Greenhouse gas emissions and nitrogen flows of multispecies pastured livestock farms in Québec, Canada

CONTEXT Conventional livestock farming is often criticized for its heavy resource use and contribution to global warming. Greenhouse gas (GHG) emissions, nutrient cycle disruption, and water pollution caused by livestock, feed production, and the decomposition of manure are the main targets of this criticism. Alternative ways of raising animals have gained popularity in certain rich countries, stimulated by societal demands for better animal welfare. These demands are partially met by farmers relying on pasture and short supply chain marketing. Operating at a smaller scale, these farmers sometimes decide to raise multiple animal species, but GHG and nutrient balance calculations are scarce for these kinds of farms. OBJECTIVE The objective of this study was to quantify the GHG emissions and nitrogen (N) flows of different scenarios of multispecies pastured livestock production. METHODS We used specialized software to model and estimate the GHG emissions and N flows of three different production scenarios based on patterns identified on alternative livestock farms in Québec, Canada. RESULTS AND CONCLUSIONS Results show that input-intensive farms with high stocking rates and higher proportions of monogastric animals (the Intensive scenario) report the highest N surpluses. Farms growing crops alongside their animal herds (the Thrifty scenario) are able to cycle most of the N flowing through their farm by fertilizing their crops with manure. In cases of N deficiency, growing N-fixing crops increases N surpluses without causing surpluses in other nutrients such as phosphorus. Farms closer to a pastured suckler beef model (the Extensive scenario) have lower stocking rates, causing lower N surpluses but very high GHG emissions due to enteric methane production. On a species-by-species basis, all three modeled scenarios emitted more GHG per unit of edible protein produced than their specialized counterparts. The only exception is the farm replacing part of its pig feed with food waste, a practice which significantly reduces GHG emissions but does not reduce nutrient inputs. SIGNIFICANCE Raising heritage breeds and relying on pasture for monogastric animals, while maintaining important genetic diversity material, local environment adaptation traits, and allowing for a better expression of natural animal behaviour, increases GHG emissions per unit of protein produced by requiring more feed to raise animals. Our results suggest incremental improvements in alternative livestock systems are insufficient to solve the environmental issues posed by the livestock sector if similar rates of consumption are maintained.