Effects of dietary graded creatine nitrate (CrN) supplementation on the relative mRNA expression for GAMT and CreaT in the liver and Pectoralis major (PM) muscle of broilers. The data are represented as the mean value ± SEM (n = 6). Means without a common letter (a, b or c) significantly differ (P < 0.05). Orthogonal polynomials were used to estimate the linear and quadratic effects of dietary CrN supplementation among the control, CrN300, CrN600, and CrN900 groups. Abbreviations: CreaT, creatine transporter; Control, basal diet; CrN300, CrN600, and CrN900, basal diets supplemented with 300, 600, and 900 mg/kg CrN, respectively; GAA600, basal diet supplemented with 600 mg/kg guanidinoacetic acid (GAA); GAMT, S-adenosyl-L-methionine: guanidinoacetate N-methyltransferase.