When digesting plant-based foods animals, known as ruminants – cows, sheep and kangaroos, for instance – produce methane gas which contributes to global warming, say many experts. Some of these animals, like kangaroos, have been thought to release less methane than others. But researchers from the University of Zurich decided to take a closer look, and found that pound for pound, kangaroos are fairly gassy.

"If you consider the absolute volume of methane per body size, kangaroos produce about as much as horses or ostriches -- i.e. significantly less than cows," Marcus Clauss, one of the study's researchers from the University of Zurich, explained in a release. "If the gas production is correlated with the amount of food ingested, however, the amount of methane is higher and therefore closer to the ruminants again."

Essentially, cows, sheep and kangaroos all produce methane because they have unique digestive systems. Instead of having one stomach compartment, like humans, these animals have four. The rumen is the largest and main digestive organ and it is teaming with icroorganisms that break down grasses and other coarse vegetation. The chewed grasses are then stored in the rumen and accumulate into balls of "chud." When the animal is full, the balls of chud then pass through the other stomach organs in order to complete digestion.

Researchers fed alfalfa to individual kangaroos housed at the New South Wales' Fowlers Gap Research Station. For the first round of feeding, they were placed on a restricted diet; the second time around they were able to eat as much as they could. Researchers then measured metabolic rates and collected their feces, which were later used to determine how much food the kangaroos had digested in relation to the amount of methane they produced, as the release confirmed.

So what did they find? They concluded that the amount of methane emitted per food intake can vary greatly over the course of a couple days. This simply means that if the animals eat less, the food remains in their foregut for longer and the microorganisms have more time to digest. This results in a higher rate of methane production per food intake.

All of this suggests that the different amounts of methane emitted by the three species of ruminents results from conditions under which the intestinal bacteria break down food products. Generally, kangaroos digest food more rapidly than cows which . This would explains why they produce less methane under standard conditions.

"If we want to reduce methane production in cows, the question is whether they can be bred so that parts of the food don't remain in the rumen for as long," researchers added in the release.

Their findings were recently published in the Journal of Experimental Biology

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