Fig. 2
The PCA, PLS-DA, and OPLS-DA score plots comparing GF (blue rotundities) and FA (green squares) pigs in positive electrospray ionization mode (ESI+) and negative electrospray ionization mode (ESI−) metabolomics profiles of serum. Panels a (ESI+) and b (ESI−) are PCA score plots. Panels c (ESI+, R2X = 0.459, R2Y = 0.996, Q2 = 0.649) and d (ESI−, R2X = 0.514, R2Y = 0.999, Q2 = 0.818) are PLS-DA score plots. Panels e (ESI+, R2X = 0.317, R2Y = 0.976, Q2 = 0.009) and f (ESI−, R2X = 0.307, R2Y = 0.926, Q2 = 0.201) are OPLS-DA score plots. GF, germ-free; FA, short chain fatty acids; PCA, principal component analysis; PLS-DA, Partial least squares discriminant; OPLS-DA, orthogonal partial least-squares discriminant