10 Medical machines and machine tools, namely, sensor tag for sensing heat, movement, steps, activity level, estrus condition, rest time, rest bout, calving, prolonged calving, for medical use; a leg tag sensor for animals for medical use for detecting animal heat, behavior, health, wellness, namely, animal movements, steps, rest and rest bout for the purpose of detecting estrus condition, low activity, calving and prolonged calving, and group stress; a leg tag sensor that provides calving birth alerts, animal respiratory behavior information, and lameness detection, all the foregoing for medical purposes; a leg tag sensor that monitors animal's behavior, wellness and health, namely, estrus condition, low activity, calving and prolonged calving, and group stress, for medical purposes and transmits the data wirelessly to a computerized central system; dairy herd computerized management system for managing cows health and making fertility decisions, gathering and analyzing data on dairy herd health, behavior, wellness and medical activity for individual cows and cow herds, and also providing health alerts, estrus detection alerts, and calving alerts, the system comprised of a cow radio-frequency identification leg tag with electronic sensor containing an accelerometer, a wireless remote RFID reader with antenna, radio receiver and microprocessor, a central identification control unit, a central control unit, a personal computer and incorporating recorded computer software for processing and analyzing the collected data