While the luteinizing hormone (LH) surge has long been accepted as the key event in the estrous cycle of the bitch, historically, there has been no practical way to identify it. In the past, the veterinary practitioner had to rely on general and/or subjective information received from vaginal cytology, physical examinations, and observations. With the recent development of in-clinic progesterone and LH assays, and the wider availability of laboratory quantitative progesterone assays, the LH surge can either be identified directly or estimated by the detection of changes in progesterone. As a result, ovulation time can now be predicted with high accuracy in a private practice setting.
