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Registered: 06-2015
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Embryo Transfer - Frequently asked Questions and Answers

In this post I am including several frequently asked questions we get regarding embryo transfer.

Since graded embryos are transferred by trained technicians, using prepared recipients why do we not always achieve optimum pregnancy rates?
In “trouble shooting” requests for help around the embryo transfer industry often the condition of the donor or even more frequently the recipients is the problem while the embryo transfer techniques are up to accepted standards. On the other hand there will be periods of frustration when nothing seems to work and one should remember we are attempting to apply 21st Century techniques to a species developed 50,000 years ago.

Why do donors and recipients have to be in the right condition?
Donors are often too fat for optimum responses to our synchronizing and superovulation drugs while this condition is regarded as the choice form for show purposes. This type of donor frequently demonstrates signs of estrous behavior but do not stand, then 7 days later cystic follicles are palpated instead of the desired corpora lutea (CLs).When recipients are overweight the incidence of ovulation decreases so 7 days after heat lutein follicles are found instead of the expected CLs. I have rejected up to 50% of a group of prepared recipients due to this problem. In addition the reproductive tract in fat donors and recipients is more difficult to palpate which may lead to inefficient flushing and accurate placement of the transferred embryo in the recipient, when even identification of a CL may be difficult in fact on examination of the reason for low pregnancy rates in recipients common problems have been incorrect identification of a CL and the embryo placed in the wrong horn. A spinal block is of significant help when transferring embryos. This discussion of CLs leads to another area where again significant costs are imposed on recipient owners.

Why do some embryo transfer technicians cull so many recipients?
I have observed recipients rejected because the CLs were considered too small, the wrong shape, or fluid was palpated in the CL. In the early days of embryo transfer embryos were transferred surgically under a general anesthetic after rectal palpation for a CL so we took the opportunity to measure the CLs and comment on their shape and size when the tract was exposed. We found no differences in these described CLs. A CL was called “cystic” when fluid was observed or palpated which is an unfortunate term because this type of CL is a normal phenomenon and cystic denotes a pathological condition. Our data confirms this statement with no reduction in pregnancies following embryo transfer. Relatively recently this type of CL has been designated a CL with fluid. With the significant increased costs of drugs, feed and labor unnecessary culling of recipients is costly.

Why do we too frequently miss observing standing heat?
Observation and recording of standing estrus can be another area of inefficiency leading to increased costs. Removal of a calf after the last prostaglandin (e.g. lutalyse) injection will improve the incidence of standing heat. The calf can be returned to the mother as soon as standing heat is observed. Repeated suckling causes increased release of a hormone called cortisone which negatively affects the reproductive hormones. We have found a thin line of pressure pack paint ( incandescent orange or fire engine red are the best colors ) on the tailhead has proved a very efficient and reliable method of detecting standing heat, particularly useful in hot humid weather when standing heat increases at night. Incidentally many owners consider a natural heat increases the chance of a pregnancy compared to an induced synchronized heat, however our data has shown there is no difference providing a CL is present.
Should we use a failed recipient a second time?
Yes, at least one more time assuming the embryos are graded 1 or 2. In one of our early experiments we implanted grade 1 or 2 embryos into crossbred beef heifers, those that failed to establish pregnancies over 3 attempts we asked the question ,did they fail because they are sterile or were they not capable of establishing a pregnancy with a transferred embryo. To clarify this question we artificially inseminated this group and after 3 attempts 88% were pregnant. So the very occasional recipient will fail due to rejection of the implanted embryo. However after one transfer a failure may be due to the embryo or due to the technician. In addition approximately $100 has been added to the cost of the recipient due to probable hand feeding, heat detection and estrus synchronization, so try her once more.

Why do some donors fail to establish regular estrous cycles after flushing?
Occasionally donors are not observed for heat after collection and do not establish regular estrous cycles. After 3 superovulations some donors will produce ovarian cysts. The most common one is a lutein cyst and in this case the donor will not demonstrate heat. Early treatment is usually successful following an injection of a PG. In other cases the donor is in constant heat indicating a follicular cyst. Treatment in this situation is manual per rectal rupture plus an injection of GnRh (e.g. cystorelin).

A common question is should we superovulate heifers?
Once again from our records it is possible to impose this treatment on heifers providing care is observed then future fertility is not affected. Often in the early days too much FSH was administered to the young animals and if they were in the mode to respond then ovaries could grow to the size of a grapefruit, when this occurs the ovaries are heavy prone to damage and significant hemorrhage leading to upper reproductive adhesions and subsequent infertility. Often the eggs disappear into the abdominal cavity, those that enter the oviducts often are not fertilized and the few embryos produced are of poor quality. However every so often many embryos are produced and these are the ones that become well known. Basically use conservative doses of FSH and make sure the heifer is cycling regularly even before estrous synchrony drugs are administered.

If you pay attention to details and learn from experience embryo transfer can be very rewarding. It has to be a team effort consisting of a good cattle manager and a competent embryo transfer technician.

Good Luck!

-Dr. Peter Elsden
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7/6/2015, 23:41 Link to this post PM via Email   PM via Forum


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