Embryo Transfer in Cattle (How it can replace conventional animal…
Embryo Transfer in Cattle
How it can improve genetic progress
The major use of these techniques is to increase the reproductive rate of valuable cows
It is likely that embryos will be genotyped by PCR for many traits or markers in the future
improvement in superovulation may not lead necessarily to an increase in demand for ET services. In fact, it might not even lead to an increase in the number of embryos produced per year.
It would, however, increase efficiency, both for the cattle owner and the ET practitioner, and probably lead to a lowering of costs to cattle owners
The widespread adoption of freezing embryos in ethylene glycol for direct transfer (DT) after thawing (Voeklel and Hu, 1992) has made the transfer of frozen-thawed embryos more practical under a wide variety of conditions in the field.
After the introduction of embryo freezing, there were no really significant additional improvements in ET technology during the 1980s
Genetically superior cows can produce more offspring per year
It is now possible to obtain up to 40 offspring from a selected female in 1 yr.
There are an estimated 150,000 potential “eggs” or ova in the female and countless billions of sperm produced by each male.
How it can replace conventional animal improvement methods
sexing embryos before transfer may soon become routine
PCR is currently being used for sexing embryos on a small scale
Semen sexing is an established technology and is likely to be used on a small scale in the near future on superovulated donors and for in vitro systems.
Although the skill-level required to transfer these embryos is unchanged from what was needed for transfer of conventionally frozen embryos, no embryologist is needed at thawing.
Consequently, a growing number of DT embryos are now being transferred by technicians with experience in AI.
ET became a much more efficient technology that was no longer dependent on the immediate availability of suitable recipient cattle
Can be used in any breed of cattle
cows will produce an average of eight to 10 calves in her entire lifetime under normal management programs.
embryo transfer is a technique that can greatly increase the number of offspring that a genetically important cow can produce
Many technicians have the equipment and expertise to freeze and store embryos for later transplantation or shipment to other countries
With the use of optimal conditions it should be possible to obtain an average of approximately eight pregnancies per successful donor
Role of embryo transfer
Much of the technology is reasonably well standardized and practitioners have reported that nearly 500,000 embryos are produced from superovulated cows yearly on a worldwide basis
In the developed countries, approximately 10% of the embryos in the ET industry are produced by in vitro technology.
Without improvements in technology, especially, superovulation, the ET industry may have little opportunity for growth
ET refers to individually or collectively to the collection, handling and transfer of embryos
Embryo transfer is currently being used for the expansion of limited gene pools whereas in the future such transfers will be for the successful proliferation of offspring from the mating of genetically superior dams and sires.
Church and Shea 1977