Background:The use of antibiotics in animal diets is facing negative feedback due to the hidden danger of drug residues to human health. Traditional Chinese herbal medicine has been used to replace antibiotics in the past two decades and played an increasingly important role in livestock production. The present study was carried out to assess the feeding effects of a traditional nourishing Chinese herbal medicine mixture on kinetics of plasma glucose, protein and energy metabolism in sheep. Ruminal fermentation characteristics were also determined. Methods:Four sheep were fed on either mixed hay (MH-diet) or MH-diet supplemented with 2%of Chinese herbal medicine (mixture of Astragalus root, Angelica root and Atractylodes rhizome;CHM-diet) over two 35-day periods using a crossover design. The turnover rate of plasma glucose was measured with an isotope dilution method using [U-13C]glucose. The rates of plasma leucine turnover and leucine oxidation, whole body protein synthesis (WBPS) and metabolic heat production were measured using the [1-13C]leucine dilution and open circuit calorimetry. Results:Body weight gain of sheep was higher (P=0.03) for CHM-diet than for MH-diet. Rumen pH was lower (P=0.02), concentration of rumen total volatile fatty acid tended to be higher (P=0.05) and acetate was higher (P=0.04) for CHM-diet than for MH-diet. Turnover rates of plasma glucose and leucine did not differ between diets. Oxidation rate of leucine tended to be higher (P=0.06) for CHM-diet than for MH-diet, but the WBPS did not differ between diets. Metabolic heat production tended to be greater (P=0.05) for CHM-diet than for MH-diet. Conclusions:The sheep fed on CHM-diet had a higher body weight gain and showed positive impacts on rumen fermentation and energy metabolism without resulting in any adverse response. Therefore, these results suggested that the Chinese herbal medicine mixture should be considered as a potential feed additive for sheep.