285 VARIATION FACTORS INFLUENCING CLEAVAGE AND EMBRYONIC DEVELOPMENT RATES OF BOVINE OOCYTES COLLECTED ON A FARM IN A COMMERCIAL OPU-IVP SYSTEM

2006 ◽  
Vol 18 (2) ◽  
pp. 250
Author(s):  
B. Marquant-Le Guienne ◽  
F. Aymar ◽  
C. Ponsart ◽  
C. Guyader-Joly ◽  
S. Ponchon ◽  
...  
Keyword(s):  
Embryonic Development ◽  
Body Condition ◽  
Body Condition Score ◽  
Calf Serum ◽  
Blastocyst Stage ◽  
Physiological Status ◽  
Cleavage Rate ◽  
Factors Influencing ◽  
Development Rates ◽  
Donor Characteristics

The aim of this work was to identify factors influencing the success rate of each production step through a retrospective study conducted for 362 commercial OPU-IVP sessions performed on a farm. Donor females were stimulated with FSH in five decreasing doses (400 μg for cows and 250 μg 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; zygotes were cultured for 6 days on Vero cell monolayers in B2 medium. Embryos were transferred as fresh to recipients on Day 7. The effects of donor characteristics, OPU and IVP conditions on cleavage, development rates, and number of transferred embryos (TE) were analyzed by ANOVA (GLM program in SAS; SAS Institute, Inc., Cary, NC, USA). Effects are mentioned when significant at P < 0.05. 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. The number of transferred embryos was higher when the dominant follicle (DF) was punctureed prior to OPU (see Table 1). This resulted in a better cleavage rate in punctured DF donor females. Higher cleavage rates were observed in infertile females as well as numbers of TE per session. Pregnancy and body condition score (BCS) recorded at OPU only influenced cleavage rates. Embryonic development rates were mainly influenced by donor breed and parity. In the Abundance breed, 87.5% of the sessions resulted in at least one embryo being transferred compared to 58.6% in Holsteins. Higher numbers of embryos were transferred per session when donor females were cows rather than heifers. Fertilization conditions (heparin and sperm concentrations) had no effect on cleavage and embryonic development rates. To conclude, cleavage and development rates were mainly influenced by donor characteristics (breed, parity, physiological status). Improvement of results may be achieved by systematic puncture of DF prior to OPU. Cleavage rates were dependent on BCS. To improve management of body condition, BCS variations before OPU could be a new parameter to be followed in donor females. Table 1. Factors affecting steps of the OPU-IVP procedure

19 Invitro embryonic development from oocytes collected by ovum pickup of superstimulated females and nonstimulated slaughterhouse ovaries of alpaca (Vicugna pacos)

2021 ◽  
Vol 33 (2) ◽  
pp. 117
Author(s):  
L. Landeo ◽  
M. Zuñiga ◽  
T. R. Gastelu ◽  
J. A. Ruiz
Keyword(s):  
Embryonic Development ◽  
Statistical Significance ◽  
Calf Serum ◽  
Oocyte Quality ◽  
Blastocyst Stage ◽  
Cleavage Rate ◽  
Hormonal Stimulation ◽  
Array Transducer ◽  
The Mean

The objective of this study was to evaluate the embryonic development of alpaca oocytes collected by ovum pickup from superstimulated females (OPU, Group 1) and from slaughterhouse ovaries of 8 non-superstimulated females (SHO, Group 2) using a conventional aspiration technique (20G needle and a 3-mL syringe). A total of 8 nonpregnant alpacas, 3 to 4 years old, were superstimulated with a single dose of 200IU of equine chorionic gonadotrophin (eCG, Day=0). Three days later, alpacas were examined by transrectal ultrasonography with a 7.5-MHz linear-array transducer to determine the number and diameter of follicles available for aspiration. A total of 101 follicles were aspirated, recovering 67 oocytes (66.3%) by OPU using an endocavity transducer attached to a 21G needle adapted for alpacas. The follicular fluid was aspirated using a regulated vacuum pump (40 mmHg) into a tube containing 5mL of phosphate-buffered saline (PBS), 0.2% bovine serum albumin (BSA), and 10IUmL−1 heparin, at 37°C. In the SHO group we used 16 ovaries maintained at 28°C. The recovery of oocytes was carried out within 3h of ovary collection. We aspirated 155 follicles from SHO and recovered 117 oocytes (75.5%). After collection, all oocytes recovered were morphologically classified into categories (I and II) and cultured for 26h in an incubator (5% CO2 in air at 38.5°C), in TCM-199 supplemented with 0.2mmol sodium pyruvate, 50µgmL−1 gentamicin sulphate, 0.02IUmL−1 FSH, 1µgmL−1 oestradiol 17β, and 10% fetal calf serum (FCS). After maturation, oocytes were invitro fertilized with epididymal spermatozoa recovered from postmortem males and co-cultured for 18 to 20h. After this period, all cleaved oocytes were incubated (5% CO2 in air, 38.5°C) for 6 days in synthetic oviductal fluid-serum medium. Number and morphological quality of oocytes collected, invitro cleaved, and embryos ratea were registered and compared between groups. Statistical significance was determined using Kruskal–Wallis test. The mean and standard error were calculated from average of the percentages obtained in each repetition. Results indicated that the mean number of oocytes collected per ovary was higher (P&lt;0.05) using SHO (7.8±2.4) than OPU (4.5±3.0). Also, the number of oocytes classified as category I, was higher in the SHO compared with OPU group (56% vs. 30% respectively; P&lt;0.05); however, category II oocytes were the same (16% vs. 15%, respectively). There was no difference in early development (cleavage) rate between OPU (57±2.0) and SHO (49±1.5) groups. However, there was difference in the rate of development (P&lt;0.05) between OPU and SHO groups to reach the morula stage (56±2.0 vs. 42±1.7, respectively) and early blastocyst stage (55±2.0 vs. 34±1.4, respectively). In conclusion, oocyte quality could be affected by hormonal stimulation or by the quality of follicles aspirated by OPU. In contrast, oocytes recovered from live animals by OPU have greater capability of embryonic development invitro than oocytes recovered from slaughterhouse ovaries.

scholarly journals Effect of body condition score and live weight of fertility of merino sheep after induction of oestrus in the out-of-breeding season

2015 ◽  
Vol 31 (2) ◽  
pp. 235-243
Author(s):  
P. Slavova ◽  
S. Laleva ◽  
Y. Popova
Keyword(s):  
Breeding Season ◽  
Body Condition ◽  
Body Condition Score ◽  
Live Weight ◽  
The Body ◽  
Physiological Status ◽  
Merino Sheep ◽  
Condition Score ◽  
Score Method ◽  
Concentrate Mixture

?bject of the study were merino sheep raised in the farm of the Agricultural institute - Stara Zagora. The experiment was conducted with a group of 68 animals of different ages, lambing after treated with hormonal preparation according to adopted scheme during the out-of-breeding season - in May. In the experimental group were included ewes which lambed earlier without making a selection in respect to their productivity. Animals were kept under the same conditions (stall-pasture) and fed the same rations with the concentrate mixture, rough, succulent feed and grazing in quantity and composition according to their physiological status and season from the fertilization until lambing. Hormonal pattern: setting pads for sheep type Sincro-part (30mg), removing pads after 12 days and giving ewes a PMSG injection at a dose of 500 UI, applying artificial insemination at the 50-55th hour. Body condition score and live weight of the animals were determined in 4 separate periods: 1st period (after mating), 2nd period (during pregnancy), 3rd period (after lambing), 4th period (before next mating service). Improving fertility in merino sheep is significantly influenced by the preparation of ewes for the mating by reaching the respective physiological status which is expressed by score over 2.5 according to the Body condition score method and live weight over 60 kg. Animals scored 2.75-3.50 before mating have a share of 91.18% from all the sheep in the flock and have the biggest number of lambs.

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

2006 ◽  
Vol 18 (2) ◽  
pp. 253
Author(s):  
C. Ponsart ◽  
F. Aymar ◽  
B. Marquant-Le Guienne ◽  
C. Guyader-Joly ◽  
S. Ponchon ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Calf Serum ◽  
Blastocyst Stage ◽  
Pregnancy Rates ◽  
National Standards ◽  
Mean Deviation ◽  
Gestation Length ◽  
Assisted Reproduction Technique ◽  
Factors Influencing ◽  
The Mean

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 < 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 >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.

scholarly journals Development of cultured bovine embryos after exposure to high temperatures in the physiological range

Reproduction ◽  
2001 ◽  
pp. 107-115 ◽  
Author(s):  
RM Rivera ◽  
PJ Hansen
Keyword(s):  
Heat Shock ◽  
Embryonic Development ◽  
High Temperatures ◽  
Deleterious Effect ◽  
Blastocyst Stage ◽  
The Body ◽  
Body Temperatures ◽  
Cleavage Rate ◽  
Development In Vitro

Embryonic development is inhibited by exposure of cultured embryos to high temperatures. However, culture temperatures used to demonstrate the effects of heat on development have been higher than the body temperatures experienced typically by heat-stressed cows. The aim of this study was to determine whether exposing bovine oocytes and embryos to temperatures characteristic of body temperatures of heat-stressed cows would affect embryonic development in vitro. The CO2 percentage of the gas phase was adjusted in all experiments to prevent pH changes in the medium caused by decreased solubility of CO2 at high temperatures. Fertilization of oocytes at 41.0 degrees C reduced cleavage rate and the percentage of oocytes that became blastocysts compared with at 38.5 degrees C. There was no deleterious effect of fertilization at 40.0 degrees C. When putative zygotes and two-cell embryos were exposed to a range of temperatures from 38.5 to 41.0 degrees C for 3, 6, 9 or 12 h, heat shock reduced the number that developed to the blastocyst stage but only after exposure to 41.0 degrees C for 9 or 12 h. In addition, it was tested whether low O2 tension would reduce the detrimental effects of heat shock. The deleterious effect of 41.0 degrees C was not dependent upon oxygen content or the gas mixture used for culture (5% versus 20.95% O2), indicating that the deleterious effects of heat shock did not depend upon a high O2 environment. In the final experiment, embryos were exposed to 24 h fluctuations in temperature designed to mimic the rectal temperatures of cows exposed to heat stress. Exposure of embryos to this pattern of temperatures starting after fertilization reduced development when embryos were exposed to this environment for 8 days but not when embryos were exposed for 1 day only. These findings indicate that embryonic development can be disrupted by a short-term severe or a prolonged mild heat shock and that the effects of heat shock are not artefacts of changes in pH or high oxygen tension.

scholarly journals Ante-partum Body Condition Score and Non-genetic Factors Influencing the Post-partum Fertility in Murrah Buffaloes

2020 ◽  
Vol 9 (11) ◽  
pp. 1152-1158
Author(s):  
Cherryl D. Miranda ◽  
A. K. S. Tomar ◽  
Gyanendra Singh ◽  
Hari Om Pandey ◽  
Pratik R. Wankhede ◽  
...  
Keyword(s):  
Body Condition ◽  
Genetic Factors ◽  
Body Condition Score ◽  
Post Partum ◽  
Murrah Buffaloes ◽  
Factors Influencing ◽  
Condition Score

281 INFLUENCE OF DEFINED AND COMPLEX CULTURE MEDIA ON FERTILIZATION AND EMBRYONIC DEVELOPMENT OF IN VITRO-MATURED CAPRINE OOCYTES

2010 ◽  
Vol 22 (1) ◽  
pp. 297 ◽  
Author(s):  
S. D. Kharche ◽  
P. Yadav ◽  
A. K. Goel ◽  
S. K. Jindal ◽  
M. C. Sharma
Keyword(s):  
Embryonic Development ◽  
Embryo Development ◽  
Culture Media ◽  
Calf Serum ◽  
Defined Medium ◽  
Cleavage Rate ◽  
Group 3 ◽  
Group 2 ◽  
Complex Culture

Complex media containing serum and/or co-culture with somatic cells result in satisfactory development, although the undefined conditions make it impossible to examine requirements of the embryos. Our objective was to compare defined and complex culture systems for their ability to support normal caprine embryonic development. In total, 3844 selected cumulus oocyte complexes (COC) were used for maturation in TCM-199 containing 10% newborn calf serum (NCS), 3 mg mL-1 BSA, 5 μg mL-1 FSH, 5 μg mL-1 LH, and 1 μg mL-1 estradiol-17β and 10 ng mL-1 epidermal growth factor. After 27 h of maturation, oocytes were separated from cumulus and corona cells by treatment with 0.1% hyaluronidase and by passing through a fine-bore pipette. They were then washed in sperm TALP and fertilized in a drop of fertilization TALP (20% estrous goat serum and 10 μg mL-1 heparin) containing 1 to 2 × 106 spermatozoa per mL. Oocytes-sperm after 18 h of co-incubation were washed in embryo development medium 15 to 20 times and randomly divided into 3 groups. Fertilized oocytes were cultured for 10 days in TCM-199 containing 10% NCS and 4 mg mL-1 BSA (group 1; n = 1511), synthetic oviductal fluid (SOF) containing 10% NCS and 4 mg mL-1 BSA (group 2; n = 1333) or potassium simplex optimization medium (KSOM) containing 10% NCS and 4 mg mL-1 BSA (group 3; n = 1000). The cleavage rate for groups 1, 2, and 3 were 13.6, 11.7, and 31.4%, respectively. All data were analyzed by one-way ANOVA; developmental data were arc sin transformed. The cleavage rate was significantly higher (P < 0.01) for group 3 than for groups 1 and 2. Similarly, embryo development up to morula stage was higher (P < 0.05) in KSOM compared with TCM-199 and SOF. This study shows that good development of embryos can be obtained in a completely defined medium and was better in KSOM than in SOF.

scholarly journals 265EFFECT OF SPECIFIC GRAVITY OF CULTURE MEDIUM ON IN VITRO EMBRYO DEVELOPMENT IN BUFFALO

2004 ◽  
Vol 16 (2) ◽  
pp. 253
Author(s):  
D.S. Arathy ◽  
S. Ashis ◽  
G.T. Sharma ◽  
A.C. Majumdar ◽  
M.S. Chauhan
Keyword(s):  
Specific Gravity ◽  
In Vitro Culture ◽  
Culture Medium ◽  
Calf Serum ◽  
Blastocyst Stage ◽  
Culture Conditions ◽  
Cleavage Rate ◽  
Embryo Production ◽  
Cell Stage

In buffalo the success rate of transferable quality embryo production through in vitro procedure is very low as compared to cattle. Sub optimal culture conditions and physical conditions such as specific gravity of the culture medium may lead to a reduced rate of transferable buffalo embryo production from the oocytes matured and fertilized in vitro (Palta &amp; Chauhan,1998 Reprod. Fertil. Dev. 10, 379–391). This experiment was therefore conducted to find out the role of specific gravity of the IVC medium on the development rate of the buffalo embryos in vitro. Follicles of slaughter house ovaries were aspirated and the collected oocytes with cumulus-oocytes complexes (COCs) were cultured in TCM-199 medium supplemented with 10% fetal calf serum, 10% buffalo follicular fluid and 0.5μgmL−1 FSH in 5% CO2 incubator at 38.5°C. The matured oocytes were then inseminated with frozen-thawed buffalo semen suspended in BO medium. After 42h of post-inseminations the cleavage rates were evaluated. The 2–4 cell-cleaved eggs (Day 2 of post-insemination) were randomly divided and cultured for eight days in vitro in 1) modified synthetic fluid (mSOF)+0.8 %BSA (control), 2) mSOF+0.8 % BSA+gelatin (1mgmL−1) 3) mSOF+0.8% BSA+1mgmL−1 gelatin+10ngmL−1 epidermal growth factor (EGF). Supplementation of gelatin increased the specific gravity of the mSOF medium from 0.9658±0.009 to 1.0331±0.013 without any change in pH (7.4). The development of embryos to the 8–16 cell-stage on day 4 of in vitro culture were significantly higher (P&lt;0.05) in mSOF+0.8% BSA+1mgmL−1 gelatin (81.8%; 27/33) than that in mSOF + 0.8% BSA (75.7%; 28/37) and mSOF+0.8% BSA+10ng/mL EGF (68.7%; 22/32). When these embryos were further cultured for another four days (Day 8), the development of transferable quality embryos (morula/blastocyst) was 42.4% (14/33), 48.7% (18/37) and 46.9% (15/32), respectively. Supplementation of gelatin increased the cleavage of eggs up to the 8–16 cell-stage embryo, but did not significantly enhance the rate of development to the morula/blastocyst stage in comparison to control and EGF-supplemented group. However, the percentage of transferable quality embryos was slightly lower in the gelatin-added group but not statistically significant than other groups. The study concluded that increase in specific gravity of the in vitro culture medium enhanced initial cleavage rate but did not have any role in transferable embryo production in buffalo.

Ovarian follicular populations, steroidogenic capacity and physiological status in post-partum suckling beef cows in high and low body condition

1989 ◽  
Vol 1989 ◽  
pp. 149-149
Author(s):  
R. Prado ◽  
S.M. Rhind ◽  
I.A. Wright ◽  
A.J.F. Russel ◽  
S.M. McMillen ◽  
...  
Keyword(s):  
Body Condition ◽  
Body Condition Score ◽  
Post Partum ◽  
Weight Maintenance ◽  
Live Weight ◽  
Beef Cows ◽  
Pulse Frequency ◽  
Physiological Status ◽  
Condition Score ◽  
Maintenance Ration

Recent evidence indicates that body condition at calving has an important effect on the length of the post-partum anoestrous period in beef cows being longer in cows calving in low body condition (Richards et al, 1986, Wright et al, 1987). It is known that body condition affects baseline concentrations of LH (Rutter and Randel, 1984) and LH pulse frequency (Wright et al, 1987). However, the effect of body condition on ovarian follicles has not been studied.An experiment was designed to examine the effect of body condition score (BCS) at calving on follicle populations, follicular steroidogenic capacity, follicular histology and patterns of gonadotropin release at two different stages of the post-partum period (5 and 9 weeks after calving) in suckling beef cows.Thirty-eight suckling Blue-Grey cows with a mean live-weight of 567 ± 9.4 kg and mean BCS of 3.0 ± 0.05 at 110 days before calving to a synchronized insemination were differentially fed so that they achieved BCS of 2.83 ± 0.05 and 2.30 ± 0.05 for cows on a high (H) and low (L) plane of nutrition, respectively. After calving cows were fed a live-weight maintenance ration according to individual requirements. Cows of each BCS were ovariectomized at either 5 (w5) or 9 (w9) weeks after calving and follicles > 3mm in diameter were dissected from the ovaries and incubated for 2 h in culture medium (Medium 199) at 37°C. Follicles were then kept in Bouin's solution until histological examination. Follicle incubates were assayed for progesterone, testosterone and oestradiol. Blood samples were taken 2 days before ovariectomy for 10 h every 15 minutes and were later assayed for LH (all the samples) and FSH (every third sample).

scholarly journals Factors influencing the rates of pregnancy, calving and peri-parturient disorders in heifers at selected char areas of Bangladesh

2016 ◽  
Vol 32 (2) ◽  
pp. 65-72 ◽  
Author(s):  
MM Hossain ◽  
MMU Bhuiyan ◽  
MM Rahman ◽  
NS Juyena
Keyword(s):  
Body Weight ◽  
Body Condition ◽  
Body Condition Score ◽  
Factors Affecting ◽  
Factors Influencing ◽  
Condition Score

The study was conducted to evaluate the factors affecting the rates of pregnancy, calving and peri-parturient disorders in heifers in selected char areas (low lying flood and erosion-prone areas in or adjacent to major rivers) of Lalmonirhat district of Bangladesh. A total of 101 artificial inseminated (AI) heifers were randomly selected for monitoring rates of pregnancy, calving and peri-parturient disorders with respect to breed of semen, source of semen, breed, age, body weight and body condition score (BCS) of heifers. The overall rates of pregnancy, calving and peri-parturient disorder were 51.5%, 45.5% and 32.6%, respectively. The differences were not significant with respect to the factors evaluated (P>0.05).Bangl. vet. 2015. Vol. 32, No. 2, 65-72

scholarly journals 299 IN VITRO DEVELOPMENT OF IMMATURE PORCINE OOCYTES FERTILIZED IN VITRO TO THE BLASTOCYST STAGE

2005 ◽  
Vol 17 (2) ◽  
pp. 300
Author(s):  
T. Somfai ◽  
K. Kikuchi ◽  
S.Y. Medvedev ◽  
A. Onishi ◽  
M. Iwamoto ◽  
...  
Keyword(s):  
Embryonic Development ◽  
Inner Cell Mass ◽  
Polar Body ◽  
Cell Mass ◽  
Cell Number ◽  
Blastocyst Stage ◽  
Oocyte Activation ◽  
Cleavage Rate ◽  
Significant Difference

In vitro fertilization (IVF) and embryonic development of mature and meiotically arrested porcine oocytes were compared in this study. After in vitro maturation (IVM) for 48 h of cumulus-oocyte complexes, 75.4% (n = 442) of them extruded a visible polar body (PB). Most oocytes with a polar body (PB+ group) were found to be at metaphase II (M-II) stage (91.4%). Most oocytes without a visible polar body (PB− group, n = 144) appeared to be arrested at the germinal vesicle (GV) (41.6%) and first meiotic metaphase (M-I) (34.0%) stages. After IVF of oocytes (the day of IVF = Day 0), there was no significant difference between PB+ and PB− groups in rates of sperm penetration, monospermy, and oocyte activation after the penetration. Embryonic development was assessed by staining with 1% orcein. On Day 2, although there was no difference between the embryo cleavage in PB+ (n = 447) and PB− (n = 217) groups (47.0% and 35.9%, respectively), PB+ embryos had more cells than the PB− embryos (3.37 and 2.81 cells, respectively) (P < 0.05; ANOVA). On Day 4, the cleavage rate of PB+ embryos was higher than that of PB− embryos (45.4% and 24.3%, respectively), and PB+ embryos had more cells than the PB− embryos (8.26 and 6.0 cells, respectively) (P < 0.05; ANOVA). On Day 6, a significantly higher number of PB+ embryos developed to the blastocyst stage than that of the PB− embryos (34.6% and 20.7%, respectively) (P < 0.05). However, by subtracting the GV oocytes from the PB− group, there was no difference in blastocyst rates between the M-I arrested and M-II oocytes (35.3% and 34.6%, respectively). The number of blastomer nuclei in embryos obtained from the PB+ group (52.0) was significantly higher than that of the PB− group (29.1); however, the proportion of inner cell mass and trophectoderm cells in PB+ and PB− blastocysts did not differ significantly (1:1.9 and 1:2.2, respectively) (P < 0.05). Chromosome analysis revealed that PB+ blastocysts had significantly more diploid blastomeres (69.7%) than PB− blastocysts (44.0%), whereas PB− blastocysts had significantly more triploid cells (34.0%) compared with PB+ oocytes (8.4%)(P < 0.05; χ2 test). These results indicate that porcine oocytes arrested at the M-I stage undergo cytoplasmic maturation during culture and have the same ability to develop to blastocysts after IVF as M-II oocytes but with a lower cell number; the latter might be caused by the slower embryonic development.

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