LAUSR

Abstract Herbal supplements are being tested as alternatives to antibiotics in enhancing the performance of livestock. The present study evaluated the effects of herbal root extracts from three traditional Chinese medicinal herbs as dietary supplements on dry matter intake (DMI), average daily gain (ADG), rumen fermentation and ruminal microbiota in early weaned yak calves (Poephagus grunniens). Twenty, four-month old weaned yak calves (72.3 ± 3.65 kg) were divided into four groups, matched for bodyweight and sex (n = 5 per group), and received either no supplement (control group) or 80 mL/kg DMI of herbal root extracts of Angelica sinensis, Codonopsis pilosula or Glycyrrhiza uralensis. The water extract (∼170 mL) was mixed with 300 g concentrate and offered to the calves each day for 60 days following a 14-day adaptation period. Dry matter intake did not differ among treatments, but ADG was highest for calves fed Codonopsis pilosula root extract (P = 0.026). Compared with control calves, calves fed root extract of Glycyrrhiza uralensis had a higher ruminal proportion of propionate (P =  0.034), calves fed root extracts of Codonopsis pilosula and Glycyrrhiza uralensis had higher ruminal proportions of isovalerate (P =  0.032) and calves fed root extract of Glycyrrhiza uralensis had a lower acetate:propionate ratio (P =  0.027) on d 30. Calves consuming Angelica sinensis and Codonopsis pilosula root extracts, and Glycyrrhiza uralensis root extract had lower ruminal NH3-N concentrations than control calves on d 60 (P