scholarly journals The incompletely fulfilled promise of embryo transfer in cattle—why aren’t pregnancy rates greater and what can we do about it?

2020 ◽  
Vol 98 (11) ◽  
Author(s):  
Peter J Hansen
Keyword(s):  
Embryo Transfer ◽  
Artificial Insemination ◽  
Blastocyst Stage ◽  
Pregnancy Rates ◽  
Bovine Embryos ◽  
Uterine Receptivity ◽  
Stage Of Development ◽  
Stage Embryo ◽  
Repeat Breeder ◽  
In Pregnancy

Abstract Typically, bovine embryos are transferred into recipient females about day 7 after estrus or anticipated ovulation, when the embryo has reached the blastocyst stage of development. All the biological and technical causes for failure of a female to produce a blastocyst 7 d after natural or artificial insemination (AI) are avoided when a blastocyst-stage embryo is transferred into the female. It is reasonable to expect, therefore, that pregnancy success would be higher for embryo transfer (ET) recipients than for inseminated females. This expectation is not usually met unless the recipient is exposed to heat stress or is classified as a repeat-breeder female. Rather, pregnancy success is generally similar for ET and AI. The implication is that either one or more of the technical aspects of ET have not yet been optimized or that underlying female fertility that causes an embryo to die before day 7 also causes it to die later in pregnancy. Improvements in pregnancy success after ET will depend upon making a better embryo, improving uterine receptivity, and forging new tools for production and transfer of embryos. Key to accelerating progress in improving pregnancy rates will be the identification of phenotypes or phenomes that allow the prediction of embryo competence for survival and maternal capacity to support embryonic development.

scholarly journals Cleavage Stage versus Blastocyst Stage Embryo Transfer in Oocyte Donation Cycles

Medicina ◽  
2019 ◽  
Vol 55 (6) ◽  
pp. 293 ◽  
Author(s):  
Kontopoulos ◽  
Simopoulou ◽  
Zervomanolakis ◽  
Prokopakis ◽  
Dimitropoulos ◽  
...  
Keyword(s):  
Embryo Transfer ◽  
Oocyte Donation ◽  
Blastocyst Stage ◽  
Pregnancy Rates ◽  
Clinical Pregnancy ◽  
Cleavage Stage ◽  
Sonographic Guidance ◽  
Stage Embryo ◽  
Day 3 Embryo ◽  
Cryopreserved Embryos

Background and Objective: During the last few years, a trend has been noted towards embryos being transferred at the blastocyst stage, which has been associated with improved rates regarding implantation and clinical pregnancy in comparison to cleavage stage embryo transfers. There is a limited number of studies investigating this notion in oocyte donation cycles employing cryopreserved embryos. The aim of this study is to evaluate the implantation potential and clinical pregnancy rates between the day 3 cleavage stage and blastocyst stage embryo transfers in oocyte donation cycles employing vitrified embryos. Methods: This is a retrospective evaluation of oocyte donation frozen–thawed transfers completed in our clinic from January 2017 to December 2017. Intracytoplasmic sperm injection was conducted for all oocytes. Following fertilization, all embryos were cryopreserved either at the cleavage or blastocyst stage. Embryo transfer of two embryos was performed under direct sonographic guidance in all cases. Results: Our results confirmed a 55.6% clinical pregnancy (CP) resulting from day 3 embryo transfers, a 68.8% CP from day 5, and 71.4% CP from day 6. Significantly improved pregnancy rates were related to embryo transfers at the blastocyst stage when compared to cleavage stage transfers (68.9% and 55.6% respectively, p = 0.016). The risk with regards to multiple pregnancies was similar. Conclusion: Our findings indicate that in oocyte donation cycles employing vitrified embryos, embryo transfer at the blastocyst stage is accompanied with a significant improvement in pregnancy rates and merits further investigation.

scholarly journals 139PROSTAGLANDIN F2± COMPROMISES DEVELOPMENT OF PRE-IMPLANTATION BOVINE EMBRYOS DURING COMPACTION

2004 ◽  
Vol 16 (2) ◽  
pp. 191 ◽  
Author(s):  
F.N. Scenna ◽  
J.L. Edwards ◽  
F.N. Schrick
Keyword(s):  
Embryonic Development ◽  
Culture Medium ◽  
Block Design ◽  
Prostaglandin F2α ◽  
Blastocyst Stage ◽  
Pregnancy Rates ◽  
Early Embryonic Development ◽  
Bovine Embryos ◽  
Stage Of Development ◽  
Morula Stage

Several studies have implicated prostaglandin F2α (PGF) as a major embryotoxic factor during early embryonic development in cattle. Elevated uterine concentrations of PGF were negatively associated with embryo development, quality and pregnancy rates (Schrick FN et al. 1993 Biol. Reprod. 49, 617–621; Hockett ME et al. 1998 J. Anim. Sci. 76 (Suppl 1), 241 abst; Seals RC et al. 1998 Prostaglandins 56, 377–389). Moreover, addition of PGF to culture medium decreased hatching rates of compacted morulae (Scenna FN et al. 2002 Theriogenology 53, 512 abst) and decreased development of pre-compacted (16–32 cell) bovine embryos to blastocyst stage (Scenna FN et al. 2003 Theriogenology 59, 335 abst). Furthermore, administration of an inhibitor of PGF synthesis at the time of embryo transfer improved pregnancy rates in cattle (Schrick FN et al. 2001 Theriogenology 55, 370 abst). The objective of the current study was to identify the period of time during early embryonic development that is most susceptible to the deleterious effects of PGF. After in vitro maturation and fertilization of bovine oocytes, putative zygotes were cultured in KSOMaa plus 0.3% BSA. On Day 4 post-insemination, pre-compacted (16–32 cell) embryos were removed from culture, evaluated for quality, and randomly assigned to one of the following treatments: 1) Control (KSOMaa plus 0.3% polyvinyl alcohol (KSOM-PVA; n=470) or 2) PGF-1 (1ngmL−1 PGF in KSOM-PVA; n=473; Scenna FN et al. 2003 Theriogenology 59, 335 abst). After 48h of incubation in assigned treatments, assessment of development to compacted morula stage was determined. Thereafter, embryos were kept separate according to treatments, sorted by stage of development and quality, and randomly assigned to receive either Control (CON) or PGF-1 supplemented medium until assessment of blastocyst development on Day 9. This random sorting resulted in the formation of four treatment groups comprising the initial treatments and assigned treatments during Days 6–9 (CON-CON, n=366; PGF-CON, n=226; CON-PGF, n=149; PGF-PGF, n=287). Analyses were performed incorporating a randomized incomplete block design using mixed models of SAS (2000) to determine effects of PGF on Days 4–6, 6–9 and 4–9 of development. Data were also analyzed using chi-square. Addition of 1ngmL−1 of PGF to culture medium on Days 4–9 decreased the percentage of pre-compacted embryos reaching blastocyst stage (CON-CON, 47.8%; PGF-PGF, 36%; P<0.05). Moreover, addition of 1ngmL−1 of PGF to the culture medium of pre-compacted bovine embryos on Days 4–6 of development decreased the percentage of compacted morulae on Day 6 (Control, 68.1%; PGF-1, 60.5%; P=0.01). However, the percentage of embryos developing to blastocyst was not decreased following addition of 1ngmL−1 of PGF on Days 6–9 of development (CON-CON, 47.8%; CON-PGF, 42.6%; P>0.05). Results suggest that morula stage embryos during compaction are most susceptible to deleterious effects of PGF.

scholarly journals Effect of progesterone, human chorionic gonadotropin and progesterone + human chorionic gonadotropin treatment on conception rates in repeat breeder cows

2020 ◽  
Vol 89 (4) ◽  
pp. 307-315
Author(s):  
Hasan Alkan ◽  
Huseyin Erdem
Keyword(s):  
Pregnancy Rate ◽  
Chorionic Gonadotropin ◽  
Human Chorionic Gonadotropin ◽  
Artificial Insemination ◽  
Fixed Time ◽  
Pregnancy Rates ◽  
Group 4 ◽  
Prostaglandin F ◽  
Repeat Breeder ◽  
Group 1

The aim of this study was to investigate the effects of hormonal support on the pregnancy rate in repeat breeder cows. Prostaglandin F2α + Ovsynch oestrus synchronization protocol was applied to the cows. Following the fixed time insemination (day 0), the cows were divided into 4 groups. In Group 1 (n = 42), progesterone releasing intravaginal device (PRID) was placed vaginally at 84 h and removed on the 9th day after the artificial insemination. In Group 2 (n = 40), the cows were administered human chorionic gonadotropin (hCG) on the 7th day. Group 3 (n = 45) was applied a combination of progesterone and hCG. Group 4 (n = 42) was not given any treatment. Blood samples were collected from all cows 4 times on days 3.5, 7, 12, and 18 to evaluate progesterone concentrations. The pregnancy rates were 40.47%, 37.50%, 44.44%, and 30.95% in Group 1, 2, 3, and 4, respectively (P > 0.05). In addition, in cows with progesterone concentrations <2 ng/ml on day 3.5, the pregnancy rates were found to be lower than in the cows with progesterone concentrations >2 ng/ml in Group 4 (P < 0.05). Progesterone supplementation in cows with progesterone concentrations < 2 ng/ml appeared to increase pregnancy rates (P < 0.05) in Groups 1 and 3. As a result, post-insemination hormonal applications in the repeat breeder cows did not increase the pregnancy rate. However, it was concluded that determination of progesterone concentrations on day 3.5 following artificial insemination and then hormonal support in the cows with low concentrations would increased the pregnancy rate.

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