Effects of Three Herbs on Methane Emissions from Beef Cattle

SIMPLE SUMMARY: Cattle represent a significant source of greenhouse gases (GHGs). In 2010, cattle emitted 5.0 gigatons of CO(2) equivalents globally, which represents about 62% of the livestock sector emissions. Therefore, mitigating GHGs such as methane (CH(4)) originating from the cattle industry, offers an opportunity to reduce GHG emissions and climate change over the short term. Ruminant nutritionists have developed different strategies, which include the use of antibiotics, herbs and chemical compounds, such as nitrate, to manipulate rumen fermentation and reduce CH(4) emissions. So, the objectives of the present work were to evaluate the in vivo antimethanogenic effects of three herbs: Cymbopogon citratus (CC), Matricaria chamomilla (MC) and Cosmos bipinnatus (CB) on beef cattle fed a high in concentrate diet and the effects of increasing levels of CC on enteric CH(4) emissions by beef cattle fed a ration low in concentrate. We concluded that CC significantly reduced methane yield (g of CH(4)/kg of DMI) by 33%, CB reduced methane yield by 28%, and MC had no significant effect. In Experiment 2, CC supplemented with 2% of the daily DMI significantly reduced the total daily CH(4) emissions by 26% without affecting the supply of nutrients to the animal. ABSTRACT: The objectives of the present work were to evaluate the in vivo antimethanogenic effects of Cymbopogon citratus (CC), Matricaria chamomilla (MC) and Cosmos bipinnatus (CB) on beef cattle fed a high in concentrate diet (forage-to-concentrate ratio [F:C] of 19.4:80.6), and the effects of increasing levels of CC (0%, 2%, 3%, and 4% of the daily DM intake (DMI)) on enteric CH(4) emissions by beef cattle fed a ration low in concentrate (F:C ratio of 49.3:50.7). Two experiments were conducted to address the objectives. For the first experiment, eight Charolais × Brown Swiss steers distributed in a replicated 4 × 4 Latin square experimental design were used. Four treatments were evaluated: (1) control diet (CO), (2) CO + 365 g dry matter (DM)/d CB, (3) CO + 365 g DM/d MC, (4) CO + 100 g DM/d CC. For Experiment 2, four Charolais x Brown Swiss steers distributed in a single 4 × 4 Latin square design were used. It was concluded that 100 g DM per day CC and 365 g DM per day CB (Experiment 1) reduced CH(4) yield of beef cattle. In Experiment 2, CC supplementation levels exceeding 2% of DMI reduced daily CH(4) emissions but at the expense of decreasing digestibility of DM.