Methods to estimate the energy expenditure of goats: From the lab to the field

To asses the energy requirements of animals in open range has been an ambitious objective. Years of laboratory work have resulted in the development of an array of methods to estimate the energy expenditure (EE) on the base of calorimetry trials. Available and more usual methods with application in grazing conditions are: mobile indirect calorimetry (MIC), factorial method, heart rate (HR), and isotopic methods (DLW—double labelled water and CER—CO2-entry rate). This paper gives an overview of these methods, their potential and real use, and an account of EE values obtained, to our knowledge, by their application in grazing goats.