With rising costs and decreasing value of cows it is more than time to tighten the belt. There is significant expense and time in preparing recipients to receive an embryo. They may have been purchased for this purpose, shipped home, vaccinated, wormed, estrous synchronized, observed for standing heat all of which results in around $100 above market price for that animal.
Recipients are selected on the basis of condition, regular estrous cycles, successful estimated time of heat, presence of a CL, a term most of you will be familiar with and must be present on the day of embryo transfer. The function of a CL is to make progesterone which helps to prepare the egg in the follicle and prepares the uterus for the anticipated pregnancy. At 120 days gestation progesterone is then made by the placenta which explains the reason that when destroying the CL with a shot of prostaglandin the pregnancy is usually not terminated. The CL can be palpated or detected by ultra-sound, they vary in size and shape which is what many base their decision on whether to use in the recipient or not.
There have been many research publications describing the shape, size, and function of CLs. The CL is situated in the ovary, partially in the tissue of the ovary and partially projecting from the surface of the ovary. CLs can be accurately palpated by an experienced technician, but ultrasound can be used. I advise my students to concentrate on accurate palpation as this skill is needed to successfully flush a donor and correctly place an embryo in the horn of a uterus with as little damage as possible. Over recent years I have noticed in some cases relying too much on ultrasound, skill in palpation has decreased which is paramount for efficient embryo transfer. A recent publication (Therio 40 35 -39) shows the size of a CL is not the only criteria for recognizing the function and success of a CL. Using sophisticated equipment they observed blood supply to the CL is the deciding factor (not size or even shape) resulting in pregnancies. Which in practical terms means the small CL can be as successful as a large CL and should not be culled. Our data from the surgical days of recovering and transferring embryos when we observed the CLs clearly demonstrated the size of the Cl is not a definitive diagnosis for selecting a recipient. So, if a CL can be palpated go ahead and transfer the embryo.
May all of your recipients be successful!
Dr. Peter Elsden
Owner / Instructor
International Embryo Transfer School