ABSTRACT
Body composition analysis must divide the whole into component parts (Fig. 1). Depending on the scientific question, those parts are different. They might be the chemical elements, e.g., carbon, hydrogen, oxygen, sodium, etc.; they might be anatomical entities, e.g., intestinal tract, liver, muscles, skeleton, etc.; or they might be defined by cellular location, e.g., cell mass, extracellular space, extracellular water, etc. Of pragmatic interest to animal scientists is the division of the eviscerated body or carcass into skeletal muscle, fat, bone, and sometimes skin. Dissection of the carcass into these components is a viable but laborious approach for large animals. The water, protein, fat, and mineral content of the body or carcass is an approximation of the muscle, fat, and bone mass. Carbohydrate is a very small percentage of the total and usually is not analyzed. The simplest compartmentalization of the body or carcass is into fat mass plus fat-free mass. This two-compartment model can be obtained by underwater weighing using estimates of the density of the two compartments.
