Free carnitine, short, medium, and long-chain acylcarnitines levels are higher in the piglet liver than the adult pig. Serum levels of free carnitine (A), short-chain acylcarnitines (B), medium-chain acylcarnitines (C), and long-chain acylcarnitines (D) from piglets and adult pigs determined by median-scaled untargeted metabolomics. (n = 6) All bars represent means ± SE. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.