distal vaginal tract in nulliparous and multiparous New Zealand White does with an on-farm evaluation of two customized 3D-printed insemination cannulas tailored to each reproductive status. A thicker cannula (maximum diameter 10 mm) was used in multiparous rabbits and a thinner cannula (maximum diameter 7 mm) in nulliparous rabbits. Histological and immunohistochemical analyses characterized the distribution of subepithelial mechanoreceptors (Pacinian, Ruffini, and Meissner corpuscles), epithelial receptors (Merkel cells), and paravaginal nerve ganglia along the first 6 cm of the vagina. Subepithelial mechanoreceptors showed the highest densities within the first two centimeters of the vaginal tract, Merkel cells increased in the third and fourth centimeters, and nerve ganglia were predominantly located at a depth of five to six centimeters. Among subepithelial mechanoreceptors, only Pacinian corpuscles were significantly more abundant in nulliparous than in multiparous females, whereas epithelial Merkel cell abundance did not differ between groups. Multiparous does showed larger paravaginal ganglia but lower neuronal density. In total, 289 inseminations were performed in receptive does using the two cannula designs, allowing the functional evaluation of these anatomically adapted devices under commercial farm conditions. Double physical stimulation resulted in fertility rates comparable to those obtained with intramuscular GnRH administration both in nulliparous does (0.93 ± 0.05 vs. 0.79 ± 0.08) and multiparous does (0.76 ± 0.05 vs. 0.85 ± 0.06), without compromising total or live litter size. The inseminations were performed by two independent operators, and no significant differences were observed between groups, confirming the reproducibility of the insemination procedure. Consequently, these findings demonstrate that appropriately designed cannulas and stimulation protocols can reliably induce ovulation in the absence of hormonal treatments, supporting the development of a sustainable artificial insemination system that maintains reproductive efficiency while enhancing animal welfare in rabbit production systems.