DIETARY REQUIREMENTS OF FUNCTIONAL AMINO ACIDS IN SWINE GESTATION, LACTATION AND GROWTH

摘要

Based on growth or nitrogen-balance studies, amino acids (AA) had been classified traditionally as nutritionally essential or nonessential for swine. Nutritionally essential AA (EAA) are defined as either those AA whose carbon skeletons cannot be synthesized de novo in animal cells or those that normally are insufficiently synthesized de novo by the animal organism relative to its needs and which must be provided in the diet to maintain maximum growth and production performance. In contrast, nutritionally nonessential AA (NEAA) are those AA which can be synthesized de novo in adequate amounts by animals to meet requirements for maintenance, growth and development and, therefore, need not be provided in the diet. A limitation of the previous classification of AA as EAA or NEAA is that regulatory roles for AA in animal metabolism had not been considered in dietary formulation. Growing evidence shows that some EAA (e.g., leucine and tryptophan) and NEAA (e.g., glutamine, glycine and arginine for swine) can activate the mammalian target of rapamycin (mTOR) cell signaling to promote protein synthesis and inhibit proteolysis in tissues. Certain AA (e.g., arginine, cysteine, glutamine, glutamate, glycine, and proline) play important roles in regulating gene expression, antioxidative responses, DNA synthesis, neurotransmission, and immune responses. Additionally, glutamate, glutamine and aspartate are major metabolic fuels for the small intestine to maintain its digestive function and protect the integrity of the intestinal mucosa. These findings lead to a new concept of functional AA (FAA), which are defined as those AA that regulate key metabolic pathways to improve the health, survival, growth, development, lactation, and reproduction of animals. Asexamples for translating this novel concept to feeding practices, supplementing FAA to conventional corn- and soybean meal-based diets enhances litter size in gestating gilts and multiparous sows, milk production by lactating sows, as well as the growthperformance of suckling neonates and growing-finishing pigs. Improvements in swine feed efficiency and productivity through the use of FAA will not only decrease the contamination of soils, groundwater, and air by excessive manure, but will also help sustain animal agriculture to produce high-quality protein for the expanding population in the face of diminishing resources worldwide.