A total of 136 adult male WistarHan rats were randomly assigned to three groups: Sham-laparotomy (Sham) group [7 days post-surgical survival time (n = 10)]; 50% partial hepatectomy (PH) group; 70% PH group. Both PH groups had three postoperative survival times of 1, 3, or 7 days (n = 21 for each time-point). Postoperative severity assessment was performed daily using a model-specific score sheet, behavioral testing in the Open Field (OF), telemetric data analysis, and analysis of blood and fecal samples. Parameters of surgical and postoperative distress and severity in the animals were analyzed. Rats were trained to the OF test thrice every alternate training day (D-20, D-18, and D-16). On D-15 (surgery I), a telemetric transmitter (hereafter referred to as transmitter implantation, TI) was surgically implanted subcutaneously in the left flank in 12 animals of each 7-day survival group. All animals in the Sham group were implanted a dummy device. Transmitter implantation was followed by a 12-day recovery phase with no further intervention. To ensure comparability, this test-free recovery period was standardized for all animals, even if they were not telemetrically monitored. Thereafter, retraining was performed on D-2 and -1 in all animals, followed by Sham, 50% PH, or 70% PH (surgery II), on D0. OF tests were performed on POD1, POD3, POD4, and POD7 (depending on survival time). Body weight was measured before individual training, as well as before and after each surgery; in addition, the body weight was measured once daily during postoperative scoring. Postoperative scoring was conducted three times a day from POD1 to POD3 and once a day in the morning from POD4 to POD7. On euthanasia day (POD1, POD3, or POD7) rats were reopened (surgery III) under general anesthesia and analgesia and were euthanized by final blood withdrawal from the inferior vena cava. Organs were removed for subsequent examinations and processed accordingly.