Alan,
There are several different syncronization protocols that AI techs will offer to you. I use the CIDR , GNRH, & PH protocol. Hopefully this will answer your questions. They are also explained in the catalog from each company.
A CIDR is the actual vaginal implant that has hormones on it. This tells the cow that she is bred & should not be ovulating, therefore it prolongs estrus. A shot of GnRH such as Cystorelin is given at the time of implantation. This is a Gonadotropin Releasing hormone that stimulates the ovarian folicle for growth & maturation. Therefore her ovaries are making & maturing her eggs but not releasing them. When the CIDR is removed a shot of Prostaglandin (Lutalayse) is given which causes the cow to come into estrus within a couple of days. Usually 48-72 hours give or take. Then it is up to you to watch her & determine when she is ready to breed & call the AI tech- Hope this helps
