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Considering the total cattle population to assess the efficiency of mitigation strategies

Cattle production is an important issue in agriculture concerning the reduction of greenhouse gas (GHG) emissions and the efficiency of resource use. The solution advocated to reduce the contribution of cattle to these impacts is usually to promote the use of specialized breeds for milk and meat production, which has led to a rapid genetic progress in both milk and meat production of specialized cattle breeds. Recent studies (Capper et al., 2009) support the idea that increased production level of dairy cows can significantly reduce livestock GHG emissions.
These studies fail to take into account that the increase in milk production decreases meat production by the dairy herd. Thus, the evaluation of the efficiency of the cattle herd for co-production of milk and meat is difficult and requires considering the whole cattle production system to make relevant conclusions.
To solve this problem, we developed a model of the French cattle herd, based on statistical data from BDNI and slaughterhouses to test different scenarios for the evolution of the dairy cow production and their consequences on direct and indirect emissions (but not on emissions generated from farm inputs) necessary for the national inventory. The model was calibrated for the situation in France in 2010 after which other scenarios were tested to find the number of dairy and beef cows needed to rebalance the national production level and to calculate the GHG emissions.

The evolution of milk production scenarios on direct and indirect emissions

Three scenarios concerning the evolution of milk production were tested. In the first scenario, the milk production of Holstein cows was increased by 20%, without changing the other parameters (DI+) or assuming that productivity would decrease due to the increase in calving interval of high producing cows (DI-). In a first step, the number of dairy and beef cows was optimized to maintain milk and meat production.
The DI+ and DI- scenarios reached a new equilibrium in which the decline in the number of dairy cows was largely compensated for by increasing the number of beef cows. The decrease in total GHG emissions from the dairy herd was only 0.8% in the DI+ scenario, and there was a 0.5% increase in GHG emissions in the DI- scenario.
A third scenario was simulated to produce 25% more milk (e.g., to simulate the abolition of milk quota) without changing meat production using the present parameters of French livestock. In this scenario, the increase of GHG emissions of cattle was only 3.9%.
These emissions do not include emissions generated by the inputs of food needed for this additional production.

Better understand the complexity of the diversity of milk and meat production systems

This model can be widely reused to test different scenarios for milk and meat production by cattle on the inventory GHG emissions. It helps to understand the complexity of the diversity of milk and meat production systems in the global efficiency of cattle production, and shows that the productivity per animal is not always the most relevant criterion to increase productivity and to reduce environmental impacts. Preliminary simulations show that the veal calf production related to the increase in the Holstein herd has a significant GHG impact and that later finishing by double-purpose breeds or by the use of sexed semen allows for an effective reduction in GHG emissions.

Bibliography

• Puillet L., Agabriel J., Peyraud J.-L., Faverdin P. 2014. Modelling cattle population as lifetime trajectories driven by management options. A way to better integrate beef and milk production in emissions assessment. Livestock Science, 165: 167-180. (DOI)
• Modèle Canapom sous Gams
• Capper, J. L., R. A. Cady, and D. E. Bauman. 2009. The environmental impact of dairy production: 1944 compared with 2007. Journal of Animal Science 87:  2160-2167. (DOI)

Contact

Philippe Faverdin, team dairy systems