Understanding the Conventional Flush Process
Conventional flushing is one method that can be used to produce more offspring from a valuable donor than she could normally produce on her own. This is accomplished by superovulating and inseminating the selected donor, surgically flushing the donor to harvest the resulting embryos, and then transferring the embryos into recipient (surrogate) females or freezing the embryos for transfer at later time.
Donor Superovulation/Insemination High
During a normal estrous cycle, a small ruminant typically ovulates only one to four oocytes that, if fertilized, will develop into 1-4 embryos. In order to generate a larger number of embryos, we must first recruit a larger number of oocytes. This is accomplished by superovulating the donor with exogenous hormones. The donor is set up with a CIDR and timed injections of follicle-stimulating hormone (FSH) to increase follicular growth. The donor is then bred by laparoscopic artificial insemination or live cover at two or three intervals to closely match the donor’s ovulations over time. Conventional flushes require at least two straws of frozen semen and additional straws may be necessary depending on semen quality. The use of shipped fresh-cooled semen is also an option that works well, wherein one jump/collection is typically able to service multiple donors.
Embryo Flush
The fertilized oocytes, now referred to as embryos, are allowed to develop in the uterus of the donor for six days following the initial insemination. At this time the donor is then anesthetized and prepared for surgery. A small incision is made to evaluate the ovaries for functional corpus luteums before a larger midline incision is made for to access both uterine horns. The embryos are then harvested, or flushed, from the uterus via surgical collection. At this time, the lab technician then evaluates these embryos for fresh transfer or freezing as well. Our reproductive technician then infuses fluids and anti-inflammatory products into the abdomen to minimize the likelihood of adhesions which negatively impact reproductive performance later on. The incision is closed with internal sutures, external skin staples and concealed with a wound spray. The animal is then allowed to recover while under supervision.
Factors Affecting Flush Results
Flush results vary on each donor and are dependent on numerous factors which include: age, breed, health status, nutritional plane, semen quality, and the effects of repeated superovulation. Sudden changes in weather such as a cold front or large storm system can also negatively affect the results of a flush. Some does or ewes may not be suitable donors for conventional flush due to physical scarring or abnormalities of the reproductive tract which prevent embryo production or collection.