Influence of Escherichia coli inclusion and soybean hulls based diets on ruminal biomethane and carbon dioxide productions in sheep

In livestock production, ruminal fermentation leads to significant loss of digestible feed energy and increase methane (CH4) and carbon dioxide (CO2) productions. These gases are the major sources of greenhouse gases that cause environmental degradation and climate change. The present study aimed at investigating the sustainable control of CH4 and CO2 production from ruminal fermentation by evaluating ruminal inclusion of Escherichia coli (E. coli) on diets containing different levels of soybean hulls (SH) replacing corn grains (CG). Three different levels of mixed ration were prepared; CG was replaced with SH at three different levels (per kg dry matter (DM)): 0 g (control), 75 g (SH 75), and 150 g (SH 150). The E. coli was used at four doses: 0, 10, 20 and 40 μL/g DM of substrate. The SH rations had decreased linear and quadratic (P < 0.05) effects on asymptotic gas production (GP). Interactions occurred between SH ration and E. coli doses (P < 0.05) on the fractional rate of GP. E. coli at all doses did not produce any effect on the CH4 production parameters. However, the control had the highest CH4 production at 40 μL/g DM E. coli addition compared to other SH rations and their respective E. coli doses. SH ration linearly (P = 0.006) decreased asymptotic CO2 production. The study established that SH ration and E. coli doses had no effect on the CH4 production; however, they had a decreased effect on asymptotic GP. This study demonstrated that inclusion of SH 150 ration at different E. coli doses reduced asymptotic CO2 production without effect on CH4 production and this may be useful for the sustainable mitigation of CO2 production from livestock production.