Two experiments were conducted to determine the potential for the essential oil blend Agolin Ruminant L (Agolin) to reduce enteric methane (CH4) emissions from beef cattle when delivered via drinking water. Experiment 1 evaluated aqueous solutions of Agolin (50 mg/L) and a nonprotein nitrogen and mineral solution (uPRO ORANGE [uPRO]; 1.7 mL/L) individually and in combination, where Agolin was added to concentrated uPRO at 3%, 4.5%, and 6% Agolin (w/w) prior to dilution with water at 1.7 mL/L, for a total of 5 treatments. These were incubated for 48 h with a medium-quality Rhodes grass (Chloris gayana) hay substrate, with gas production, CH4 concentration in gas, and digestibility measured in vitro. In experiment 2, Droughtmaster steers (n = 24) were fed a basal diet of Rhodes grass hay and were allocated to 1 of 3 water treatments (n = 8 per treatment) supplemented with either uPRO (2.27 mL uPRO/L water), or 1 of 2 inclusion rates of Agolin in combination with uPRO (2.27 mL uPRO and 6 µL Agolin/L water or 2.27 mL uPRO and 24 µL Agolin/L water) with enteric CH4 emissions, feed and water intake, and live-weight gain (LWG) measured over 56 d. In experiment 1, the inclusion of Agolin in uPRO at 6% (w/w) resulted in a reduction in CH4 production (15.8%; P = 0.003) and the proportion of CH4 in the gas produced (24.5%; P < 0.001). In experiment 2, steers consuming the lower quantity of Agolin via drinking water had a 16.4% (P = 0.0027) reduction in CH4 production over the experiment, declining from 140 g/d during week 1 to 117 g/d in week 8. This inclusion rate of Agolin in the drinking water also resulted in a 25 g (17.6%) CH4/d decrease in emissions by steers compared to control steers (P = 0.0205). However, no significant differences in CH4 yield (g CH4/kg dry matter intake), or CH4 intensity (g CH4/kg LWG) by steers were observed between treatments. These results demonstrated that Agolin reduces CH4 emissions when mixed in an aqueous solution under in vitro and in vivo conditions, providing a potential method to reduce enteric CH4 emissions from cattle in extensive production systems.
Keywords: greenhouse gas; imbibe; live-weight gain; ruminant.
Most research conducted to reduce methane (CH4) emissions from cattle has focused on intensive feeding systems, such as dairy and feedlots, where feeding management is tightly controlled. The delivery of CH4 mitigants to ruminants grazing in extensive pasture-based systems requires attention. Two experiments were conducted to investigate the delivery of an essential oil blend called Agolin Ruminant L (Agolin) to beef cattle via drinking water to reduce CH4 emissions. The first experiment measured gas production and CH4 emissions when increasing quantities of Agolin were added to an aqueous solution and a medium-quality forage substrate in vitro. The second experiment delivered 2 different concentrations of Agolin to yearling steers fed the same forage as that used in the first experiment, with CH4 emissions, feed and water intake, live-weight gain (LWG), rumen fermentation parameters, and the blood biochemical profile measured. Both experiments demonstrated that CH4 production was reduced with the inclusion of Agolin in an aqueous solution, while feed and water intake, LWG, and rumen fermentation parameters were unaffected. The results demonstrated that drinking water presents a viable option for the delivery of Agolin to reduce enteric CH4 emissions from beef cattle.
© The Author(s) 2024. Published by Oxford University Press on behalf of the American Society of Animal Science.