Regarding the role of arginine in vasodilatation and reduction of blood pressure and the possibility of replacing this amino acid with guanidinoacetic acid, a test was conducted with 400 chicks in 5 treatments (control, two levels of 0.5 and 1% arginine, and two levels of 0.15 And 0.3% Guanidininostech) in four replications in a completely randomized design. Birds were subjected to a cold temperature program for induction of pulmonary hypertension syndrome. Blood parameters (RBC, hemoglobin, hematocrit and heterophile / lymphocyte), biochemical parameters (lactate, urea, uric acid and nitric oxide), enzymatic parameters (LDH, AST, ALT, CK) and antioxidant TAS, MDA, GPX, SOD) in plasma were measured at the end of the experiment (day 42). The results showed that supplementation of 1% arginine and 0.15% guanidinoacetic acid significantly decreased the heterophilic/ lymphocyte index, hematocrit, urea and uric acid, and increased nitric oxide (P <0.05). Treatment with 1% arginine and 0.15% guanidinoacetic acid reduced malondialdehyde and increased activity of superoxide dismutase and creatine kinase in plasma (P <0.05). The level of 1% of arginine also significantly increased the activity of glutathione peroxidase enzyme in the plasma. Other measured parameters were not significantly affected by experimental treatments (P> 0.05). In general, the results of this experiment showed that, given the lower price of guanidinoacetic acid compared to arginine, it is possible to effectively use 0.15% guanidinoacetic acid to replace arginine supplementation in preventing reduce stress.