Abstract
Some feed additives that mitigate enteric methane (CH(4)) production can result in an increase in hydrogen (H(2)) production. When expelled to the environment, H(2) may intensify competition for hydroxyl radicals, prolonging CH(4) 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 CH(4) and H(2) 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 μM BE (BES); (3) BES + 2.5 μM 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 CH(4) and H(2) production were calculated by multiplying the total volume of gas produced by the concentration of CH(4) and H(2) 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 P ≤ 0.05. The BES, BM, and BC treatments did not differ in CH(4) production (g/h) at 4 and 8 h of incubation, averaging 0.005 and 0.013 ± 0.0020 g/h, respectively, but CH(4) production was reduced compared with the CON (0.017 and 0.047 ± 0.0018 g/h CH(4), respectively). At 8 h, BES increased H(2) production relative to BM and BC (0.002 and 0.0014 ± 0.0002 g/h H(2), respectively), but all treatments containing BES were significantly greater than CON (0 vs. 0.002 ± 0.0002 H(2) g/h). In conclusion, treatments containing BES reduced CH(4), and the addition of calcium propionate or monensin may serve as a short-term strategy for the reduction of H(2) resulting from mitigation of enteric CH(4) production.