Master of Science (MS)
Animal Science (Animal, Dairy, and Poultry Sciences)
Incomplete zona hatching or failure of the zona to rupture compromises post-transfer embryo viability and conceptus development. Assisted hatching prior to the transfer of frozen-thawed bovine embryos has been proposed as a means to increase recipient pregnancy rates. The objective of this study was to determine if laser-assisted hatching would improve in vivo-produced frozen-thawed bovine embryo hatching and pregnancy rates. In Experiment I,II and III frozen direct-transfer embryos received either two a or three symmetrical rents at either 40% or 80% through the outer zona surface using the Hamilton Thorne XYClone® (Hamilton Thorne Biosciences) diode laser at 90% power with a 600 µsecond pulse (Treatment A) or no zona renting (Treatment B). Embryo hatching rates combined were 51% of 86 embryos for Treatment A and 54% of 86 embryos for Treatment B. In Experiment IV, in vivo-produced nonsurgically collected direct transfer frozen-thawed Hereford embryos (n = 64) were utilized. In Experiment V, in vivo-produced nonsurgically collected glycerol frozen-thawed Brangus embryos (n = 46) were utilized. In Experiments IV and V, embryos received three symmetrical rents ~40% through outer zona surface at 90% power with a 600 µsecond pulse (Treatment A) or no zona renting (Treatment B). In Experiment IV, treatment did not affect pregnancy rates at 35 days or 60 days of gestation and were 41% and 28% for Treatment A and 44% and 41% for Treatment B, respectively. Likewise, there was no difference in calving rate for recipients confirmed pregnant at 60 days for Treatment A (89%) and Treatment B (77%). In Experiment V, pregnancy rates at 35 days and at 60 days of gestation were not affected by treatment and were 65% and 65% for Treatment A and 78% and 65% for Treatment B, respectively. Calving rates were not different for those recipients in Experiment V confirmed pregnant at 60 days for Treatment A (73%) and Treatment B (73%). In conclusion, laser-assisted hatching does not increase the number of in vivo-produced bovine embryos that hatch following in vitro culture or increase pregnancy rates of recipients receiving in vivo-produced frozen-thawed embryos.
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Chiasson, Mindy Kaye, "Laser-assisted zona pellucida hatching of frozen-thawed in vivo-produced bovine embryos" (2010). LSU Master's Theses. 2295.