370 Liquid supplement with pure molasses and essential oils reduced daily CH4 emissions by 10% in beef steers.

Abstract Methane (CH4) is the largest greenhouse gas (GHG) emitted from livestock production, prompting continuous efforts to reduce emissions and discover new methods for its mitigation. Plants containing essential oils (EOs) have been researched vastly for their anti-methanogenic effects when supplemented to ruminants. The objective of this study was to investigate the effect of a molasses-essential oil mixture offered free-choice on CH4 emissions from beef cattle. A total of 40 steers were randomly assigned to a control (no liquid supplement) or a molasses-EO treatment group. Both groups received a diet of oaten hay, provided through electronic feeders (Intergado Ltd, Betim, MG, Brazil) and barley-based pellets delivered via a GreenFeed unit (GF; C-Lock inc., Rapid City, SD, USA). Dry matter intake (DMI), average daily gain (ADG), and water consumption were measured using the Intergado® system, while GHG emissions were quantified using the GF system. The molasses-EO supplement was not provided during the first week for baseline measurements, and it was then diluted with pure molasses and provided free-choice and to allow for ad-libitum consumption to the treatment group for 56 days resulting in an average intake of 0.6 ± 0.02 kg DM d-1. A mixed-effects linear regression model was used, with animal as the random effect, and period (baseline and treatment), treatment (control and molasses-EO), and their interaction as fixed effects. Logarithmic transformations were performed on hydrogen and supplement intake data to normalise their distributions, and the raw data was filtered for illogical values before analysis. Period summary values were calculated for each variable and significance was declared at P ≤ 0.05 and tendencies discussed at 0.05 < P ≤ 0.10. During the treatment period, steers fed molasses-EO had greater total DMI (7.8 vs 7.2 ± 0.21 kg d-1), metabolizable energy intake (63.1 vs 54.0 ± MJ ME d-1), water soluble carbohydrates intake (0.7 vs 0.3 ± 0.01 kg d-1), crude protein intake (0.6 vs 0.5 ± 0.001 kg d-1), and water intake (60.0 vs 33.2 ± 2.18 L d-1), compared to the control steers, respectively (P < 0.05). Molasses-EO steers had 10% lower daily CH4 (195.9 vs 211.7 ± 5.46 g d-1) and lower CH4 intensity (269.7 vs 700 ± 190.22 g kg-1 ADG; P < 0.05) compared to control. No differences between treatments were observed in the baseline period (P > 0.05), and no detrimental effects on animal performance or health were observed. Research with longer feeding periods is encouraged. A new delivery method of supplementation for forage-fed animals using plant extracts containing essential oils mixed with molasses presents another promising tool for cattle producers to implement more environmentally friendly livestock management practices.