Animals receiving adequate nutrition normally have deposits of white or yellow fat around the kidneys, heart and intestines and in the bone marrow. Animals that are sick or are receiving insufficient feed normally metabolize this fat to meet body needs, leaving a gelatinous red deposit in the bone marrow. Internal fat is metabolized first while fat in the bone marrow is metabolized last during starvation. Breaking the large leg bones permits examination of the bone marrow. Some caution is necessary in evaluating bone marrow fat deposits in healthy young animals making rapid growth. Their bone marrow may be red from extensive red blood cell production to meet body needs and may have little stored fat.
The contents of the stomach and intestines are indicators of health. Normally, healthy ruminants (cattle, sheep, goats and other animals with multiple stomachs) older than weaning age will have a rumen (first compartment) that is one-third to one-half full of food. The rumen is not fully developed at birth, but the abomasum (fourth compartment) is fully functional. The abomasum is the functional stomach in nursing young and should contain milk. A small, empty rumen is normal in nursing young for the first 2 to 3 weeks. A mixture of milk and vegetation in the rumen is normal from then until weaning age when the rumen is fully functional.
Partially digested foods should be present through the rest of the gut and the feces (in the large intestine) should be relatively firm. Exceptions as noted earlier include animals on concentrates and lush green feeds.
When dietary contents such as excessive amounts of grain or poisonous plants are a possible cause of death, the contents of the stomach and intestines should be noted. Samples of the stomach contents should be taken for analysis if poisonous plants or other toxic agents are suspected.
Lungs and Respiratory Tract
Pneumonia is a relatively common cause of animal death and is evident in lung tissue by fluid accumulation and other lesions in the affected areas. Healthy lungs are pink, spongy and lightweight with sharp, well defined edges on the lobes. Infected lung tissue is dark colored, firmer and heavier than healthy lung tissue. Some diseases cause abscesses in lung tissue. These abscesses may be filled with pus and often have a hard outer shell. Incisions through sections of normal and infected lung tissue will demonstrate these differences.
The trachea and bronchi should be opened from above the larynx into the lungs to check for infection and other abnormalities. Animals killed by a bite in the throat frequently have physical injury to the larynx and trachea. Also, these bites frequently cause hemorrhage and foam in the trachea which contribute to death by suffocation.