Dietary arginine supplementation enhances the immune status and protein synthesis in early-weaned pigs. However, the underlying mechanisms remain largely unknown. To investigate how arginine affects the expression of key proteins that regulate growth and nutrient transport of jejunum, a total of 12 healthy piglets （21 day-old, similar body weight, Landrace x Yorkshire） delivered by four sows were randomly divided into two groups. Piglets in the test group were reared with feed supplemented L-arginine at a concentration of 6.0 g/kg, while piglets in the control group were fed with feed supplemented L-alanine at a concentration of 12.3 g/kg （isonitrogenous control）. After 7 d, jejunum mucosae was collected and analyzed with the 2-D PAGE MS technology. Compared with the control pigs, arginine decreased the levels of proteins that regulate the protein syn- thesis, intermediary metabolism and tissue growth （ similar to anterior gradient 2 homolog, cyclophilin_ABHJike, hypothetical protein FLJ39502 and tetratrioopeptide repeat domain 16, similar to KIAA0156, mitechondrial ATP synthase, hydrion transporting F1 complex, beta subunit and alpha-tu- bulin ubiquitous isoform 19, prolyl 4-hydroxylase, beta subunit precursor）. In addition, arginine increased the levels of proteins that are involved in proteolysis and immune response （ PGAM1, T cell receptor beta variable 20, membrane steroid binding protein, similar to myomesin-1, and chain A, structure of pig muscle Pgk complexed with MgATP）. Therefore, arginine influences the immune response and protein synthesis mechanisms as well as improves eady weaned stress syndrome of piglets.
