The effect of lecirelin (GnRH) dosage on the reproductive performance of nulliparous and lactating rabbit does

The present study attempted to evaluate the effect of different doses of lecirelin intramuscularly administered at the moment of insemination on parameters such as the conception rate, the total number of rabbits per litter, the number of stillborns per litter and the abortion rate in nulliparous and lactating crossbred rabbit does. The experiment was performed with 295 crossbred female rabbits Hyplus strain PS 19 that were housed in a rabbit farm. Six days before insemination, the light-dark cycles were as follows: 16-h light (70 lx and more):8-h dark, and all does were subcutaneously injected with 25 IU of eCG 48 h before insemination. The doses of lecirelin were as follows: 0.05, 0.1, 0.2, 0.3, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, and 4.0 microg/doe, and were tested in both nulliparous and lactating female does; the doses were applied at the moment of insemination. The conception rate in nulliparous does ranged significantly from 10.0% (0.05 microg) to 89.5% (1.5 microg). The conception rate in lactating does was the lowest at a dose of 0.05 microg (10.0%), as compared with the doses starting from 0.3 microg, and was confirmed statistically significant. The lowest number of rabbits per litter was found at a lecirelin dose of 0.1 microg (6.64). This finding was statistically significant, as compared with doses equal to or exceeding 0.3 microg. No statistical differences were found for doses ranging from 0.3 to 4.0 microg in nulliparous does (9.06 versus 10.29, respectively). The lowest number of rabbits per litter in lactating does was found at a dose of 0.05 microg (8.28) while the highest number of rabbits was detected at a dose of 4.0 microg (10.73), without statistically significant differences among individual doses. Generally, the number of rabbits per litter in lactating rabbit does was higher than that in nulliparous does (P<0.05). One negative finding is that abortions occurred in lactating does at the intramuscular application of a dose equal to or exceeding 1.5 microg, and in nulliparous does at a dose equal to or exceeding 2.0 microg.