Changes in free amino acids in the brain during embryonic development in layer and broiler chickens.

Developmental changes in the levels of the excitatory amino acids L-glutamate (Glu) and L-Aspartate (Asp) and inhibitory amino acids glycine (Gly) and gamma-amino butyric acid (GABA), as well as taurine and its related amino acids L-methionine (Met), L-cysteine (Cys) and L-serine (Ser) in the brain and pectoralis muscle at various embryonic stages and hatch in broiler and layer type chickens were determined. Brain concentrations of Asp, GABA and taurine were higher than those in the muscle, but the difference in the two types was small. The concentrations of the precursors of taurine including Met, Cys and Ser were lower than that of taurine. In conclusion, the synthesis of some amino acids and their metabolites such as Asp, GABA and taurine in the chick embryo is very high in order to support brain development.