Embryo transfer


Embryo transfer is a procedure where several embryos (fertilized eggs) from the high-valuable mothers (embryo donors) are transplanted into less valuable individuals (the recipients of the embryo). Recipient completes the gestation and lambs offspring of high genetic value. Donor returns to a normal cycle where it can be mated naturally or again subjected to a new ET program after 6-8 weeks. ET procedures can increases several times the number of offspring that one highly valuable sheep can be produced in their lifetime. Up to 15 embryos can be collected by one embryo flushing procedure, although the typical number of recovered embryos ranging from 5 to 10. In the course of a year, one sheep can provide more than 30 descendants.

              Embryo transfer as a technique is increasing in popularity among small ruminants worldwide. Thanks to technological advances, embryo collecting is an effective and minimally invasive technique, which enables the production of multiple embryos from the same donor. For ET procedures can be used even sheep that are excluded from reproduction for different reasons, for example. mastitis, lameness, age, etc.

              The optimum number to start the ET is 3-5 mothers as donors and 6 sheep per donor. Donor sheep should have a good body condition, correct udder and good reproductive history. Donor sheep are programmed with hormone injections to stimulate the ovaries to produce multiple follicles, and thus more eggs (oocytes). Sheep are bred naturally or by laparoscopic insemination. The embryos are surgically taken after 5 days of insemination. Embryos are graded after collection, and those ineligible for transfer are identified and removed. Embryo transfer can be done on the farm or at laboratory facilities of RAM GEN. Donor sheep can be reprogrammed for a new flushing cycle or natural mating after 7-8 weeks. Achieved pregnancy after ET ranges between 40% - 70%.




                                   Embriomanipulator for in embryo production



A successful ET program "on-farm" with satisfactory results is possible, but it requires a very good system of governance. The program should be planned 6 - 8 weeks prior to the transfer, even longer if the sheep-embryo recipients must be purchased. During this time, it is necessary to solve a number of things: • proper nutrition of donors and the recipients of the embryos; • selecting and handling of the donor and embryo recipient; • arrange semen control from liquid nitrogen tank or from rams; • contact vets in RAM GEN Center in order to be fully informed about the plans and the process of preparing for insemination; • organize objects - objects should be under a roof and protected from drafts; • 4 - 5 weeks before the expected date of the operation, the work program will be forwarded together with the appropriate drugs, hormones, etc. This program will be outlined on a daily basis in the course of events intended to achieve a successful result. All items must be carefully, promptly and fully implemented. Any deviation from the program must be declared. Necessary facilities for the implementation of insemination, embryo flushing, and ET don't need any special facilities. All it needed is a space under roofed space that can protect from the weather conditions (wind, rain, snow, and sun). After the program starts, it can not be changed at the day of execution in case of bad weather. It is, therefore, necessary to provide any accommodation for this purpose. Also, the facility must have a source of electricity. In case of severe winter must be provided a warm room to avoid the so-called. "Cold shock" of embryos and their deaths.


PROCEDURES AT COLLECTIONS Collection embryo embryos are normally performed on the 6th day after fertilization (insemination or mating). Flushing is a procedure that can take 20-30 minutes. The collected liquid after uterus washing is examined under microscope and collected embryos are transferred into a special liquid for storing embryos. Procedure search may take some time because the embryos are very small and often difficult to find in the petri dish with debris that is usually present in the flush. The embryos are examined and graded according to quality. After that embryos are packed in straws or transferred to other sheep, or frozen or discarded if are not suitable for the transfer.


ET training in Australia (at Dr Marrais facilities)

SHEEP recipient of embryos and embryo transfer (ET)

The correct and appropriate selection and management of recipients is vital to the success of ET. Management of recipients from the first day of the program until lambing may affect the success of the whole operation. Many programs can bring lower productivity and poorer results because of poor care of embryo recipients. Before ET, ovaries are controlled regarding hormone reaction and willingness to accept embryos. If the animal is considered ready to accept an embryo, the horn is removed through a small incision in the abdomen and the embryo is introduced into the uterine cavity of the recipient sheep. The recipient is then released. Ultrasound examination of the pregnancy can be done 6 weeks after transplantation, to confirming the status of the recipient. The success of fresh embryo transfer may vary from 60-70%.

              Using specific embryo freezing media, equipment and procedure, the embryos may be frozen and stored in liquid nitrogen. The average pregnancy rate with frozen embryos ranges from 45 to 50%.


ET to recipient