Cattle emission confusion

Sunday, November 7, 2010

by PATRICIA GROTENHUIS

Dairy farmers considering using estimates to reduce methane production in their herd may want to hold off for a bit.

Results of a study conducted jointly by researchers from the University of Guelph, the United States and the Netherlands indicate current prediction methods are inadequate.

“We point to the need to move towards better estimation methods so that the models can be used to make better estimations to farmers,” says Jennifer Ellis, one of the University of Guelph researchers who worked on the study.

The researchers have been evaluating methane output prediction methods for dairy cattle and comparing results with observed values since 2008.

They reviewed nine estimation models, all of which took into consideration management factors such as feeding systems, manure, impact of animals and crops.

In each case the estimated values differed from the actual outputs on the farm. Some methods were more accurate than others, but all had room for improvement, says Ellis.

The study “will have impact for governments and government agencies attempting to estimate greenhouse gas emissions. We encourage the use of more detailed/complex prediction equations being used to stimulate methane emissions, or the use of mechanistic models,” says Ellis.

Brian Terpstra, a dairy farmer from Donegal in Perth County, says if more accurate estimation methods can be found, “some farmers will watch closely and make adjustments.” Especially if “carbon credits amount to being something.”

But any changes farmers make would depend on whether cow health and production can be maintained, he says.

Methane gas is 25 times more potent as a greenhouse gas than carbon dioxide, according to a University of Guelph release. That means reducing one unit of methane would equate to 25 carbon credits.

Shelley Crabtree, assistant director of sustainable development with the Dairy Farmers of Canada, says operating efficiency improvements in Canadian dairy farms reduced the farms’ carbon emissions by 25 per cent between 1981 and 2006.

“Dairy Farmers of Canada is building on this base and investing in further research to find ways to mitigate greenhouse gas emissions from dairy farms, including looking at feed,” says Crabtree.
 
One reason offered for the discrepancies was variations caused by dry matter intake and type of diet. The team’s research showed that fat, starch and sugar content affect methane emissions. Overall amount of intake also appears to affect total emissions. BF