“…The energy cost of producing the two types of feed is calculated based on data taken from Naredo and Campos [29] and Pimentel [58]. More specifically, the energy cost of producing hay is assumed to be 2.5 MJ kg −1 , while for oats, barley, sunflower, peas, broad beans, corn, soya, and wheat, the energy cost of production is estimated at 4.3, 4.2, 5.4, 4.4, 4.7, 4.1, 5.9, and 4.9 MJ kg −1 , respectively (adapted from [40,56]). In the case of flour/oil cakes, the expenses of cleaning, mixing, and packing (0.36 MJ kg −1 ), and, additionally, milling (0.46 MJ kg −1 ) need to be added to the energy cost of fodder (adapted from [59,60]).…”