Induction of Ovulation after Artificial Insemination in Rabbits: Intramuscular In-jection of Gonadotropin-Releasing Hormone (GnRH) Agonist vs. Intravenous Administration of Mated Doe Serum

Rabbits are induced ovulators with the ovulatory process being triggered by neuro-hormonal impulses gen-erated during natural mating. When applying artificial insemination (AI), an array of biostimulation techniques and/or exogenous hormones, such as gonadotropin-releasing hormone (GnRH) or its analogues must be used to induce ovulation. However, the effect of biostimulation techniques and exogenous hormones is not always satisfactory and the use of GnRH analogues is asso-ciated with high production costs. Therefore, the development of an alternative inexpensive, efficient, and safe treatment for ovulation induction in artificially inseminated does is urgently needed.

In the present study, we examined and compared the effects of mated doe serum (MDS) and GnRH analogue (Gonadorelin) administered immediately after AI on the circulating concentrations of luteinizing hormone (LH) and fertility in New Zealand does.

Forty artificially inseminated does were allocated to four equinumerous groups. The Control G, Treatment G, Control M, and Treatment M groups received 0.2 mL of saline intramuscular (IM), 0.8 μg of Gonadorelin dissolved in 0.2 mL of saline IM, 2.5 mL of mixed-sex normal rabbit serum intravenous (IV),and 2.5 mL of MDS/doe IV, respectively.

A peak in systemic LH concentrations occurred earlier in Treatment M, compared to Treatment G does (71 vs. 107 min post-AI, respectively; P≤0.05). Mean LH concentrations did not vary (P≤0.05) from the pre-AI values in neither of the control groups. Serum LH concentrations remained higher (P≤0.05) in the Treatment M group, in comparison with Treatment G does during30-90 min post-AI. However, LH was higher (P≤0.05) in the Treatment G group than the Treatment M group 120 and 160 min post-AI. Gonadorelin and MDS injections both resulted in the same kindling rate of 80% at each of the four con-secutive AIs (initiated 30 days postpartum) and were significantly greater than that recorded in the control animals (20%).

It can be concluded that MDS administration is an effective treatment for inducing ovulation in rabbits with repeatability similar to that achieved with a GnRH analogue