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

Abstract

The main objective of this study was to investigate the effect of supplementing beef cattle with incremental levels of <i>Desmanthus leptophyllus</i> cv. JCU1 and <i>Desmanthus bicornutus</i> 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 <i>Desmanthus</i> species and offered a basal diet of Rhodes grass (<i>Chloris gayana</i>) hay plus fresh <i>Desmanthus</i> at 0%, 15%, 22%, and 31% of dry matter intake (DMI). The 15% and 31% <i>Desmanthus</i> periods lasted 21 days and the 22 and 0% <i>Desmanthus</i> 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 <i>Desmanthus</i> 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, <i>Desmanthus</i> 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 <i>Desmanthus</i> may be a combination of rumen fermentation and tannin effects.