Amino acids nutrition
Twenty amino acids are the building blocks of proteins (Table 1). Some of them can not be synthesised, or not in sufficient quantities, by animals; they must therefore be supplied through the feed and are referred to as indispensable amino acids. The indispensable amino acids could differ depending on the species (Table 2). To maintain good health and growth performance, feeds must provide the indispensable amino acids in sufficient quantities to cover the requirement of animals.
| Alanine | Ala | Leucine | Leu |
| Arginine | Arg | Lysine | Lys |
| Asparagine | Asn | Methionine | Met |
| Aspartic acid | Asp | Phenylalanine | Phe |
| Cysteine | Cys | Proline | Pro |
| Glutamic acid | Glu | Serine | Ser |
| Glutamine | Gln | Threonine | Thr |
| Glycine | Gly | Tryptophan | Trp |
| Histidine | His | Tyrosine | Tyr |
| Isoleucine | Ile | Valine | Val |
Table 1. The 20 amino acids encoded directly by the genetic code and their 3-letter abbreviations
| Amino acids involved in the biological functions that are necessary for life supplied through the diet or synthesised de novo by animals. |
| EAA that can not be synthesised de novo or at a sufficient rate to maintain the associated biological functions | Lys | Lys |
| Thr | Thr |
| Met | Met |
| Trp | Trp |
| Val | Val |
| Ile | Ile |
| Leu | Leu |
| His | His |
| Phe | Phe |
| Arg |
| EAA that can be synthesised de novo but that could become indispensable in specific situations when the synthesis become not sufficient to cover the requirement | Cys | Cys |
| Tyr | Tyr |
| Arg | |
| EAA that can be synthesised de novo by animals in a sufficient rate in any cases | Glu, Gln, Gly, Ser, Pro, Asp, Asn, Ala |
Table 2. Classification of the 20 amino acids encoded directly by the genetic code, for pigs and broiler
