Methane gas is a potent greenhouse gas produced in the rumen of cattle during the normal process of feed digestion and represents a significant loss of feed energy that increases feed costs. For example, a lactating dairy cow produces about 400 grams of methane each day. These methane losses quickly add up. In one year, the amount of methane a dairy cow produces is equivalent to the greenhouse gas emissions from a mid-sized vehicle driven 20,000 kilometres.
Agriculture and Agri-Food Canada (AAFC) scientists at the Lethbridge Research Centre in Alberta are developing methane mitigation strategies for the beef and dairy industries.
Dr. Karen Beauchemin, a livestock specialist with AAFC, is finding ways to measure and curb methane gas emissions. She believes that since approximately 40 per cent of agricultural emissions in Canada come directly from methane, with 90 per cent from cattle and sheep as a result of feed digestion, agricultural methane emissions can be reduced through livestock feeding and management systems.
"We have conducted feeding trials to determine how various diets can lower methane emissions from cows," explains Dr. Beauchemin. The team used specialized instrumented rooms at the Lethbridge Research Centre to measure methane losses from the animals and also recorded effects of the various diets on milk and meat production and feed efficiency.
So far, several feeding strategies show promise. For example, increasing the level of dietary fat by feeding a diet of crushed oilseeds (sunflower seed, canola seed or flaxseed) or dried corn distillers grain reduced the energy lost as methane by up to twenty percent. Similar reductions in methane were also seen when other fat sources, such as whole cottonseed, plant oils, and some ethanol byproducts were added to the diet. Overall methane was lowered by 5 percentage units for each percentage of crude fat added to the dietary dry matter.
Adding more grain in the ration also reduced methane emissions, but the scope for increasing the amount of grain fed to ruminants is fairly limited as this ignores the importance of ruminants in converting fibrous feeds, unsuitable for direct human consumption, to the high quality protein sources milk and meat. Diets based on corn grain, compared with barley grain, reduce methane emissions, as does feeding high quality forages such as corn silage and alfalfa. Ionophores, antimicrobials that target the ruminal bacterial population and increase production efficiency, also reduce methane emissions at least for a short time.
The team is also examining feed additives, including plant extracts (condensed tannins, saponins, essential oils) and rumen modifiers (yeast, bacterial direct fed microbials, and enzymes). In a recent study, they supplemented the cattle diet with commercial active dried yeast products including a new product selected on its ability to improve fiber digestion in the rumen. This combination was found to reduce methane by six percent and demonstrates the possibility of developing yeast products to improve cattle digestion.
Other research teams in New Zealand and in Australia are also exploring innovative ways of eliminating the microbes in the rumen that produce the methane, such as vaccines. This research is expected to lead to practical solutions that can be used to reduce methane from beef and dairy cattle in the future.
Feed conversion efficiency
Because methane production increases as the animal eats more feed, improving feed conversion efficiency, the amount of feed consumed per kilogram of milk produced or weight gained, decreases methane output. Diets that are more highly digestible lower the amount of methane emitted per product produced. It may also be possible to breed more efficient cattle that produce less methane. Researchers in Canada, Australia and New Zealand are currently evaluating methane production in beef and dairy cattle selected for high- versus low-feed conversion efficiency.
Management practices that reduce animal numbers on beef and dairy farms also help reduce methane production. For example, improving reproductive performance of cows leads to fewer replacement heifers, which helps reduce methane emissions.
Livestock producers wanting to gain a better understanding of the greenhouse gas emissions from their farms can use the Holos greenhouse gas calculator developed by Agriculture and Agri-Food Canada. Holos estimates carbon dioxide, nitrous oxide and methane emissions from rumen fermentation, manure management, cropping systems and energy use.
The program was designed to help farmers envision and test possible ways of reducing greenhouse gas emissions on their farms and has been evaluated across Canada by the Soil Conservation Council of Canada's (SCCC) Taking Charge Teams. These teams, located in every province, tested the program by plugging in real data provided by farmers.
The program allows farmers to select farm management practices that best describe their operation. It then allows the user to enter options that might reduce emissions and estimate how those options would affect whole-farm emissions.
"Livestock operations are complex ecosystems because of the various components that interact, including the soils, crops, feeds, animals and manure," explains Dr. Beauchemin. On a typical beef or dairy farm methane from the animals and their manure accounts for more than half of greenhouse gas emissions, nitrous oxide from cropping and soils accounts about a third, and carbon dioxide from on-farm energy use accounts for the rest.
"It is important to ensure that a reduction in methane resonates throughout the farm to decrease total greenhouse gas emissions. In some instances, reducing methane emissions from cows can lead to an undesirable increase in the other greenhouse gases emitted by the farm." There are already a number of options for livestock producers wanting to take advantage of methane reduction and more solutions are expected in the future (see table below). The bottom line is that controlling the loss of feed energy as methane helps improve efficiency of cattle production and is an environmentally sound goal for the livestock industry.
|Timeline for development||Mitigation practice for the dairy industry||Expected reduction in methane|
|Immediate||Feeding oils and oilseeds.||5 to 20%|
|Higher grain diets.||5 to 10%|
|Using legumes rather than grasses.||5 to 15%|
|Using corn silage or small grain silage rather than grass silage or grass hay.||5 to 10%|
|Lonophores||5 to 10%|
|Herd management to reduce animale numbers.||5 to 20%|
|Best management practices that increase milk production per cow.||5 to 20%|
|5 years||Rumen modifers (yeast, enzymes, directly fed microbials).||5 to 15%|
|Plant extracts (tannins, saponins, oils).||5 to 20%|
|Animal selection for increased feed conversion efficiency.||10 to 20%|
|10 years||Vaccines||10 to 20%|
|Strategies that alter rumen microbial populations.||30 to 60%|