205 INCREASED PREGNANCY RATES OF POOR QUALITY BOVINE EMBRYOS BY ASSISTED HATCHING

2007 ◽  
Vol 19 (1) ◽  
pp. 219
Author(s):  
A. Taniyama ◽  
Y. Watanabe ◽  
Y. Nisino ◽  
T. Inoue
Keyword(s):  
Embryo Transfer ◽  
Zona Pellucida ◽  
Poor Quality ◽  
Pregnancy Rates ◽  
Assisted Hatching ◽  
Bovine Embryos ◽  
Production Rates ◽  
Chi Square ◽  
Chi Square Test ◽  
Rectal Palpation

Embryo transfer after superovulation is commonly used for efficient embryo and animal production and for genetic improvement in cattle. However, the quality of collected embryos varies greatly, which affects pregnancy rate. Usually, poor quality embryos are related to low pregnancy rates after embryo transfer and low viability after cryopreservation. Therefore, it is important to improve chances for survival of poor quality embryos after embryo transfer. The objective of this experiment was to improve pregnancy rates by applying the assisted hatching technique to poor quality embryos. Embryos were collected from Japanese Black cows after superovulation on Day 7 post-insemination. After being washed, embryos were morphologically classified. Embryos having more than 30% degenerated cells were assigned as poor quality embryos. The assisted hatching of embryos (cutting the zona pellucida) was performed under a stereoscope or an inverted microscope by making a cutting slit on the zona pellucida for about 20% of its circumference using a micromanipulator equipped with a cutting needle and holding pipette. After cutting, single or two embryos were transferred fresh to one uterine horn of recipient cows on Day 7 of the estrous cycle. Pregnancy and calf production rates were compared between 2 embryo transfer groups composed of fresh zona-cut embryos (ZC group) or fresh embryos with non-cut zonae pellucidae (NZC group). Pregnancy rates were determined by rectal palpation on Day 45, and calf production rates were calculated by the following formula: number of calves born/number of pregnancies. Statistical analysis was carried out using the chi-square test. Pregnancy rates of poor quality embryos in the double ET ZC group (60.3%; 44 pregnancies/73 transfers) were significantly higher (P < 0.05) than those in the single ET NZC group (25.0%; 6 pregnancies/24 transfers) and in the single ET ZC group (44.0%; 37 pregnancies/84 transfers). Calf production rates were 67.3%, 45.5%, and 35.6% for the double ET ZC group, the double ET NZC group, and the single ET ZC group, respectively. Pregnancy rates of poor quality bovine embryos after double ET were remarkably improved by assisted hatching compared with those of single ET with non-assisted hatching. These results suggest that the combined methods of assisted hatching and double ET may be beneficial to produce calves from poor quality embryos.

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.

86 Difficulty of Transfer of In Vivo-Derived Bovine Embryos and Route of Administration of Flunixin Meglumine at the Time of Transfer may Affect Pregnancy Rate

2018 ◽  
Vol 30 (1) ◽  
pp. 182
Author(s):  
J. Duran ◽  
D. Argudo ◽  
S. Bravo ◽  
C. Soria ◽  
G. Guevara ◽  
...  
Keyword(s):  
Embryo Transfer ◽  
Bos Taurus ◽  
Bos Indicus ◽  
Prostaglandin F2α ◽  
Bovine Embryos ◽  
Chi Square ◽  
Evaluation Systems ◽  
Flunixin Meglumine ◽  
Chi Square Test

Recipient handling during embryo transfer (ET) induces prostaglandin F2α (PGF2α) production in 2 periods: an early transient and rapid increase around the time of ET, followed by another 2 to 4 h later. This PGF2α is associated with embryonic loss during early gestation by affecting both the embryo and the corpus luteum. To control this, antiprostaglandins such as flunixin meglumine (FM) have been applied IM at the time of ET with varying results. In such studies, the interaction of IM administration of FM and difficulty of transfer has not always been evaluated, possibly confusing the interpretation of the results. Furthermore, IV FM injection at ET and its relationship with pregnancy rates (PR) has not been determined. The objectives were (1) to determine the relationship between difficulty of ET and PR; and (2) to evaluate the efficacy of IM v. IV FM on pregnancy outcomes. One hundred and ten crossbred (Bos taurus × Bos indicus) heifers (18-24 months old) from 3 farms were used as recipients. Two evaluation systems of ET difficulty were used: (1) duration of transfer (objective determination of the elapsed time measured in seconds between the introduction of the catheter and embryo release), and (2) level of difficulty experienced by the practitioner (subjective determination; 1 = minimum and 2 = medium to extreme manipulation). Quality 1 and 2 fresh embryos from superovulated cows were transferred by the same practitioner. At ET, recipients were randomly divided into 3 groups: (1) Control (no treatment, n = 31); (2) FM-IM (n = 39): injected IM with 2.2 mg kg−1 FM at ET; and (3) FM-IV (N = 40): injected with 2.2 mg kg−1 FM IV at ET. Pregnancy was diagnosed at 30 to 40 and 60 to 90 days after ET. Spearman’s test was performed to determine the correlation between duration and difficulty at ET and Chi-square test was used to compare PR. The mean duration of transfer for all heifers was 62.3 ± 57.5 s (11 to 357 s; median: 44.5 s). There was a high correlation (0.8; P < 0.001) between the ET difficulty evaluation systems. Overall, ET difficulty 1 had higher PR than ET difficulty 2 (64.2 v. 40.7; P = 0.013). The PR was significantly improved (P < 0.01) in the FM-IV group (75 and 70% at 30 and 60 days after ET) compared with control (45.2 and 32.3%) and FM-IM (33.3 and 30.7%). In conclusion, results indicate that the difficulty of transfer affects PR achieved following the transfer of in vivo-derived bovine embryos. Treatment with FM-IV following transfer resulted in significantly higher PR compared with control and FM-IM recipients. The IV injection of FM may antagonize the very early and transient increase of PGF2α caused by genital tract manipulation (even gently performed) at embryo transfer. Further research is necessary to confirm the results of the present study.

204 RELATIONSHIP BETWEEN RESPIRATORY ACTIVITY AND THE PREGNANCY RATE OF BISECTED BOVINE EMBRYOS IN VIVO

2007 ◽  
Vol 19 (1) ◽  
pp. 219 ◽  
Author(s):  
S. Moriyasu ◽  
H. Hirayama ◽  
K. Sawai ◽  
S. Kageyama ◽  
S. Aoyagi ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Pregnancy Rate ◽  
Embryo Transfer ◽  
Respiratory Activity ◽  
Pregnancy Rates ◽  
Bovine Embryos ◽  
Chi Square ◽  
Important Indicator ◽  
Consumption Rates

Oxygen consumption is an important indicator of the metabolic activity of living cells, which may provide valuable information for evaluating embryo quality. We have found that the bovine embryos with high oxygen consumption possess stronger potential for further development. However, the relationship between respiratory activity and the pregnancy rate of embryos is still unclear. In this study, we investigated the respiration rates of bisected bovine embryos and the pregnancy rates of demi-embryos after embryo transfer. Compact morula-stage embryos were bisected evenly by micro glass needle. One hundred bisected embryos were incubated for 24 h in embryo culture medium (IVD101; Research Institute for the Functional Peptides, Yamagata, Japan) at 39�C under 5% CO2, 5% O2, 90% N2. After the incubation, demi-embryos were classified into 2 groups: blastocoel-formed (BC) and blastocoel-not-formed (CM) embryos. Oxygen consumption rates of demi-embryos were measured by scanning electrochemical microscopy (SECM; Hokuto Denko Corporation, Tokyo, Japan). Within 3 h after the measurement, 80 demi-embryos were transferred into recipient cows (one demi-embryo/one recipient) at 7–8 days after estrus. Recipient cows were diagnosed for pregnancy by ultrasonography approximately 40 days after estrus. Statistical difference was analyzed by Tukey's post-hoc test and chi-square test. A total of 27 recipient cows became pregnant; the pregnancy rates for cows with CM and BC demi-embryos were 40.6% (13/32) and 29.2% (14/48), respectively. Mean oxygen consumption rates (� 10-14 mol s-1) in pregnant and non-pregnant cows were 0.47 and 0.39 for CM demi-embryos and 0.63 and 0.52 for BC demi-embryos, respectively. Retrospective analysis showed that the respiratory activity of demi-embryos in the pregnant group was higher than those in the non-pregnant group. In particular, the pregnancy rates for demi-embryos with respiratory activity higher than 0.35 in CM and 0.40 in BC groups were 52.0% (13/25) and 35.9% (14/39), respectively. On the other hand, cows with demi-embryos having an oxygen consumption rate under 0.35 in CM (n = 7) and 0.40 in BC (n = 9) groups did not become pregnant. These results demonstrated that bovine demi-embryos with higher respiratory activity showed a high pregnancy rate after embryo transfer. It is generally known that the pregnancy rate after the transfer of bisected embryos is lower than that of whole embryos. The measurement of oxygen consumption by SECM procedures is a useful tool to assess the quality of pre-implantation embryos and may contribute to the improvement of the success rate for bisected embryo transfer.

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.

176 PREGNANCY AND PREGNANCY LOSS RATES OF ACYCLIC RECIPIENT MARES TREATED WITH TWO DIFFERENT LONG-ACTING PROGESTERONE CONCENTRATIONS

2010 ◽  
Vol 22 (1) ◽  
pp. 246 ◽  
Author(s):  
G. M. Greco ◽  
J. A. Dell'aqua Jr ◽  
M. A. Alvarenga
Keyword(s):  
Embryo Transfer ◽  
Pregnancy Loss ◽  
Estradiol Benzoate ◽  
Pregnancy Rates ◽  
Chi Square ◽  
Chi Square Test ◽  
Group 2 ◽  
Long Acting ◽  
Group 1 ◽  
Loss Rates

Long-acting progesterone compounds containing concentrations of 150 mg mL-1 (P4LA150) have been routinely used in Brazil, especially at the beginning and end of the breeding season when the percentage of recipient mares showing normal estrous cycles is low compared to donors (Greco GM et al. 2008 Proceedings 7th International Symposium on Equine Embryo Transfer, 59-60). However, recipients treated with P4LA150 must receive weekly administrations until pregnancies achieve 100 days. The present study aimed to evaluate pregnancy and pregnancy loss rates from acyclic mares treated at 7-day intervals with P4LA150 and 14-day intervals with a long-acting progesterone formulation containing 300 mg mL-1 (P4LA300). Acyclic Campolina breed mares (n = 80) ranging from 4 to 13 years old showing considerable endometrial edema 2 days after estradiol benzoate injection (5 mg, i.m.) were split in 2 groups. Group 1 mares (n = 40) received 10 mL of P4LA150 (1500 mg) i.m. every 7 days, whereas Group 2 mares (n = 40) were treated with 10 mL of P4LA300 (3000 mg) i.m. every 14 days. Steroid hormone formulations were produced in our research laboratory, at São Paulo State University, Botucatu, Brazil. Embryos 7 to 8 days of age were transferred into the uteri of recipients between 4 and 7 days after the first progesterone administration. Following a positive pregnancy diagnosis at 14 to 15 days, mares were examined at Days 50 and 100, when progesterone treatment was discontinued. These evaluations were conducted in order to determine pregnancy loss rates during both periods. Results were analyzed through the chi-square test and significance was set at P < 0.05. Pregnancy rates and pregnancy loss rates at Day 50 from mares treated with P4LA150 (Group 1) and P4LA300 (Group 2) did not differ. Pregnancy rates were 60.0% (24/40) and 75.0% (30/40) at Day 50 for mares treated with P4LA150 (Group 1) and P4LA300 (Group 2), respectively (P > 0.10). Pregnancy loss rates at Day 50 were 8.3% (2/24) and 10.0% (3/30) for mares treated with P4LA150 and P4LA300, respectively (P > 0.10). Pregnancy losses were not identified at Day 100. Based on the results from the present study, we concluded that acyclic recipient mares treated with P4LA150 or P4LA300 are able to obtain satisfactory pregnancy rates with low pregnancy losses. Moreover, the use of 3000 mg of long-acting progesterone every 14 days reduces overall progesterone administrations, minimizes stress in horse handling, and makes the choice for acyclic recipient mares more appealing in commercial embryo transfer programs. Authors would like to thank FAPESP for financial support.

scholarly journals Assisted Hatching of Poor-quality Bovine Embryos Increases Pregnancy Success Rate After Embryo Transfer

2011 ◽  
Vol 57 (4) ◽  
pp. 543-546 ◽  
Author(s):  
Atsushi TANIYAMA ◽  
Yasutaka WATANABE ◽  
Youji NISHINO ◽  
Tetsurou INOUE ◽  
Yasuho TAURA ◽  
...  
Keyword(s):  
Success Rate ◽  
Embryo Transfer ◽  
Poor Quality ◽  
Assisted Hatching ◽  
Bovine Embryos

THE EFFECT OF ASSISTED HATCHING IN FROZEN-THAWED EMBRYO TRANSFER CYCLES

2016 ◽  
pp. 80-84
Author(s):  
Thi Tam An Nguyen ◽  
Minh Tam Le ◽  
Ngoc Thanh Cao
Keyword(s):  
Embryo Transfer ◽  
Zona Pellucida ◽  
Assisted Hatching ◽  
Implantation Failure ◽  
Multiple Pregnancies ◽  
Recurrent Implantation Failure ◽  
Key Words Laser ◽  
Implantation And Pregnancy Rates ◽  
Frozen Thawed Embryo Transfer ◽  
Thawed Embryo Transfer

Background: Laser assisted hatching technique based on the hypothesis to make an artificial hole on zona pellucida (ZP) that can help embryo hatching out of ZP easily. This technique has been shown to increase implantation and pregnancy rates in women of advanced age, in women with recurrent implantation failure and following the transfer of frozen–thawed embryos. This study described the outcome of frozen–thawed embryo transfers with laser assisted hatching (LAH), which is one of the safest method in nowadays. Purpose: To assess the effect of assisted hatching technique on the clinical outcomes in vitrified-warmed transfer cycles. Method: A total of 65 thawed-transfer cycles with 153 thawed-embryos undertaken within a 12-month period were analysed, Assisted hatching with laser zona thinning was performed with one-quarter of the zona pellucida circumference. The overall thawed-embryos (day 3) were kept in culture overnight. Patient were prepared the suitable endometrium and transferred embryos advantageously. Results: In which, having the rate of survival embryos were 143 occupying 94.3%, the percentage of grade 1 and 2 embryos occupied 55.9% and 29,3% respectively, and that were enrolled LAH before transfering of frozen–thawed embryos. The average transferred embryos were 2.4±0.8, The rate of implantation per transferred embryos and per transferred embryos cycles was 19.5% and 43.1% respectively. The rate of clinical pregnancies per embryo transfer cycles occupied 33.8% with percentage of early miscarriages (biochemical pregnancies and early clinical miscarriages) was 12.3%. The rate of ongoing pregnancies was 30.8% and multiple pregnancies was low just 12.3%. This result was equal or higher than other researchs in embryos transfer had or no LAH. Conclusion: LAH contributed to stable frozen–thawed embryos transfer effectiveness. Key words: Laser assisted hatching, frozen–thawed embryos transfer, zona pellucida (ZP)

scholarly journals Calving sub-season and reproductive efficiency of beef cows

2010 ◽  
Vol 39 (10) ◽  
pp. 2182-2186
Author(s):  
Cristiane Reinher ◽  
Júlio Otávio Jardim Barcellos ◽  
Vanessa Peripolli ◽  
Ênio Rosa Prates ◽  
Maria Eugênia Andrighetto Canozzi
Keyword(s):  
Pregnancy Rate ◽  
Beef Cows ◽  
Pregnancy Rates ◽  
Reproductive Efficiency ◽  
Climate Variations ◽  
Southern Brazil ◽  
Chi Square ◽  
Chi Square Test

It was evaluated in this work the effect of calving sub-season on the pregnancy rate of 7,726 multiparous Hereford beef cows grazing on natural pastures in southern Brazil, from 1994 to 2007. Calving sub-season periods were divided in 20-day intervals from August 12th to 31st; from September 1st to 20th; from September 21st to October 10th; from October 11th to 31st; from November 1st to 20th. Calving in each sub-season and pregnancy rate (PR) were analyzed by the Chi-square test. Overall means of each sub-season were 92.7% (from August 12th to 31st), 90.6% (from September 1st to 20th), 82.1% (from September 21st to October 10th), 77.7% (from October 11th to 31st), and 70.6% (from November 1st to 20th). Calving sub-season significantly influenced pregnancy rate. Cows which calved in the initial sub-season showed higher pregnancy rates than cows which calved from the fourth calving sub-season. However this difference did not occur in 1999 and in 2007 since calving rates did not statistically differ among the five sub-seasons. In 1998 and 2004, calving rates were lower and the effects of calving sub-season on pregnancy rates were higher, possibly due to climate variations. In general, pregnancy rate decreases as calving occurs later in the year, particularly in years when the weather adversely affects pasture growth.

scholarly journals 243 PREGNANCY RATES IN THE FIELD AFTER THE TRANSFER OF BOVINE IVP EMBRYOS VITRIFIED BY THE CRYOLOGIC VITRIFICATION METHOD

2005 ◽  
Vol 17 (2) ◽  
pp. 272 ◽  
Author(s):  
R. Fry ◽  
C. Earl ◽  
K. Fry ◽  
W. Lindemans
Keyword(s):  
Large Scale ◽  
Bos Taurus ◽  
Bos Indicus ◽  
Pregnancy Rates ◽  
Chi Square ◽  
Full Field ◽  
Transfer Programs ◽  
Short Period ◽  
Rectal Palpation ◽  
User Friendly

Although large numbers of IVP embryos can be produced from donor cattle in a short period of time, commercial acceptance of the technology depends on the ability to cryopreserve these embryos and achieve a 50% pregnancy rate in large-scale embryo transfer programs. Many studies have reported low pregnancy rates of about 20% after the transfer of cryopreserved IVP embryos. We have developed the user friendly CryoLogic Vitrification Method (CVM) that vitrifies embryos on a solid surface at −196°C and warms them rapidly in a one-step procedure prior to transfer (Lindemans et al. 2004 Reprod. Fertil. Dev. 16, 174). We present an overview of the pregnancy rates in the field after vitrification of bovine IVP embryos by the CVM. The bos taurus IVP embryos in southern Australia (bT) and the bos indicus-based IVP embryos in northern Australia (bI) were produced by our standard TVR and IVP methodology (Fry et al., 2003 Theriogenology 59, 446). Pregnancy was determined by rectal palpation between Day 40 and Day 90 and differences between treatments were analyzed by chi-square. The development of the CVM has enabled the successful cryopreservation of bovine IVP embryos. In the laboratory the typical survival (90% re-expansion) and development (80% hatching) of IVP embryos post-vitrification is high and, as demonstrated here, the pregnancy rates after transfer are approaching commercially acceptable levels. However, further research is required to identify factors that may influence success under full field conditions, for both the IVP and the vitrification technologies. Table 1. Pregnancy rates for fresh IVP, CVM-vitrified IVP, and traditionally flushed embryos cryopreserved in glycerol

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