Amino acids as the major energy source in fish tissues

Amino acids (AAs) and proteins are major macronutrients in feedstuffs and fish. Due to a paucity of information about tissue-specific AA nutrition in aquatic animals, this review highlights the important energetic roles and functions of AAs (particularly glutamate, glutamine, and aspartate) in some tissues (particularly skeletal muscle, liver, kidney, and intestine) of fed fish. Although AAs have long been known to provide most of the energy utilized by fish, roles of specific AAs in certain tissues are unknown. Recent studies with hybrid striped bass and largemouth bass indicated that glutamate, glutamine and aspartate are major metabolic fuels in the proximal intestine, liver, kidney and skeletal muscle. Although these amino acids are abundant in both plant- and animal-source feedstuffs, their provision in compound feeds may be inadequate for optimum intestinal health or optimum growth performance of fish. Dietary supplementation with of glutamate, glutamine and aspartate may be crucial for the health of the organs and the whole body of fish, particularly under stress conditions. Knowledge of AA nutrition in fish will help to improve the growth, development and health of fish, as well as the efficiency of aquaculture worldwide.