Abstract
A discovery project to identify non‐invasive biomarkers that can detect subtle metabolic discrepancies for cattle feed efficiency was performed using untargeted and targeted urine metabolomics by ultra-performance liquid chromatography-mass spectrometry. Individual feed intake and body weight gain were measured in crossbred steers (n = 80) on a forage-based growing ration (stage-1) followed by a high-concentrate diet finishing ration (stage-2). Urine was collected on study days 0, 21, 42, 63, and 83 for each dietary stage. In total, 28 steers with the greatest and the least average daily-gain (ADG) within 0.32 SD of the mean of dry-matter-intake (DMI) were used. A principal component analysis of the untargeted metabolites fully segregated the highest-ADG and lowest-ADG animals, with overlap across diets (both stages). The urinary untargeted metabolites that segregated the ADG-groups (n = 199; P < 0.05), included steroid-hormones, bile-acids, alpha-linolenic acid metabolites, vitamin-B6, along with products of glycine, serine and threonine metabolism (metabolic pathway analysis: impact-value > 0.50; FDR < 0.10). Bile acids and steroids were then quantified in urine and their associations with animal performance and carcass composition evaluated by correlation and multiple logistic regression AUC-ROC curve analyses. In stage-1, urine concentration of cortisone was associated (P < 0.05) with ADG (r = -0.28), DMI (r = -0.40) and ribeye-area (r = -0.28); cortisol was associated with DMI (r = -0.32; P < 0.01) and testosterone was associated with ADG (r = -0.28; P < 0.01). The urine concentrations of 18 measured bile acids were negatively associated (P < 0.05) with DMI, and secondary bile acids were negatively associated (P < 0.01) with marbling and hot-carcass-weight. In stage-2, negative association between the bile acids glycocholic acid and deoxycholic acid with marbling and hot-carcass-weight were identified. Urine metabolomics provide new insight into the physiological mechanisms and potential biomarkers of cattle feed efficiency. USDA is an equal opportunity provider and employer.