Supplementing Northern Australian Beef Cattle with Desmanthus Tropical Legume Reduces In-Vivo Methane Emissions.

Bénédicte Suybeng,Aduli E.O Malau-Aduli,Bunmi S Malau-Aduli,Christopher P Gardiner,Edward Charmley

doi:10.3390/ani10112097

Abstract

Simple SummaryThe problem addressed in this study is that of mitigating methane emissions by tropical beef cattle with the aim of reducing the impact of climate change and greenhouse gas emissions in Northern Australia. The primary objective was supplementing tropical beef cattle on poor quality hay with incremental levels of Desmanthus leptophyllus cv. JCU1 and Desmanthus bicornutus cv. JCU4 to evaluate their in-vivo antimethanogenic effect. Results showed that, irrespective of cultivar, incremental supplementation with up to 31% of Desmanthus led to a 10% linear decrease in methane emissions without reducing dry matter intake. This finding makes a significant novel contribution to a better understanding of the impact of supplementing beef cattle with Desmanthus on in vivo methane reduction and the role of condensed tannins in rumen fermentation. The practical implication of this finding is that Desmanthus, an adapted tropical legume, has the potential to mitigate in vivo methane emissions by beef cattle in the drier parts of Northern Australia and contribute to the larger global effort of reducing the impact of climate change and greenhouse gas emission.The main objective of this study was to investigate the effect of supplementing beef cattle with incremental levels of Desmanthus leptophyllus cv. JCU1 and Desmanthus bicornutus cv. JCU4 on in vivo methane (CH4) emissions and the role of tannins in rumen fermentation. Fourteen yearling Droughtmaster steers were allocated to each of the two Desmanthus species and offered a basal diet of Rhodes grass (Chloris gayana) hay plus fresh Desmanthus at 0%, 15%, 22%, and 31% of dry matter intake (DMI). The 15% and 31% Desmanthus periods lasted 21 days and the 22 and 0% Desmanthus periods, 14 days. Methane production was measured by open-circuit gas exchange in the last two days of each period. The results showed a linear increase in DMI and reduction in CH4 yield with the increasing level of Desmanthus and subsequently condensed tannins in the diet. The added tannin binder polyethylene glycol-4000 did not affect CH4 yield but increased rumen NH3-N and iso-acid concentrations. Therefore, on a low-quality diet, Desmanthus has the potential to increase intake and reduce CH4 emissions. Even though its tannins can bind rumen proteins, the beef cattle anti-methanogenic response to supplementation with Desmanthus may be a combination of rumen fermentation and tannin effects.

Highlights

Agriculture accounted for 14% of Australia’s greenhouse gas (GHG) emissions with enteric methane (CH4 ) fermentation contributing up to 10% of its GHG in 2018 [1]
Mitigating the CH4 produced by the cattle industry especially in Northern Australia, would offer an opportunity to reduce the impact of GHG emissions and climate change
The quality variation between JCU1 and JCU4 might be due to species differences where the crude protein (CP) in the current trial averaged 11.0% and 14.6% for JCU1 and JCU4, respectively

Summary

Introduction

Agriculture accounted for 14% of Australia’s greenhouse gas (GHG) emissions with enteric methane (CH4 ) fermentation contributing up to 10% of its GHG in 2018 [1]. The state of Queensland has 12 million cattle which accounted for 47.2% of Australian beef and veal production in 2018–2019 [2]. GHG is the principal source of global climate change [3]. Mitigating the CH4 produced by the cattle industry especially in Northern Australia, would offer an opportunity to reduce the impact of GHG emissions and climate change. Half of Australia’s beef cattle population is found in Northern Australia, which is characterized by a tropical and arid climate with rainfall occurring mainly during the wet season of November to April.

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