E test feed ingredient were analyzed as described by Li et al. [91,94] to calculate the true ideal digestibilities of AA [2]. Data are means for 8 chicks per ingredient, with pooled SEM values being less than 0.8 . 2 Pigs (50- to 65-d-old). Ileal digestae were obtained from 50- to 65-d-old cannulated pigs [93] at 6 h after they were fed either a nitrogen-free purified diet (consisting of 94.9 cornstarch, 2 LY2510924MedChemExpress LY2510924 soybean oil, 1.65 dicalcium phosphate, 0.5 vitamin premix, 0.5 mineral premix, 0.25 NaCl, and 0.2 chromic oxide) or a diet containing the test feed ingredient (consisting of 79.9 cornstarch, 15 test ingredient, 2 soybean oil, 1.65 dicalcium phosphate, 0.5 vitamin premix, 0.5 mineral premix, 0.25 NaCl, and 0.2 chromic oxide). The amount of the diet was provided to overnight (16 h)-fasted pigs at 12 g/kg body weight. Amino acids in the diet, as well as the digestae from pigs fed either the nitrogen-free purified diet or the diet containing the test feed ingredient were analyzed as described by Li et al. [91,94] to calculate the true ideal digestibilities of AA [2]. Data are means for 6 pigs per ingredient, with pooled SEM values being less than 1.2 .Wu Journal of Animal Science and Biotechnology 2014, 5:34 http://www.jasbsci.com/content/5/1/Page 7 ofsignaling, nutrient transport and metabolism, intestinal microbiota, anti-oxidative responses, and immune responses PubMed ID:https://www.ncbi.nlm.nih.gov/pubmed/25112874 [1,2]. Based on these lines of compelling evidence from animal studies, Wu and colleagues proposed the new concept of functional AA, which are defined as those AA that participate in and regulate key metabolic pathways to improve health, survival, growth, development, lactation, and reproduction of the organisms [1,2,16]. Metabolic pathways include: (a) intracellular protein turnover (synthesis and degradation) and associated events; (b) AA synthesis and catabolism; (c) generation of small peptides, nitrogenous metabolites, and sulfur-containing substances (e.g., H2S); (d) urea cycle and uric acid synthesis; (e) lipid and glucose metabolism; (f) one-carbon-unit metabolism and DNA synthesis; and (g) cellular redox signaling. Functional AA can be nutritionally “essential”, “nonessential”, or conditionally essential AA. Notably, the concept of functional AA in nutrition has also been adopted for fish [72-74], poultry [75-79], and small laboratory animals (e. g., mice and rats) [80-83]. Readers are referred to recentreviews and original research article on these new developments [24,84-101].Texas A M University’s optimal ratios of amino acids in diets for swine and chickensThe carbon skeletons of EAA (including tyrosine and cysteine) are not synthesized from non-AA substances in animals [2]. As noted previously, synthesis of NEAA from EAA in animals is inadequate for their maximal growth, milk production, and reproduction performance or for optimal development and health. Thus, the traditional classification of AA as EAA or NEAA is purely a matter of definition. For example, emerging evidence shows that arginine, glutamine, glutamate, and glycine play important roles in regulating gene expression, cell signaling, antioxidative responses, and immunity [51-56]. Additionally, glutamate, glutamine, and aspartate are major metabolic fuels for enterocytes [6] and also regulate intestinal and neurological development and function [2]. In addition, glutamine is essential for ATP production, synthesis of nucleotides,Table 6 Texas A M University’s optimal ratios of true digest.