• Journal of Embryo Transfer
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• v.13 no.1
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• pp.61-67
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• 1998

This study was carried out to establish an effective system for embryo transfer techniques by analyzing several factors affecting in-vivo embryo transfer in Korean cattle. Embryos produced in-vivo were transferred into a total of 301 recipients The results obtained in studies on the factors affacting pregnancy rate after embryo transfer by condition of recipients were as follows ; 1. The pregnancy rate by age and parity of recipients showed high in 5~8 and over 12 years old(72.7~73.9%), and 3rd~4th parity(82.1%) for fresh embryos(P<0.05). The pregnancy rate did not differ by age and parity of recipients in frozen embryos. The pregnancy rate of frozen embryos tended to be similar to that of fresh embryos(38.5% and 25.0~36.7%). 2. The number of observation for normal estrus cycles of recipients did not differ In pregnancy rate between one and 2 times in fresh embryos(64.9%, 69.8%). The pregnancy rate by transferred frozen embryos showed significantly higher after 2 times of observation(P<0.05, 16.3%, 37.5%). The pregnancy rate by days open did not differ between fresh and frozen embryos. But the pregnancy rate was slightly higher in 12 months and 6 months of days open for fresh and frozen embryos, respectively(70.1~71.1% and 24.5%, respectively). 3. The pregnancy rate of transferred fresh and frozen embryos into right and left side of uterine horn did not differ(62.1% : 65.9% 25.0% : 24.3%, respectively). The pregnancy rate by the grade of CL was not different in fresh embryos, but the pregnancy rate was significantly higher in the grade A than B for frozen embryos(P<0.01, 43.2%, 16.2%).

• Korean Journal of Veterinary Research
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• v.32 no.1
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• pp.143-151
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• 1992

Sixty Four fresh and 142 frozen embryos of dairy cattle were transferred to synchronized dairy, beef or Korean Native Cattle nonsurgically at National Animal Breeding Institute from 1985 to 1990. The results obtained were as follows ; 1. The pregnancy rate of fresh embryos(39.1%) was higher than that of frozen embryos(32.4%) and average pregnancy rate was 34.5%. 2. The pregnancy rate of grade 1 embryos was higher than that of grade 2 embryos for both fresh(41.3% vs 33.3%) and frozen embryos(35.4% vs 25.6%). 3. The pregnancy rate according to development stage of fresh embryos was increased with maturity as 29.2%, 33.3%, 50.0% and 54.5% for morula, early blastocyst, blastocyst and expanded blastocyst, respectively. For frozen embryos, the pregnancy rate of blastocyst(44.4%) was higher than those of morula(31.3%) and early blastocyst(28.0%). 4. The pregnancy rate according go recipient-donor synchrony for fresh embryos was higher when the recipients exhibited estrus 1 day earlier than the donors(43.8%) than when the recipients exhibited estrus 1 day later than the donors(38.1%) or when the recipients and donors exhibited estrus at the same time(37.0%). For forzen embryos, the pregnancy rate was decreased when the recipients and donors exhibited estrus at the same time(37.9%), when the recipients exhibited estrus 1 day later than the donors(32.0%) and when the recipients exhibited estrus 1 day earlier than the donors(23.5%), in sequence. 5. The pregnancy rate of heifers was higher than that of cows for both fresh(50.5% vs 37.9%) and frozen embryos(39.7% vs 25.7%). 6. The pregnancy rate according to recipient breed for fresh embryos was higher in dairy cattle(42.1%) and beef cattle(40.%) than in Korean Native Cattle(33.3%). For frozen embryos, the pregnancy rate was decreased beef cattle(39.1%), dairy cattle(30.3%) and Korean Native Cattle(14.3%), in sequence. 7. The pregnancy rate according to equilibrium steps of glycerol and freezing rate was higher when transferred after 3-steps equilibrium and freezing by the rate of $0.3^{\circ}C$/min from $-6^{\circ}C$ to $-35^{\circ}C$ and $0.1^{\circ}C$/min to $-38^{\circ}C$(39.4%) than when transferred after 6-steps equilibrium and freezing by the rate of $0.5^{\circ}C/min$ from $-6^{\circ}C$ to $-30^{\circ}C$(30.3%).

• Journal of Veterinary Clinics
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• v.5 no.1
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• pp.1-7
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• 1988

An observational study was conducted to evaluate the effect of anterior pituitary gonadtropin on super-ovulation in donors, embryo quality, development stage of embryo, transfer location, corpus luteum quality of recipient, ease of transfer and induced versus natural estrus on pregnancy rates. The data were collected from 451 non-surgical transfers of fresh and frozen bovine embryos. 1. The average number of CL, formed in ovaries which were stimulated with follicular stimulating hormone, and/or APG, were 11. 1${\pm}$1.21, 12.3${\pm}$1.84, respectively. The numbers of embryos recovered were 8.2${\pm}$1.35, 8.7${\pm}$ 1.39, and the numbers of transferable embryos were 6.4${\pm}$0.98. 6.6${\pm}$1.01. respectively. 2 There was no effect of spontaneous versus prostaglandin-induced estrus of recipients on pregnany rates of either fresh (61.5% vs. 59.5%) or previously frozen(54.5% vs. 58.5%) embryos. 3. There were significant differences(p<0.05) in pregnancy rates for embryo grade 1(63.6%), grade 2 (45.4%) and grade 3 (30.4％) in fresh group and for grade-1 (60.5%), grade-2 (47.8%) and grade-3 (18.1%) in previously frozen embryos. 4. The recipients transfered with embryo morulae were found to have a lower (p<0.05) pregnancy rates than those transfered with embryos of blastocyst in be th fresh and previously frozen embryos. 5. There was no significant difference between transfer locations in pregnancy rates using both fresh and frozen embryos. 6. Attempts to select recipients for high pregnancy rates on the basis of corpus luteum (CL) quality were performed. CL were classified into 3 quality grades, on the basis of size and prominence. Quality grades 1 and 2 group had higher (p<0.05) pregnancy rates than grade-3 group using both fresh and frozen embryos. 7 Ease of transfer was ranked to a scale of one to three on the basis of increasing difficulty (time required). Transfers ranted as ease score 1 and 2 had significantly higher (P<0.05) pregnancy pregnancy rates (45.8%, 66.6%) than ease score 3 (27.7%, 31.8%) using both fresh and frozen embryos respectively.

• Journal of Animal Science and Technology
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• v.65 no.4
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• pp.779-791
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• 2023

This study aimed to assess the effects of embryonic developmental stage, quality grade, and fresh or frozen/thawed conditions on the pregnancy rate and sex ratio of live offspring in Hanwoo (Bos taurus coreanae) cows. The quality and developmental stage of in vivo-derived (IVD) transferred embryos were evaluated using the standard criteria of the International Embryo Technology Society. The recipient cows were synchronized using conventional (estradiol benzoate and progesterone) protocols before embryo transfer. Embryos were transferred to 297 cows, and pregnancy was monitored for 60-70 days after embryo transfer. The pregnancy rates of fresh and frozen/thawed embryos were 56.90% and 52.49%, respectively. Pregnancy rates varied according to embryo quality (56.18% for grade 1 vs. 36.67% for grade 2). Pregnancy rates also varied by developmental stage and cryopreservation (67.86% vs. 63.49% for stage 4-1, 64.00% vs. 54.72% for 5-1, and 50.00% vs. 47.83% for 6-1, in fresh embryos vs. frozen/thawed embryos, respectively). For stage 7-1, the pregnancy rates were 72.73% for fresh embryos and 20.00% for frozen/thawed embryos. In 66 fresh embryos, the sex ratio of live offspring was 5:5, whereas it was 4(female):6(male) for frozen/thawed embryos among the 95 frozen/thawed embryos. The miscarriage rate was approximately 3% higher for frozen/thawed embryos than for fresh embryos (18.1% for fresh vs. 21.1% for frozen). Seasonal fertility rates were 33.3% in spring, 55.67% in summer, 52.8% in autumn, 60.0% in winter. The following male-to-female ratios were observed in different seasons: 6.7:3.3 in spring, 4.0:6.0 in summer, 5.5:4.5 in autumn, and 3.3:6.7 in winter. The current data revealed no significant differences in pregnancy rates between fresh and frozen/thawed IVD embryos. However, there was a lower pregnancy rate with advanced-stage frozen/thawed embryos (stage 7-1). The current study provides comprehensive results for the better optimization of embryo transfer in Hanwoo cattle to obtain the desired fertility rate, pregnancy rate, and sex ratio of calves. These results provide important insights into the factors that influence the viability and success of IVD embryo transfer in Hanwoo cows and may have practical applications for improving breeding programs and reducing production costs.

• Journal of Embryo Transfer
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• v.13 no.1
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• pp.53-60
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• 1998

This study was carried out to establish an effective system for embryo transfer techniques by analyzing several factors affecting in-vivo embryo transfer in Korean cattle. Embryos produced in-vivo were transferred into a total of 301 recipients. The results obtained in studies on the factors affecting pregnancy rate after embryo transfer by condition of embryos were as follow ; 1. The pregnancy rate of 301 recipients was 45.2% and higher with fresh embryos than with frozen embryos(63.5% : 21.4%, P<0.01). Embryos superovurated by FSH-P had slightly greater than by SUPER-OV in pragnancy rate, athough these were no difference between two treatments. 2. The pregnancy rates of transferred morulae and blastocysts showed no difference between fresh and frozen embryos(63.5% : 63~6% ; 20.0% : 25.8%). However, the pregnancy rates by quality of flesh and frozen embryos were significantly different(P<0~05). The pregnancy rates were outstandingly high in the grade A, B of fresh embryos(59.0~66.4%), and in the grade A of frozen embryos(43.6%). 3. The number of transferred embryos showed no difference in pregnancy rate, but when frozen embryos transferred, the pregnancy rate was slightly higher with two embryos than that with one embryo.

• Proceedings of the Korean Society of Developmental Biology Conference
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• 2003.10a
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• pp.80-80
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• 2003

In cryopreserved rat embryos, survival rates obtained in vitro are not always consistent with the rates obtained in vivo. To determine the optimal conditions for in vivo development to term, rat embryos at the 4-cell, 8-cell and morula stages were vitrified in EFS40 by a 1-step method and transferred into oviducts or uterine horns of recipients at various times during pseudopregnancy. Vitrified and fresh 4-cell embryos only developed after transfer into oviducts of asynchronous recipients on Day -1 to -2 of synchrony, i.e., at a point in pseudopregnancy that was 1-2 days earlier than the embryos. However, although about half the vitrified embryos transferred into oviducts on Day -1 developed to term, only a minority of embryos transferred at later times did so, whether vitrified (10-34%) or fresh (24-33%), suggesting that this may not be the most suitable stage for cryopreservation. Very few 8-cell embryos, either vitrified or fresh, developed when transferred into oviducts on Day 0 to -0.5. However, when transferred into uterine horns, high proportions of vitrified 8-cell embryos (-63%) developed to term in reasonably synchronous recipients (Day 0 to -0.5) but not in more asynchronous ones (6%; Day-1). A majority of vitrified morulae also developed to term (52-68%) in a wider range of recipients (Day 0 to -1), the greatest success occurring with recipients on Day -0.5. Similar proportions of vitrified and fresh 4-cell embryos, 8-cell embryos and morulae developed to term when there was appropriate synchronization between embryo and recipient. Thus vitrification of preimplantation stage rat embryos does not appear to impair their developmental potential in vivo.

• Journal of Embryo Transfer
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• v.13 no.1
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• pp.69-76
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• 1998

This study was carried out to establish an effective system for embryo transfer techniques by analyzing several factors affecting in-vivo embryo transfer in Korean cattle Embryos were transferred into a toral of 301 recipients. The results obtained in studies on the factors affecting pregnancy rate after embryo transfer by condition of transfer time were as follows ; 1. The pregnancy rate by the seasons of transferred fresh and frozen embryos were not different, but the pregnancy rate was slightly higher in summer(80.8%). 2. The pregnancy rate by the days of embryo transfer after estrus were not different when fresh embryos were transferred, but the pregnancy rate was highest at 8 days when frozen embryos were transferred(P<0.01, 40.0%). 3. The pregnancy rate at estrus synchronization was remarkably higher with PGF$_2$$\alpha$ treated than natural (P<0.05, 70.4%, 43.4%). 4. The pragnancy rate by the degree of estrus synchronization was best when the estrus was synchronized in both fresh and frozen embryos (83.3% and 29.7%, respectively), but the pregnancy rate was not different among $\pm$2 days. But the pregnancy rate of frozen embryos were slightly higher when the recipients exhibited estrus earlier than donors.

• Clinical and Experimental Reproductive Medicine
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• v.51 no.1
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• pp.85-90
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• 2024

Objective: The purpose of this study was to compare fresh and frozen-thawed euploid blastocyst transfer protocols following preimplantation genetic screening (PGS) in cases of advanced maternal age. Methods: A total of 330 patients were examined retrospectively. PGS was performed on the embryos of 146 patients for whom fresh transfers were chosen. In contrast, frozen-thawed euploid single embryo transfer (ET) was selected after PGS for 184 patients, and their embryos were vitrified. The percentage of euploid embryos and rates of implantation, pregnancy, and pregnancy continuity, as well as clinical and biochemical abortion rates, were compared. Results: The numbers of retrieved oocytes, metaphase II oocytes, and fertilized ova were greater in the frozen-thawed group. The percentages of euploid embryos were comparable between the fresh and frozen-thawed groups (32% vs. 34.8%, respectively). The rates of implantation (46.6%vs. 62.5%), pregnancy (50% vs. 66.8%), ongoing pregnancy (38.4% vs. 53.8%), and live birth percentage (37.0% vs. 53.8%) were significantly higher in the frozen-thawed group. However, no significant differences were found in the clinical and biochemical abortion rates. Conclusion: The use of frozen-thawed single euploid ET is associated with increased implantation and pregnancy rates compared to fresh single euploid ET with PGS.

• Journal of Embryo Transfer
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• v.10 no.1
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• pp.65-72
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• 1995

The purposes of this study were to produce cloned rabbit embryos and offsprings by nuclear transplantation(NT) using in vitro matured oocytes as nuclear recipient cytoplasm and to determine the effect of frozen nuclei donor embryos on the production efficiency of cloned embryos. The 8cell embryos were collected from the mated does by flushing oviducts with Dulbecco's phosphate buffered saline containing 10% fetal calf serum(FCS) at 40 hours after hGG injection. A portion of collected embryos were preserved at 4$^{\circ}C$ for 24 hours and a portion of them were frozen by vitrification method. The embryos used for donor nuclei were synchronized in the phase of Gi /S transition. The in vitro matured oocytes were used as recipient cytoplasm following removing the nucleus and the first polar body. The synchronized blastomeres from fresh, cooled or frozen embryos were injected into the enucleated oocytes by micromanipulation and were electrofused by electrical stimulation of three pulses for 60 $\mu$sec at 1.0 W /cm in 0.28 M mannitol solution. The fused oocytes were co-cultured with a monolayer of rabbit oviductal epithelial cells in M-199 solution containing 10% FCS for 120 hours at 39$^{\circ}C$ in a 5% $CO_2$incubator. Following in vitro culture of the NT embryos to blastocyst stage, they were stained with Hoechst 33342 dye for counting the number of blastomeres by fluorescence microscopy. The nuclear transplant embryos developed in vitro to 2- to 4-cell stage were transferred into the oviducts of synchronized recipient does. The results obtained were summarized as follows: 1. The fusion rates of the blastomeres from fresh, cooled and frozen embryos with the in vitro matured and enucleated oocytes were 100, 95.8 and 64, 3%, respectively. 2. Development in vitro to blastocyst was significantly(p<0.05) different between the cloned embryos with the blastomeres from fresh, cooled or frozen embryos as 39.0, 20. 9 and 15.7%, respectively. 3. The mean numbers of cell cycle per day during in vitro culture of cloned embryos blastomeres from fresh, cooled or frozen embryos was 1.31, 1.29 and 1.16, respectively. 4. A total of 77 nuclear transplant embryos were transferred into 6 recipient does, of which two offsprings were produced from a foster mother 31 days after embryo transfer.

• Journal of Embryo Transfer
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• v.12 no.1
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• pp.11-20
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• 1997

The influence of cryopreservation of donor embryos on the in vitro developmental potential in the nuclear transplant rabbit embryos was evaluated. The embryos of 16-cell stage were collected and cryopreserved with EFS solution by vitrification method. The frozen embryos were thawed and synchronized to S and G$_1$ phase of 32-cell stage. The recipient/ cytoplasms were obtained by removing the first polar body and chromosome mass from the oocytes collected by non-disruptive microsurgery procedure. The separated S and G$_1$ phase blastomeres of 32-cell stage were injected into enucleated recipient cytoplasms by micromanipulation. After culture until 20 hrs post-hCG injection, the nuclear transplant oocytes were electrofused and activated by electrical stimulation. The fused nuclear transplant embryos were co-cultured with rabbit oviduct epithelial cells. After in vitro culture for 120 hrs, the nuclear transplant embryos developed to blastocyst stage were stained with Hoechst 33342 dye and their blastomeres were counted. The electrofusion rate was significantly (P<0.05) reduced in the frozen nuclear donor,compared with fresh donor nuclei as 80.0 vs 62.8% in S phase and 81.7 vs 64.8% in G$_1$phase, respectivley. The in vitro developmental rate to blastocyst stage with the S and G$_1$phase of fresh embryos(26.3 and 61.1%, respectively) was found significantly (P<0.05) higher, compared to the S and G]phase of frozen embryos(11.9 and 34.6%, respectively). When frozen as well as fresh donor embryos were synchronized to G$_1$ phase, the in vitro developmental rate to blastocyst stage was significantly (P<0.05) higher, compared with S phase donor nuclei. The cell counts of nuclear transplant embryos developed to blastosyst stage were significantly (P<0.05) more in G$_1$ phase of fresh or frozen embryos (180.1 and 125.7 cells, respectively), compared with S phase nuclear donor (145.1 and 103.7 cells, respectively). From the above results it was concluded that the rabbit embryos cryo- preserved by vitrification might be available as nuclear donor, though the developmentalpotential and cell counts of nuclear transplant rabbit embryos were decreased significantly.