Evaluation of different strain mice during in vitro fertilization and embryo development in response to superovulation

Background: Mice are the most commonly used animal in reproductive research and following the urgent need for these type of studies and also due to the increased interest in the ethical principle of animal rights, four various inbred and outbred strains of the laboratory mouse were evaluated to select the more efficient one for reproductive research. Materials and methods: 60 female and 16 male of strains (C57, CD1, NMRI, and Balb/c) weighing 25 to 30g and aged 6 to 8 weeks were evaluated under same conditions at different stages of mature oocyte collection, fertilization and in vitro embryo development up to the blastocyst stage. The data were analyzed using a chi-square test, and the selected significance level was p<0.05. Results: Among the four strains, the highest to lowest fetal survival rates were for the CD1, NMRI, Balb /C and C57 mice, respectively and  their values ​​were 38.9, 14.4, 9.1 and 3.1%, individually. Conclusion: Considering the results, we conclude that it is not possible to obtain optimal results for some strains due to using same instructions. The results showed that the highest rate of fertilization and embryo development up to the 8-cell stage was observed in the outbred CD1 mice. It seems that this strain is more applicable than others for reproductive research. In addition, we believe that using different medium during fertilization and embryo development as well as laboratory conditions, probably assist in improving the embryo production while minimized the required number of animals and allowed the achievement of the desired result.