Meeting livestock nutritional requirements is extremely important in maintaining acceptable performance of neonatal, growing, finishing and breeding animals. Animal nutrition focuses on the dietary needs of animals, primarily those in agriculture and food production, but also in zoos, aquariums, and wildlife management. Animal nutrition entails the study of the composition and characteristics of the material consumed by the animal, the manner in which this material is metabolised (converted, utilised, and excreted) in the digestive tract and body cells of monogastric animals (pigs, broilers, layers), ruminants (sheep, cattle, goats), and lower digestive tract fermenters (horses, ostriches). The nutrient requirements of different species animals for various production functions are also addressed. Finally, this information is integrated in an economically feasible and practical system of animal nutrition to ensure that the optimal genetic production potential of animals is achieved.