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The types of food consumed by dairy cows can modify the characteristics of the milk produced, but also of methane emissions. The goal is to find out if it is possible to both improve the quality of the milk while at the same time reducing methane emissions. A new study by the research institute INRAE (the French Institute of Agricultural and Environmental Research) is aiming to find out.

In Europe, products from cattle farming are criticized particularly for their elevated carbon footprint via their strong contribution to greenhouse gas emissions and, more specifically, their methane emissions coming from the fermentation of food in the gut (rumen).

We know that the food given to ruminants like cattle is one way that their milk performance can be modified, in particular the composition of fatty acids in the milk, but also as a way to vary the methane emissions. These can be decreased through carbohydrate or lipid supplementation in their food supply as well as by the nature of the supplements used.

The goal of this work was to determine if certain food strategies to reduce methane emissions applied to dairy cows can at the same time preserve dairy performance, particularly the lipid quality of the milk.

During initial experimentation, a diet based on grass silage enriched with starch was compared to an equivalent diet, but enriched in fibers. The diet enriched with starch reduced methane emissions, but caused a reduction in the lipid quality of the milk, which ended up more rich in saturated fatty acids. In a follow-up experiment, diets based on corn silage (and thus rich in starch) supplemented with different several different types of fatty acids were compared to a non-supplemented control diet. The methane emissions were comparable across all the diets, however the diet supplemented in one particular type of fatty acid (C18:1cis9) improved the nutritional quality of the milk for human consumption by increasing its content of linolenic acid, which as an omega 3 fatty acid.

In order to verify the long-term persistent effects of these different mitigation food strategies, the effects of these food will be monitored during the first six months of lactation of the dairy cows. This research to find a compromise between mitigating methane emissions and improving the quality of milk fat during lactation is part of a change in the multi-criteria evaluation process for ruminant food strategies.