A team of Australian and Japanese scientists are investigating ways to cut global greenhouse gas emissions from cattle, while increasing the amount of meat and milk they produce.

Researchers estimate that the world cattle herd yields around 15-20 per cent all methane (CH4) generated by human activity up to 100 million tonnes per year. Methane is 25 times more potent than CO2 in causing global warming.

The methane is generated by bacteria in the cow's stomach breaking down the fodder which the animal has consumed. On average, 6-7 per cent of the animal's total food intake is turned into gas and each beast puts out between 60 and 113 kilos of CH4 a year.

New research by a joint team led by Dr Graeme McCrabb of CSIRO Tropical Agriculture and Dr Mitsunori Kurihara of Japan's National Institute of Animal Industry has identified a way both to cut gas emissions and to lift production of meat and milk especially in the tropics, where at least half the world's cattle herd resides.

Over the past year the team has carried out measurements of methane produced by Brahman cattle fed on diets typical of Northern Australia and other tropical regions of the world. This work is ongoing, and is providing more accurate estimates for international greenhouse inventories.

They have observed that the amount of methane produced by the cow varies dramatically according to the quality of the diet it is fed on -- animals on poor quality feed, which is common in warm climates, generate a lot more gas and produce less meat or milk.

They also found that better quality diets led to improved production from the animals faster growth rates and a greater overall yield of milk and meat.

"It's perfectly logical the energy that is being wasted as gas emissions from animals on a poor diet is instead converted to production in a balanced, high quality diet," Dr McCrabb says.

"We found cattle on a forage diet produced four and a half times as much methane for every kilo gain in liveweight as cattle on a high-quality grain-based diet."

The research offers the prospect of substantial gains in efficiency for the Australian northern beef cattle herd while at the same time lowering the national level of greenhouse emissions in a meaningful way, he says.

"This research indicates it is possible not only to reduce methane emissions from ruminant animals such as cattle and goats in the tropics, but at the same time to increase total food protein output, and so improve the diets of millions of people."

Dr McCrabb said that most of the research into cattle methane production to date had taken place in temperate breeds of cattle, under temperate climatic conditions.

This is the first research to look specifically at the gas output of warm-climate cattle, which make up about half the world herd.

The world currently has 1.33 billion cattle and 1.1 billion sheep and goats, predominantly in the tropical and subtropical regions, and subsisting on poor diets. India has the largest cattle herd, followed by Brazil and China.

The project is one of several under way at CSIRO investigating techniques for lowering methane emissions from livestock.

Dr Kurihara's laboratory in Japan is investigating greenhouse gas production from dairy cattle and reporting on total Japanese emissions from the country's livestock industries. So similar is the work being carried out by Australian and Japanese scientists, they are pooling their expertise and resources.

More information:
Dr Graeme McCrabb, CSIRO Tropical Agriculture 07 4923 8193
Dr Mitsunori Kurihara +81 298 388655
Grant McDuling, CSIRO Tropical Agriculture 07 3377 0361