Embryo mortality in maiden hereford x friesian heifers following embryo transfer

1992 ◽  
Vol 1992 ◽  
pp. 46-46
Author(s):  
D. Pullar ◽  
K F D Brown ◽  
A E Wrathall
Keyword(s):  
Pregnancy Rate ◽  
Embryo Transfer ◽  
Pregnancy Loss ◽  
Early Embryo ◽  
Cattle Breeding ◽  
Embryo Mortality ◽  
Cytogenetic Abnormalities ◽  
Frozen Embryos ◽  
Fresh Embryos

Early embryo mortality results in significant inefficiency in cattle breeding. A pregnancy rate of 65-70% to a single service, AI or transfer of fresh embryos is considered to be very good indeed. A pregnancy rate of 55-60% using frozen embryos would also be considered very good. Of the 30%, or so, of cattle which do not become pregnant to a single service, approximately one quarter are accounted for by fertilisation failure (Diskin and Sreenan, 1980; Roche et al, 1981) and another quarter by cytogenetic abnormalities in the embryos, which usually occur within the first few days after fertilisation (Hare et al. 1980; Gayerie de Abreu et al, 1984). Failure in the communication between embryo and uterus probably accounts for the remaining 50% of pregnancy loss. Fertilisation failure and early deaths due to cytogenetic abnormalities are by-passed by embryo transfer (ET) so that other causes of loss become rather more significant.

scholarly journals Embryo transfer as an option to improve fertility in repeat breeder dairy cows

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Arkadiusz Nowicki
Keyword(s):  
Dairy Cows ◽  
Pregnancy Rate ◽  
Embryo Transfer ◽  
Oocyte Quality ◽  
Poor Quality ◽  
Early Embryo ◽  
Reproductive Disorder ◽  
Uterine Environment ◽  
Repeat Breeder

Abstract Repeat breeding is a serious reproductive disorder in dairy cattle. The causes of repeat breeding are multifactorial and there are two main mechanisms: failure of fertilisation or early embryo death, mainly due to poor quality of oocytes and an inadequate uterine environment. Many methods have been used to increase the pregnancy rate for repeat breeder cows, such as intrauterine infusion of antibacterial agents or antibiotics, hormonal treatments for oestrus synchronisation and induction of ovulation, and progesterone supplementation or induction of accessory corpus luteum; however, the results were inconsistent between studies. Embryo transfer (ET) has the capability to minimalise the effects of poor oocyte quality and unfavourable uterine environments on early embryo development during the first seven days after ovulation in repeat breeder cows, and several studies showed that ET significantly improved the pregnancy rate in this group of animals. Thus, ET can be considered an option to increase the conception rate in repeat breeder dairy cows.

scholarly journals Live Birth Rate of Fresh Embryo Transfer with GnRH Agonist Long Protocol is Higher Than Frozen Embryo Transfer

2020 ◽  
Author(s):  
Xiaoyan Ding ◽  
Jingwei Yang ◽  
Lan Li ◽  
Na Yang ◽  
Ling Lan ◽  
...  
Keyword(s):  
Pregnancy Rate ◽  
Embryo Transfer ◽  
Live Birth ◽  
Pregnancy Loss ◽  
Birth Rate ◽  
Implantation Rate ◽  
Live Birth Rate ◽  
Clinical Pregnancy ◽  
Fresh Embryo Transfer ◽  
Long Protocol

Abstract Background: Along with progress in embryo cryopreservation, especially in vitrification has made freeze all strategy more acceptable. Some studies found comparable or higher live birth rate with frozen embryo transfer (FET) than with fresh embryo transfer（ET）in gonadotropin releasing hormone antagonist (GnRH-ant) protocol. But there were no reports about live birth rate differences between fresh ET and FET with gonadotropin releasing hormone agonist (GnRH-a) long protocol. The aim of this study is to analyze whether patients benefit from freeze all strategy in GnRH-a protocol from real-world data.Methods: This is a retrospective cohort study, in which women undergoing fresh ET or FET with GnRH-a long protocol at Chongqing Reproductive and Genetics Institute from January 2016 to December 2018 were evaluated. The primary outcome was live birth rate. The secondary outcomes were implantation rate, clinical pregnancy rate, pregnancy loss and ectopic pregnancy rate.Results: A total of 7,814 patients met inclusion criteria, implementing 5,216 fresh ET cycles and 2,598 FET cycles, respectively. The demographic characteristics of the patients were significantly different between two groups, except BMI. After controlling for a broad range of potential confounders (including age, infertility duration, BMI, AMH, no. of oocytes retrieved and no. of available embryos), multivariate logistic regression analysis demonstrated that there was no significant difference in terms of clinical pregnancy rate, ectopic pregnancy rate and pregnancy loss rate between two groups (all P>0.05). However, the implantation rate and live birth rate of fresh ET group were significantly higher than FET group (P<0.001 and P=0.012, respectively).Conclusion: Compared to FET, fresh ET following GnRH-a long protocol could lead to higher implantation rate and live birth rate in infertile patients underwent in vitro fertilization (IVF). The freeze all strategy should be individualized and made with caution especially with GnRH-a long protocol.

97 BOER GOAT OFFSPRING BORN FOLLOWING TRANSFER OF CRYOPRESERVED EMBRYOS

2010 ◽  
Vol 22 (1) ◽  
pp. 207
Author(s):  
K. C. Lehloenya ◽  
J. P. C. Greyling
Keyword(s):  
Survival Rate ◽  
Pregnancy Rate ◽  
Genetic Material ◽  
Embryo Survival ◽  
Boer Goat ◽  
Frozen Embryos ◽  
Group 2 ◽  
The University ◽  
Fresh Embryos ◽  
Cryopreserved Embryos

Cryopreservation of embryos is an important technique in the whole MOET program, which could help improve the transportation of genetic material across South Africa and globally. This trial evaluated the survival rate of goat embryos following transfer with cryopreserved Boer goat embryos. Twenty-seven multiparous Boer goat recipients were synchronized with CIDR for 16 days and injected with 300 IU of eCG at CIDR withdrawal. The recipients were allocated into 3 groups (n = 9). Group 1 received fresh embryos; Group 2 received slow frozen embryos; and Group 3 received vitrified embryos. Expanded blastocysts used were surgically collected from donors superovulated with pFSH on 7 following AI. Two blastocysts were transferred laparoscopically to the uterine horn ipsilateral to functional CL. A pregnancy rate of 85.7% (6) was obtained following the transfer of fresh embryos and tended to be better than in the does receiving slow frozen and vitrified embryos, (n = 4; 50.0% and n = 3; 37.5% does pregnant, respectively) with no significant differences. The kidding rate of the recipient does declined to 57.0% (4) and 25.0% (2) for fresh and slow frozen groups, respectively. The embryo survival rate of 35.7% (n = 5) for fresh, 25.0% (n = 4) for conventional slow freezing and 31.3% (n = 5) for vitrification was obtained and was not affected by the number of CL present on the respective ovaries at the time of embryo transfer. Although the pregnancy rate following the transfer of fresh embryos was satisfactory, the embryo survival rate following the transfer of fresh or cryopreserved embryos tended to be lower. The authors acknowledge the University of the Free State for financial and facility support and National Research Foundation (Thuthuka) for financial support for conducting this trial.

To trigger or not to trigger ovulation in a natural cycle for frozen embryo transfer: a randomized controlled trial

2020 ◽  
Vol 35 (5) ◽  
pp. 1073-1081
Author(s):  
S Mackens ◽  
A Stubbe ◽  
S Santos-Ribeiro ◽  
L Van Landuyt ◽  
A Racca ◽  
...  
Keyword(s):  
Pregnancy Rate ◽  
Embryo Transfer ◽  
Pregnancy Loss ◽  
Controlled Trial ◽  
Frozen Embryo Transfer ◽  
Natural Cycle ◽  
Randomized Controlled ◽  
Biochemical Pregnancy ◽  
Group A ◽  
Group B

Abstract STUDY QUESTION Is the clinical pregnancy rate (CPR) following a frozen embryo transfer (FET) in a natural cycle (NC) higher after spontaneous ovulation than after triggered ovulation [natural cycle frozen embryo transfer (NC-FET) versus modified NC-FET]? SUMMARY ANSWER The CPR did not vary significantly between the two FET preparation protocols. WHAT IS KNOWN ALREADY Although the use of FET is continuously increasing, the most optimal endometrial preparation protocol is still under debate. For transfer in the NC specifically, conflicting results have been reported in terms of the outcome following spontaneous or triggered ovulation. STUDY DESIGN, SIZE, DURATION In a tertiary hospital setting, subjects were randomized with a 1:1 allocation into two groups between January 2014 and January 2019. Patients in group A underwent an NC-FET, while in group B, a modified NC-FET was performed with a subcutaneous hCG injection to trigger ovulation. In neither group was additional luteal phase support administered. All embryos were vitrified-warmed on Day 3 and transferred on Day 4 of embryonic development. The primary outcome was CPR at 7 weeks. All patients were followed further until 10 weeks of gestation when the ongoing pregnancy rate (OPR) was defined by the observation of foetal cardiac activity on ultrasound scan. Other secondary outcomes included biochemical pregnancy rate, early pregnancy loss and the number of visits, blood samples and ultrasonographic examinations prior to FET. PARTICIPANTS/MATERIALS, SETTING, METHODS A total of 260 patients (130 per study arm) were randomized, of whom 12 withdrew consent after study arm allocation. A total of 3 women conceived spontaneously before initiating the study cycle and 16 did not start for personal or medical reasons. Of the 229 actually commencing monitoring for the study FET cycle, 7 patients needed to be switched to a hormonal replacement treatment protocol due to the absence of follicular development, 12 had no embryo available for transfer after warming and 37 had a spontaneous LH surge before the ovulation trigger could be administered, although they were allocated to group B. Given the above, an intention-to-treat (ITT) analysis was performed taking into account 248 patients (125 in group A and 123 in group B), as well as a per protocol (PP) analysis on a subset of 173 patients (110 in group A and 63 in group B). MAIN RESULTS AND THE ROLE OF CHANCE Demographic features were evenly distributed between the study groups, as were the relevant fresh and frozen ET cycle characteristics. According to the ITT analysis, the CPR and OPR in group A (33.6% and 27.2%, respectively) and group B (29.3% and 24.4%, respectively) did not vary significantly [relative risk (RR) 0.87, 95% CI (0.60;1.26), P = 0.46 and RR 0.90, 95% CI (0.59;1.37), P = 0.61, respectively]. Biochemical pregnancy rate and early pregnancy loss were also found to be not statistically significantly different between the groups. In contrast, more clinic visits and blood samplings for cycle monitoring were required in the NC-FET group (4.05 ± 1.39) compared with the modified NC-FET group (3.03 ± 1.16, P = &lt;0.001), while the number of ultrasound scans performed were comparable (1.70 ± 0.88 in group A versus 1.62 ± 1.04 in group B). The additional PP analysis was in line with the ITT results: CPR in group A was 36.4% versus 38.1% in group B [RR 1.05, 95% CI (0.70;1.56), P = 0.82]. LIMITATIONS, REASONS FOR CAUTION The results are limited by the high drop-out rate for the PP analysis in the modified NC-FET group as more than one-third of the subjects allocated to this group ovulated spontaneously before ovulation triggering. Nonetheless, this issue is inherent to routine clinical practice and is an important observation of an event that can only be avoided by performing a very extensive monitoring that limits the practical advantages associated with modified NC-FET. Furthermore, although this is the largest randomized controlled trial (RCT) investigating this specific research question so far, a higher sample size would allow smaller differences in clinical outcome to be detected, since currently they may be left undetected. WIDER IMPLICATIONS OF THE FINDINGS This RCT adds new high-quality evidence to the existing controversial literature concerning the performance of NC-FET versus modified NC-FET. Based on our results showing no statistically significant differences in clinical outcomes between the protocols, the treatment choice may be made according to the patient’s and treating physician’s preferences. However, the modified NC-FET strategy reduces the need for hormonal monitoring and may therefore be considered a more patient-friendly and potentially cost-effective approach. STUDY FUNDING/COMPETING INTEREST(S) No specific funding was available for this study. None of the authors have a conflict of interest to declare with regard to this study. TRIAL REGISTRATION NUMBER NCT02145819. TRIAL REGISTRATION DATE 8 January 2014. DATE OF FIRST PATIENT’S ENROLMENT 21 January 2014.

363 FACTORS INFLUENCING PREGNANCY RATES FOLLOWING TRANSFER OF BOVINE IN VIVO EMBRYOS BIOPSIED FOR SEX DETERMINATION

2007 ◽  
Vol 19 (1) ◽  
pp. 297
Author(s):  
S. Li ◽  
W. Yu ◽  
J. Fu ◽  
Y. Bai ◽  
F. Jin ◽  
...  
Keyword(s):  
Pregnancy Rate ◽  
Embryo Transfer ◽  
Pregnancy Rates ◽  
Chi Square ◽  
Embryo Survival ◽  
Chi Square Test ◽  
First Time ◽  
Fresh Embryos

Data collected from commercial embryo transfer programs in 63 farms in China during June 2002 to December 2005 was analyzed to examine the effects of various factors (biopsy, freezing, sample size, embryo development and quality, in vitro culture, and recipient quality) on pregnancy rates of in vivo-biopsied embryos. Embryos were flushed from superovulated dairy cattle and subjected to a biopsy for sexing determination using protocols and sexing kits supplied by AB Technology Ltd. Fresh embryos were implanted on the same day or frozen with AG freeze medium (AB Technology Ltd., Pullman, WA, USA) for later transfer. Recipients were synchronized with CIDA + PG protocols. Embryos were cultured in 6-well dishes containing 1.3 mL of holding medium (AB Technology Ltd.) in each well at room temperature (20–25�C) for examination of embryo survival in vitro. The chi-square test was used in statistic analysis. The implantation of fresh embryos after biopsy did not affect pregnancy rates (49.6%, 257/518) compared to that of non-biopsied fresh and frozen–thawed embryo groups (52.9%, 47/140 and 46.6%, 177/380, respectively). However, for biopsied embryos subjected to frozen and thawed procedures before implantation, particularly for those subjected to the removal of a larger biopsy, a reduced pregnancy rate was observed (41.8%, 297/710; P &lt; 0.01). Pregnancy rates among biopsied embryos at 3 different development stages (morula-early blastocyst, blastocyst, and expanded blastocyst) were not different. Similar results were found between embryo groups of grade 1 and 2. A significant decrease in pregnancy rate (0/10) was observed with embryos held in vitro for a longer period of time (&gt;5 h), suggesting detrimental effects of in vitro conditions on embryo survival. The highest pregnancy rate (68.0%) was observed in recipients synchronized for the first time before being implanted with biopsied embryos. Significant decreases in such rates were found in recipients synchronized for the second or third times or those with an abortion history at the first or second synchronization-implantation treatment (P &lt; 0.01). Better pregnancy rates (45.6%, 41/90; 46.1%, 76/165; and 45.5%, 5/11) were obtained for recipients implanted with biopsied embryos at Days 7.5, 8.0, and 8.5 post-heat detection, respectively, compared to 16% at Day 7 (3/18, P &lt; 0.05). It is concluded that mechanical treatment (cutting) does not reduce the survival of biopsied embryos; however, cryopreservation reduces their ability to survive in vivo. The analyses also suggest that holding embryos in vitro should not be longer than 5 h unless more favorable in vitro conditions can be provided. To achieve better results of implantation of biopsied embryos, embryo transfer should be performed during 7.5–8.5 days post-estrus, and the healthy recipients synchronized for the first time should be used.

Combined treatment of prednisone and hydroxychloroquine may improve outcomes of frozen embryo transfer in antinuclear antibody-positive patients undergoing IVF/ICSI treatment

Lupus ◽  
2021 ◽  
pp. 096120332110558
Author(s):  
Rui Gao ◽  
Wei Deng ◽  
Cheng Meng ◽  
Kemin Cheng ◽  
Xun Zeng ◽  
...  
Keyword(s):  
Pregnancy Rate ◽  
Embryo Transfer ◽  
Pregnancy Loss ◽  
Loss Rate ◽  
Implantation Rate ◽  
Clinical Pregnancy ◽  
Frozen Embryo Transfer ◽  
Clinical Pregnancy Rate ◽  
High Quality ◽  
Biochemical Pregnancy

Background The influence of anti-nuclear antibody (ANA) on induced ovulation was controversial, and the effect of prednisone plus hydroxychloroquine (HCQ) treatment on frozen embryo transfer outcomes of in-vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) for ANA-positive women was unclear. Methods Fifty ANA-positive women and one-hundred ANA-negative women matched for age and anti-Mullerian hormone (AMH) were included from a Reproductive Medical Central of a University Hospital. Sixty-one oocytes pick-up (OPU) cycles in ANA+ group and one-hundred OPU cycles in ANA− group were compared; 30 frozen embryo transfer cycles without treatment and 66 with prednisone plus HCQ treatment among ANA-positive women were compared. Results There was no statistical difference in number of retrieved oocytes (13.66 ± 7.71 vs 13.72 ± 7.23, p = .445), available embryos (5.23 ± 3.37 vs 5.47 ± 3.26, p = .347), high-quality embryos (3.64 ± 3.25 vs 3.70 ± 3.52, p = .832), and proportion of high-quality embryos (26.5% vs. 26.7%, p = .940). Biochemical pregnancy rate (33.3% vs. 68.2%, p < .05), clinical pregnancy rate (20.0% vs. 50.1%, p < .05), and implantation rate (5.6% vs. 31.8%, p < .05) were lower, and pregnancy loss rate (83.3% vs. 23.1%, p < .05) was higher in patients with treatment than no treatment. Conclusion The influence of ANA on number of retrieved oocytes, available embryos, high-quality embryos, and proration of high-quality embryos was not found. The treatment of prednisone plus HCQ may improve implantation rate, biochemical pregnancy rate, and clinical pregnancy rate, and reduce pregnancy loss rate in frozen embryo transfer outcomes for ANA-positive women.

MOET results from a dispersed hybrid nucleus programme in dairy cattle

1993 ◽  
Vol 57 (03) ◽  
pp. 369-378
Author(s):  
M. M. Lohuis ◽  
C. Smith ◽  
J. C. M. Dekkers
Keyword(s):  
Pregnancy Rate ◽  
Embryo Yield ◽  
Frozen Embryos ◽  
Fresh Frozen ◽  
Selection For ◽  
Selection Intensities ◽  
Practical Field ◽  
Viable Embryo ◽  
Size And Structure ◽  
Fresh Embryos

AbstractA dispersed hybrid MOET nucleus project was implemented in the Canadian dairy industry. Embryo yield, pregnancy rate, and effects of management and selection practices are reported. Repeatability of viable embryo yield was 0.31. Average viable embryo yield was 6.85 (s.e. 5.35) embryos per collection, with average pregnancy rates of 0.58, 0.46 and 0.51 for grade 1 fresh, frozen, and split embryos, respectively. Of the donors selected, 80% produced enough embryos to form a family of at least 15 offspring. Based on observed results, expectations of family size and structure and generation intervals were calculated. Only 10% of completed families are expected to result in less than three milking daughters. Generation interval for sib-tested sires was 58 months of age under practical field conditions, which was shorter by a factor of 0.19 than a traditional progeny test but longer than original theoretical estimates by a factor of 0.32. Realized selection intensities for a total merit index were 2.22 for sires and 3.77 for dams of embryos. Accuracies of selection for sires and dams were 0.93 and 0.73 respectively. To improve the scheme, use of more fresh embryos, embryo splitting and less delay in transferring frozen embryos are recommended.

scholarly journals Fertility outcomes in women after controlled ovarian stimulation with gonadotropin releasing hormone agonist long protocol: fresh versus frozen embryo transfer

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Xiaoyan Ding ◽  
Jingwei Yang ◽  
Lan Li ◽  
Na Yang ◽  
Ling Lan ◽  
...  
Keyword(s):  
Pregnancy Rate ◽  
Embryo Transfer ◽  
Live Birth ◽  
Pregnancy Loss ◽  
Birth Rate ◽  
Implantation Rate ◽  
Live Birth Rate ◽  
Gonadotropin Releasing Hormone ◽  
Releasing Hormone ◽  
Long Protocol

Abstract Background Along with progress in embryo cryopreservation, especially the vitrification, freeze all strategy has become more acceptable than ever. Some studies have found comparable or higher live birth rate with frozen embryo transfer (FET) than with fresh embryo transfer(ET)in gonadotropin releasing hormone antagonist (GnRH-ant) protocol. However from our literature research, there have been no reports about live birth rate comparison between fresh ET and FET with gonadotropin releasing hormone agonist (GnRH-a) long protocol. The aim of this study is to retrospectively investigate whether patients benefit from freeze all strategy in GnRH-a protocol using real-world data. Methods This is a retrospective cohort study, in which women undergoing fresh ET or FET with GnRH-a long protocol at Chongqing Reproductive and Genetics Institute from January 2016 to December 2018 were evaluated. The primary outcome was live birth rate. The secondary outcomes were implantation rate, clinical pregnancy rate, pregnancy loss and ectopic pregnancy rate. Results A total of 7,814 patients met inclusion criteria, implementing 5,216 fresh ET cycles and 2,598 FET cycles, respectively. The demographic characteristics of the patients were significantly different between fresh ET and FET groups, except BMI. After controlling for a broad range of potential confounders including age, infertility duration, BMI, AMH, number of oocytes retrieved and of available embryos, multivariate logistic regression analysis demonstrated that there was no significant difference in clinical pregnancy rate, ectopic pregnancy rate and pregnancy loss rate between two groups (all P > 0.05). However, the implantation rate and live birth rate in fresh ET group were significantly higher than FET group (P < 0.001 and P = 0.012, respectively). Conclusions Under GnRH-a long protocol, compared to FET, fresh ET was associated with higher implantation rate and live birth rate in infertile patients that underwent in vitro fertilization (IVF). The freeze all strategy should be individualized and made with caution especially with GnRH-a long protocol.

scholarly journals Effects of parity and season on pregnancy rates after the transfer of embryos to repeat-breeder Japanese Black beef cattle

2016 ◽  
Vol 59 (1) ◽  
pp. 45-49 ◽  
Author(s):  
T. Ono ◽  
T. Isobe ◽  
Y. Morita ◽  
L. T. K. Do ◽  
F. Tanihara ◽  
...  
Keyword(s):  
Heat Stress ◽  
Beef Cattle ◽  
Embryo Transfer ◽  
Reproductive Performance ◽  
Pregnancy Rates ◽  
Frozen Embryos ◽  
Repeat Breeder ◽  
Fresh Embryos

Abstract. Repeat-breeder (RB) cows are a major source of economic waste due to their decreased fertility. Embryo transfer (ET) is an alternative tool to improve the fertility of RB cows. The aims of the present study were to evaluate the effects of recipient parity and the season on pregnancy rates following ET in RB Japanese Black beef cattle. Embryos were transferred nonsurgically to recipients, consisting of 155 heifers (< 2 years old) and 172 cows (< 8 years old), which were defined as RB cattle. Of the recipients that were presented for ET, 57 recipients received a fresh embryo and 270 recipients received a frozen embryo. There were no differences in the pregnancy rates between cattle that received fresh embryos or frozen embryos. The rates of recipients with pregnancy, abortion, stillbirth, and normal calving were similar between heifers and cows. In cows, the pregnancy rates were lower (P < 0.05) in summer (June to August) than in spring (March to May) and winter (December to February). In heifers, however, there were no differences in the pregnancy rates among the seasons. Our findings indicate that in RB Japanese Black beef cattle, the parity of the recipients does not have an effect on the pregnancy rates following the transfer of fresh and frozen embryos. However, heat stress may affect reproductive performance in RB Japanese Black cows.

145 FACTORS AFFECTING PREGNANCY RATE FOLLOWING TIMED EMBRYO TRANSFER PROGRAM IN CATTLE UNDER FIELD CONDITIONS

2009 ◽  
Vol 21 (1) ◽  
pp. 172 ◽  
Author(s):  
F. N. Scenna ◽  
C. J. Munar ◽  
I. Mujica ◽  
E. Martin ◽  
P. Lafarga ◽  
...  
Keyword(s):  
Pregnancy Rate ◽  
Embryo Transfer ◽  
Embryo Development ◽  
Body Condition ◽  
Body Condition Score ◽  
Uterine Horn ◽  
Field Conditions ◽  
Successful Outcome ◽  
Frozen Embryos ◽  
Condition Score

Hormonal estrus synchronization followed by heat detection of recipient animals is a widely used technique in embryo transfer (ET) programs around the world. However, the successful outcomes of ET rely heavily on appropriate heat detection of recipient animals. Additionally, limited availability of personnel and time to detect heat makes ET impractical at times. Therefore, pregnancy rates (PR) following a timed embryo transfer (TET) program were evaluated taking into account different variables of recipient cows, donor embryos, and season of transfer under field conditions in Argentina. Recipient cows were synchronized utilizing a progesterone (P4) intravaginal device (DIB, Syntex, Argentina) for 7 days. On Day 0 (day of DIB insertion) 2 mg of estradiol benzoate (EB) i.m. was administered and immediately after DIB removal on Day 7, 500 μg of D(+) Cloprostenol i.m. (PG, Ciclase, Syntex), 400 IU of eCG i.m. (Novormon, Syntex) plus 1 mg of cypionate estradiol i.m. (ECP; König, Agentina) were administered to all recipient cows. Fresh (n = 1746) and frozen (n = 2047) beef bovine embryos were nonsurgically transferred into recipient cows on Day 9 after PG. The effects of body condition score (1–9, BCS I: ≤5, n = 804 and BCS II: ≥6, n = 2989), corpus luteum (CL) score (CL1: prominent papilla, n = 932, CL2: small papilla, n = 2028, and CL3: asymmetric, n = 833), location of embryo placement in uterine horn (upper, n = 3566, and lower, n = 227), and type of recipient such as heifer (n = 487), lactating (n = 1010), or dry cows (n = 2296) on PR were evaluated. Additionally, stage of embryo development (4–7), quality (1–3), and season of transfer (spring, summer, fall, and winter) were included in the analysis. Pregnancy rate was confirmed by rectal palpation 60 days after ET. Data were first screened by chi square and then analyzed by Proc Logistic of SAS (SAS Institute Inc., Cary, NC). Overall PR was 54.7%. body condition score, CL, type of recipients, stage of embryo development, and year were not significantly (P > 0.05) associated with PR. As expected, cows that received direct fresh embryos had 1.49 times greater odds of conceiving (odds ratio, OR = 1.49, 95% CI: 1.22 to 1.82) than those receiving frozen embryos. Additionally, cows receiving embryos graded as quality 1 had greater probability to conceive (OR = 1.62, 95% CI: 1.34 to 1.95, or OR = 1.64, 95% CI: 1.25 to 2.21) compared to quality 2 or 3 respectively. Moreover, embryos placed into the upper portion of uterine horn were more likely (OR = 1.48) to conceive than those placed in the lower uterine portion. Regardless of embryos and recipient cow variables analyzed, there was a greater probability for cows to conceive during winter (OR = 1.41, 95% CI: 1.13 to 1.95) as compared with summer. In conclusion, synchronized recipient animals for a TET program resulted in acceptable PR for both fresh and frozen embryos. Results suggested that the quality and location of embryos (upper portion) in uterine horn were the most important variables associated with PR in recipient cows. Therefore, TET is a viable and practical option allowing a successful outcome for many beef operations where availability of personnel is limited.

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