Desmanthus: A tropical legume for reducing methane emissions in Northern Australian beef cattle A,D B A C Bénédicte Suybeng , Edward Charmley , Christopher P. Gardiner , Bunmi S. Malau-Aduli and Aduli A A B E.O. Malau-Aduli | College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, Qld 4811; CSIRO Agriculture and Food, Townsville, Qld 4811; C College of Medicine and Dentistry, James Cook University, Townsville, Qld 4811; D Corresponding author: [email protected] Introduction Results & Discussion Desmanthus is a tropical pasture legume that can Results showed no differences in methane emissions persist in semiarid clay soil regions with a productivity between Desmanthus cultivars. However, a significant of about 30% legumes and 70% grasses. Progardes decrease in CH4 emissions with increasing level of Desmanthus has been sown in about 35,000ha of Desmanthus (p=0.0144) was observed. The decrease commercial paddocks across principally Queensland in methane followed a linear pattern (Fig. 2) and but also northern New South Wales and the Northern showed a CH4 reduction of about 12% for 48% Territory. The legume showed promising results in Desmanthus inclusion. decreasing methane emissions in vitro [1,2] and improving animal performance in vivo [3-7]. The objective of this study was to investigate the effects of supplementing incrementally beef cattle with two species of Desmanthus (D. leptophyllus cv. JCU1 and D. bicornutus cv. JCU4) on methane emissions and estimate the carbon credit unit that a northern Australian farm could earn by using Desmanthus as a supplement.

Materials & Methods Fourteen Droughtmaster steers were allocated to Fig 2. Preliminary results of methane emissions from tropical beef cattle in function of the Desmanthus treatment (12, 24, 36, JCU1 (N=7) and JCU4 (N=7) Desmanthus cultivars. 48%). Basal Rhodes Grass (Chloris gayana) was offered to the animals plus fresh Desmanthus at 0, 12, 24, 36 and 48 % of dry matter in each period. Every period lasted at least 14 days and methane production was Conclusion measured by open-circuit gas exchange in the last 2 The study demonstrated that these two cultivars of days of every period. Desmanthus can reduce in vivo methane emissions from cattle. An average beef farm in Northern Australia of 1,576 head [8] would generate a gross amount of $4,785/year of Australian carbon credit units (ACCU) with 48% Desmanthus inclusion (assuming a global warming potential of 25 for methane [9], a CH4 emissions per animal of 200g/d [10] and an average price of $13.87/ACCU) [11].

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Acknowledgements: Funding: The authors gratefully acknowledge James Cook University (JCU) College of Public Health, Medical and Veterinary Sciences, This research is partially funded by the Australian Government through a Cooperative Research Centres Projects (CRC-P) grant Cooperative Research Centre for Developing Northern Australia (CRC-DNA), Meat and Livestock Australia (MLA) and the [grant number CRC P-58599] and a PhD scholarship funded by the College of Public Health, Medical and Veterinary Sciences, Commonwealth Scientific and Industrial Research Organisation (CSIRO)-JCU-Agrimix Joint Research Project. James Cook University, Queensland, Australia, awarded to the first-named author.