Fig. 2

PCA (a) and OPLS-DA with the corresponding coefficient loading plots (b), (c), (d) score plots. The color map in the (b), (c) and (d) shows the significance of metabolite variations between the two classes. The peaks in the positive direction indicate the metabolites that are more abundant in the groups in the positive direction of the first principal component. The metabolites that are more abundant in the groups in the negative direction of the first primary component are presented as peaks in the negative direction. The significant discriminatory metabolites were indicated in red color whereas blue color shown no significance. Principal component analysis (PCA), orthogonal projection to latent structure-discriminant analysis (OPLS-DA), the plasma sample at postpartum d0 of sows fed the control diet (CON-d0), the plasma sample at postpartum d0 of sows fed DL-methionine diet (DLM-d0), the plasma sample at postpartum d0 of sows fed DL-2-hydroxy-4-methylthiobutanoic acid diet (HMTBA-d0), the plasma sample at postpartum d7 of sows fed the control diet (CON-d7), the plasma sample at postpartum d7 of sows fed DL-methionine diet (DLM-d7), the plasma sample at postpartum d7 of sows fed DL-2-hydroxy-4-methylthiobutanoic acid diet (HMTBA-d7), 3-hydroxybutyrate (3-HB), acetamide (AA), acetate (Ace), alanine (Ala), asparagine (Asn), betaine (Bet), choline (Cho), citrate (Cit), creatinine (Cn), creatine (Cr), 3, 4-dihydroxymandelate (DHM), dimethylamine (DMA), glycerol (G), glucose (Glc), glycerolphosphocholine (GPC). Low density lipoprotein, CH3-(CH2)n- (L1). Very low density lipoprotein, CH3-(CH2)n- (L2). Low density lipoprotein, CH3-(CH2)n- (L3). Lipid, =CH-CH2-CH = (L8). Lipid, −CH = CH- (L9). Lysine (Lys), myo-inositol (m-I), phenylalanine (Phe), succinate (Suc), valine (Val)