Effect of long-term selection for early postnatal growth rate on survival and prenatal development of transferred mouse embryos

Reciprocal embryo transfer procedures were performed among mouse selection lines to examine prenatal maternal effects on survival and development of t ransferred embryos. Mice were from generations 28 and 29 of an experiment t o select for (i) increased body weight gain from 0 to 10 days (E+); (ii) de creased body weight gain from 0 to 10 days (E-); or (iii) a randomly bred c ontrol line (C). A total of 118 embryo transfer procedures performed 12 h a fter conception resulted in 983 progeny born to 89 litters. There was a 39% overall embryo survival rate and 75% overall pregnancy success rate. Respo nse to superovulation and oestrous synchronization was significantly lower (P < 0.01) in the E+ Line. E+ individuals that did superovulate produced an average of 37 oocytes per flush, which was significantly higher than in th e control line mice (29 oocytes per flush; P < 0.01). The ability to comple te pregnancy successfully was not influenced by uterine environment or embr yo-uterine interaction. In contrast, embryo survival in successful pregnanc ies was significantly affected by uterine environment. There were large mat ernal effects for body weight and tail length at birth; E+ recipients produ ced pups that were significantly larger than E- recipient pups (P < 0.01), which in turn were significantly larger than pups gestated by control recip ients (P < 0.01).