The individual difference of superovulatory responses and inferior embryo quality in superovulated cattle may cause disturbances in the endocrine profile, follicular steroidogenesis, nuclear maturation of nocyte, fertilization and cleavage of embryos. However, the reasons why those disturbances are occurred were not understood. The methods of the improvement of superovulatory response and embryo production were the use of anti-PMSG if PMSG used, pure FSH or controlled FSH-LH inducer, priming dose of gonadotropin in the first few day of the estrous cycle and GnRH or analogue. However, all of the above methods were not reduced the individual differences but improved embryo production We must continue the fundamental studies to understand the mechanism.

Total thirty of flushing were attempted on day 4 to 15 of estrus cycle with S heifers and 9 cows by nonsurgical method. The flushed or recovered rate among flushings was 86.7% (26/30) or 88.5% (23/26), respectively. There was no difference in the recovered rate between heifers (85.7%,6/7) and cows (89.5%, 17119). The embryo was recovered on day 4 to 15 of estrus cycle from the donors in natural heat without any technical difficulties.The I2FG Foley catheter used for pubertal heifers had sometimes plug in it with uterine mucus during flushing of uterine horn. But the problem could be overcomed by pumping the catherter with fluthing solution or by changing the catheter. Three normal embryos were recovered from 3 pubertal (10-11 month old) heifers. The rate of normal and abnormal eggs was 60.9% (14123) and 39.1% (9/23), respectively. The abnormal eggs were on degenerating except one unfertilized egg and were mostly recovered from heifers or cows flushed consecutively during the estrus cycle. The developmental states of normal embryos were l6-cells on day 5, 32-cells on day 6, compacted-morula on day 7, early-to expanded-blastocyst on day 8-to 9, and hatching-to hatched-blastocyst on day 10 to 11 of estrus cycle. The stage of embryos on day 8 to 10 showed varities among donors. On day 8 to 9 of estrus cycle hatching-blas tocyst was recovered from some donors.

This study was carried out to investigate the seasonal effect on the recovery rate of embryos in donors and on the conception rate in recipients following embryo transfer. The results obtained from this experiment were summarized as follows: 1. The ovulation point in winter and summer was 28.6 and 28.6, respectively. There was no difference in ovulation point between two seasons. More embryos recovered in the winter (27,0) than the summer (20.9). 2. The number of CL, unruptured follicle, hemorrhagic follicle, young born and pregnancy rate in the winter were 6.0,4.8,1.5,1.8 and 75%, and those in the summer were 2.9,5.7, 3.8, 2.2 and 46.7%, respectively. The rate of synchronization of recipients in the winter showed better results than that in the summer.