Indirect calorimetry: assessing animal response to heat and cold stress

Calorimetric thermal stress studies where indirect calorimetry is used as a tool to estimate energy expenditure have been undertaken since this technique was developed. Some examples of these studies are presented in this chapter. The measurement of gas exchange by means of an open-circuit respiration chamber have been done in studies where climate needs to be
constant but also in studies where animal reactions to differences in climate as part of the experimental design. In the past and in present, animal studies are done in chambers with and without integrated climate controls. Changing climate factors, e.g. temperature, relative humidity, and air speed, may change an animal’s physiological responses. As climate can also affect energy metabolism it is necessary to have a well-designed, accurate and reliable air conditioning system inside a respiration chamber to rule out the unwanted effects of an uncontrollable climate. In this chapter important issues related to the design of climate control
in respiration chambers are described and methods for improving accuracy are discussed. We conclude that the design of chambers with and without climate control should be undertaken by those that understand animal biology as well as technicians and engineers. Furthermore, the basic physics of heat measurement are discussed and we elaborate about possible biases
from biological factors and physical factors and how to deal with them.