Animal Reproduction (AR)
Animal Reproduction (AR)
Original Article

Effect of meiotic stage on viability and developmental competence of bovine oocytes vitrified in TCM-199 and bovine follicular fluid

E.S.C. Siqueira-Pyles, F.C. Landim-Alvarenga

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Cryopreservation techniques for unfertilized oocytes have great potential for cattle breeding; however, the overall success remains low. Oocytes were divided in 8 treatment groups: Immature control, Mature control, Immature oocytes vitrified in Holding Medium (HM), Immature oocytes exposed to cryoprotectors in HM, Immature oocytes vitrified in Follicular Fluid (FF), Immature oocytes exposed to cryoprotectors in FF, Vitrified mature and Exposed mature. Viability and nuclear maturation were analyzed using propidium iodide and Hoescht 33342. Cleavage rate was determined on day 3 and blastocyst formation on day 7 after fertilization. After treatments, all non-vitrified oocytes were viable; however, after vitrification the viability was significantly reduced. Nuclear maturation analysis indicated that vitrification released oocytes from meiotic arrest. However after 22 – 24 hours of in vitro maturation no statistical differences were observed between groups (P > 0.05). A significantly higher number of zygotes underwent cleavage in the control group compared to the other groups (P < 0.05). No statistical differences were observed in numbers of blastocyst between control and exposed oocytes (P > 0.05), but blastocyst formation of vitrified oocytes was significantly lower (P< 0.05). According to the results obtained, oocytes are sensitive to osmotic and toxic damage during incubation with cryoprotectants and also during vitrification. Although most of the literature reports higher survival and developmental competence for oocytes vitrified after maturation, the present experiment showed no difference between immature and mature oocytes.


Bovine, oocytes, vitrification, follicular fluid, mature/immature
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