Effect of maternal genotype on embryo and foetal survival using rabbit as a model

Actually, the influence of maternal and embryonic genotype in prenatal survival continues being unclear. However, it is know that maternal genotype partially determines the uterine environment, leading to the possibility of induced helpful or detrimental long term effects in the developing fetus. Whilst several studies have linked prenatal survival with maternal genotype, others suggest that embryonic genotype could modify uterine secretions, so that prenatal survival no longer depended exclusively on maternal factors. Specifically, in rabbit has been demostrated that both embryonic and maternal genotype can affected embryo survival. In the current study, we aimed to evaluate the maternal effect on embryo and foetal survival using superovulation treatment and embryo transfer technology to discard the embryonic effect. Maternal effect was determined by comparison among the three different genotypephenotype: two lines selected for reproductive traits but with different genetic selection processes, named line A and line V and one line selected by individual selection on daily gain from weaning to slaughter age (28 and 63 days), named line R. Nulliparous donors from line R were superovulation with one subcutaneous injection of corifollitropin alfa (3 µg, Elonva®). Sixty hour after, does were inseminated (AI) and the embryos were collected 72 h after AI. Embryos from each donor were distributed equally (7-10 embryos) among maternal genotypes to discard the embryonic genotype influence, and transferred into multiparous does using laparoscopic technique. A total of 453 embryos from 13 donors were transferred (151 in each line). The embryo survival rates were assessed by laparoscopy at day 14 and at birthday noting implantation rates and birth rates, respectively. A GLM was used (SPSS 21.0 software package). The error was designated as having a binomial distribution using probit link function. A P value of less than 0.05 was considered to indicate a statistically significant difference. The data presented as least square mean ± standard error mean. Our results indicate a clearly influence of maternal genotype on embryo and foetal survival. Specifically, lines selected for reproductive traits showed a significantly higher implantation rate and development to term (63 ± 4.0% and 36 ± 4.0% and 59 ± 4.0% and 32 ± 4.0%, for line A and V, respectively) than that line selected by daily gain (47 ± 4.3% and 24 ± 3.6%, line R). Foetal losses were similar between groups (21 ± 4.8%, 20 ± 4.8% and 18 ± 4.8%, for line A, V and R respectively). Results showed that after transplantation one peak of loss occurs before implantation, but after implantation till the end of gestation all maternal genotypes followed similar paths. In conclusion, our observation appears to be explained by the importance of the intrauterine environmental differences.