Carbon footprint of dairy production systems in Québec: barley versus corn silage

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Source: Government of Canada

Citation

J. Dairy Sci. Vol. 100 (Suppl. 2):265.

Plain language summary

In Canada, corn silage is increasingly fed to lactating dairy cows at the expense of barley silage and other forages, as its high-energy content can improve animal performance. Moreover, corn silage is known to reduce
methanogenesis in the rumen compared to barley silage. A life cycle analysis was conducted to compare whole
farm total greenhouse gas emissions (kilogram CO2-equivalent per kilogram of milk) of corn- and barley- based dairy production systems. For this purpose, a virtual farm representative of typical dairy production systems in Quebec was used to simulate the 6-year lifespan of a dairy cow, from calving to culling. Within a forage type, increasing silage energy content reduced greenhouse gas intensity. Overall, the greenhouse gas intensity of dairy production systems was lower with high digestible barley silage compared to low digestible corn silage showing the importance of producing forages with high digestibility that maximize milk production.

Abstract

In Canada, corn silage (CS) is increasingly being fed to dairy cows at the expense of barley silage (BS), as its lower fiber and higher starch content improves animal performance and reduces enteric methane (CH4) emissions. A life cycle analysis was conducted to compare the carbon (C) footprint (total greenhouse gas [GHG] as CO2 equivalent/L of fat- and protein-corrected milk) of milk production from Canadian confinement dairy systems using CS or BS. A typical farm in Québec (Canada) was simulated to represent the 6-year lifespan of a dairy cow, from calving to culling. Diets fed to cows consisted of 54% CS or BS, 6% grass hay and 40% concentrates (dry matter basis). The impact of digestibility (measured as total digestible nutrient [TDN] content) of each of these silages on GHG emissions was also investigated. Based on an experimental work, milk production was assumed to average 34.7 and 31.9 kg/day for cows fed CS and BS of medium TDN content respectively. Milk production was assumed to be positively correlated with the TDN content of silages and the number of cows was adjusted to obtain similar milk production between farms. We assumed that forages as well as barley and corn grains were cultivated on-farm whereas all other feed ingredients were purchased. Greenhouse gas emissions were quantified with the Holos model. Methane emissions included enteric fermentation and manure storage, assuming that percentage of energy intake lost as CH4 was constant regardless of silage TDN content. Carbon dioxide emissions included energy for crop production and processing and transportation of purchased feed. Nitrous oxide emissions accounted for nitrogen (N) degradation from manure, N leaching and volatilization. For medium TDN content silages, total GHG emissions were 13% lower for farms using CS compared with BS, even if the lower enteric CH4 emission with CS was partially offset by increased CO2 emissions from the additional purchased feed protein sources (+9%). For both forage sources, increasing silage TDN content reduced the C footprint of the dairy farm. Finally, when the dairy farm used highly digestible BS, the C footprint was lower than when using the least digestible CS.