Maize grain is the most important grain used as an energy supplement in livestock rations. Considered as a standard grain, maize grain is a palatable source of energy, low in crude cellulose. Furthermore, maize contains no significant anti-nutritive substances and can be used in animal nutrition with minimal processing. Ruminants efficiently consume corn processed as whole, lightly cracked, crushed or cooked (flaked), while poultry consume corn after it has been ground to a certain particle size. Grain corn is also used in fish and pet diets.