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BACKGROUND: Guanidinoacetic acid (GAA) is an essential precursor of creatine and plays a vital role in maintaining energy metabolism and muscle function in cattle. However, the mechanisms by which GAA exerts its effects remain unclear. This study used transcriptomic profiling combined with phenotypic analysis to evaluate the impact of dietary GAA supplementation at levels of 0.04%, 0.08% and 0.12% on metabolic pathways in the liver and pectoral muscles of Holstein castrated cattle, linking gene expression changes to key physiological and biochemical traits. RESULTS: Dietary supplementation with GAA activated the AMPK signaling pathway in liver tissue, enhanced fatty acid β-oxidation, and moderately suppressed immune-related pathways (e.g., NF-κB and IL-17), suggesting a balance between energy efficiency and immune regulation. In muscle, GAA promoted creatine biosynthesis, facilitates intramuscular fat deposition via PLIN2, induced muscle fiber remodeling, and triggered a metabolic shift toward glycolytic metabolism. Furthermore, the 0.08% GAA level achieved a coordinated balance between liver energy metabolism and fat deposition in the pectoral muscles. These molecular changes were consistent with phenotypic outcomes, as intramuscular fat content exhibited a significant quadratic increase (P = 0.0049), peaking at 0.08% GAA, and plasma glucose levels increased linearly with supplementation (P < 0.01), indicating improved systemic energy availability. CONCLUSIONS: These findings demonstrate that GAA exerts dose-dependent and tissue-specific effects on bovine energy metabolism and muscle development, with 0.08% appearing to be the optimal supplementation level.
Wei et al. (Wed,) studied this question.