When using frozen semen, We have had success with both Dr. Smith and Dr Esmond with using Progesterone tests and doing Surgical implants or transcervicals well after a progesterone rise of 20. although not all dogs rise the same, making progesterone tests necessary every day after they reach 5 which is ovulation. Some dogs will rise quickly and will be inseminated well over 25, and others stop rising. I had one female that only rose 1 nanogram a day, and we did a transcervical of frozen semen when her progesterone hit 18. She had eight puppies. This is more of a rare case as most dogs rise at least two nanograms a day and are bred at well over a progesterone level of 20-30. We continue progesterone tests all the way through insemination for documentation of progesterone levels. Many vets use the LH Rise level instead of the progesterone level and some use both. It is not necessary to do two breedings, but it does give you more coverage. I usually only do one.