The Influence of Bromoform Dose on In Vitro Rumen Fermentation Characteristics in Rumen Fluid Obtained from Cannulated Steers Fed a Medium-Quality Grass Hay Diet

This study aimed to evaluate the effect of bromoform (CHBr3) dose on in vitro rumen fermentation and on CHBr3 and dibromomethane (CH2Br2) concentrations in solution and the gas cap. In vitro treatments consisted of CHBr3 (DOSE: 0, 1, 10, 100, 1000, 10,000 µg of CHBr3), with five replicates per DOSE at each time-point (TIME: 0, 0.25, 0.5, 1, 2, 3, 4, 5, 6, 12, 24, 48, and 72 h). The 10,000 µg CHBr3 DOSE inhibited fermentation completely and was removed from the dataset. The acetate:propionate ratio, nitrogen, and methane (CH4) produced per gram of DMD decreased as DOSE increased (p = 0.01). As the DOSE increased, CH4 decreased, and H2 increased in a dose-dependent manner (p < 0.01). The CHBr3 concentration dropped below the detection limit within 3 h of incubation. Dibromomethane concentrations for DOSE 1000 and 100 µg of CHBr3 increased in solution and gas cap beginning at 0.25 h and 1 h post incubation and plateaued by hour 3 and 5, respectively (p < 0.01). The addition of CHBr3 alters the molar proportion of volatile fatty acids, decreases CH4, and increases H2 production, and it is dehalogenated to CH2Br2 within 3 h of incubation in an in vitro system.