The main objective when formulating a livestock diet is to combine different feed ingredients in order to meet the energy and protein requirements of the bred animal. However, it is also important to keep the fiber content of feed ingredients in mind when feeding livestock such as poultry. While limited amounts of fiber can have a positive dietary effect on digestion, high contents have adverse effects, because fiber is indigestible for them. Feed ingredients that can be used directly in feed formulation are called primary feed ingredients such as cereal grains. Feed ingredients that require several steps of processing before incorporating them in feed formulation are called by-product feed ingredients such as soybean meal, wheat bran, corn gluten meal, fish meal to name a few.