Performance and Rumen Fermentation in Finishing Steers Fed a Total Mixed Ration Supplemented with a Blend of Essential Oils, Tannins, and Bioflavonoids or Monensin

This study investigated the effects of adding a blend of essential oils, tannins, bioflavonoids (ANAVRIN®, VetosEurope, Lugano, Swuitzerland), monensin, and their combination on the performance and rumen fermentation of finishing steers fed a total mixed ration (TMR). Thirty finishing steers (441 kg body weight, 34.3 months old) consuming a TMR were blocked by BW and randomly assigned to three treatments according to the addition of: 1) EOTB (ANAVRIN® at 0.35 g/100 kg body weight); 2) MON (monensin at 0.033 g/kg dry matter); and 3) EOTB+MON (at the same dose as in 1 and 2). A 60-day feeding trial was conducted, including a 14-day adaptation period. Data collected included daily dry matter intake (DMI), average daily gain (ADG), feed conversion ratio (FCR), and rumen fermentation parameters (pH, N-NH3 and volatile fatty acids (VFA) concentration). EOTB resulted in higher DMI compared to EOTB+MON, while no significant differences were observed in ADG or FCR. Ruminal pH and N-NH3 concentration were similar among treatments, but there were interactions treatment×hour for VFA. The EOTB+MON led to a more stable VFA concentration in rumen, suggesting possible complementary supplementation effects. However, more studies are needed to confirm this, going deeper in the mechanism of action beyond.