An analysis of the effect of the PMSG-HCG interval on the two-cell block

The effect of increasing the interval between the administrations of pregnant mare's serum gonadotrophin and HCG to female mice from 48 to 60 h on the mating frequency, ovulation rate, fertilization rate and development through the two-cell stage has been investigated. It is concluded that use of the longer interval is of no advantage, and may be disadvantageous.