We have the the Estrotect patches and like them. The problem of some cows losing them can be solved by putting a little extra glue on them. Get the glue that is used for Kamars (another type of patch) and you will have to work to get the patch off. A bigger problem is the cows rub them under tree limbs. Usually you can tell the difference between a mark made by a tree limb and a mount from another cow.
Good luck.
Farmgirl