Factors affecting the survival of sheep embryos after transfer within a MOET program

University of Wales, Cardiff, Wales, United Kingdom
Theriogenology (Impact Factor: 1.85). 03/2003; 59(5-6):1265-75. DOI: 10.1016/S0093-691X(02)01162-7
Source: PubMed

ABSTRACT Multiple ovulation and embryo transfer (MOET) has the potential to increase the rate of genetic improvement in sheep. However, better realization of this potential requires maximum survival rates of transferred embryos of high genetic merit after transfer into recipient ewes. These studies were therefore conducted to investigate the effect of both embryonic and recipient ewe factors on the survival rate of transferred embryos. Survival rate was similar after transfer of morula or blastocyst stage embryos, and these were higher (P<0.05) than for very early morulae and early morulae. Advanced embryos (Day 5 blastocyst) had an advantage (P<0.05) in survival rate over retarded embryos (Day 6 morula). Grades 1 and 2 embryos survived significantly (P<0.05) better than Grades 3 or 4 embryos. There was no difference in embryo survival rate following transfer to recipients with different numbers of corpora lutea. In general, age or parity of recipient ewes did not affect embryo survival rate, although a higher (P<0.05) embryo survival rate was observed for yearling recipients. Buserelin (GnRH agonist) treatment of recipient ewes 5 or 6 days after transfer of embryos (Day 12 of the cycle) did not improve embryo survival rate. These results confirm that both embryonic and recipient factors can play an important role in the success of a MOET program in sheep.

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Available from: Will Haresign, Jul 28, 2015
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    • "corpus luteum produced in response to exogenous GnRH treatment is similar to that of a corpus luteum induced by natural mating, the corpus luteum does not reach maximal diameter until after Day 7 after mating (Ratto et al., 2006). Plasma progesterone levels in alpacas are likely to be at their highest 7 or 8 days after induction of ovulation (Ratto et al., 2006; Trasorras et al., 2010) and may contribute to higher success rates of embryo transfer in this study on Days 7 and 8. Significantly lower pregnancy rates following embryo transfer in the early stages of the recipient ovarian cycle (Days 5, 5.5 and 6) have also been shown in cattle (Wright, 1981) and sheep (Bari et al., 2003). The interval in days between ovarian synchrony of donor and recipient females was +1 day in 21 donorrecipient pairs (6 crias born, ET success rate 28.6%), 0 days in 501 pairs (214 crias born, ET success rate 42.7%), −1 day in 3904 pairs (1665 crias born, ET success rate 42.6%) and −2 days in 76 pairs (6 crias born, ET success rate 7.9%). "
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    ABSTRACT: Embryo transfer offers great advantages to South American camelid farmers to reach their breeding goals but the technology still plays a relatively minor role in comparison to other domestic farm animals like cattle. The aim of the present study was to analyse a data set of 5547 single or multiple ovulation embryo transfers performed in commercial alpaca farms in Australia to determine the factors that influence number and quality of embryos produced, embryo transfer success (percentage of crias born) and gestation length following transfer. Logistic binary regression identified the variables day of flushing after mating, embryo diameter, embryo quality, day of transfer after GnRH, and the age of the recipient to have significant impact on the outcome measure embryo transfer success. Transfer of smaller embryos or lower quality embryos resulted in decreased transfer success rates. Optimal days for obtaining embryos from donors were Days 8 and 9 after mating, optimal days for transfer into recipients were Days 7 and 8 after GnRH treatment. Age (>15 years) and body condition of recipients <2 also lowered transfer success rates, while the summer heat had no adverse impact. However, season did influence gestation length, while cria gender did not. In conclusion, results from the analysis of this very large dataset can underpin new recommendations to improve embryo transfer success in alpacas.
    Animal reproduction science 10/2012; 136(3). DOI:10.1016/j.anireprosci.2012.10.010 · 1.58 Impact Factor
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    • "nsemination was also found in this study . This result is in accordance with other studies ( Rexroad and Powell 1991 ; Jabbour and Evans 1991 ; Kuhholzer et al . 1997 ; Luther et al . 2007 ) . The lower fertilization rate after natural mating is believed to have been caused by a deficiency in the intrauterine sperm migration ( Naqvi et al . 2001 ; Bari et al . 2003 ; Betteridege 2006 ) . In the present study , the high fertilization rate in laparoscopic intrauterine insemination technique could be attributed to the fact that semen was deposited directly to the uterus avoiding the hostile environment of vagina and cervix ."
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    ABSTRACT: The effect of GnRH administration on superovulatory response of ewes treated with equine chorionic gonadotrophin (eCG) in breeding and nonbreeding seasons and the contribution of laparoscopic insemination to the improvement of fertilization and embryo recovery were investigated. Twenty-four nonpregnant Awassi ewes of 3-4 years of age were randomly allocated into two groups (n = 12). Each ewe was treated with a progesterone impregnated intravaginal sponge for 12 days. The following superovulation treatment was used: ewes of group 1 received 1,200 IU of eCG once as an intramuscular injection 48 h prior to sponge withdrawal; ewes of group 2 also received 1,200 IU of eCG once as an intramuscular injection, 48 h prior to sponge withdrawal and after 24 h of sponge removal. Ewes were injected with 80 μg of GnRH. Ewes of groups 1 and 2 were further subdivided into four equal groups (n = 6). Subgroups A and C (superovulated with eCG and eCG plus GnRH, respectively) were mated naturally at least two times with Awassi rams of proven fertility at 8-h intervals. Subgroups B and D (same as A and C) had intrauterine insemination at 44-46 h after sponge removal, under laparoscopic visualization of uterine horns, depositing 1 ml of diluted semen containing 100 × 10(6) motile sperm in the distal portion of each uterine horn. Ovarian response was assessed by determining the number of corpora lutea by laparoscopy at day 6 after mating. Embryo recovery was performed by using a semi-laparoscopic flushing procedure in both uterine horns. Results of the present study showed that ewes treated in breeding season with eCG plus GnRH has a higher number (P < 0.05) of corpora lutea than eCG alone as 7.33 ± 0.54 and 4.33 ± 0.39, respectively. There was no significant difference in the number of corpora lutea in nonbreeding season when ewes treated with eCG and eCG plus GnRH. The number of unovulated follicles was significantly higher (P < 0.05) in eCG treated ewes than in ewes treated with eCG plus GnRH, both in the breeding and nonbreeding seasons. The number of recovered embryos from ewes treated with eCG plus GnRH and eCG differ significantly (P < 0.05) as 4.32 ± 0.56 and 1.06 ± 0.26, respectively, in the breeding seasons. No significant difference was observed when these hormones used for superovulation in the nonbreeding season. A higher number of unfertilized ova (P < 0.05) was observed in ewes when naturally inseminated than in ewes inseminated using the intrauterine laparoscopic technique. Higher rate of embryo recovery (P < 0.05) was achieved when ewes were inseminated via intrauterine (4.66 ± 0.66) compared with ewes naturally mated (2.16 ± 0.74). The fertilization rate in ewes inseminated intrauterine using laparoscopic techniques and naturally mated were 91.5% and 44.8%, respectively. Fertilization failure in ewes inseminated intrauterine using laparoscopic techniques and naturally mated were 8.4% and 55.2%, respectively. It could be concluded that administration of GnRH 24 h after sponge removal increased ovulation rate of Awassi ewes treated with eCG for superovulation in the breeding season. The use of eCG to induce superovulation in Awassi ewes combined with laparoscopic intrauterine insemination increases the fertilization rate.
    Tropical Animal Health and Production 04/2011; 43(7):1351-5. DOI:10.1007/s11250-011-9856-7 · 0.97 Impact Factor
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    • "Thus, multiple ovulation and embryo transfer (MOTE) could be a useful tool to preserve animals of the Morada Nova breed, since embryo recovery and fertilization rates were considered satisfactory. The mean embryo recovery rate in the present study (64.6%) is comparable to rates using the same surgical method (Torres and Sevellec, 1987; Baril et al., 1995; Cordeiro et al., 2003; Blanco et al., 2003). In addition, the fertilization rate in our experiment was higher than in other studies that applied superovulatory treatments in sheep (Moor et al., 1985; D'Alessandro et al., 1996). "
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    ABSTRACT: In order to evaluate embryo production in Morada Nova (white variety) ewes superovulated with porcine follicle-stimulating hormone, 20 cycling ewes were used as embryo donors and allocated into two groups according to age: group 1 (ewes aged 1-2 years; n = 9) or group 2 (ewes aged 3-4 years; n = 11). Embryo recovery was performed by laparotomy 5-6 days after oestrus. The evaluation of embryos was made under stereomicroscope according to International Embryo Transfer Society rules. The overall recovery rate was 64.6% (5.0 +/- 0.7 structures per ewe) and 86.3% of the recovered structures were fertilized. Group 1 was superior (p < 0.05) to group 2 according to recovered (6.6 +/- 0.9 vs 3.6 +/- 0.8) and fertilized structures (5.6 +/- 1.1 vs. 3.5 +/- 0.7) per ewe. In conclusion, the ovarian response and the embryo production in Morada Nova (white variety) sheep subjected to a standard superovulation treatment were considered satisfactory. In addition, the use of multiple ovulation and embryo transfer in younger ewes ( < or = 2 years old) of this sheep breed appears to be an efficient tool to accelerate the preservation of the Morada Nova (white variety) breed, since younger ewes are as responsive as older ones.
    Tropical Animal Health and Production 10/2006; 38(7-8):555-61. DOI:10.1007/s11250-006-4344-1 · 0.97 Impact Factor
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