Partially substituting alfalfa hay with hemp forage promotes the health and well-being of goats via altering ruminal and plasma metabolites and metabolic pathways

Hemp forage (HF) seems a suitable forage for ruminants for its high nutritional value and rich phytochemicals that exert health and growth-promoting activities. We investigated the effects of hemp-related phytochemicals on rumen and plasma metabolism using metabolome when partially substituting alfalfa hay with HF in goat diets. Numbers of differential metabolites linearly increased with increasing HF substituting rate, approximately 50% of which were phytochemicals. Metabolic pathway enrichment analysis showed that the inclusion of HF greatly promoted steroid hormone biosynthesis, one carbon pool by folate, and retinol metabolism pathways in both rumen and plasma, which are beneficial for promoting animal health and well-being and enhancing the quality of animal products. Some phytochemicals showed inhibitory activities on the growth of certain ruminal bacteria; meanwhile, the detected intermediate metabolites indicated degradation of the phytochemicals by ruminal microbes. These phytochemicals work individually and synergistically to alter ruminal and plasma metabolic pathways, thus exerting benefits in promoting the health and well-being of animals.