11.3 Agonal Changes

Endo- and epicardial haemorrhage - these are splashes and streaks (petechiae and ecchymoses) of haemorrhage commonly found on the surfaces of the heart and extending sometimes deep into the mycocardium. They are most pronounced on the endocardium. These are a normal post mortem finding in cattle especially if euthanased by gunshot or captive bolt. They are caused by the heart pumping forcefully and intermittently against greatly increased resistance to blood flow through peripheral vasculature as the animal dies. The haemorrhages may extend into the mediastinum and costal pleura. Haematomas or haemorrhages elsewhere in the body are more likely to be abnormal and may be associated with generalized viral or bacterial infections (causing septicaemia/toxaemia) or a clotting defect, but other supporting signs should be looked for.

Haemorrhage and congestion of adrenal glands - this is an agonal change caused by increased central blood pressure as peripheral vascular resistance increases as the animal dies. It can also occur with septicaemia in which case there would be other lesions present.

Oedema of the heart valves - all four major heart valves, especially the cusps, may be markedly thickened with clear watery fluid. It is suspected to be caused by the rapid slowing of blood flow when an animal dies.

Pulmonary emphysema - this is due to terminal gasping as the animal dies. Large bullae may be present. Finding more air in the lungs than normal is of no significance unless there is a history of respiratory distress. White areas on a dark lung may be normally aerated alveoli in a severely congested lung.

Rumen content in nasal cavity - this is mostly from a terminal eructation (burping) event, the food forced there by pressure of rumen gas after death.

Rumen content in the trachea and lungs - this may be from aspiration as a recumbent animal dies in which case there may be an early tissue reaction. Sometimes it is from food and fluid in the nasopharynx, pushed there by rumen gas, draining into the trachea and lungs when the dead animal is lifted or dragged by the head.

Tracheal froth - in the absence of pulmonary oedema, tracheal froth, even if it pours in abundance from the nostrils, is unlikely to be significant. It is generated by rapid terminal respiratory movements forcing air over moist respiratory surfaces.

Splenic enlargement - this may occur with euthanasia using barbiturates. The spleen is soft and bleeds freely when cut. It may also occur with anthrax or tick fever in cattle, both of which will be accompanied by other changes in the carcass.