Reproductive Performance of Rabbit Does Artificially Inseminated via Intravaginal Administration of [des‐Gly 10, d‐Ala6]‐LHRH Ethylamide as Ovulation Inductor

Abstract

This study was aimed to evaluate the reproductive performance of rabbit does artificially inseminated (AI) with a GnRH analogue [des-Gly10, D-Ala6]-LHRH. ethylamide to induce ovulation by intravaginal administration, delivered in the seminal dose. In a preliminary experiment, 39 does were divided into three groups (n = 13) that, at the time of AI, received the following ovulation induction treatments: (i) control group: 20 microg of gonadorelin administered intramuscularly; (ii) 25 microg of the GnRH analogue added to the seminal dose; (iii) 30 microg of the GnRH analogue added to the seminal dose. Fertility did not differ between the three groups (control: 80.6%, group 2: 82.8%, group 3: 73.3%). In a second experiment, a large-scale field trial was conducted to test the use of 25 microg of the GnRH analogue [des-Gly10, D-Ala6]-LHRH ethylamide delivered in the seminal dose (n = 270) against 20 microg of gonadorelin administered intramuscularly. Fertility was higher (p < 0.05) when ovulation was induced by intravaginal administration of the GnRH agonist (91.1% vs 85.6%). Prolificacy or mortality at birth was never affected by the ovulation induction treatments. In a third experiment, two groups of does [control group (n = 39): ovulation was induced using 20 microg of gonadorelin administered intramuscularly; treatment group (n = 40): ovulation was induced using 25 microg of [(des-Gly10, D-Ala6)-LHRH ethylamide added to the seminal dose] were inseminated at 42-day intervals for five successive AI cycles, to test the response to the GnRH agonist after repeated intravaginal administration to the same animals. Fertility and prolificacy were not influenced by the ovulation induction treatment neither there was an interaction between treatment and parity. The last experiment was aimed to determine whether it could be possible to add the GnRH agonist to the semen in the AI Center, just after semen collection and dilution, or it would have to be added in the farm, immediately before AI. Kindling rates did not significantly differ when ovulation was induced by intramuscular injection of gonadorelin (84.5%) or when the GnRH agonist was added to the seminal dose just at the moment (93.8 %) or 24 h before AI (90.4 %), but it was significantly lower when the hormone was added to the semen 32 h before AI (76.3 %). Prolificacy, however, was not influenced by the ovulation induction treatment.