Efecto del tipo genético materno sobre el embrión, la supervivencia fetal y las características de crecimiento en conejos

Nowadays, the influence of maternal and prenatal embryonic genotype on prenatal survival is not clear. However, it is known that mother's genotype (uterine environment) can affect fetal and postnatal development. While several studies have referred prenatal survival with the maternal genotype, others suggest that the embryonic genotype may modify the uterine environment. Consequently, the prenatal survival depends not only of maternal factors. These effects have been shown in the rabbit, however, this study aimed to evaluate the effect of different maternal environments on the embryonic and gestational survival. In addition, we also study the effect of this maternal environment in the rabbit's growth at prenatal and postnatal stage. The maternal effect was determined by comparing three different genotypes, two of them selected by reproductive characters, but with different genetic selection methods (genotype A and V), and the third selected by average daily gain during fattening (genotype R). To rule out the effect of embryonic genotype, all embryos was obtained from genotype R. Donor rabbit (n equal to 39) were superovulated with a subcutaneous injection of corifollitropin alfa (0.75 pg per kg, Elonva0). Sixty hours later, they were inseminated (Al) and induced to ovulate, recovering embryos 72 h after Al. Only, the females who provided at least 21 embryos was classified as transferable and used as donors (n equal to 13). Embryos were distributed in the three receptor genotypes (R, A and V), transferring between 7 to 14 embryos per recipient. In total, 453 embryos (151 in each genotype) were transferred by laparoscopy in 39 females. Embryonic survival (embryo implanted/embryos transferred), gestational survival (kits born alive/embryos transferred) and fetal loss (rabbits unborn/implanted embryos) was determined by laparoscopy at 10th day of gestation. In addition, the size of the fetus was determined during gestation by ultrasound (My Lab 70 x V6 portatil-Esaote) at intervals of 2 days, starting on day 10 and ending on day 27. Litter size was determined and each newborn was individually identified by microchip and weighted. The daily middleweight gain (DMG) was estimated until the age of 63 days, and also the survival rate during this stage was calculated. DMG was calculated during the lactation and fattening (until 63 days). Our results shown that embryonic survival rate was influenced by maternal genotype, being higher in the maternal genotypes (A and V) than in the paternal genotype R (0.62 plus minus 0.04 and 0.58 plus minus 0.04 vs 0.47 plus minus 0.04 for genotype A and V vs R, respectively). However, in the survival gestational and fetal losses any effect was observed. On prenatal growth, any effect between 10 to 19 days of pregnant was noticed. However, from day 21 of pregnant, the fetus in the uterine environment of R genotype increased their body length, maintaining this difference until the birth. Although any effects were observed on litter size, the weight at birth showed a higher value for the fetus developed in the uterine environment of genotype R (72.7 plus minus 2.2g vs 67.0 plus minus 2.1g and 61.7 plus minus 2.0g for R vs genotype A and V, respectively). During lactation, R genotype reached the highest DMG (21.1 plus minus 0.9 g/d vs 18.7 plus minus 0.8 g/d and 18.3 plus minus 0.7 g/d, for genotype R vs genotype A and V, respectively). However, during the fattening stage, the postnatal survival and DMG were not affected by maternal effect. In conclusion, maternal effect has an effect on embryonic survival but not in gestational survival, fetal loss and postnatal survival. In addition, the maternal effect on the fetal growth and until lactation was observed. Later this effect is compensated during fattening stage.