**3.3. Dietary available energy determination**

The N-corrected apparent metabolisable energy (AMEn) of the diets was calculated as described by [34].

A comparative slaughter technique [35] was used to determine the energy retained in the carcase of birds. In brief, dietary NE was calculated using the following equation:

$$\text{NE (MJ/kg)} = (\text{REc} + \text{FHP})/\text{FI}.\text{L}$$

Where: FI is the dry matter (kg) consumed for the experimental period. REc is the total energy retained in the carcass (see [50]).

The fasting heat production (FHP MJ/bird) was estimated to be 0.450 MJ/d per kg of metabolic body weight (BW)0.70 per day, which correspond to the asymptotic heat production at zero activity (as proposed by [36]).
