Wallabies battle cattle farts

Cork me kangaroo’s bot, Scott

The Tammar Wallaby’s digestive system is getting agricultural researchers excited, after researchers from Australia’s science agency CSIRO found its gut generates far lower methane emissions than cattle.

Methane poses a greenhouse conundrum for policy makers: our dependence on livestock for meat means we keep lots of ruminants around, which generate lots of methane. Since most countries are reluctant to impose a state-sponsored vegetarianism, researchers are working hard to cut down the world's vast cloud of ruminant methane.

Enter the Tammar Wallaby: it generates 80 percent less of the gas per unit of digestible energy than livestock animals. Mark Morrison, an Ohio State University animal sciences professor who is also science leader in metagenomics at CSIRO’s Livestock Industries division, says the efficiency of the macropod’s digestive system offers another payoff – better nutrient retention.

The key lies in a bacterium in the wallaby’s gut, which Morrison’s group sequenced and isolated and believe could be used to augment the microbes normally present in livestock digestive systems.

Marsupials and ruminants share a “pre-digestive” fermentation process to break down plant food, and this fermentation produces methane. However, it’s been known for some time that while cattle and sheep turn as much as 10 percent of their food into methane, the Tammar Wallaby produces only 1 percent to 2 percent.

The CSIRO researchers have identified the key bacterium in the marsupial: a member of the Succinivibrionaceae called WG-1, which produces succinate rather than methane as a by-product of fermentation. The succinate locks up hydrogen and carbon that would otherwise by grabbed by methane-producing bacteria.

Morrison says that Succinivibrionaceae also exist in ruminants, but have not been a focus of study in the past. “Our findings with the Tammar wallaby were a bit of a surprise, but we think they provide an important clue for how rumen fermentation might be directed away from methane formation." ®

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