Metabolome analyses of the rumen, feces and blood reveal separate and simultaneous impacts of increased dietary concentrate and hindgut starch flow in Holstein cows

Introduction The combined effects of increased dietary concentrate and hindgut starch supply on the cow metabolome remain poorly understood. Objective To evaluate the impacts of high concentrate feeding and the impacts of increased hindgut starch supply on the metabolome of rumen, feces and blood of Holstein cows. Methods Either a 40% (Control) or a 65% concentrate diet (High) was fed. In addition, cows were abomasally infused with either water or starch (3 kg/day). Metabolomic analysis of rumen, feces and blood were performed with HPLC-MS/MS and anion exchange chromatography coupled to high-resolution mass spectrometry. Results Ruminal pH duration < 5.8 was 69 and 249 min/day for Control and High, respectively; fecal pH was 6.58 and 6.33 for water- or starch-infused cows, respectively. Independent of abomasal starch infusion, High increased ruminal concentration of several amino acids, nucleosides, and lipid-related metabolites, and enriched metabolic pathways for purine metabolism, urea cycle and amino acid metabolism. In feces, both High and abomasal starch infusion increased metabolites related to fatty acid and nitrogen metabolism, and enriched pathways for bile acid biosynthesis, amino acid metabolism, α-linolenic acid and biotin metabolism. In blood, Control enriched metabolic pathways for amino sugar metabolism, aspartate metabolism, fatty acid biosynthesis and malate-aspartate shuttle, regardless of abomasal starch infusion. Conclusion High enhanced metabolic pathways mainly for ruminal nitrogen metabolism. Both High and abomasal starch infusion influenced fecal metabolic pathways; whereby, the increased ethanolamine suggests its potential as a biomarker for gut acidosis. Compared to abomasal starch infusion, High had greater impacts on the blood metabolome.