Induction of ovulation after artificial insemination in rabbits: Intramuscular injection of gonadotropin-releasing hormone (GnRH) agonist vs. intravenous administration of mated doe serum

Abstract

BACKGROUND: Rabbits are reflex ovulators with the ovulatory process triggered by neuro-hormonal impulses generated during natural mating. When applying artificial insemination (AI), an array of biostimulation techniques and/or exogenous hormones (e.g., gonadotropin-releasing hormone (GnRH) or its analogues) must be used to induce ovulations in female rabbits. However, the effectiveness of various biostimulation techniques and exogenous hormones is not always satisfactory and the use of GnRH analogues is additionally associated with high production costs. Therefore, developing an alternative inexpensive, efficient and safe treatment for the induction of ovulation in artificially inseminated does is urgently needed. OBJECTIVES: In the present study, we examined and compared the effects of mated doe serum (MDS) and GnRH analogue (Gonadorelin) administered immediately after artificial insemination on circulating concentrations of luteinizing hormone (LH) and fertility in New Zealand does. METHODS: Forty artificially inseminated does were allocated to four equinumerous groups that received: 0.2 ml of saline i.m. (Control G), 0.8 µg of Gonadorelin dissolved in 0.2 ml of saline i.m. (Treatment G), 2.5 ml of mixed sex normal rabbit serum i.v. (Control M) or 2.5 ml of mated doe serum (MDS)/doe i.v. (Treatment M). RESULTS: A peak in systemic LH concentrations occurred earlier in Treatment M compared with 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 both control groups. Serum LH concentrations remained higher (P≤ 0.05) in Treatment M compared with Treatment G does from 30 to 90 min post-AI but they were greater (P≤ 0.05) in Treatment G than in Treatment M group at 120 and 160 min after AI. Gonadorelin and MDS injections both resulted in the same kindling rate (80%) at each of the four consecutive AI’s (initiated 30 days post-partum) and they were significantly greater than those recorded in control animals (20%). CONCLUSION: It can be concluded that MDS administration is an effective treatment to induce ovulations in rabbits, with the repeatability like that achieved with a GnRH analogue.