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Abstract
The viability of microblade-bisected Day-7 embryos transferred to recipients without zona pellucidae directly after splitting or after overnight storage at 4°C was investigated in two experiments. In Experiment 1, 26 demi-embryos of excellent or good quality and two of fair quality were transferred to 28 heifer recipients 1-3 h after splitting. The transfers resulted in 20 pregnancies (71.4% pregnancy rate), and 19 calves were born (one pregnant heifer was slaughtered). Another 14 demi-embryos were cultured 1 to 3 h at room temperature, transported for 3 h at 8-10°C and stored for 12 h in a refigerator at 4°C, Twelve of the 14 demi-embryos were considered transferable after storage and nine of these were transferred to nine recipients, of which five became pregnant. Four live calves were born. In Experiment 2, 21 excellent or good quality demi-embryos were transferred into 21 heifer recipients to produce 12 pregnancies (57.1%) and 10 live calves. Another 19 demi-embryos (17 excellent to good quality and two fair quality) were transferred after storage for 1-2 h at 8°C and 18 h at 4°C. Five recipients became pregnant, of which four delivered live calves. It is concluded that a high pregnancy rate can be achieved after the transfer of fresh demi-embryos produced by a simple method of embryo bisection under farm conditions. Although the transfer of demi-embryos stored overnight at 4°C results in decreased pregnancy rates, refrigeration of demiembryos may be useful in certain practical situations. However, further experiments are needed to determine the optimal conditions for overnight storage of demi-embryos.
Highlights
In Experiment 2, 21 excellent or good quality demi-embryos were transferred into 21 heifer recipients to produce 12pregnancies (57.1%) and 10 live calves
The highest pregnancy rates following transfer of demi-embryos have been achieved after splitting Day 7 embryos at the late morula and early blastocyst stages (Williams et al 1984) with the survival rate being similar to or only slightly lower than that following transfer of fresh whole embryos (Leibo and Rail 1987, Williams and Moore 1988, Seike et al 1989)
The data reported here demonstrate that simple and rapid embryo splitting with a microblade can be used to produce a high proportion of viable demi-embryos under farm conditions
Summary
In Experiment 2, 21 excellent or good quality demi-embryos were transferred into 21 heifer recipients to produce 12pregnancies (57.1%) and 10 live calves. Another 19 demi-embryos (17 excellent to good quality and two fair quality) were transferred after storage for 1-2 h at B°C and 18 h at 4°C. It is concluded that a high pregnancy rate can be achieved after the transfer of fresh demi-embryos produced by a simple method of embryo bisection under farm conditions. Overnight storage of bisected embryos without freezing would allow transport of excess demi-embryos to other locations for transfer, an alternative that has not received much attention. Nine of 19 transfers of embryos refrigerated for 24 h resulted in pregnancies and seven of 21 recipients became pregnant following transfer of embryos refrigerated for 48 h (Jaakma and Miiiirsepp 1991)
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