Influence of dietary protein restriction on ovulation, fertilization rates and pre-implantation embryonic development in mice.
Eggs were recovered from 153 adult female mice fed either a normal (27% protein) or a protein-deficient (8% protein) diet from day 15 (Group I) or 30 (Group II) before mating until sacrifice. The females were mated with fertile males and sacrificed 48, 72, 96 or 120 hours after observation of vaginal plugs. The study was performed with females that ovulated spontaneously and with females induced to ovulate by injection of pregnant mare's serum gonadotrophin and human chorionic gonadotrophin. Without gonadotrophin treatment, significantly fewer eggs were recovered from malnourished than from normal females. However, after hormonal treatment, the number of eggs ovulated by malnourished and normal females increased similarly. About 50% of the eggs recovered from malnourished females in both groups I and II were cleaved whereas 90% of the eggs recovered from well-nourished females were cleaved. The development of the cleaved eggs from protein deficient females was delayed and asynchronous in comparison with that of eggs from normal females. Embryos recovered from malnourished females also were retarded in differentiation of morulae to blastocysts. It is concluded that a protein-restricted diet adversely affects the fertilization of eggs as well as their early development and differentiation.