The aim of this study was to investigate the effects of three herb supplementations on blood metabolites, hormones, antioxidant activity, immunoglobulin (Ig) G concentration, and ruminal fermentation in steers. Four Holstein steers in a 4×4 Latin square design received four herb treatments. The treatments consisted of the steers' regular diets with addition of: 1) nothing (control), 2) peppermint, 3) clove, and 4) lemongrass at 5% of the diet (DM basis). Clove supplementation increased the

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... a concentration of cholesterol by about 10% (from 79 to 87 mg/dl). Peppermint and lemongrass feeding resulted in an increase in the concentrations of plasma urea nitrogen (from 5.9 to 6.9 and 6.4 mg/dl, respectively). The three herb treatments had no effect on other metabolites and hormones. Steers receiving clove supplementation showed a higher plasma antioxidant activity. The three herb treatments caused lower concentrations of IgG in the blood. Peppermint and lemongrass feedings increased, and clove feeding decreased ruminal concentrations of ammonia. There were no significant differences in VFA concentrations among herbal treatments, except for the decrease in propionate concentration in steers receiving clove treatment. This study suggested that clove feeding changed cholesterol metabolism and increased antioxidant activity in plasma, and feeding of three herbs affected immunity system and ruminal fermentation in steers. (Asian-Aust.