Day of embryo collection, quality and pregnancy rates in cattle

In 1300 donor cows, total embryos increased from 8.5 to 15.3, (P less than 0.001), the mean number of transferable embryos from 3.1 to 6.5 (P = 0.067) and pregnancies increased from 1.3 to 3.3 (P = 0.584) as the day of collection increased from six to 7.5. Most of the embryos recovered on day 6, 7.5 and 8 were morulae, early blastocysts and late blastocysts respectively. Morulae formed the majority of the embryos collected on days 6 and 6.5. Pregnancy rates in early and late blastocysts were highest on days 7 (54.4 and 60.2 per cent) and 7.5 (53.6 and 53.1 per cent, P = 0.009 and 0.004). There were significant differences in pregnancy rates between embryo stages on days 7 and 7.5 (P less than 0.001), embryo grades on days 7, 7.5 and 8 (P less than 0.001), and within embryo grades 1 (P = 0.015) and 3 and 4 (pooled, P = 0.009). On all days combined there were significant differences in pregnancy rates between both embryo stages (P = 0.007) and embryo grades (P less than 0.001). It appears that the concept of embryo fitness may be applied to blastocysts but not to morulae.     

Effect of oestrous synchrony between embryo donors and recipients,embryo quality and state on the pregnancy rate in beef cattle

This study aimed to evaluate the effect of oestrous synchrony between donors and recipients and the embryo quality on the pregnancy rate in beef cow recipients. The experiment was performed over two years at an embryo transfer (ET ) centre in Southern Brazil. Ninety Aberdeen Angus cows were subjected to superovulation (SOV ) protocols, resulting in the recovery of 1,048 transferable embryos. Eleven groups were formed with intervals of 6 hr, from ?30 to +30 hr, with respect to recipient versus donor oestrous detection. Evaluation of embryo quality was according to the IETS guidelines. The overall pregnancy rate was 52%. Effects related to donor and recipient oestrous synchronization on pregnancy rate were observed (p  =  .01), ranging from 36% to 50%. The embryo quality rate affected the pregnancy rate, where Grade I resulted in 57% and Grade III in 43% of pregnancy (p  <  .001). The embryonic state (frozen or fresh) showed no (p  >  .05) effect on pregnancy rate: 53% for fresh embryos and 44% for frozen embryos. The odds ratio for explanatory variables causing pregnancy indicated that Grade III embryos had 31% less chance of conception compared to Grade I. Thus, oestrous synchrony between donor and recipient, considering ±30 hr apart, can affect the pregnancy rate along with embryo quality.     

胚胎质量和发育阶段对奶牛胚胎移植妊娠率的影响

[目的]为了评估胚胎质量和发育阶段对奶牛胚胎移植妊娠率的影响。[方法]使用63头青年奶牛作为供体进行超数排卵,评估回收胚胎质量和发育阶段。选择334头青年奶牛作为受体鲜胚移植不同质量和发育阶段胚胎。对胚胎质量分布、发育阶段分布、不同质量胚胎和不同发育阶段胚胎移植30 d妊娠率进行统计分析。[结果]可用胚胎中A级胚胎比例(60.78%)显著高于B级和C级胚胎比例(36.70%和2.52%)(P<0.05);致密桑椹胚比例(54.36%)显著高于早期囊胚,囊胚和扩张囊胚比例(18.35%,25.0%和2.29%)(P<0.05)。A级和B级胚胎移植30 d妊娠率(63.55%和64.35%)显著高于C级胚胎移植30 d妊娠率(44.44%)(P<0.05);致密桑椹胚、早期囊胚、囊胚和扩张囊胚移植30 d妊娠率差异不显著(P<0.05),早期囊胚、囊胚移植30 d妊娠率高于致密桑椹胚、扩张囊胚移植30 d妊娠率(P<0.05)。[结论]选择不同发育阶段的A级和B级胚胎能够获得较高胚胎移植妊娠率,增加早期囊胚和囊胚阶段胚胎移植数量能够提高胚胎移植妊娠率。     

Transfer of Bovine Blastocysts Derived from Short-term In Vitro Culture of Low Quality Morulae Produced In Vivo

The aim of this study was to evaluate if blastocysts arising from in vitro culture of Grade 3 bovine morulae produced in vivo can promote acceptable pregnancy rates when transferred into recipients. Embryos of different stages and qualities were recovered from superovulated Bos taurus and B. indicus donors. Grade 3 morulae were cultured in either Holding Plus® or TCM‐199 (supplemented with 10% bovine fetal serum) media for 24 h at 38.5°C. After this culture period, the resulting blastocysts were morphologically classified (Grades 1, 2 and 3) and transferred into recipients previously synchronized with the donors. Non‐cultured Grades 1 and 3 morulae were used as control. Pregnancy diagnosis was carried out 60 days after embryo transfer and the data were analysed by logistic regression, considering variables, such as embryo quality (Grade), donor breed, culture medium, donor‐recipient synchrony and seasonality. Embryo quality was the only variable, showing significant effect on the pregnancy rate. Pregnancy rates for non‐cultured Grade 1 and 3 morulae, and blastocysts arising from cultured Grade 3 morulae were 58.1% (n = 31), 17.1% (n = 35) and 51.1% (n = 47), respectively (p < 0.05). There were no statistical differences between non‐cultured Grade 1 morulae and cultured blastocysts. Pregnancy rates for Grades 1 (65.0%) and 2 (60.0%) were higher than Grade 3 (29.4%) cultured blastocysts (p < 0.05). It was concluded that short‐term in vitro culture is a very convenient method of identifying morphologically low quality morulae with higher chances of continuing development after the transfer into recipients.     

Asynchronous Embryo Transfer in Sheep:Lack of Survival in Progestinized Recipient Ewes

Synchronization of development between the embryo and uterus is required for successful pregnancy establishment.Transfer of early embryos requires synchrony with the recipient uterus of 2 days or less in sheep,because asynchrony of 3 days or more results in failure of pregnancy recognition signaling for maintenance of corpus luteum (CL) and progesterone (P4) production and/or uterine support of the embryo.The objective was to determine if P4 treatment of recipient ewes would obviate the need for pregnancy recognition signaling and maintain a uterine environment conducive to embryo survival after asynchronous transfer,thereby establishing a universal recipient.Embryos (morulae/blastocysts) were recovered on day 6 from super-ovulated donor ewes.Recipient ewes received 25 mg P4 daily from day 6 post-estrus until 60 days after embryo transfer.Embryos were transferred into recipients on day 6,9,12,18,or 30 post-estrus.The pregnancy rate on day 22 post-transfer was 60% for synchronous transfers to day 6 ewes,44% and 22% for asynchronous transfers to day 9 and 12 ewes,and 0% for asynchronous transfers to day 18 and 30 ewes.On day 39 post-transfer,pregnancy rates remained 60% for day 6 ewes,33% for day 9 ewes,and 0% for day 12,18,and 30 ewes.The P4 treatment did extend the window of uterine receptivity to early embryos in ewes by one day,but did not create a universal recipient.Available results support the idea that a window of uterine receptivity to the conceptus exists in sheep that is independent of pregnancy recognition signaling.     

Embryo collection in prepubertal gilts and attempts to develop an improved embryo transfer technique

Prepubertal gilts were treated with 1,500 iu equine chorionic gonadotrophin, followed 72 hours later by 500 iu human chorionic gonadotrophin (hCG), and inseminated 36 and 48 hours later. Embryos were collected at slaughter 168 hours after the hCG treatment. Blastocysts classified as 'good' or 'fair' were transferred to synchronised recipients, either by conventional surgical means or by a 'semi-endoscopic' approach, and the recipients were slaughtered four weeks later. Of 238 donor gilts, 98.4 per cent had responded with a mean (se) 23.5 (1.0) ovulations and 19.1 (1.0) ova or embryos, of which 47 per cent were considered morphologically intact and transferable. The large proportion of non-transferable embryos was not associated with the age or weight of the gilts, the season or with their housing conditions. Conventional surgical transfer of 15 to 20 (mean 17.4) blastocysts to synchronised recipients yielded 88 percent (14 of 16) pregnancies with between seven and 14 (mean 8.2) viable fetuses, and an embryo survival rate of 47 per cent in the pregnant recipients and 41 per cent in all the recipients. The corresponding data for the semi-endoscopic transfers were 16 to 20 (mean 17.7) blastocysts transferred, 47 per cent (eight of 17) pregnancies, four to 12 (mean 7.3) viable fetuses per pregnant recipient and an embryo survival rate of 41 per cent in the pregnant recipients and 19 per cent in all the recipients. Significantly fewer of these recipients became pregnant and a significantly smaller proportion of the embryos survived (P<0.05).     

Techniques and success of embryo transfers in Angora goats

Thirty-five mixed-age Angora does were subjected to superovulation and oestrous synchronization and of the 34 which were subsequently entire mated, 33 were subjected to surgical egg recovery approximately five days after oestrus. These 33 donors averaged 8.8 ovulations and 2.5 large (>5 mm) follicles. All corpora lutea in six donors were undergoing premature regression. The average donor egg recovery rate, egg fertilization rate and percent of eggs transferable was 82, 87 and 81%, respectively, giving 6.8 eggs, 6.0 embryos and 5.5 transferable embryos per donor. Egg recovery was reduced dramatically when premature regressing corpora lutea were present. Recipient feral does were synchronized and 183 embryos transferred surgically to 133 recipients.

Eighty-eight (66%) of the recipients kidded producing 118 kids (64% embryo survival). The 35 potential donors produced 36 kids from their natural mating which occurred shortly after surgery. Thus the donors produced a total of 154 kids from embryo transfer and natural mating, an average of 4.4 kids/doe/breeding season. This rate of reproduction is four to five times faster than normal and confirms that the technique achieves its objective of rapidly increasing the number of offspring from selected animals.     

Techniques and success of embryo transfers in Angora goats

Thirty-five mixed-age Angora does were subjected to superovulation and oestrous synchronization and of the 34 which were subsequently entire mated, 33 were subjected to surgical egg recovery approximately five days after oestrus. These 33 donors averaged 8.8 ovulations and 2.5 large (>5 mm) follicles. All corpora lutea in six donors were undergoing premature regression. The average donor egg recovery rate, egg fertilization rate and percent of eggs transferable was 82,87 and 81%, respectively, giving 6.8 eggs, 6.0 embryos and 5.5 transferable embryos per donor. Egg recovery was reduced dramatically when premature regressing corpora lutea were present. Recipient feral does were synchronized and 183 embryos transferred surgically to 133 recipients. Eighty-eight (66%) of the recipients kidded producing 118 kids (64% embryo survival). The 35 potential donors produced 36 kids from their natural mating which occurred shortly after surgery. Thus the donors produced a total of 154 kids from embryo transfer and natural mating, an average of 4.4 kids/doe/breeding season. This rate of reproduction is four to five times faster than normal and confirms that the technique achieves its objective of rapidly increasing the number of offspring from selected animals.     

Some Factors Affecting the Rate of Pregnancy after Embryo Transfer Derived from the Brazilian Jumper Horse Breed

This study aimed to evaluate the effects of certain embryo transfer parameters on the pregnancy rate after equine embryo transfer of the Brazilian Jumper Horse breed. The size, embryonic development stage, embryo quality, and synchronization of ovulation between the donor (n = 120) and recipient (n = 420) were evaluated in 396 embryos. Embryo recovery was performed on Day 6-9 after ovulation (Day 0 = day of ovulation). The recipient mares were chosen on the day of embryo recovery, and the transfers were performed that same day. The embryo size (diameter including envelopes; n = 396) ranged from 150 to 3000 μm; 67.1% measured between 400 and 1199 μm. The embryo size (400-1199 μm vs. ≤399 μm); stage of development (n = 396; blastocyst and expanded blastocyst versus compact morula and early blastocyst); quality (n = 396; grade 1 [excellent]), 2 [good], or 3 [poor]); and synchronization of ovulation between the donor and recipient (0, 1, 2, 3, and 4 days versus −1, 5, and 6 days, respectively) all affected pregnancy rate (P < .05). The pregnancy rate did not differ significantly among transfers performed on Days 0, 1, 2, 3, and 4. In conclusion, embryos measuring 400-1199 μm produced higher pregnancy rates in recipients than embryos measuring 150-399 μm, and blastocysts and expanded blastocysts produced pregnancy more efficiently than morulae and early blastocysts. The embryo quality also affected the pregnancy rate. Synchronization of donor and recipient ovulation to Days 0-4 improved the efficiency of embryo transplant.     

小鼠胚胎的玻璃化冷冻研究

用不同冷冻载体(玻璃管、塑料管和0.25 mL细管)及不同冷冻方法(程序化冷冻和玻璃化冷冻)对小鼠3.5 d~4 d桑椹胚和囊胚进行冷冻保存,并与不做任何冷冻保存处理直接培养进行对比。结果表明,使用玻璃管、塑料管和0.25 mL细管作为胚胎的承载材料进行玻璃化冷冻,效果差异不显著;采用程序化冷冻与OPS玻璃化冷冻法,对小鼠胚胎进行冷冻保存可以取得较好的结果。从而得出,用不同材质的冷冻载体进行玻璃化冷冻,可以获得与程序化冷冻相同的良好效果。     

Preliminary observations on reproduction in a female sheep-goat chimaera.

Four oestrous cycles of a female sheep-goat chimaera were monitored by using a vasectomised ram. The mean (+/- se) length of the cycle was 18.5 +/- 0.64 days with a range from 17 to 20 days. The chimaera was superovulated twice, bred to fertile rams, and the embryos recovered by laparotomy 13 or five days after oestrus, so that karyotype analysis could reveal the genotype of the oocyte. After the first superovulation one ovine day-13 embryo was collected; two fragments of another embryo (or embryos) were also collected, but readable chromosome spreads were not obtained from these embryos or from the two four-cell embryos that were collected five days after the second superovulation. Two surgical embryo transfers to the chimaera resulted in pregnancies. The first transfer involved an eight-cell ovine embryo and two caprine morulae and ended in the abortion of an ovine fetus between days 110 and 130. The second pregnancy occurred after the transfer of two ovine and two caprine morulae. A healthy lamb was born on day 147 of pregnancy. Both placentae had small numbers of cotyledons. A histological evaluation of the cotyledons revealed an abnormal placentome structure in the first pregnancy but not in the second.     

影响受体牛冷冻移植胚胎效果的主要因素

试验研究影响受体牛移植冷冻胚胎效果的主要因素,目的是解决胚胎移植产业化中容易出现的技术问题,以提高牛胚胎移植妊娠率。在季节、饲养管理、同期发情处理和胚胎移植技术以及环境条件等基本相同的情况下,结果表明:西门塔尔杂交牛的移植利用率和移植妊娠率高于黄牛杂交牛和黑白花奶牛,但各组间无显著性差异(P>0.05);2～6周岁的受体牛移植利用率和移植妊娠率高于7周岁以上和2周岁以下的受体牛,但各组间无显著性差异(P>0.05);经产1～3胎受体牛移植利用率显著高于4胎以上的受体牛(P<0.05),而移植妊娠率则无显著性差异(P>0.05);体况上等与中等的受体牛移植利用率和移植妊娠率无显著性差异(P>0.05);同期发情处理时卵巢处于黄体期的移植利用率显著高于卵泡期,差异极显著(P<0.01);左侧卵巢有黄体的子宫角胚胎移植妊娠率显著高于右侧(P<0.05);胚龄对胚胎移植妊娠率高低依次为早期囊胚、桑椹胚和囊胚,但无显著性差异(P>0.05)。     

Feline embryo transfer during the non-breeding season

To obtain normal kits by embryo treansfer (ET) during the non-breeding season, maintenance of pregnancy was carried out by administration of sustained action progesterone (P4) in queens. Embryos were recovered six days after mating from five donor queens in which ovulation was induced by administration of eCG and hCG. The number of embryos recovered ranged from 24 to 53 (mean: 37.2 +/- 6.4) per animal and most embryos were compacted morulae. The yield of embryos was 49.0-93.3% (mean: 73.8 +/- 9.6%). As for recipients, porcine pituitary gland preparation and hCG were administered to 19 queens and estrus and ovulation were induced in 18 queens (94.7%). These queens underwent intrauterine ET of five compacted morulae and 17 cats (94.4%) were impregnated. The number of implantations was 2-5 (mean: 3.7 +/- 0.3). Among these impregnated queens, 15 cats received P4 adminstration starting on day 24 of gestation and 1-5 newborns (mean: 3.4 +/- 0.3) were obtained by normal delivery or caesarean section on day 64-69 of gestation. However, two animals that were not treated with P4 underwent spontaneous abortion about the mid gestational period. Therefore, it is possible to obtain normal kits from queens in the non-breeding season by ET with maintenance of pregnancy by P4 administration.     

Folliculogenesis, embryo parameters and post-transfer recipient pregnancy rate following equine follicle-stimulating hormone (eFSH) treatment in cycling donor mares

Background Induction of multiple ovulations, or superovulation, may potentially increase the efficiency of equine embryo transfer programs. Our objective was to investigate the effects of equine follicle‐stimulating hormone (eFSH) treatment on the success rate of embryo transfer programs in mares. Methods In the research facility of the University of Saskatchewan, Canada, we studied 12 donor mares and 37 recipient mares during the physiological breeding season. Donor mares were used in two consecutive oestrous cycles: the first served as the control cycle and in the second an eFSH regimen was applied (eFSH cycle). In the control cycle, mares were administered human chorionic gonadotropin (hCG) to induce ovulation when a follicle ≥35 mm in diameter was detected by transrectal ultrasonographic examination. In the second oestrous cycle, twice‐daily eFSH treatment was initiated when a follicle ≥25 mm was detected and treatment ceased when a follicle ≥35 mm was present, at which time hCG was administered. All donor mares were artificially inseminated while in oestrus using fresh semen collected from a stallion of proven fertility. At 8 days post‐ovulation, embryos were recovered transcervically and transferred individually to the uterus of a synchronised recipient mare. Results The eFSH treatment stimulated the ovary and resulted in greater numbers of ovulations and recovered embryos; however the recovered embryos tended to have a lower morphological grade than the control embryos, and the recipient pregnancy rate per transferred embryo was lower than anticipated. Conclusion The numbers of recipient pregnancies and foals born that resulted from eFSH treatment were not different from the control.     

A Programme for Oestrus Synchronization and Embryo Transfer in Sheep

Eighty-five animals were used to develop an embryo transfer programme including a study on how oestrus synchronization influenced the ovulation rate. The animals, both ewes and ewe lambs, were divided into three groups: donors, recipients and controls. Oestrus was synchronized in donors and recipients by the use of progesterone-impregnated vaginal pessaries. The donors also received one injection of 600 IU PMSG. Samples for microbiological investigation of the vaginal flora were taken in connection with synchronization. The ovulation rate was determined by laparoscopy in the control animals and by laparotomy in the donors and recipients. The embryos were surgically recovered from the donors by flushing of the uterine horns seven days after pessary removal. The embryos were classified according to developmental stage and quality. At transfer each recipient received 2–4 embryos (moruhs or blastocysts) by a surgical method. A ± 1 day asynchrony in oestrus between donors and recipients was tolerated. All synchronized animals came into oestrus within 2.5 days after pessary removal. The interval was shorter if the animals had been injected with PMSG. The largest number of ovulations occuwed in the synchronized and PMSG-treated animals (mean 4.5 ± 2.1). Synchronized animals that did not receive PMSG had almost the same ovulation rate as the control animals (2.6 ± 0.9 versus 2.5 ± 0.7). The pessary treatment influenced the bacterial flora of the vagina. The number of ewes with bacterial growth in the vagina increased. The number of isolated organisms also increased. The embryo recovery rate was 80.8% and 3.7 ± 2.7 ovas was recovered on average. Eighty-eight percent of all donors yielded transferable embryos. Morulas and blastocysts comprised 84.4% of the recovered oocytes/embryos. Only 5.2% of these were of poor quality. Of the transferred embryos, 65.1% developed into lambs and 91.3% of the recipients lambed. The ewe lambs were as suitable as donors and recipients as the older ewes.     

A new method for bovine embryo production: a potential alternative to superovulation

Eight cows were used to study the feasibility of transvaginal ultrasound-guided puncture of follicles as a method for the collection of immature oocytes for embryo production in vitro. In six trials at intervals of seven days, 104 oocytes were collected. After in vitro maturation and fertilisation the 104 oocytes were transferred to the oviducts of sheep. Six days later, 75 oocytes were recovered by flushing the oviducts. Twenty-four per cent of the recovered oocytes/embryos had developed into transferable and viable morulae and, or, blastocysts. The data show that this non-surgical and repeated collection of immature oocytes can be used successfully for the in vitro production of bovine embryos. The procedure may produce yields of embryos comparable to those obtainable by conventional superovulation procedures.     

Successful Vitrification of In vivo Embryos Collected from Superovulated Japanese Black Cattle (Wagyu)

The aim of this study was to determine whether vitrification is an effective method when used for Japanese Black Cattle (Wagyu) in vivo‐derived embryos, collected following a superovulation treatment and embryo transfer (MOET) programme. In vivo‐derived morula and blastocysts collected on day 7 after artificial insemination, were vitrified using a modified droplet vitrification (MDV) procedure and subsequently warmed for transfer (ET) into synchronized recipients. Fresh embryos, and embryos cryopreserved using a standardized slow freezing procedure (direct thaw/direct transfer, DT) served as ET controls. Two different follicle‐stimulating hormone (FSH) sources, Folltropin^® Canada (FSH BAH, 24 donors) and a brand prepared by the Chinese Academy of Science (FSH CAS, 16 donors), were compared in a series of superovulation outcomes following well‐established FSH administration protocols. Following data analysis, the total number of ovulations recorded at the time of embryo flushing (10.5 vs 8.5; p = 0.28) and the total number of transferable embryos (6.2 vs 5.1; p = 0.52) were similar between the two FSH sources. ET for MDV (39.7%, n = 78), DT (35.2%, n = 71) and fresh controls (47.1%, n = 34) resulted in similar pregnancy rates (p > 0.05). When MDV was used, a higher pregnancy rate (42.6%) resulted from the transfer of vitrified morulae, when compared to the DT counterparts (24.3%), (p = 0.05). Transfer of vitrified morulae resulted also in higher pregnancy rate, when compared to the transfer of vitrified blastocysts (42.6% vs. 29.4%; p < 0.05). Transfer of DT blastocysts resulted in higher pregnancy rate than morulae, similarly cryopreserved (47.1% vs. 24.3%, p < 0.05). In conclusion, MDV is an effective alternative methodology for cryopreservation of in vivo‐derived embryos. This study gives also indication that, compared to vitrified blastocysts, MDV of morula stage embryos results in higher pregnancy rates following warming and transfer into synchronized recipients.     

应用体细胞克隆技术和胚胎移植技术生产克隆水牛

为了解决克隆水牛技术在供核细胞、受体细胞中的选用问题,探索不同条件对移植受孕的影响,完善克隆技术的理论体系。试验以摩拉奶水牛的耳成纤维细胞作为供核细胞,本地水牛卵母细胞为受体胞质进行细胞克隆构建重组胚胎;将发育5～10 d的重组胚胎移植于本地水牛、杂交水牛的子宫内,观察不同发情方式、胚胎类型、胚龄及季节对移植受孕的影响。结果表明:水牛的克隆胚胎妊娠率较低,分别为12.05%、12.04%、13.95%。自然发情和同期发情对克隆胚胎移植受胎率的影响差异不显著;鲜胚胎移植186头,受胎22头,受胎率为11.83%(22/186);冻胚胎移植174头,受胎23头,受胎率为13.22%(23/174)。克隆水牛从出生至12月龄体尺增长明显高于本地水牛;水牛克隆胚胎移植受胎在秋季最好,秋季受胎数占全年的53.33%,显著高于其他季节。     

An Earlier Uterine Environment Favors the In Vivo Development of Fresh Pig Morulae and Blastocysts Transferred by a Nonsurgical Deep-uterine Method

This study aimed to evaluate the effect of recipient-donor estrous cycle synchrony on recipient reproductive performance after nonsurgical deep-uterine (NsDU) embryo transfer (ET). The transfers (N=132) were conducted in recipients sows that started estrus 24 h before (–24 h; N=9) or 0 h (synchronous; N=31), 24 h (+24 h; N=74) or 48 h (+48 h; N=18) after the donors. A total of 30 day 5 morulae or day 6 blastocysts (day 0=onset of estrus) were transferred per recipient. The highest farrowing rates (FRs) were achieved when estrus appeared in recipients 24 h later than that in the donors (81.1%), regardless of the embryonic stage used for the transfers. The FR notably decreased (P<0.05) when recipients were –24 h asynchronous (0%), synchronous (61.3%) or +48 h asynchronous (50%) relative to the donors. No differences in litter size (LS) and piglet birth weights were observed among the synchronous and +24 h or +48 h asynchronous groups. While a +24 h asynchronous recipient was suitable for transfers performed with either morulae (FR, 74.3%; LS, 9.2 ± 0.6 piglets) or blastocysts (FR, 84.6%; LS, 9.8 ± 0.6 piglets), a + 48 h asynchronous recipient was adequate for blastocysts (FR, 87.5%; LS, 10.4 ± 0.7 piglets) but not for morulae (FR, 30.0%; LS, 7.3 ± 2.3 piglets). In conclusion, this study confirms the effectiveness of the NsDU-ET technology and shows that porcine embryos tolerate better a less advanced uterine environment if they are nonsurgically transferred deep into the uterine horn.     

Surgical and non-surgical transfer of bovine embryos

Methods of transferring one bovine embryo to the ipsilateral uterine horn have been compared. In heifers mid-ventral surgical laparotomy under general anaesthesia (n=22) was compared with flank surgery with paravertebral anaesthesia (n=21). Pregnancy rate was higher with a midventral approach (P less than 0.05) (77.3 per cent of 42.9 per cent respectively). In heifers mid-ventral surgery (n=36) was compared with two methods of non-surgical transfer either using the Cassou insemination gun (n=36) or a modification of it (n=39) with embryos collected on days 7, 8 or 10 after oestrus. There were no differences in pregnancy rate between methods or different ages of embryos (methods: 55.6, 55.6, 43.6 per cent respectively; Day: 48.8, 55.8, 48.1 per cent respectively) but the condition score of recipients affected success (P less than 0.05). Of 10 cows which each received an embryo using the modified Cassou gun eight became pregnant.