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... Sanchez i wsp. (27) porównywali kompetencje rozwojowe zarodków uzyskiwanych technikami OPU--ICSI z oocytów pobieranych od klaczy w wieku do 3 lat i klaczy starszych > 3-24 lat. Aspirowano wszystkie pęcherzyki jajnikowe o średnicy powyżej 5 mm co 14-21 dni. ...
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The aim of the study is to present current knowledge on the mechanisms regulating puberty in mares and the possibility of shortening the intergenerational period in horses through modern animal reproduction biotechnology. The study discusses fetal sex recognition in horses by means of ultrasound, pre- and postnatal development of mare gonads, oogenesis and folliculogenesis, as well as the process of selection and elimination of oocytes. It also describes the role of gonadotropins, ovarian hormonal activity and morphological changes occurring during sexual maturation. It has been shown that about 37% of mares attain sexual maturity in the first year of life. It has also been documented that one-year and two-year-old fillies produce normal embryos that can be used for transplantation and give offspring. It has also been proved that embryos can be produced in vitro from oocytes of juvenile mares. There is hope that acquiring preantral follicles from the ovary and their in vitro culture until the oocyte reaches full maturity for fertilization will permit us to obtain embryos and offspring from mares, including those sexually immature. These methods, combined with in vitro fertilization and embryo transfer techniques, have already made it possible to obtain normal embryos and even live-born offspring in other mammals.
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Background: Proper timing for embryo collection and transfer in horses -which is critical for the success of this biotechnology- is still debated. Additionally, there is little information on this technology under tropical conditions. Objective: To determine the best day for collection and transfer of embryos in Mangalarga Marchador mares under Brazilian northeast’s conditions. Methods: Donors (n= 30) and recipients (n= 76) in diestrus phase were selected based on both clinical and gynecology examinations. Estrus was induced on both donor and recipient mares by intramuscular injection of 5 mg Dinoprost, aiming to obtain an ovulation interval of -1 to +3 between recipient and donor. Ovulation was induced with buserelin acetate when the largest follicle reached at least 35 mm in diameter. At this time, mares were subjected to artificial insemination at 48-hour intervals until ovulation. The embryos were collected on days 7, 8, and 9 after ovulation. Results: The embryo collection on day 8 was more efficient (p<0.05) than on day 7, but it was not more effective (p>0.05) than day 9, which presented the same efficiency (p>0.05) as day 7. From a total of 76 embryos transferred to the recipients, that were between days 4 and 9 after ovulation, there was no influence (p>0.05) of the day of transfer on pregnancy rate. Conclusions: The embryo collection must be performed on day 8 after ovulation, and transfer can be performed on any day of that interval (4-9) without affecting the pregnancy rate.
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Limited clinical information is available regarding sperm population parameters that are important for use with equine intracytoplasmic sperm injection (ICSI). Therefore, the appropriateness of a sample of sperm is typically not known before ICSI. The aim of our study was to determine which sperm population characteristics were predictive of ICSI outcome. Frozen-thawed sperm samples (n = 114) from 37 stallions in a clinical program were analyzed after ICSI for percentages of normal morphology (MORPH+), live as assessed by eosin/nigrosin stain (LIVE+), membrane intact as assessed by hypoosmotic swelling test (HOS+), and DNA fragmentation determined by sperm chromatin dispersion (DNA-). ICSI was performed on 147 oocytes, and cleavage (≥2 cells), embryo development (morula or blastocyst), and pregnancy status after embryo transfer were determined. Among the examined sperm parameters, LIVE + correlated positively with MORPH+ and HOS+, and MORPH + negatively with DNA-; no other significant correlations were observed. When used for ICSI, sperm population percentages for MORPH+ and DNA- were not predictive of ICSI outcome, including cleavage, embryo development, and establishment of a pregnancy. Sperm population percentages significantly affecting ICSI outcomes were LIVE+ and HOS + for oocyte cleavage, LIVE + for embryo development, and HOS + for establishment of a pregnancy. The probability of a pregnancy was significantly higher for sperm populations having HOS+ ≥40% than populations having HOS+ ≤20%. The mean age of the donor mare per sperm-injected oocyte did not differ for oocyte cleavage, embryo production, or establishment of pregnancy. In our study, the probability of sperm-injected oocytes to develop into an embryo (morula or blastocyst) improved when sperm were selected from a population with higher indicators of membrane integrity (LIVE+ and HOS+).
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