ABSTRACT
The term lipid includes fats, oils, and other compounds that are insoluble in water but soluble in nonpolar organic solvents. In general, the term “fats or oils” is used to refer to lipids that are solid or liquid, respectively, at normal room temperature. Animal and poultry fats and fish oils are highly digestible energy sources for animals and poultry, and fish oils are also an excellent source of omega-3 fatty acids and vitamins A and D. The quality of feed-grade fats can be assessed by the composition, hardness, color, impurities, and stability. Composition refers to the fatty acid profile, and hardness is affected by chain length and degree of unsaturation of fatty acids. Color may not be associated with nutritional value, but it can indicate the composition and/or source of products. Impurities can be natural constituents and degradation products of lipids, contaminants from the processing, and others. Moisture or unsaponifiable matters have no nutritional value, and ether insolubles
INTRODUCTION
The competition between humans and animals for quality sources of nutrients is likely to increase continuously because of the ever-increasing world population and an increase in the economic development of both newly industrialized and less economically developed countries. It is therefore important not only to improve feed efficiency but also to explore all potential sources as a feed ingredient. Animal, poultry, and marine by-products have been used as a source of nutrients for many years. Considering alternative disposal methods, not utilizing those resources as a feed ingredient would have adverse impacts on the economy, environment, and ecology, as well as on animal and human health. It is likely that by-product feeds will play even more important roles in the future. The objective of this entry is to review briefly selected by-product feeds of animal, poultry, and marine origins used for food animal and poultry production.
