Differential metabolites identification
Among the 5566 positive ion and 5983 negative ion metabolites in the uterine secretion of cows, the first principal component variable projection importance >1, difference multiple (FC) > 2 or < 0.5, and p < 0.05 were selected as thresholds for the screening of significant metabolites (Table 1). In Figure 4, the abscissa represents the logarithm of the differential multiple of differential metabolites log2(FC), and the vertical axis represents the negative logarithm of the p-value log10 (p-value), black represents the metabolite with no significant difference (none), red represents upregulated metabolites (up), and green represents downregulated metabolites (down). Figure 5 shows metabolites with significant differences between uterine secretions from healthy cows and those with clinical endometritis, which can be used as the basis for functional analysis of metabolic pathways. Differential metabolites between the uterine secretion metabolomes of healthy versus clinical endometritis samples are listed in Supplemental Figures S1 and S2.