The present study was carried out to investigate the effect of different levels of guanidine acetic acid (GAA) on the performance, carcase yield and energetic molecular metabolites of breast muscle in broiler chickens fed with wheat-soy diet containing different levels of nutrient densities. 450- day-old male broiler chicks (Ross 308), assigned in a completely randomised design experiment with factorial arrangement 3
3, 9 treatments and 5 replicates of 10 birds each. The diets included three levels of GAA supplementation (0, 0.6, 1.2 g/kg of diet) and three dietary nutrient density (ND) levels (low; 2800 kcal ME/kg, medium; 2950 kcal ME/kg and high; 3100 kcal ME/kg with constant rates of ME to other nutrients). The experimental diets were fed ad libitum from 1–42 days of age. One bird per pen was euthanized on day 10 and 42 to determine the energetic molecular metabolites concentrations of adenosine phosphate (ATP, ADP and AMP), phosphocreatine (PCr) and creatinine (CRN) in breast muscles. The inclusion of 0.6 g/kg GAA in wheat–soy diet, improved production performance, the relative weight of breast yield and increased the concentration of high phosphate energy metabolites (PCr, ATP/ADT and PCr/ATP) in breast muscle. The supplementation of high-density diet with GAA compared with the lowdensity diet improved broiler chicken’s performance. It is concluded that the use of GAA in diet may facilitate the conversion of high-energy phosphates to form ATP in muscles and thus improve broiler chicken’s performance.

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