Essential Oil and Rumensin Affect Ruminal Fermentation in Continuous Culture

The combination of Rumensin® and essential oil could be beneficial for ruminal fermentation by suppressing protozoa and their associated methanogens, while maintaining normal rumen function. The objective of this study was to determine the effects of feeding Rumensin® and Cinnagar® (essential oil from cinnamon and garlic) in diets on ruminal fermentation characteristics. Four continuous culture fermenters were modified to retain protozoa (slower stirring and a special filter apparatus) and maintained at a liquid dilution rate of 7%/h and a solids dilution rate of 5%/h in 4 periods of 10 d each (7 d of adaptation, 3 d of sample collection) in a 4 X 4 Latin square design. Four dietary treatments (fed in 1 meal per day) were arranged in a 2 x 2 factorial: (1) control diet, 40 g of a 50:50 concentrate: forage (ground alfalfa hay) diet (40% neutral detergent fiber, 17% crude protein) containing no additive; (2) Rumensin® at 11g/ 909 kg of dry matter; (3) Cinnagar® at 0.0043% (DM basis); and (4) combination of Rumensin® and Cinnagar®. There were no effects of treatment on NDF or organic matter digestibility, concentrations of NH3-N or total volatile fatty acid, or percentage of protozoal generic distribution. Rumensin® (main effect, no interaction) decreased (P < 0.05) molar percentages of acetate (62.6 vs 64.4) and valerate (1.78 vs 1.86); decreased acetate: propionate ratio (2.69 vs 3.04); and increased (P < 0.05) molar percentages of propionate (23.3 vs 21.3) and isovalerate (1.94 vs 1.67). Rumensin® increased (P < 0.05) the protozoa generation time (27.6 vs 21.6 h). Cinnagar® tended (P = 0.11) to increase molar percentage of isovalerate (1.77 vs 1.67) and decrease protozoa counts (14.9 vs. 18.5 x 10^3/ml). Rumensin® and Cinnagar® tended (P = 0.06) to interact for methane production (29.3, 22.4, 21.8, and 36.7 mmol/d, respectively). Under the conditions of our study, we did not detect an additive response for Rumensin® and Cinnagar® to either decrease protozoal counts or methane production.ElancoProvimi-North AmericaNo embarg