Supplementing Forage with Traditional Chinese Medicine Can Increase Microbial Protein Synthesis in Sheep

Traditional Chinese medicine (TCM) encompasses a wide range of natural herbs and plants that are used to treat or prevent diseases or promote health. This study aimed to evaluate the effect of feeding a TCM formula extract on nitrogen (N) balance, microbial nitrogen supply (MNS), and plasma leucine kinetics in sheep. Six sheep were fed with mixed hay (Hay-diet) only or supplemented with 2% TCM (mixture of Astragalus root, Angelica root, and Atractylodes rhizome; TCM-diet) in a crossover design over two 21-day periods. An isotope dilution of [1-13C]leucine was used to measure the rate of plasma leucine turnover. Purine derivative (PD) excretion in urine was determined to estimate the MNS. The TCM-diet significantly increased N intake (p < 0.01) and N digestibility (p = 0.02) compared to the Hay-diet, with less N excretion (p = 0.02) in feces, while no significant difference was observed between diets in terms of N excretion in urine and N retention. Total PD excretion and MNS were higher (p < 0.01), as well as the turnover rate of plasma leucine tended to be higher (p = 0.06) with the supplementation of TCM. The present results suggested that the TCM formula could be considered as a potential feed additive for ruminant production.