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

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

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

289 EFFECTS OF YEAR PERIOD, TECHNICAL TEAM, AND BREED ON THE PREGNANCY RATES AFTER TRANSFER OF IVF BOVINE EMBRYOS IN THE SOUTHERN REGION OF RIO DE JANEIRO

2010 ◽  
Vol 22 (1) ◽  
pp. 301
Author(s):  
B. G. Moura ◽  
J. Almeida ◽  
F. L. Lima ◽  
G. Balbi ◽  
R. Calmerani ◽  
...  
Keyword(s):  
Beef Cattle ◽  
Dairy Cattle ◽  
Embryo Transfer ◽  
Pregnancy Rates ◽  
Chi Square ◽  
Chi Square Test ◽  
Few Data ◽  
Rectal Palpation ◽  
Fresh Embryos

The aim of the work was to study the effects of year period, technical team, breed, beef cattle and dairy cattle on the pregnancy rates in fresh embryos used in bovine transfer of IVF programs. The study was carried out at the fertilization laboratory In Vitro Nyltta Britto de Carvalho, in partnership with In Vitro Brazil, located at the Boa Vista farm, Barra do Pirai, during August 2007 to September 2008, seeking subsidies to improve the use of the technique in the field. During that period, aspirations and inovulations in 3 different periods I (August to December), II (January to April), and III (May to September) were carried out. The jobs were accomplished by 9 technical teams (A, B, C, D, E, F, G, H, and I) rendering services to the laboratory, by working with 2 beef breeds (Brahman and Nelore) and 3 dairy breeds (Gir, Girolando, and Holstein). The different breed receivers were synchronized, and in general, from 6 to 8 days after heat, they received embryo transfer, the cervical way, under low epidural anesthesia, where each female received 1 fresh embryo of IVF. All cows were submitted to gestation diagnosis by rectal palpation and ultrasonography, in general, 42 days after embryo transfer. The numbers of embryo transferred and pregnancy rates were submitted to the chi-square test, which presented significant differences (P < 0.05). There were pregnancy rates of 36.25%a (n = 960), 39.83%a (n = 1180), and 32.59%b (n = 919) in the I, II, and III periods, respectively. Among the 9 technical teams, there were verified pregnancy rates (%) of 33.51d (n = 1313), 30.30d (n = 330), 35.00cd (n = 405), 39.24cd (n = 1060), 59.25a (n = 7), 33.33d (n = 24), 53.57bc (n = 28), 43.31c (n = 157), and 58.33ab (n = 12) for A, B, C, D, E, F, G, H, and I teams, respectively. Among breeds there were rates (%) of 36.89ab (n = 412), 34.68b (n = 1286), 35.13ab (n = 74), 38.94a (n = 1140), and 37.80ab (n = 82) for Brahman, Nelore, Gir, Girolando, and Holstein, respectively. In the study, pregnancy rates (%) of 35.21b (n = 1698) in beef cattle and 38.65a (n = 1296) in dairy cattle were observed. The differences in pregnancy rates with respect to the evaluated factors, may be explained by individual, breed, and nutritional variations of the animals. There are few data in the literature with results on the embryo transfer use of IVF bovine under field conditions.

60 Reproductive Performance After Timed Artificial Insemination Followed by Timed Embryo Transfer of In Vitro-Produced Embryos in Beef Cattle

2018 ◽  
Vol 30 (1) ◽  
pp. 169
Author(s):  
G. Holguin-Sanabria ◽  
F. J. F. Collares ◽  
E. P. Silva ◽  
L. H. Aguiar ◽  
P. Rodriguez-Villamil ◽  
...  
Keyword(s):  
Beef Cattle ◽  
Embryo Transfer ◽  
Breeding Season ◽  
Reproductive Performance ◽  
Bos Taurus ◽  
Pregnancy Rates ◽  
Release Device ◽  
Chi Squared ◽  
Rectal Palpation

The combined use of timed AI (TAI) and embryo transfer (TET) has the potential to increase reproductive efficiency in beef cattle. This study evaluated reproductive performance in beef cattle after TAI followed by TET of in vitro-produced embryos at the onset of the breeding season. A total of 476 multiparous non-suckling Bos taurus females (body condition scores of 2.9 ± 0.4 on 1 to 5 scale) were oestrous synchronized with 2 mg of oestradiol benzoate (IM) and a 1.9-g intravaginal progesterone release device (Day –11), which was removed on Day –2, followed by 0.48 mg of sodium cloprostenol, 400 IU of eCG, and 0.5 mg of oestradiol cypionate (IM). In experiment I [no heat detection (HD), or no HD, n = 387], TAI was carried out 48 h later (Day 0), whereas in experiment II (after HD, n = 89), AI was performed 12 h after the onset of oestrus up to 48 h after intravaginal insert removal, when remaining females were inseminated (Day 0). Day-7 blastocysts produced by IVF from abattoir-derived oocytes were individually transferred (TET) 7 days after TAI (Day 7) to 186/387 and 44/89 females in experiments I and II, respectively, ipsilateral to the corpus luteum. Then, fertile mature Bos taurus bulls were introduced on Day 12 into the herds (1:25) up to Day 90. Determinations of pregnancy outcome after TAI, TAI+TET or natural mating, twinning rates, and pregnancy losses were done by ultrasonography and rectal palpation on Days 30, 60, and 125. Data were analysed by the Chi-squared test (P < 0.05). Pregnancy rates (Day 30) were lower after TAI (104/201, 51.7%) than after TAI+TET (126/186, 67.7%) with no HD (experiment I), but similar between TAI (32/45, 71.1%) and TAI+TET (30/44, 68.2%) after HD (experiment II). Twinning rates were lower in TAI groups with no HD (6/104, 5.8%) and after HD (2/32, 6.2%) than in TAI+TET groups with either no HD (42/126, 33.3%) or with HD (14/30, 46.7%). Overall pregnancy was similar between groups after the end of the breeding season: 90.0% (181/201) and 90.3% (168/186) for TAI and TAI+TET with no HD, and 84.4% (38/45) and 84.1% (37/44) for TAI and TAI+TET after HD. Pregnancy losses were higher after TAI+TET with no HD (27/126, 21.4%) than TAI+TET after HD (3/30, 10.0%), and TAI with (2/32, 6.3%) or without (9/104, 8.7%) HD. The TAI+TET with no HD resulted in fewer fetuses per served (0.69) and pregnant (1.30) female than TAI+TET after HD (0.89 and 1.44), whereas TAI with no HD had fewer fetuses than TAI after HD per served (0.50 v. 0.69) but not per pregnant female (1.05 v. 1.03), with both being lower than the TAI+TET groups. In summary, TET after TAI with no HD increased pregnancy and twinning rates. Also, heat detection increased pregnancy rates after TAI and twinning rates after TAI+TET. The TAI+TET combination may be advisable for reproductive schemes with no HD, whereas no benefit of TAI+TET was seen over TAI regarding pregnancy rate if TAI is coupled with HD, but HD may increase prolificacy after TAI+TET. The economics of the use of TAI+TET is under evaluation, by assessing calving, weaning, and postnatal weight gain rates between groups.

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

2006 ◽  
Vol 18 (2) ◽  
pp. 203
Author(s):  
C. Ponsart ◽  
H. Quinton ◽  
A. Rohou ◽  
J. Kelhembo ◽  
G. Bourgoin ◽  
...  
Keyword(s):  
Pregnancy Rates ◽  
Chi Square ◽  
Frozen Embryos ◽  
Multivariate Logistic Model ◽  
Parity Number ◽  
Embryo Stage ◽  
Chi Square Analysis ◽  
Fresh Embryos ◽  
Donor Cows

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. >4 h = 55.5% (n = 155); P > 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 < 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.

034 Impact of Progesterone Supplementation on Pregnancy Rates Following Timed AI or Embryo Transfer in Beef Cattle Consuming Endophyte-Infected Fescue

2016 ◽  
Vol 94 (suppl_1) ◽  
pp. 17-17
Author(s):  
J. C. Mackey ◽  
T. L. Devine ◽  
P. M. Kennedy ◽  
A. M. Tyson ◽  
M. H. Poore ◽  
...  
Keyword(s):  
Beef Cattle ◽  
Embryo Transfer ◽  
Pregnancy Rates ◽  
Progesterone Supplementation

scholarly journals The incompletely fulfilled promise of embryo transfer in cattle—why aren’t pregnancy rates greater and what can we do about it?

2020 ◽  
Vol 98 (11) ◽  
Author(s):  
Peter J Hansen
Keyword(s):  
Embryo Transfer ◽  
Artificial Insemination ◽  
Blastocyst Stage ◽  
Pregnancy Rates ◽  
Bovine Embryos ◽  
Uterine Receptivity ◽  
Stage Of Development ◽  
Stage Embryo ◽  
Repeat Breeder ◽  
In Pregnancy

Abstract Typically, bovine embryos are transferred into recipient females about day 7 after estrus or anticipated ovulation, when the embryo has reached the blastocyst stage of development. All the biological and technical causes for failure of a female to produce a blastocyst 7 d after natural or artificial insemination (AI) are avoided when a blastocyst-stage embryo is transferred into the female. It is reasonable to expect, therefore, that pregnancy success would be higher for embryo transfer (ET) recipients than for inseminated females. This expectation is not usually met unless the recipient is exposed to heat stress or is classified as a repeat-breeder female. Rather, pregnancy success is generally similar for ET and AI. The implication is that either one or more of the technical aspects of ET have not yet been optimized or that underlying female fertility that causes an embryo to die before day 7 also causes it to die later in pregnancy. Improvements in pregnancy success after ET will depend upon making a better embryo, improving uterine receptivity, and forging new tools for production and transfer of embryos. Key to accelerating progress in improving pregnancy rates will be the identification of phenotypes or phenomes that allow the prediction of embryo competence for survival and maternal capacity to support embryonic development.

188 EFFECT OF TRANSFER OF FROZEN-THAWED IVF EMBRYOS ON PREGNANCY IN REPEAT-BREEDER INSEMINATED OR NON-INSEMINATED HOLSTEIN CATTLE

2006 ◽  
Vol 18 (2) ◽  
pp. 202 ◽  
Author(s):  
O. Dochi ◽  
M. Tanisawa ◽  
S. Goda ◽  
H. Koyama
Keyword(s):  
Pregnancy Rate ◽  
Embryo Transfer ◽  
Calf Serum ◽  
Pregnancy Rates ◽  
Holstein Cattle ◽  
Chi Square ◽  
Vitro Fertilization ◽  
Chi Square Test ◽  
Repeat Breeder

Repeat-breeding is one of the important factors that affect dairy management. The objective of this study was to investigate the effect of transfer of frozen–thawed IVF embryos on pregnancy in repeat-breeder Holstein cattle. Cumulus–oocyte complexes (COCs) were collected by aspiration of 2–1-mm follicles from ovaries obtained at a local abattoir. COCs were matured for 20 h in TCM-199 supplemented with 5% calf serum (CS) and 0.02 mg/mL of FSH at 38.5°C under a 5% CO2 atmosphere in air. Matured oocytes were inseminated with spermatozoa of 5 × 106/mL in BO solution (Brackett and Oliphant 1975 Biol. Reprod. 12, 260–274) containing 10 mM hypotaurine and 4 units/mL heparin. After 18 h of gamete co-culture, presumptive zygotes were cultured in CR1aa (Rosenkrans et al. 1991 Theriogenology 35, 266) supplemented with 5% CS for 8 days at 38.5°C under 5% CO2, 5% O2, 90% N2 atmosphere in air. After in vitro fertilization, Day 7 and Day 8 blastocysts were frozen in 1.5 M ethylene glycol (EG) in Dulbecco's PBS (DPBS) supplemented with 0.1 M sucrose and 20% CS. Embryos were transferred into a freezing medium, loaded into 0.25-mL straws, and allowed to stand for 15–20 min for equilibration. The straws were then plunged into a −7°C methanol bath of a programmable freezer for 1 min, seeded at −7°C, maintained at −7°C for 15 min, cooled to −30°C at the rate of −0.3°C/min, and then plunged into liquid nitrogen. Recipient animals (43 heifers, 131 cows) included those that did not conceive after being artificially inseminated (AI) 3 to 15 times. The frozen–thawed IVF embryos were directly transferred to the recipient animals 7 days after estrus or AI. Pregnancy rates were analyzed by chi-square test. The results are presented in Table 1. There were no significant differences in the pregnancy rates between treatments. However, a slightly higher pregnancy rate was achieved by embryo transfer after AI. These results suggest that embryo transfer may increase the pregnancy rate in repeat-breeder Holstein cattle. Table 1. Pregnancy rates after transfer of IVF frozen–thawed embryos in repeat-breeder Holstein cattle

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

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

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

Embryo mortality in maiden hereford x friesian heifers following embryo transfer

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

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

84 Effect of Embryo Stage and Cryopreservation Method on Pregnancy Rates Obtained Following the Transfer of In Vivo-Derived Ovine Embryos on Small-Scale Farms in Thailand

2018 ◽  
Vol 30 (1) ◽  
pp. 181
Author(s):  
S. Khunmanee ◽  
J. Suwimonteerabutr ◽  
M. Techakumphu ◽  
T. Swangchan-Uthai
Keyword(s):  
Pregnancy Rate ◽  
Embryo Transfer ◽  
Blastocyst Stage ◽  
Pregnancy Rates ◽  
Slow Freezing ◽  
Small Scale ◽  
Tropical Conditions ◽  
Frozen Embryos ◽  
Embryo Stage ◽  
Cryopreservation Method

Assisted reproductive technologies including superovulation, laparoscopic AI (LAI), and embryo transfer (ET) are important tools for genetic improvement in the sheep industry. The present study aimed to determine the effects of embryo stage and cryopreservation method on field trial outcomes of embryo transfer on small-scale farms in Thailand. Black Dorper ewes (n = 16) were used as donors and mixed breed ewes (n = 21) were used as recipients. Donors were superovulated as previously described (Tríbulo et al. 2012 Theriogenology 77, 1679-1685, 10.1016/j.theriogenology.2011.12.013) and inseminated by LAI within 22 to 24 h after standing heat (Day 0). Donors females were flushed on Day 2 to recover 2- to 8-cell embryos (n = 8) or on Day 6 to recover blastocyst-stage embryos (n = 8). Recovered embryos were randomly cryopreserved by either slow freezing or vitrification methods. Into 21 recipients was inserted an intravaginal device impregnated with CIDR® that was left in place for 10 days. Those received 300 IU of pregnant mare serum gonadotropin (PMSG) on Day 9 and randomly assigned to receive embryos on either Day 2 or 6 after oestrus. Two- to 8-cell embryos were thawed and transferred into the ipsilateral oviduct (n = 1-5 embryos/recipient) on Day 2. Five recipients received 15 slow-frozen embryos and 5 received 13 vitrified embryos. Blastocyst stage embryos were thawed and transferred into the ipsilateral uterine horn (n = 1-4 embryos/recipient) on Day 6. Five recipients received 11 slow-frozen embryos and 4 received 7 embryos. Pregnancy diagnosis was determined by ultrasonography 45 days after embryo transfer. Pregnancy rate was calculated as the proportion of ewes with at least one pregnancy out of the total number of ewes that received embryos. Chi-squared analysis was used to determine the effects of embryo freezing technique and embryo stage on pregnancy rate (SAS 9.2, SAS Institute Inc., Cary, NC, USA). All donor ewes responded to the superovulation program (donor had 3 to 6 corpora lutea). The mean number of viable embryos recovered was 4.3 ± 2.4 and 3.1 ± 3.7 for Day 2 and Day 6, respectively. Nineteen of the 21 recipient ewes responded to the synchronization program and received embryos in the study. There was no effect (P > 0.05) of embryo stage (5/10 = 50% v. 3/9 = 33.3% for 2- to 8-cell v. blastocyst, respectively) or cryopreservation method (4/10 = 40% v. 4/9 = 44.4% for slow-freezing and vitrification, respectively) on pregnancy rate following embryo transfer. Results of the present study suggest that similar pregnancy rates following embryo transfer in sheep under tropical conditions in Thailand can be obtained using either 2- to 8-cell embryos or blastocyst-stage embryos and with embryos that have been cryopreserved by slow-freezing or vitrification. Further research with larger numbers of animals is necessary to confirm the preliminary results of the present study.

Evaluating recipient and embryo factors that affect pregnancy rates of embryo transfer in beef cattle

2001 ◽  
Vol 56 (2) ◽  
pp. 287-297 ◽  
Author(s):  
A.R. Spell ◽  
W.E. Beal ◽  
L.R. Corah ◽  
G.C. Lamb
Keyword(s):  
Beef Cattle ◽  
Embryo Transfer ◽  
Pregnancy Rates
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