Urine metabolome reveals candidate biomarkers for divergent residual feed intake in beef cattle

We analyzed the amine/phenol-metabolome of urine samples to identify urinary metabolic biomarkers associated with residual feed intake in beef cattle. A group of 56 crossbred growing beef steers (average BW ​= ​261 ​± ​18.5 ​kg) were adapted to a high-forage total mixed ration in a confinement dry lot equipped with GrowSafe intake nodes for period of 49 ​d to determine their residual feed intake classification (RFI). After RFI determination, weekly urine samples were collected three times from beef steers with negative RFI (most efficient (HFE); RFI ​= ​- 1.93 ​kg/d, n ​= ​8) and positive RFI (least efficient (LFE); RFI ​= ​+ 2.01 ​kg/d, n ​= ​8). Urine samples collected were then composited for each steer. Metabolome analysis was conducted using a chemical isotope labeling/liquid chromatography–mass spectrometry, specifically for the analysis of metabolites containing amine/phenol-chemical groups, which are metabolites associated with metabolisms of amino acids. A total number of 557 amine/phenol-containing metabolites were detected and identified. Biomarker analysis of the urinary amine/phenol-metabolome identified N-acetyl-l-tyrosine, O-methyl-l-threonine, uridine, and threoninyl-hydroxyproline as candidate biomarkers of RFI (false discovery rate ≤0.05; Area Under the Curve ≥0.85). In conclusion, the results of our study revealed that alteration in urine amine/phenol-metabolome is associated with selection for low or high RFI in beef steers and urine is a potential source of metabolite biomarkers associated with RFI in beef cattle.