EDMONTON -- Canada's cattle industry is producing more beef with less greenhouse gas emissions, says a new study.

Researchers at the University of Manitoba and Agriculture Canada found a 15 per cent reduction in methane emissions on a production basis between 1981 and 2011, and a 16 per cent cut in nitrous dioxide from manure.

The results were achieved partly by feeding cattle grain instead of grass and other forage when they are being fattened before slaughter, says the study published in the journal Animal Production Science.

"A lot of our efficiencies in Canada have to due with the use of grain in feedlot diets," Tim McAllister, a research scientist with Agriculture Canada said Monday.

"They get more energy from it and with less digestive problems."

Changes in management practices have allowed cattle to be sent for slaughter at a younger age, around 18 months, rather than 24 months in the past.

The study compared the cattle herd, the amount of land required for beef production and the change in greenhouse gas emissions in the production of Canadian beef.

The results show the industry has become more efficient, with about 15 per cent fewer emissions overall.

"A significant reduction in GHG intensity over the past three decades occurred as a result of increased daily gain and slaughter weight, improved reproduction efficiency, reduced time to slaughter, increased crop yields and a shift toward high-grain diet that enabled cattle to be marketed at an earlier age," reads the study.

The beef industry accounts for 3.6 per cent of Canada's total greenhouse gas emissions, a figure that hasn't changed much over the years, McAllister said.

Agriculture Canada once estimated that one lactating dairy cow produces a similar amount of greenhouse gas emissions as a mid-sized vehicle driven 20,000 kilometres in one year.

The Canadian Cattlemen's Association hopes the study helps counter some of the criticism the beef industry has received over the years about how it affects the environment.

Tom Lynch-Staunton, an association spokesman, said many producers have changed how they operate.

"It tells us that our changes in management practices are actually having a positive impact," he said.

The industry includes 68,500 beef farms, mainly in Western Canada.

The study was commissioned and paid for by Agriculture Canada and by beef producers through a levy on cattle sales.

McAllister said the study is the first part of a multi-phase review of how Canada's beef industry is affecting the environment. Future reports are to cover the effect of the beef industry on water use, air quality and biodiversity.