A large variety of processes - physical, chemical and/or biotechnological - is currently applied to cereals (Table 1).
Among physical treatments, grinding is the most comnon ; it does not modify the chemical characteristics of the grains but improves the accessibility of the enzymes of the gut to their substrates by disrupting endosperm and aleuron cell walls. Thus, milling exposes the interior parts of the grain to the digestive enzymes. Some physical processing of barley grain, such as rolling, is necessary to give optimum digestion of the nutrients by cattle (ORSKOV, 1976). This treatment, applied to barley, appears to be beneficial for young species (KREFT and BOYLES, 1989). Pigs eat whole or very coarsely milled grain reluctantly (MAXWELL et al., 1970) and utilize whole barley poorly (LAWRENCE, 1970). For this reason, barley grain is commonly milled before feeding. Grinding of maize using a roller mill does not modify average daily gain, feed intake, feed conversion and fattening time of pigs. However, sensory evaluation tests, meat from control pigs fed untreated maize is preferred to meat from pigs given rolled maize (ITOH et al., 1986). However, finely ground barley causes a strong increase in the frequency of oesophagogastric lesions whereas diets countaining coarsely ground barley or crushed oats caused few lesions. Balance trials on lamb indicate that whole maize have more digestible, metabolizable and net energy than ground maize (BONSEMBIANTEE et al., 1988).