Agriculture and Agri-Food Canada (AAFC) researchers are finding new ways to optimize dairy cow diets and reduce the environmental impact of milk production. When cows digest their food, they belch and burp up methane, a potent greenhouse gas (GHG). This “enteric methane” contributes one-third to one-half of all the GHG emissions from milk production on the farm (the others being manure, feed production, transportation, and other farm and milk processing operations). Many milk processing companies worldwide have pledged to reduce GHG emissions at the farm level to meet the commitments of the Paris Agreement. But how do you reduce the amount of methane a cow produces? Could a diet hack hold the answer?
Research by AAFC found that partially or fully replacing soybean meal with canola meal in the diets of dairy cows reduced (by up to 14 percent) enteric methane production while increasing nutrient intake, milk yield (+3 kg/day), and milk protein yield (milk fat yield was unaffected). Soybean meal and canola meal are routinely used as protein supplements for lactating dairy cows—Canada produces more than a million tonnes per year of each of these products, and they are a cost-effective way to increase protein in a cow’s diet. Soybean or canola meal usually accounts for up to 24 percent of the dry matter fed to cows.
However, while tweaking a cow’s diet shows promise in terms of reducing GHG emissions, it’s not as simple as it sounds, because a change in diet could result in increased emissions from transportation of the new feed to the farm. Knowing that GHG emissions from feed production and transportation combined make up almost 30 percent of the GHG emissions of milk production, the AAFC research team set out to understand the full implications of diet change. They conducted farm-gate life cycle assessments of milk production to see how using soybean meal versus canola meal in cow diets would affect overall GHG intensity.
Assessing farms in both eastern and western Canada, the researchers found that canola meal resulted in fewer methane emissions from the cows compared with soybean meal. Using a life cycle assessment that considered all sources of GHGs, the researchers found that using canola meal produced in western Canada in diets fed to dairy cows in Eastern Canada reduced the GHG emission intensity by 6.6 percent because of the lower carbon footprint of canola meal produced in western compared with eastern Canada. The GHG mitigation benefit of using canola meal from the west held true even when the greater emissions of transporting the canola meal across the country was factored in. For western Canadian dairy farms, the carbon footprint of milk was 3 percent less when canola meal was used.
These findings that inclusion of canola meal in dairy cow diets can reduce the net GHG emissions associated with milk production will help producers reduce emissions on the farm without sacrificing the quantity or quality of their product. Although this study focused on milk production in Canada, the concepts and methodology are transferable and could improve GHG mitigation strategies in other parts of the world too.
Sherbrooke Research and Development Centre: Dr. Chaouki Benchaar, Dr. Fadi Hassanat, Dr. Daniel Ouellet, Lisa Croteau, Mathieu Béchard, Cassandra Bourdeau; Danielle Bournival, and the barn staff
Lethbridge Research and Development Centre: Dr. Lucia Holtshausen, Dr. Roland Kröbel, Dr. Karen A. Beauchemin
Collaborator: Dr. G. Gislon, Dipartimento di Scienze Agrarie e Ambientali-Produzione, Università degli Studi di Milano, Italy
Originally published in AAFC Weekly Science Story, October 20, 2021.
Benchaar, C., Hassanat, F., Beauchemin, K.A., Gislon, G. and Ouellet, D.R., 2021. Diet supplementation with canola meal improves milk production, reduces enteric methane emissions, and shifts nitrogen excretion from urine to feces in dairy cows. Journal of Dairy Science, 104(9), pp.9645-9663.