Effects of 2-bromoethanesulfonate alone or in combination with calcium propionate or monensin on methane and gaseous hydrogen production during in vitro rumen fermentation

Some feed additives that mitigate enteric methane (CH₄) production can result in an increase in hydrogen (H₂) production. When expelled to the environment, H₂ may intensify competition for hydroxyl radicals, prolonging CH₄ persistence in the atmosphere. Therefore, the objective of the experiment was to determine the effects of adding 2-bromoethanesulfonate (BE) alone and in combination with monensin or calcium propionate on in vitro ruminal CH₄ and H₂ production. Using 3 separate runs, 1 g of 50% corn silage and 50% alfalfa (DM basis) was fermented (1) alone (control; CON); (2) CON with 100 μ<i>M</i> BE (BES); (3) BES + 2.5 μ<i>M</i> monensin (BM); and (4) BES + 2.5% DM calcium propionate (BC). Inoculum was obtained by collecting a mixture of rumen fluid from 2 steers (BW = 657 ± 12.5 kg) consuming a diet of 30% concentrate and 70% roughage. For each treatment within run, gas production was measured over a 48-h period using 2 randomly assigned paired and separate modules. Total CH₄ and H₂ production were calculated by multiplying the total volume of gas produced by the concentration of CH₄ and H₂ determined by gas chromatography at 0, 4, 8, 18, 24, and 48 h. Data were blocked by run and analyzed as a repeated measures randomized complete block design using the GLIMMIX procedure of SAS (v. 9.4) where treatment, time and the interaction between these 2 factors were considered as fixed effects and module, run and the interaction were included as random effects. Significance was declared at <i>P</i> ≤ 0.05. The BES, BM, and BC treatments did not differ in CH₄ production (g/h) at 4 and 8 h of incubation, averaging 0.005 and 0.013 ± 0.0020 g/h, respectively, but CH₄ production was reduced compared with the CON (0.017 and 0.047 ± 0.0018 g/h CH₄, respectively). At 8 h, BES increased H₂ production relative to BM and BC (0.002 and 0.0014 ± 0.0002 g/h H₂, respectively), but all treatments containing BES were significantly greater than CON (0 vs. 0.002 ± 0.0002 H₂ g/h). In conclusion, treatments containing BES reduced CH₄, and the addition of calcium propionate or monensin may serve as a short-term strategy for the reduction of H₂ resulting from mitigation of enteric CH₄ production.