Assessment of body composition in cats and dogs.

The assessment of body composition in any species is important to the understanding of subjects such as the control of obesity, the realimentation of sick animals and the evaluation of energy requirements. In most cases our requirement is to assess the chemical constituents of the body by the measurement of the fat and fat-free mass (FFM) of the subject. There may also be a requirement to break down the FFM mass into its component parts and measure the tissue distribution within the body. Clearly in the understanding of the causes and effects of obesity in companion animals, the evaluation of the actual level of obesity is fundamental. Similarly, whilst classifying the effectiveness of a weight loss programme it is vital that the reduction in weight loss and the distribution of tissue types can be accurately recorded by the veterinary surgeon or clinician. This review covers the theory of body composition measurement and the techniques which have been developed, together with their relevance to studies with companion animals. Most techniques are based on indirect methods which use the model of the body being at least two chemically distinct compartments, the fat and the FFM. In more complex analyses four and even six compartment models are considered which include concepts such as protein content, cell and osseous mineral content. The techniques to be covered include the measurement of total body water (for example by the use of isotope dilution), anthropometric techniques (skinfold thickness and dimensional evaluation), densitometry, total body potassium, muscle metabolite markers, absorptiometry, neutron activation analysis, electrical conductance, ultrasound, near infrared interactance, computed tomography and magnetic resonance imaging.(ABSTRACT TRUNCATED AT 250 WORDS)