301 EFFECT OF CO-CULTURE WITH DIFFERENT STAGE EMBRYOS ON DEVELOPMENT OF ALGINATE-ENCAPSULATED SMALL NUMBER BOVINE EMBRYOS

2007 ◽  
Vol 19 (1) ◽  
pp. 266
Author(s):  
S. Kobayashi ◽  
M. Sakatani ◽  
Y. Inaba ◽  
S. Kobayashi ◽  
K. Imai ◽  
...  

Previous studies show that embryos cultured in large numbers have better developmental competence than those in small numbers in mice, sheep, and cattle. We have reported that co-culture of bovine embryos encapsulated in calcium-alginate gel (microcapsule) improves the development of embryos cultured in small numbers (Kobayashi et al. 2006 Reprod. Fertil. Devel. 18, 248). This method is beneficial for culture of small numbers of embryos such as OPU-derived embryos by recognizing the individual donor cows with abattoir-derived unidentified IVF embryos. In the previous study, we used the same stage embryos for co-culture of encapsulated embryos. However, in the case of unavailability of the same stage embryos, encapsulated embryos may be co-cultured with different stage embryos. Effect of different stage embryos on co-culture of encapsulated embryos is not clear. In the present study, we investigated the effect of co-culture of different stage embryos on development of encapsulated small number embryos. In vitro-matured and fertilized zygotes from abattoir derived ovaries were used for the experiment. Small numbers of zygotes were encapsulated by alginate-gel microcapsule to distinguish from co-cultured embryos. Encapsulation was carried out by putting the 1% sodium alginate solution containing zygotes slowly into 0.1% calcium chloride solution (microcapsule). The embryos used for co-culture were produced by IVF 1-3 days before preparation of encapsulated zygotes (Day 1, Day 2, and Day 3). Five encapsulated zygotes were cultured with 15 embryos for co-culture in one droplet (100 �L) made by CR1aa + 5% CS, at 38.5�C, CO2 in air. Encapsulated zygotes co-cultured with the same stage of zygotes were assigned as a control (Day 0). The rates of cleavage on Day 2 and development to blastocyst stage on Day 9 were recorded. Data were analyzed by Student's t-test. No significant difference was observed in the rate of cleavage in all experimental groups compared with control (Day 1: 72.5% (n = 80) vs. control: 75.7% (n = 70); Day 2: 76.3% (n = 80) vs. control: 82.5% (n = 80); and Day 3: 78.7% (n = 75) vs. control: 70.8% (n = 65). There was not a significant difference in the rate of development to the blastocyst stage in all experimental groups compared with control (Day 1: 42.5% vs. control: 44.3%; Day 2: 43.8% vs. control: 38.8%; Day 3: 44.0% vs. control: 35.4%). These results indicate that co-culture of different stages of embryos can normally support the development of small numbers of encapsulated embryos. These methods are useful to improve the development of small numbers of embryos derived from OPU-IVF embryos without synchronization of the developmental stage of co-cultured embryos.

2007 ◽  
Vol 19 (1) ◽  
pp. 206
Author(s):  
I. G. F. Goovaerts ◽  
J. B. P. De Clercq ◽  
M. Nichi ◽  
P. E. J. Bols

An in vitro production system where a single oocyte can be followed from the ovary to the blastocyst stage would be a useful tool for studies concerning developmental competence or follicular environment. Unfortunately, until now, only low blastocyst rates could be obtained after single embryo production, and there is still discussion about the ideal droplet size. The objective of the present experiment was to compare the developmental competence of single cultivated zygotes in 20- and 500-µL droplets. Cumulus–oocyte complexes were obtained from slaughterhouse ovaries and were matured and fertilized in groups of 100 for 22 h; the presumptive zygotes were divided into 4 groups. In treatment 1, 25 zygotes were transferred into 50 µL of SOF medium supplemented with 5% serum under oil, whereas in treatment 2, 25 zygotes were transferred into 500 µL of medium. Zygotes were cultivated separately in treatments 3 and 4: in treatment 3 in 20 µL of medium under oil and in treatment 4 in 500 µL of medium. Cleavage rates and division stages were assessed after 3 days of cultivation (5% CO2, 5% O2, 90% N2); blastocyst rates were determined after 7 days. Statistical analysis was performed by logistic regression using SAS (PROC LOGISTIC). There was no difference in cleavage rates between the 2 group treatments or between the 2 single treatments. Also, the division stages were not different between the 2 single treatments (16-cell: 2.0 vs. 1.3%; 8-cell: 25.8 vs. 31.6%; 4-cell: 41.2 vs. 38.0%; and 2-cell: 31.0 vs. 29.1% for the 20 µL and the 500 µL droplet sizes, respectively). Group cultivation after 7 days in 50 µL was significantly better than in 500 µL; however, both treatments resulted in significantly higher blastocyst rates compared with the individual cultures in 20 or 500 µL, between which no significant difference could be found. Noteworthy, only 4-cell and 8-cell stages on Day 3 resulted in blastocysts on Day 7 of cultivation. In conclusion, these results indicate that cultivation in groups gives higher blastocyst rates, although the same embryo density is used as in individual cultivation (1 embryo 20 µL in treatments 2 and 3). Moreover, no significant difference could be found between single cultivation in small and big droplets. This is confirmed by the cleavage stages on Day 3, which indicate no difference in timing of cleaving between small and big droplets; time of cleaving is indicative of further developmental capacity. Table 1.Cleavage and blastocyst rates after single and group cultivation


2006 ◽  
Vol 18 (2) ◽  
pp. 248 ◽  
Author(s):  
S. Kobayashi ◽  
M. Sakatani ◽  
S. Kobayashi ◽  
M. Takahashi

Ova are genetic resources that can be obtained from slaughterhouse ovaries or live cows by ovum pickup (OPU). However, the number of oocytes recovered by OPU is low. Previous studies show that embryos cultured in large numbers have better developmental competence than those in small numbers in mice, sheep, and cattle. Therefore, to improve development of small numbers of embryos, co-culture with other types of embryos is an efficient way. However, it is necessary to distinguish the desired embryos from the co-cultured embryos. Recently, encapsulation of embryos using calcium-alginate was reported to be useful for handling and in vivo culture of porcine embryos (Iwamoto et al. 2003 Theriogenology 59, 261). In the present study, we investigated the effect of co-culture of embryos encapsulated with calcium-alginate on development of small numbers of embryos. In vitro-matured and fertilized zygotes from slaughterhouse-derived ovaries were used for the experiment, and data were analyzed by Student t-test. Encapsulation was carried out by putting the 1% sodium alginate solution containing zygotes slowly into 0.1% calcium chloride solution (microcapsule). We used the microcapsule for the following experiments. In Experiment 1, twenty zygotes were cultured in CR1aa containing 5% FCS with a capsule containing 20 zygotes or without (control) a microcapsule. The rate of cleavage (capsule: 80.0% vs. control: 72.1%) and development to blastocyst stage (capsule: 31.7% vs. control: 33.7%) were not significantly different. This result indicates that the microcapsule is not toxic to embryo development. In Experiment 2, five zygotes were co-cultured with 15 zygotes (microcapsule), and culture of five zygotes without capsules served as a control. The rate of cleavage (co-culture: 81.4% vs. control: 80.0%) was not significantly different, but the rate of development to the blastocyst stage was significantly higher (P < 0.05) in the co-culture (47.1%) than in the control (30.6%). This result indicates that co-culture with a microcapsule including zygotes enhances the development of small numbers of embryos. In Experiment 3, five zygotes derived from a single cow were encapsulated, and four microcapsules from different cows were cultured in the same droplet. The microcapsules could be distinguished by the inclusion of different numbers of glass beads with the zygotes. Culture of five zygotes without capsules was assigned as a control. The rate of cleavage (co-culture: 75.6% vs. control: 69.6%) was not significantly different, but the rate of development to the blastocyst stage was significantly higher (P < 0.05) for the co-culture (30.6%) than for the control (17.8%). These results indicate that co-culture with bovine embryos encapsulated with calcium-alginate may improve development of small numbers of embryos.


2005 ◽  
Vol 17 (8) ◽  
pp. 751 ◽  
Author(s):  
Mona E. Pedersen ◽  
Øzen Banu Øzdas ◽  
Wenche Farstad ◽  
Aage Tverdal ◽  
Ingrid Olsaker

In this study the synthetic oviduct fluid (SOF) system with bovine oviduct epithelial cell (BOEC) co-culture is compared with an SOF system with common protein supplements. One thousand six hundred bovine embryos were cultured in SOF media supplemented with BOEC, fetal calf serum (FCS) and bovine serum albumin (BSA). Eight different culture groups were assigned according to the different supplementation factors. Developmental competence and the expression levels of five genes, namely glucose transporter-1 (Glut-1), heat shock protein 70 (HSP), connexin43 (Cx43), β-actin (ACTB) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), analysed as mRNA by using reverse transcription–polymerase chain reaction, were measured on bovine embryos cultured for 9 days. Gene expression of these in vitro-produced embryos was compared with the gene expression of in vivo-produced embryos. There was no significant difference found in embryo developmental competence between the Day 9 embryos in BOEC co-culture, FCS and BSA supplements in SOF media. However, differences in gene expression were observed. With respect to gene expression in in vivo and in vitro embryos, BOEC co-culture affected the same genes as did supplementation with FCS and BSA. HSP was the only gene that differed significantly between in vitro and in vivo embryos. When the different in vitro groups were compared, a significant difference between the BOEC co-culture and the FCS supplementation groups due to Glut-1 expression was observed.


2020 ◽  
Vol 21 (23) ◽  
pp. 8888
Author(s):  
Bárbara Melo-Baez ◽  
Yat S. Wong ◽  
Constanza J. Aguilera ◽  
Joel Cabezas ◽  
Ana C. F. Mançanares ◽  
...  

During early development, embryos secrete extracellular vesicles (EVs) that participate in embryo–maternal communication. Among other molecules, EVs carry microRNAs (miRNAs) that interfere with gene expression in target cells; miRNAs participate in embryo–maternal communication. Embryo selection based on secreted miRNAs may have an impact on bovine breeding programs. This research aimed to evaluate the size, concentration, and miRNA content of EVs secreted by bovine embryos with different developmental potential, during the compaction period (days 3.5–5). Individual culture media from in vitro–produced embryos were collected at day 5, while embryos were further cultured and classified at day 7, as G1 (conditioned-culture media by embryos arrested in the 8–16-cells stage) and G2 (conditioned-culture media by embryos that reached blastocyst stages at day 7). Collected nanoparticles from embryo conditioned culture media were cataloged as EVs by their morphology and the presence of classical molecular markers. Size and concentration of EVs from G1 were higher than EVs secreted by G2. We identified 95 miRNAs; bta-miR-103, bta-miR-502a, bta-miR-100, and bta-miR-1 were upregulated in G1, whereas bta-miR-92a, bta-miR-140, bta-miR-2285a, and bta-miR-222 were downregulated. The most significant upregulated pathways were fatty acid biosynthesis and metabolism, lysine degradation, gap junction, and signaling pathways regulating pluripotency of stem cells. The characteristics of EVs secreted by bovine embryos during the compaction period vary according to embryo competence. Embryos that reach the blastocyst stage secrete fewer and smaller vesicles. Furthermore, the loading of specific miRNAs into the EVs depends on embryo developmental competence.


2017 ◽  
Vol 29 (1) ◽  
pp. 178
Author(s):  
E. Mellisho ◽  
A. Velasquez ◽  
M. J. Nuñez ◽  
L. Rodriguez-Alvarez

Pre-implantation embryos secrete extracellular vesicles (EV) most likely to communicate with the surroundings. The objective of this study was to determine the distribution (size and concentration) of EV secreted by bovine pre-implantation embryos with different developmental competence. The IVF bovine embryos were produced from oocytes recovered from slaughterhouse ovaries. Presumptive zygotes were in vitro cultured (IVC) in groups in 4-well plates (30 zygotes per 500-µL well) using SOFaa medium at 39°C under 5% CO2, 5% O2, and 90% N2 until the morula stage (Day 5 post IVF). Morulae were cultured individually in 96 well at 39°C under until blastulation time (Day 6.5–7.5) in EV-free SOF medium. Culture medium was collected only from embryos that developed to the blastocyst stage that were classified in a group of early (Day 6.5) or late (Day 7.5) blastulation. Blastocysts were kept in culture until Day 11 to assess embryo developmental competence, considering embryo size (>350 µm) and total cell count (>500 blastomeres). For EV analysis, 4 groups were organised a posteriori: G1: Day 6.5-competent; G2: Day 6.5-not competent; G3: Day 7.5-competent; G4: Day 7.5-not competent. The EV in culture media were analysed using a nanoparticle tracking analysis (Nanosight NS300). Statistical analysis was performed using the InfoStat program (Buenos Aires, Argentina). Differences were considered significant at P < 0.05. Early blastulation rate (Day 6.5) was 40.3% (112/278), whereas late blastulation rate (Day 7.5) was 20.5% (57/278), showing a significant difference (P < 0.0001). Embryos derived from Day 6.5 blastocysts have a higher probability (39.3%: 44/112) of posthatching development [until Day 11; Day 7.5, 10.5% (6/57); P = 0.0001]. At Day 11, competent embryos (G1) derived from Day 6.5 blastocysts have a higher diameter and total cell number (447 µm; 688 cells) than those derived from Day 7.5 blastocysts (G3; 405 µm, 598 cells; P < 0.05 for both parameters). It was possible to detect EV from collected medium of individual embryos independent of their competence. Neither the EV size nor the EV concentration was statistically different between Day 6.5 and Day 7.5 blastocysts (without considering their further competence; 2.9 × 108, 147 nm; and 3.0 × 108, 149 nm, respectively). However, independent of the day of blastulation, competent embryos had a significantly lower concentration of EV (2.7 × 108 v. 3.3 × 108; P = 0.03). Moreover, competent embryos from early and late blastocysts (G1 and G3) tend to produce a lower amount of EV (G1: 2.8 × 108; G2: 3 × 108; G3: 2.6 × 108; G4: 3.5 × 108; P = 0.05). Furthermore, EV concentration was statistically different between G3 and G4 (P = 0.002). No differences in EV size were observed among groups (G1: 145 nm; G2: 148 nm; G3: 146 nm; G4: 151 nm). Our results provide an initial approach to study the EV secreted by individual pre-implantation embryos to assess their competence. From these results, we can conclude that blastulation time affects the future development of bovine embryos and a model based on blastulation time and EV secretion could be a simple noninvasive tool to improve embryo selection.


2002 ◽  
Vol 45 (6) ◽  
pp. 547-556
Author(s):  
N. R. Mtango ◽  
M. D. Varisanga ◽  
D. Y. Juan ◽  
P. Wongrisekeao ◽  
T. Suzuki

Abstract. This study was designed 1) to determine the effectiveness of two in vitro maturation (IVM) media (tissue culture medium [TCM] and modified synthetic oviduct fluid supplemented with amino acids [mSOFaa]), 2) to compare the effects of two in vitro fertilization (IVF) media (modified Tris-buffered medium [mTBM] and mSOFaa) on the developmental competence of pig oocytes, and 3) to test the activation ability of IVM pig oocytes matured in TCM or mSOFaa, electroactivated and cultured in mSOFaa. The nuclear maturation rates were similar between IVM media (91.0 % vs. 89.0 %). A similar result was obtained when the activation rates were 54.2 % in TCM and 56.0 % in mSOFaa, and the blastocyst rates were 7.9 % and 6.1 %, respectively. There was no significant difference between mSOFaa and mTBM in the percentage of embryos with two pronuclei 33.2 % vs. 13.8 % or polypronuclei 5.3 % vs. 13.4 %. The cleavage rate was the same in both media. The medium mSOFaa gave a significantly higher (P< 0.05) blastocyst rate than mTBM (12.7 % vs. 3.9 %). We concluded that mSOFaa can enhance in vitro maturation, fertilization and culture of pig oocytes.


2015 ◽  
Vol 27 (1) ◽  
pp. 208
Author(s):  
S. Matoba ◽  
T. Somfai ◽  
T. Nagai ◽  
M. Geshi

Previously, an early first cleavage and a second cleavage after IVF with a normal cleavage pattern defined by even blastomeres without fragments or protrusions was found to be a potent marker for the selection of embryos with high developmental competence (Sugimura et al. 2012 PLoS ONE 7, e36627). The aim of this study was to investigate the effects of bulls and X-sorting of sperm on the ability of these simple noninvasive markers to predict the potency of bovine IVF embryos to develop to the blastocyst stage in vitro. Immature oocytes were matured in TCM199 supplemented with 0.02 armour unit mL–1 FSH and 5% calf serum at 38.5°C in 5% CO2 and 95% air for 22 to 23 h. After maturation, oocytes were inseminated with either of non-sorted frozen-thawed sperm from 3 bulls (A–C) or X-sorted sperm of bull A. Putative zygotes were cultured (IVC) in CR1aa medium supplemented with 5% calf serum and 0.25 mg mL–1 linoleic acid albumin at 38.5°C in 5% CO2, 5% O2, and 90% N2 for 216 h. Embryo kinetics were observed individually by time-lapse cinematography (CCM-1.3Z; Astec, Fukuoka, Japan; Sugimura et al. 2010 Biol. Reprod. 83, 970–978). First and second cleavage kinetics and pattern were categorized according to Sugimura et al. (2012). For each bull, blastocyst development from embryos possessing the following 3 selection markers was compared: (marker 1) the first cleavage within 28 h after IVF, (marker 2) marker 1 combined with 2 even blastomeres without fragments or protrusions, and (marker 3) marker 2 combined with the second cleavage within 50 h after IVF with ≥6 even blastomeres without fragments or protrusions, respectively. Data were analysed by the Yates' corrected chi-square test. A total of 823 oocytes were used in at least 3 replications. When non-sorted sperm was used for IVF, there was not difference (P > 0.05) in total blastocyst formation rates on Day 8 (Day 0 = IVF) among bulls (ranging between 49.5 and 60.8%); however, blastocyst formation rate of embryos generated from X-sorted sperm of bull A (39.5%) was lower (P < 0.05) compared with other groups despite of similar cleavage rates. Embryos having marker 3 criteria developed to the blastocysts stage at significantly higher rates than those having marker 1 criteria in case of non-sorted sperm of bulls A, B, C, and X-sorted sperm of bull A (75.9, 87.0, 90.0, and 75.0% v. 59.5, 62.2, 63.6, and 46.3%, respectively). In groups produced from non-sorted sperm of bulls A, B, C, and X-sorted sperm of bull A, blastocyst development rates of embryos with marker 2 criteria (73.7, 75.0, 90.0, and 65.8%, respectively) were higher (P < 0.05) than those of embryos having marker 1 criteria but did not differ significantly from those with marker 3 criteria. Our results reveal that a first cleavage within 28 h after IVF to 2 even blastomeres without fragments or protrusions are potent predictive markers of the developmental competence of bovine embryos to the blastocyst stage regardless of bulls and sperm sorting.Research was partly supported by JSPS KAKENHI (26450388).


2013 ◽  
Vol 25 (1) ◽  
pp. 266
Author(s):  
S. Matoba ◽  
S. Sugimura ◽  
H. Matsuda ◽  
Y. Aikawa ◽  
M. Ohtake ◽  
...  

Recently, we reported that high rates of good-quality blastocysts can be produced by IVF of in vivo-matured oocytes, obtained by ovum pick-up (OPU) after superstimulation in Holstein cows, with X-sorted sperm [Matoba et al. 2012 Reprod. Domest. Anim. 47(Suppl. 4), 515]. However, we have limited knowledge concerning the normality of embryonic cleavages in such embryos. The present study examined their kinetics and pattern of the first cell cycle. In vivo-matured oocytes were collected by OPU from non-lactating Holstein cows just before ovulation after superstimulation and ovulation induction by gonadotropin-releasing hormone. The oocytes were inseminated with 5 × 106 sperm mL–1 of X-sorted sperm and cultured in CR1aa supplemented with 5% newborn calf serum and 0.25 mg mL–1 of linoleic acid albumin at 38.5°C in 5% CO2, 5% O2, and 90% N2 for 216 h. Embryo kinetics were observed individually using a microwell culture dish and time-lapse cinematography (CCM-1.4MZS, Astec, Fukuoka, Japan) (Sugimura et al. 2010 Biol. Reprod. 83, 970–978). Photographs of each embryo were taken every 15 min during the in vitro culture period, and images were analysed by CCM-1.4 software (Astec). The cleavage pattern was categorised into normal cleavage (2 even blastomeres without fragment or protrusion) or abnormal cleavage (those with 2 uneven blastomeres, with fragments or protrusions and those dividing into 3 to 5 blastomeres at the first cleavage). Data were analysed by ANOVA, chi-square, and discriminant function. A total of 117 embryos were examined; of this number, 63.2% developed to the blastocyst stage and the rest were degenerated. A high rate of normal cleavage and a low rate of abnormal cleavage, including those with 2 uneven blastomeres and those with fragments or protrusions in the first cleavage pattern, were recorded in embryos that could develop to blastocysts compared with degenerated ones (P < 0.01 or P < 0.05, respectively; Table 1). No significant difference was found in those dividing into 3 to 5 blastomeres between the blastocysts and degenerated embryos (Table 1). Embryos developing to the blastocyst stage had a shorter duration of the first cell cycle [27.2 ± 2.3 h post-insemination (hpi)] compared with those undergoing degeneration (30.6 ± 5.7 hpi; P < 0.001). The threshold of duration of the first cell cycle was calculated by (X – 27.2)/2.3 = (30.6 – X)/5.7, resulting in X = 28.2. Blastocysts with a short duration of the first cell cleavage (≤28.2 hpi) showed a higher frequency of the normal cleavage pattern than those with a duration of the first cell cleavage longer than 28.2 hpi (71.7 and 53.6%, respectively; P < 0.05). Our results revealed that those IVF embryos that finished their first cleavage before 28.2 h of IVF and showed a normal cleavage pattern had superior developmental competence. Table 1.The first cleavege pattern reflects the developmental competence: blastocysts versus degenerated embryos This work was supported by the Research and Development Projects for Application in Promoting New Policy of Agriculture, Forestry and Fisheries (22016).


2010 ◽  
Vol 79 (9) ◽  
pp. S55-S61 ◽  
Author(s):  
Jaroslava Hlavicová ◽  
Miloslava Lopatářová ◽  
Svatopluk Čech

The aim of this study was to establish the effect of two-step vitrification on survival rate of bovine embryos produced in vitro (method A) and in vivo (method B) from Holstein-Friesian cattle. The embryos suitable for vitrification were frozen by a two-step technique, using increasing concentrations of dimethyl sulphoxide (DMSO) and ethylene glycol (EG). After thawing, the quality grade and developmental stage of embryos was assessed. In vitro developmental competence of embryos of different quality grade obtained by method B (n = 82) was significantly higher (p < 0.001) compared to method A (n = 98). The best results were detected when we vitrified the embryos of the grade 1 quality; namely, the hatched blastocyst stage was reached by 6.9% (2/29) of embryos retrieved by method A and by 36.7% (11/30) of embryos retrieved by method B (p < 0.01). In the case of developmental competence of embryos at different developmental stages we reached significantly better results (p < 0.001) when we vitrified the embryos produced by method B (n = 84) in comparison with method A (n = 67). We noted a higher hatching rate at the stage of expanded blastocyst; namely, the hatched blastocyst stage was reached by 7.4% (2/27) of embryos produced by method A and by 30.8% (8/26) of embryos produced by method B (p < 0.05). In general, the hatched blastocyst stage was reached by 15.1% (50/331) of all thawed embryos retrieved by method A and B. In conclusion, when we applied two-step vitrification on the grade 1 quality embryos at the stage of expanded blastocyst produced in vitro or at the stage of morula produced in vivo we achieved the highest hatching rates.


2005 ◽  
Vol 17 (2) ◽  
pp. 225 ◽  
Author(s):  
M. Schmidt ◽  
B. Avery ◽  
T. Greve

For stem cell production and detailed morphological analysis 12–14-day-old bovine embryos are suitable. However, it has been proven to be difficult to extend the in vitro culture period beyond Days 8–9, and it was the aim of the present experiment to examine whether it might be possible to culture 6–7-day-old in vitro-produced (IVP) embryos for a period of 5–7 days in the uterine horns of heifers. The IVP embryos were produced by standard procedures. Briefly, IVM took place in DMEM medium supplemented with 5% serum, EGF, and eCG/hCG, and IVF was carried out in TALP medium under 5% CO2 in humidified air and at 38.5°C. IVC took place in SOFaaci supplemented with 10% serum under 5% CO2, 5% O2 and 90% N2 at 38.5°C .The embryos were cultured in vitro to Days 6–7 post insemination, when morulas and blastocysts of excellent quality were placed in HEPES-buffered TCM199 with 10% serum, loaded in numbers of 10–30 into 0.25 mL straws, and then transported to the place of transfer in a portable incubator at 38.5°C. The embryos were transferred nonsurgically to the mid or distal part of the uterine horns of 28 dairy heifers which were heat synchronized with injections of cloprostenol (Estrumat Vet, Schering-Plough, Farum, Denmark) to a cycle stage of embryo age +1 day. In 16 heifers, embryos were transferred into both sides and for the remaining ones only into the horn ipsilateral to the ovary bearing the corpus luteum. After 5–7 days, the heifers were flushed nonsurgically by standard method, using a flushing catheter of large caliber (Minitab® 18 G) and slow infusion and evacuation of the fluid. The differences in recovering rate among horns were identified by Fisher's Exact test. Data are given as LS means ± SEM values and statistical differences assigned at the P < 0.05 level. In 6 of the 28 heifers no embryos were obtained; in these 6 cases, the quality of the transferred embryos, the transfer procedure, the heifers, and the flushing procedures did not differ in any obvious way from those of the successful flushings, which numbered 22 (79%). The mean embryo recovery rate was 40 ± 3% with a variation from 7% to 93%. There was a minor but not statistically significant difference between the overall recovery rate of embryos from the ipsi- versus contralateral horn, respectively (44 ± 5% vs. 38 ± 6%). In only 4 of the 16 heifers where transfer occurred to both horns was the recovery rate higher in contralateral side, compared to 9 heifers where the highest recovery rate was seen in the ipsilateral side. The oldest elongated embryos were in one occasion damaged and in another tangled, making it difficult to isolate the individual embryo; apart from that, all of the embryos seemed of excellent quality making it possible to isolate the embryonic discs. It can be concluded that it is possible to culture in vitro produced Day 6–7 bovine blastocysts in the uterus of synchronized heifers and to achieve an acceptable recovery of Day 12–14 embryos.


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