Recipient Parity Research Articles

MOET Efficiency in a Spanish Herd of Japanese Black Heifers and Analysis of Environmental and Metabolic Determinants.

Simple SummaryEmbryo transfer procedures have been widely implemented in bovine all around the world. These techniques help to accelerate the increase in the genetic merit and to keep the level of inbreeding under control, which is especially important in breeds, such as Japanese Black cattle, in areas outside of Japan, where there are scarce individuals and few herds. Our study describes an adequate embryo productivity of Japanese Black heifers under Spanish management and environmental conditions, like that which has been previously reported, demonstrating the adequate adaptation capacity of these animals. No effect on embryo production or quality was found due to plasma metabolic parameters of the donors, suggesting an optimal nutritional and body conditioning of the donors’ herd. Pregnant recipients after embryo transfer showed significantly higher levels of cholesterol-related parameters, glucose, and urea, which may be related to higher availability of nutrients for the future pregnancy. Heat stress at embryo transfer negatively impacted conception rates as expected, while larger parity and ET number corresponded to numerically higher conception rates.Multiple ovulation and embryo transfer (MOET) systems have been intensively implemented in Japanese Black cattle in Japan and to create Japanese Black herds out of these areas. Environmental conditions influence MOET efficiency. Thus, we describe results of 137 in vivo, non-surgical embryo flushings performed between 2016–2020, in a full-blood Japanese Black herd kept in Spain and the possible effects of heat, year, bull, donor genetic value, and metabolic condition. Additionally, 687 embryo transfers were studied for conception rate (CR) and recipient related factors. A total of 71.3% of viable embryos (724/1015) were obtained (5.3 ± 4.34/flushing). Donor metabolites did not affect embryo production (p > 0.1), although metabolite differences were observed over the years, and by flushing order, probably related to the donor age. CR was not affected by embryo type (fresh vs. frozen), recipient breed, and whether suckling or not suckling (p > 0.1). CR decreased significantly with heat (44.3 vs. 49.2%; (p = 0.042)) and numerically increased with recipient parity and ET-number. Pregnant recipients showed significantly higher levels of cholesterol-related metabolites, glucose, and urea (p < 0.05). Therefore, adequate MOET efficiency can be achieved under these conditions, and heat stress should be strongly avoided during Japanese Black embryo transfers. Moreover, recipients’ metabolites are important to achieve pregnancy, being probably related to better nutrient availability during pregnancy.

"Which Factors Affect Pregnancy Until Calving and Pregnancy Loss in Buffalo Recipients of in vitro Produced Embryos?"

In vitro embryo production and embryo transfer (ET) in buffaloes has been developed for decades. However, most studies are focused on the donor or laboratory improvements, and there is a lack of reports regarding the recipients. Therefore, our aim was to investigate factors associated to pregnancy (P/ET), pregnancy loss (PL), and calving rates in buffalo recipients. The studied factors were season, recipient parity, the synchronization protocol, the CL diameter, asynchrony between the embryo and the recipient, the day of the recipient estrous cycle, the embryo (fresh vs. vitrified), the day of embryo development, and the embryo stage. These retrospective data, from a program of in vitro produced embryos, were analyzed by logistic regression, and the odds ratio was also estimated. Two factors were related to P/ET and the calving rate: (1) progesterone associated to estradiol plus eCG protocol for fixed time ET tended to affect positively P/ET on day 30 (41.9 vs. 36.1%, respectively; P = 0.07; AOR = 1.28) and P/ET on day 60 (37.8 vs. 36.1%, respectively; P = 0.09; AOR = 1.08) compared to the Ovsynch protocol; and (2) the CL diameter (≥14.5 mm) at transfer increased P/ET on day 30 (47.4 vs. 32.5%; P < 0.01; AOR = 1.87) and on day 60 (45.3 vs. 27.7%; P < 0.01; AOR = 2.16), and also the calving rate (37.9 vs. 21.7%; P < 0.01; AOR = 2.20). PL was greater when ET was done in the nonbreeding season compared to the breeding season (PL 30–60: 12.8 vs. 0.0%, P = 0.01; AOR > 999.99; PL 60-calving: 26.8 vs. 3.6%, P = 0.03; AOR = 9.90; and PL 30-calving: 36.2 vs. 3.6%, P = 0.01; AOR = 15.30). In conclusion, the data of our study indicated that the synchronization protocol, the CL diameter, and ET during the breeding season impacted the reproductive efficiency of buffalo recipients.

Institutional Innovations and Their Challenges in the Green Climate Fund: Country Ownership, Civil Society Participation and Private Sector Engagement

This article investigates the institutional innovations within the Green Climate Fund (GCF), a new international organization that finances climate mitigation and adaptation in developing countries. In particular, donor–recipient parity in decision making, civil society participation and private sector involvement are explored. The aim of this study is to lay the institutional groundwork for a larger study that will be analyzing the effect of these institutional innovations on the design and result of the fund’s projects. An exploratory qualitative case study approach is used that includes the review of the secondary literature, official sources from the GCF, participant observation and semi-structured interviews. This article concludes that the GCF indeed implemented important institutional innovations that are unique for a major international organization. At the same time, this article reveals that these innovations have created some important challenges for the functioning of the fund. For example, donor–recipient parity, in combination with consensus orientation, initially led to gridlock. It is also difficult for the GCF to balance the goal of transparency and civil society participation with the need for secrecy of private contracts and a speedy process demanded by the private sector.

Oocyte donor age has a significant impact on oocyte recipients' cumulative live-birth rate: a population-based cohort study

To study the impact of the donor's and recipient's age on the cumulative live-birth rate (CLBR) in oocyte donation cycles. A population-based retrospective cohort study. Not applicable. All women using donated oocytes (n = 1,490) in Victoria, Australia, between 2009 and2015. None. The association between the donor's and recipient's age and CLBR modeled by multivariate Cox proportional hazard regression with the covariates of male partner's age, recipient parity, and cause of infertility adjusted for, and donor age grouped as <30, 30-34, 35-37, 38-40, and ≥41years, and recipient age as <35, 35-37, 38-40, 41-42, 43-44, and ≥45years. The mean age of the oocyte donors was 33.7years (range: 21 to 45years) with 49% aged 35years and over. The mean age of the oocyte recipients was 41.4years (range: 19 to 53years) with 25.4% aged ≥45years. There was a statistically significant relationship between the donor's age and the CLBR. The CLBR for recipients with donors aged <30years and 30-34years was 44.7% and 43.3%, respectively. This decreased to 33.6% in donors aged 35-37years, 22.6% in donors aged 38-40years, and 5.1% in donors aged ≥41years. Compared with recipients with donors aged <30years, the recipients with donors aged 38-40years had 40% less chance of achieving a live birth (adjusted hazard ratio 0.60; 95% CI, 0.43-0.86) and recipients with donors aged ≥41years had 86% less chance of achieving a live birth (adjusted hazard ratio 0.14; 95% CI, 0.04-0.44). The multivariate analysis showed no statistically significant effect of the recipient's age on CLBR. We have demonstrated that the age of the oocyte donor is critical to the CLBR and is independent of the recipient woman's age. Recipients using oocytes from donors aged ≥35years had a statistically significantly lower CLBR when compared with recipients using oocytes from donors aged <35years.

100 FACTORS AFFECTING PREGNANCY RATES IN THE TRANSFER OF IN VITRO-PRODUCED JAPANESE BLACK CATTLE EMBRYOS

Despite the rapid expansion of in vitro embryo production (IVP) technology for genetic improvement in the cattle industry in the last decades, pregnancy rates by the transfer of IVP embryos are still lower than those derived from in vivo-produced embryos. The objective of this study was to analyse factors affecting pregnancy rates after the transfer of IVP Japanese Black cattle embryos under farm conditions. Holstein heifers (n = 4,475) and cows (n = 8,541) were selected as recipients. Most cows (80%) were managed in tie-stall barns and most heifers (80%) were managed in pens. Embryo transfers were performed for 9 years, from 2004 to 2012. The embryos were produced from oocytes derived from a local abattoir and semen from 14 proven bulls by the Livestock Improvement Association of Japan (Hamano and Kuwayama 1993 Theriogelogy 39, 703–712). The fresh IVP embryos (quality; IETS code 1) that reached the blastocyst stage after 7 to 8 days (insemination = Day 0) were transported by an airplane (2 h) and subsequently by a car (1.5 h). Embryos were non-surgically transferred to each recipient on Day 7 to 9 of their natural oestrous cycle on farms. Pregnancy was diagnosed on Day 40 to 60 after oestrus. Pregnancy results were statistically analysed using the GLM procedures of SAS. The following variables were included in the model: recipient parity (0, 1, 2, or 3), day (7, 8, or 9) of the oestrous cycle at the time of embryo transfer, oestrus behaviour (increased activity observed by farmers), presence of mucus at oestrus, presence of blood after oestrus, and year (1, 2, 3, 4, 5, 6, 7, 8, or 9) and season (April–June as spring, July–September as summer, October–December as fall, or January–March as winter) of embryo transfer. The Bonferroni correction was used to counteract the problem of multiple comparisons. Heifers had significantly higher pregnancy rates than cows (51.0% v. 37.9%, respectively; P &lt; 0.01), and first parity cows had higher pregnancy rates than third parity cows (42.9% v. 35.7%, respectively; P &lt; 0.01). Pregnancy rates were significantly higher in recipients that received an embryo transfer on Day 8 of their oestrous cycle, than on Day 7 (46.6% v. 42.4%, respectively; P &lt; 0.01). Recipients without oestrus behaviour had higher pregnancy rates than those with oestrus behaviour (46.3% v. 43.4%, respectively; P &lt; 0.01). The presence of mucus and/or blood after oestrus and the season of transfer were not found to significantly affect pregnancy rates. The results of this study indicated that performing IVP embryo transfers on Day 8 of a recipient’s oestrous cycle will improve the pregnancy rate, season does not have an effect on pregnancy rate, and the detection of oestrus by monitoring increased activity is not always reliable and instead should be determined by multiple symptoms on farm conditions.

Factors affecting the success of a large embryo transfer program in Holstein cattle in a commercial herd in the southeast region of the United States

The objectives of this study were to evaluate factors affecting in vivo embryo production and pregnancy per embryo transfer (P/ET) in Holstein cattle in the southeast region of the United States. Data from a total of 516 embryo collections and 10,297 ETs performed from 2011 to 2014 were available. For embryo production, the effects of donor parity (nulliparous [N], primiparous [P], multiparous [M]), average temperature-humidity index (THI) at embryo collection, days in milk at embryo collection, occurrence of calving problems, and occurrence of metritis postpartum were evaluated. For P/ET, the effects of donor parity (N or parous), recipient parity (N, P, and M), embryo type (fresh, frozen, IVF, and IVF-frozen), embryo developmental stage (4–7), embryo quality (1–3), recipient estrous cycle day at ET (6–9), average THI at ET, days in milk at ET, milk yield at ET, occurrence of calving problems (abortion, dystocia, twins, fetal death, or retained placenta), and occurrence of metritis postpartum were evaluated. Pregnancy was diagnosed at 41 ± 3 days of gestation. Continuous and binary data were analyzed using the MIXED and GLIMMIX procedures of SAS, respectively. Parity affected embryo production; M had greater number and percentage of unfertilized embryos and lesser percentage of viable embryos than P and N. Recipient parity, embryo type, embryo stage, embryo quality, estrous cycle day at ET, and THI at ET affected P/ET. There was an interaction between recipient parity and THI at ET. P/ET was greater for N than P and greater for P than M, greater for fresh embryos than others, greater for stage 7 than others, greater for quality 1 than 2 and greater for quality 2 than 3, and greater for ET on estrous cycle Day 7 and 8 than 6. P/ET was decreased for THI ≥80 in N and THI ≥72 in P and M. Calving problems and metritis also affected P/ET in P and M and was lesser for cows that had calving problems and metritis. In conclusion, embryo production was affected by donor parity, and P/ET was affected by embryo type, embryo stage, embryo quality, recipient estrous cycle day at ET, THI, calving problems, and metritis.

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

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 (&lt; 2 years old) and 172 cows (&lt; 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 &lt; 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.

Impact of Donor and Recipient Sex and Parity on Outcomes of HLA-Identical Sibling Allogeneic Hematopoietic Stem Cell Transplantation

Allogeneic hematopoietic stem cell transplantation (SCT) may cure patients with hematologic malignancies, but it carries significant risks. Careful donor selection is an important component of the clinical transplantation decision-making process and includes evaluation of HLA typing and other criteria, the most controversial of which is parity. We examined the effect of donor sex and parity on outcomes of HLA-identical sibling SCT. Because the effect of recipient sex/parity has never been explicitly evaluated, we also analyzed the effect of recipient sex/parity on outcomes of transplantation. We found that (1) parous female donors result in an increased risk of chronic graft-versus-host disease (GVHD) in all recipients, (2) the magnitude of this increased risk is similar in male and female recipients, and (3) nulliparous female donors increase the risk of chronic GVHD in male recipients to a degree comparable to that from parous donors. A decrease in the risk of relapse was not observed, and there was no effect on overall survival, acute GVHD, or transplant-related mortality. Recipient parity had no independent effect on any endpoint. Until the effects of pregnancy on the maternal immune system are better understood, it is appropriate whenever possible to avoid parous female donors and to choose male donors for male recipients in HLA-identical related donor SCT.

290 THE FACTORS ON RATES OF ABNORMALITY, DISEASE AND MORTALITY OF CALVES DERIVED FROM IN VITRO EMBRYOS OF KOREAN NATIVE CATTLE

In Korea, in vitro production and transfer of bovine embryos has advanced remarkably and applied commercially. However, in vitro-produced embryos result in lower pregnancy and higher abortion rates and in some cases increased rates of abnormality and mortality in calves. The present study was conducted to investigate the effects of various factors such as recipient parity, delivery season, offspring number, pregnancy period, delivery type, midwifery type, dystocia and vaccination, on the viability of calves derived from embryos produced in vitro. Korean Native Cow ovaries were obtained from local slaughterhouse and cumulus-oocyte complexes (COCs) were aspirated from 2 to 8 mm follicles. Selected COCs were matured in TCM-199 supplemented with 10% fetal calf serum (FBS), 1 �ML FSH, 10 �ML LH and 1 �ML Estradiol-17� for 20-22 h. In vitro-matured oocytes were fertilized using frozen-thawed percoll separated semen (Day 0) in fer-TALP medium for 20 h. The presumptive zygotes were cultured in CR1aa medium supplemented with 0.3% BSA (before Day 3) or 10%FBS (After Day 3). All types of cultures were made in an incubator at 38.5�, 5% CO2 in air. Statistical analysis was performed using the Chi-square test. Two blastocysts were transferred to the Holstein recipients (n = 1888). The parturition was occurred in total 755 recipients. There was no difference in the abnormality of calves among treatments. The incidence of disease was significantly higher in single calf than twin calves (18.4 vs. 6.7%), in multiparous than nulliparous group (40.0 vs. 9.9%), in eutocia than dystocia group (20.0 vs. 4.8%), in spring and winter groups than summer and autumn groups (20.3, 22.7 vs. 4.3, 0.0%), and in non-vaccinated than vaccinated group (22.7 vs. 1.6%), respectively (p &lt; 0.05). The rate of mortality was significantly higher when transferred into nulliparous than multiparous (22.3 vs. 0.0%), when were dystocia than eutocia group (71.4 vs. 14.1%), when were non-midwifery than midwifery (45.0 vs. 13.6), when delayed midwifery than earlier midwifery (31.6 vs. 11.5%), and when were non-vaccinated than vaccinated group (28.0 vs. 9.8%), respectively (P &lt; 0.05). The present study suggested that the viability of bovine calves derived from in vitro was affected by the recipient parity, parturition treatment technique and vaccination. This study was supported by the BIO-GREEN 21 PROGRAM.

291 VARIOUS FACTORS INFLUENCING PREGNANCY RATES AND CALVING CHARACTERISTICS FOLLOWING TRANSFER OF OPU-IVP EMBRYOS PRODUCED IN A COMMERCIAL SYSTEM

OPU-IVP is nowadays an assisted reproduction technique in which output for each step is variable. The aim of this work was to identify factors influencing calving rate and calf characteristics through a retrospective study conducted from 356 OPU sessions and 137 pregnancies on a farm. Donor females were stimulated with FSH in five decreasing doses (400 �g for cows and 250 �g for heifers). Collected oocytes were matured for 24 h in M199 plus fetal calf serum, FSH, epidermal growth factor (EGF), and estradiol. They were then fertilized in TALP with frozen-thawed semen and zygotes were cultured for 6 days on Vero cell monolayers in B2 medium. Embryos were transferred as fresh to recipients on Day 7; 137 pregnancies were followed up to calving. Gestation length, calving conditions and calf characteristics (sex and birth weight assessed by farmers) were recorded and compared to national standards (UPRAs data). The mean number of collected oocytes per session was 14; 11.6 were selected for IVM, 8.5 cleaved, and 3.9 developed to the blastocyst stage (40.4% of the embryos were Grade 1, 35.3% G2, and 20.5% G3). On average, 2.9 embryos were transferred into recipients, leading to an average of 1.6 pregnancies on Day 35 and 1.4 on Day 90 (76% of recipients were heifers). Pregnancy rates were higher in heifers than in cows (54.5% vs. 47.8%; P &lt; 0.05). Pregnancies led to birth of a healthy calf in 81.9% of the OPU sessions (1.1 per session), the 18.1% losses being divided between 4.4% abortion (n = 6) and 13.7% perinatal mortality (n = 18). Gestation length from IVF pregnancies was longer than in national breeds standards (trial = 291 vs. national = 287 days). Moreover, 10% of calvings were induced. Calving conditions were mainly dependent on age of recipients: 70% of the heifers were assisted compared to 40.9% of the cows. No effect of gestation length or sex of calf was observed on calving difficulties. Sex ratio did not deviate in calves produced by OPU-IVF (52.3% of males and 47.7% of females). However, it was influenced by embryo quality, with the proportion of males decreasing from 56.3% to 44.4% for G1 to G3 embryos. The mean weight of healthy calves issued from IVP embryos averaged 47.1 kg � 10.1 and was not significantly higher than the national breed standards. The deviation (kg) from national breeds standards ranged from -20 kg to 0 in 68.8% (n = 90), from 1 to 15 kg in 16.0% (n = 29), and greater than 15 kg in 9.2% (n = 12) of the calves. Even if the mean deviation was not significant, those 12 calves in the &gt;15 kg group should be considered as large. However, they were issued from two different donor females, so that this effect could also be attributed to a mother effect. To conclude, the effect of recipient parity on pregnancy rates was confirmed. The OPU-IVP system used in this trial did not seem to influence significantly sex ratio and weight of calves. Further studies are needed to investigate the sources of variation of gestation length.

191 INFLUENCE OF THE DIFFERENT TIME COMPONENTS BETWEEN FLUSHING AND TRANSFER ON PREGNANCY RATES OF FROZEN CATTLE EMBRYOS

Previous studies have shown that the time between flushing and freezing of bovine embryos can influence pregnancy rates (PRs) following embryo transfer (ET). The aim of this study was to determine which time components can influence ET results. Time components between flushing of a superovulated donor and freezing of the collected embryos were investigated under field conditions. Embryos were frozen in 1.5 M ethylene glycol (EG) for direct transfer. During January 2003, ET technicians (EmbryoTop, Rennes cedex, France) recorded systematically times corresponding to each step comprising the time spent in vitro (TIV) from 153 recovery sessions (RS) with freezing: end of flushing, beginning and end of search of embryos, start of equilibration in EG, beginning and end of straw loading, introduction to −7°C in the freezer, and seeding. Numbers of donor cows and ET technicians doing the freezing (n = 5) were noted for each RS. Embryo (stage, quality) and recipient (breed, parity) characteristics were also noted. A total of 548 frozen embryos were transferred and PRs were assessed. Variability of time components was investigated (Bourgoin et al. 2004 Reprod. Fertil. Dev. 16, 207). The influence of time components and other variation factors was tested on PRs (t-tests and chi-square analysis). The TIV averaged 210 ± 80 min and did not influence PR (≤4 h = 51.9% (n = 393) vs. &gt;4 h = 55.5% (n = 155); P &gt; 0.05), as well as duration of flushing (32 ± 8 min), interval between end of flushing and search (31 ± 27 min), duration of search (45 ± 25 min) and interval between end of search and beginning of freezing (101 ± 63 min). Only significant factors were kept for further analysis. The effects of recipient parity, number of donor cows per RS, and interval between introduction of straw to −7°C, and seeding were tested in a multivariate logistic model. PR varied strongly with parity of recipient (+25% in heifers vs. cows; P = 0.001). PRs were higher when the interval between straw introduction in the freezer and seeding lasted at least 5 min (2–4 min = 48.0% (n = 254) vs. 5–8 min = 57.1% (n = 294); P = 0.009). Time and operator effects were confounded. Overall PR results for the two technicians who used mostly 2–4 min intervals averaged 47% (operator values = 35.6, 48.9, and 54.5) whereas PRs were 54.9 and 60.5% for those waiting 5 min or more before inducing seeding (n = 2). PRs were higher when at least two donor cows were collected per RS (1 donor cow = 49% (n = 259) vs. ≥2 donor cows = 56.4% (n = 289); P = 0.003). This was not in agreement with previous observations in fresh embryos (Bourgoin et al. 2004). However, the number of donor cows strongly influenced the number of viable embryos per RS (1 donor cow = 11 ± 5 vs. ≥2 donor cows = 18 ± 8.5; P &lt; 0.05) and could permit the choice of more embryos to be frozen. These results show that good PR may be achieved with a delay of several hours between flushing and freezing, when heifers are used as recipients. Moreover, confirmed from higher numbers of operators, these data show that it is better to wait at least 5 min to achieve equilibration of the embryo before seeding.

Impact of Prior Pregnancy on Outcomes of Allogeneic Hematopoietic Stem Cell Transplantation.

Allogeneic hematopoietic stem cell transplantation (HSCT) can cure adults with hematologic malignancies, but results in significant morbidity and mortality. Graft-vs.-host disease (GVHD) is a major complication; attempts to reduce the risk of GVHD include selecting donors based on several characteristics, including parity, a criterion which has been controversial. This retrospective cohort study using data from the Center for International Blood and Marrow Transplant Research (CIBMTR) is the first multi-center analysis of the effects of donor and recipient parity on outcomes of HSCT in the modern transplant era.Methods: We studied patients at least 18 years old who received a non-T-cell-depleted, myeloablative HLA-identical sibling HSCT between 1995 and 1999, for acute lymphoblastic or myelogenous leukemia or chronic myelogenous leukemia. The study endpoints included acute and chronic GVHD, overall survival, and relapse. There were 2,626 patients who met inclusion criteria and had complete information on both donor and recipient pregnancy status. Donors and recipients were categorized as: males, nulliparous females, or parous (one or more pregnancies) females.Analysis: We compared all possible combinations of donor and recipient pregnancy status (9 groups in total); the reference group was male donor/male recipient pairs. Multivariate Cox proportional hazards regression was used to adjust for other prognostic factors. Because multiple groups were compared, significant p-values were considered to be less than or equal to 0.006.Results: After controlling for important patient-, disease-, and transplant-related covariates, the risk of chronic GVHD was significantly increased in parous female donor/male recipient pairs (HR 1.56, 95% CI 1.23 – 1.94, p < 0.0001). Neither donor nor recipient parity had an impact on overall survival, acute GVHD, or relapse risk.Conclusions: This multi-center retrospective registry study showed that parous female donors resulted in a significantly increased risk of chronic GVHD in male recipients, but without concomitant reduction in relapse. Thus, H-Y antigens may be important targets of GVHD, but not of a graft-versus-leukemia effect. As when selecting unrelated donors, avoidance of parous female donors, particularly for male patients, in HLA-identical sibling transplants is recommended when possible.

170INFLUENCE OF FACTORS ASSOCIATED WITH EMBRYO RECOVERY AND POLICY OF TRANSFER ON PREGNANCY RATES AFTER TRANSFER OF BOVINE FRESH EMBRYOS

Success of embryo transfer (ET) is related to many well identified factors such as quality and stage of embryos, or parity of recipients. However, there are no data on the effects of factors associated with embryo recovery and ET policy (proportion of embryos transferred as fresh or frozen) on pregnancy rates (PR) after ET. A retrospective study was designed to study how these factors affect PR achieved with fresh embryos (FE). A total of 3380 embryo recovery sessions (RS) realized by Embryotop (France) between 1995 and 2002 were studied, corresponding to 14,755 transfers with FE. Forty-four RS were made with only frozen embryos and removed from data set. A total of 1716 RS involved transfer from both frozen and FE, whereas in 1620 RS all transfers were made with FE. The organization of RS was assessed by the number of operators (OP) per RS and per donor cow, the number of embryos collected per RS and per OP. The operator at RS and ET was also noted. Embryo characteristics such as stage and quality (according to IETS criteria), paternal origin, and breed of donor cow were recorded together with the breed, date of ET and parity of recipients. The association between each variable and PR was analyzed by Chi-square. Only the significant factors were considered for further analysis (P&amp;lt;0.05) and introduced with a stepwise procedure in a multivariate model of logistic regression to calculate adjusted odds ratio (OR). The number of RS was stable among years (463 to 493), whereas the number of embryos collected increased by 10% from 1995 to 2002. For 681 RS (20.4%), more than one donor cow were used for collection. Mean number of donor cows per RS and OP increased from 1.16 in 1995 to 1.34 in 2002. The mean number of transfers of FE per RS and OP was quite stable (3.82 in 1995 to 4.16 in 2002). This was explained by the increase in the number of frozen embryos per OP, averaging 1.99 in 1995 and 4.14 in 2002. The proportion of RS with only transfers of FE decreased by 20 points from 1995 (57%) to 2002 (36%). The number of transfers of FE per RS and OP was highly variable, ranging from 0 to 26. PR with FE averaged 52.1% and were significantly influenced by the number of donor cows per OP, operator of RS, embryo quality and paternal origin as well as recipient parity. Transfer of FE collected in RS with one donor cow resulted in higher PR than when more than one cow (53.0% v. 49.9%, OR=1.12, P=0.003). This could be partly explained by a higher mean number of transfers per RS and OP (1 donor cow=3.7±2.0 v.&amp;gt;1=5.3±3.1; P&amp;lt;0.05) as well as a higher proportion of RS with only FE transferred (1 donor cow=51.2% v.&amp;gt;1=38.5% ; P&amp;lt;0.05). Although the embryo quality was lower in RS combining ET of both frozen and FE than when only FE were transferred, these effects were not related to the lower quality of FE used in RS involving more than 1 donor cow (1 donor cow=1.74±0.50 v.&amp;gt;1=1.75±0.44; P&amp;gt;0.05), but may be explained by a longer time between embryo recovery and ET. After adjustment for the usually well identified sources of variation of PR, the conditions of RS as well as ET policy (leading to the selection of the best embryos for transfer as frozen and to influence on the quantity of work per OP) can significantly influence PR. These sources of variation should be taken into account when analyzing PR results.

168FACTORS AFFECTING ON EMBRYO TRANSFER PREGNANCY RATES OF IN VITRO-PRODUCED BOVINE EMBRYOS

The objective of this study was to analyze factors affecting the pregnancy rates after transfer of IVF-derived Japanese Black embryos. Holstein cows and heifers (n=7250) were selected as recipients, and embryo transfers were performed for 3yr (between 1998 and 2000). The IVM-IVF procedure was performed according to a method previously described (Hamano S and Kuwayama M 1993 Theriogenology 39, 703–712). IVF-derived embryos that developed into expanded blastocysts (grade 1, manual of IETS) after 7 to 8 days (insemination=Day 0) were used for this study. Some of these embryos were frozen in TCM-199 supplemented with 1.4M glycerol, 20% calf serum, and 0.25M sucrose. The embryos were seeded at −6°C, held at −6°C for 10min, and then cooled to −25°C at a rate of 0.33°Cmin−1. Frozen embryos were thawed in a 30 to 35°C water bath after 10s of air thawing. Fresh (n=3952) or frozen-thawed (n=3298) embryos were nonsurgically transferred to recipients on Days 6 to 9 of the estrous cycle. Data collected at the time of embryo transfer included recipient parity (cow or heifer), whether recipient estrus was natural or synchronized with PGF2α, cloprostenol or CIDR, methods of estrous confirmation (showing standing heat, rectal palpation of ovary without standing heat, or showing only mucous vulvular discharge), number of examinations of the CL by palpation per rectum (twice on the day before embryo transfer and the day of embryo transfer, or once on the day of embryo transfer), type of embryos (fresh or frozen), and day of the estrous cycle at the time of embryo transfer. CATMOD procedures of SAS were used to determine the factors affecting the pregnancy rate. Overall pregnancy rates were 37.3% (n=2704). Whether recipient estrus was natural or synchronized and the type of embryos did not influence the pregnancy rates. Heifers had significantly higher pregnancy rates than cows (44.0% v. 33.0%, respectively, P&amp;lt;0.05). Pregnancy rates among the subset of heifers and cows showing standing heat were significantly higher than those showing only mucous vulvular discharge (39.5% v. 33.5%, respectively, P&amp;lt;0.05). Examining the CL twive had a significantly higher pregnancy rate than did a single examination of the CL (41.1% v. 35.6%, respectively, P&amp;lt;0.05). Pregnancy rate on Day 8 (38.4%, 1358/3533) of the estrous cycle at the time of embryo transfer was significantly higher than on Days 6 (27.7%, 23/83) and 7 (36.2%, 1235/3408) (P&amp;lt;0.05), and the pregnancy rate on Day 6 of the estrous cycle at the time of embryo transfer tended to be lower than on Day 9 (38.9%, 88/226) (P&amp;lt;0.08). These results demonstrate that confirming standing heat, performing CL examination twice before embryo transfer, freezing high quality embryos, and performing embryo transfers on Day 8 resulted in an improved pregnancy rate for the transfer of IVF-derived embryos.