The present study was to examine the effect of chitooligosaccharides on pre-implantational development of mouse embryos. Chitooligosaccharides at different concentrations 0 μg·m L-1(control), 5, 10, 50, 100, and 200 μg·m L-1 were added into the culture medium. Pronuclear-stage embryos derived from in vivo and in vitro fertilization were randomly divided into six groups. The rate of cleavage, blastocyst formation, and blastocyst quality(total cell number and the ratio of inner cell mass(ICM) to total cell nu...