Does Mechanical Manipulation of the Reproductive Organs Cause a Prostaglandin Release in the Heifer During Embryo Transfer?

One of the problems encountered in embryo transfer (ET) in cattle is the wide variation in pregnancy rates. Many factors, of either embryonic, maternal or environmental origin, influence the result of the ET (Sreenan & Diskin 1987). An important environmental factor is the method of transfer. Pregnancy rates are generally lower following non-surgical, compared with surgical transfer. In addition, the skill and experience of the operator is of great importance. Furthermore, pregnancy rates tend to decrease the longer the transfer catheter remains in the uterus (Rowe et al. 1980). One suggested reason for this is uterine trauma or irritation caused by the catheter with a subsequent endometrial inflammation. As the uterine environment is of great importance for the establishment of pregnancy, an inflammatory reaction would certainly diminish the chances for embryo survival. There is a possibility that the endometrium becomes damaged mechanically during the transfer procedure. This might be more pronounced in animals where ET is difficult to perform, due to anatomical reasons and/or, an inexperienced operator. Furthermore, when a longer time is needed for passing the cervix and placing the embryo in the tip of the uterine horn, the pregnancy rate seems to be influenced negatively.