B.GBP.0026 - Feeding leucaena to manage the rumen for maximum beef profit

Summary

Psyllid-resistant leucaena 'Redlands' addresses a pest issue but performance of the new cultivar for beef productivity and efficacy of the rumen bacteria that de-natures the compound DHP is limited. Industry needs science-based evidence of the current acreage production potential of new cultivar the efficacy of the existing inoculant with new varieties and the greenhouse gas abatement potential of Leucaena. This project addresses these issues.

Objectives

• Demonstrate comparative animal performance of the new psyllid resistant cultivar Redlands against a standard modern cultivar, Wondergraze, from stand establishment and over three growing seasons.

• Quantify the reduction in methane emissions by cattle from the above cultivars using a 'dose response' method.

• Determine the efficacy of the current and modified Leucaena inocula for cattle grazing the new psyllid resistant and future sterile cultivars (see QDAF final report).

Key findings

• Cultivar had no effect on any salient parameters measured.

• Methane emission reduction per unit of DM intake was maximised with leucaena included at 36% of the diet, demonstrating a 12% reduction in methane yield.

• Mean individual liveweight gains of 1kg/d were achieved but declined when leucaena biomass was reduced under grazing pressure.

Benefits to industry

Redlands and Wondergraze represent two cultivars which will increase animal production and reduce methane emissions when grown in areas for which they are climatically and edaphically adapted.

Both cultivars can sustain excellent animal gains of over 1kg/d, provided leucaena intake accounts for around 30 to 40% of the diet.

The opportunity to derive income from avoided methane emissions exists, and this research will assist in development of an accepted methane avoidance methodology.

MLA action

Data on methane mitigation will inform the industry at large, MLA and the government, on the role leucaena can play in reaching carbon neutrality. The results will lead to the approval of a carbon methodology that will allow producers to earn carbon credits from the property emissions avoided though the inclusion of these cultivars in their production systems.

Future research

Future research should focus on the co-measurement of animal productivity and methane emissions under practical production conditions. This can be achieved using GreenFeed gas emission monitors (c-lockinc.com) that operate in the field. These units, which are now available, allow the methane production of individual grazing animals to be measured. On commercial properties, it is important to compare both productivity and emissions in paired paddocks with and without leucaena. The proportion of leucaena in the grazing area and in the diet should also be measured through ground-based measurement or via satellite imagery, coupled with faecal samples to discriminate between C3 (leucaena) and C4 (tropical grasses) plant species.