2.5.2 Calculating the energy expenditure
We calculated the EE of collared sheep using previously derived relationships between triaxial accelerometer data and animals’ energetics from experimental trials of various types of animal species as well as farm ruminant animals (Halsey et al., 2011; Miwa et al., 2015). The link between sheep energetics and collar data is given by
\begin{equation} \text{VO}_{2}=15.139M^{0.794}+{38.467M}^{0.835}(ODBA)\nonumber \\ \end{equation}\begin{equation} r^{2}=0.908\nonumber \\ \end{equation}
here \(\text{VO}_{2}\) \((ml/min)\) amount of oxygen consumed over 1 min, and overall dynamic body acceleration ODBA (g ) is the sum of the absolute value of each accelerometer axis summed over 1 min (Miwa et al., 2015). Oxygen consumption was then converted to kilojoules expended per 20.46 J /ml (McLean, 1972). We then estimated the sum of energy expenditure (kilojoules) as the sum of kilojoules expended per minute over each 1-min period between successive data collection.