Postmortem Macroscopic Changes in Rats under Rat House Conditions


  • Masupa Boonmayaphan National Laboratory Animal Center, Mahidol University
  • Panida Butrat National Laboratory Animal Center, Mahidol University


Postmortem changes , Postmortem interval , Postmortem macroscopic changes , Ocular changes


This research aims to study the postmortem macroscopic changes in rat under rat house conditions. The results of this study will help researchers or veterinarians determine causes of animal death in colonized animals and research studies. This study used thirty-six healthy rats with body weights from 190 to 230 g. Throughout this study, the Animals were housed under controlled environmental conditions of the National Laboratory Animal Center, Mahidol University (22 ± 3gif.latex?^{\circ}C, 30 - 70% relative humidity). After euthanasia, animals were maintained in the ventral recumbency position in their cages. Macroscopic changes in the laboratory rat carcasses were observed. Ocular changes were evaluated at 0, 1, 2, 4, 6, 8, 12, 18, 24, 36, and 48 h postmortem. Gross appearances were investigated at 4, 8, 12, 24, and 48 h postmortem in accordance with necropsy examination of internal organs. The results showed that rat carcasses had different characteristics at different times. Ocular changes began immediately 0-4 h after euthanasia, and progressed to total sunken eyes at 24 h. Skin discoloration appeared 8 h after death. Internal findings from livor mortis observations of the internal organs showed that lividity varied from red to purple and became darker with the increasing postmortem interval, especially in the liver and spleen. Moreover, the decomposition of internal organs disintegrated at different rates. The pancreas, gastrointestinal tract, liver, and thyroid showed autolysis early in the postmortem interval (PMI) and increased their severity with time. At 48 h, necropsy revealed that the internal organs were vigorously twisted, collapsed, softened, liquefied, and dissolved. Our results suggest that postmortem ocular changes and macroscopic changes are useful for differentiating postmortem changes from antemortem and can aid in PMI estimation in laboratory rats, which will be beneficial for death investigations concerning laboratory rats.



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How to Cite

Boonmayaphan, M., & Butrat , P. . (2022). Postmortem Macroscopic Changes in Rats under Rat House Conditions. Journal of Applied Animal Science, 15(1), 9–22. Retrieved from



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