Embryo Transfer: how it works

In order to better understand the variations in the procedure, here is a brief description of embryo transfer in horses. The mare is inseminated and 7 to 8 days later, she is “flushed” by a veterinarian. In the method that I am familiar with, a bivona is inserted into the mare’s uterus. This is a long rubber tube that has one section that can be filled with air. This part is in the uterus and inflated to create a bubble that keeps the bivona in the uterus during the entire flush. Next, fluid that is special flush media containing some nutrients and antibiotics is run into the uterus one liter at a time. The fluid is then allowed to leave the uterus and flows into a small cup that had a very fine mesh filter at the base and the flush media flows through it, hopefully trapping an embryo. The whole idea behind flushing a mare is that the embryo is a loose body in the uterus and by filling the uterus to capacity many times the embryo bounces out of the uterus and ends up in the cup. It is believed that if there is any embryo in the mare, it will be out of the uterus after the first 2 liters. A very small amount of the fluid is kept in the cup and transferred to a Petri dish where it is examined by the veterinarian, under a microscope. The mare that has just been flushed will usually receive a shot of prostaglandin, depending on the value of the horse, we used lutalyse or estramate. The prostaglandin lyses any follicles forming or if there was an embryo that for some strange reason did not come out in the flush, it will abort the potential pregnancy. If there is an embryo found in the cup, it is washed with a special solution that does not harm the embryo and then it can either be shipped in cool solution or transferred to a recipient mare that has been synchronized and will carry the embryo. The transfer involves implanting the embryo via a catheter into the uterus of the recipient mare. The recipient mare then will get a caslicks which is the sewing together of labia so that air or bacteria will not get into the uterus and disrupt the pregnancy. She is also given 5-10 cc of progesterone and 10cc gentozen (an antibiotic) and the mares where I was were kept on Regumate to maintain progesterone levels until they were checked in foal at 60 days.

So this is a general understanding of embryo transfer, I will be researching other methods and talking in depth about the particulars and why certain drugs are used etc.