Interpretive Summary: The effects of improved performance in the U.S. dairy cattle industry on environmental impacts between 2007 and 2017
By: Anne Wallace
Environmental impacts of agricultural and livestock production systems are a serious topic of global concern. Methane waste and water/land use associated with animal production systems, in particular, have known impacts on the environment and greenhouse gas (GHG) emissions. Social and political policy discussion has taken a specific interest in the production systems of animal source foods, which by current estimates accounts for 14.5% (livestock) and 2.9% (dairy), respectively, of GHG emissions globally.
More efficient livestock production systems have a reduced environmental impact. Consistent improvements in the productivity of livestock and dairy systems have occurred over the last several decades, for instance, by researching and implementing scientific and technological advancements in animal nutrition, genetics/breeding, and production systems. However, studies documenting how the environmental impacts of these systems have changed are out of date and may not accurately represent the current systems, which are continually being improved. According to the authors of this January 2020 Journal of Animal Science article, the last most recent study on whole-system environmental impact analyses of U.S. dairy production was by Capper et al., in 2009, almost a full decade ago.
The authors’ objective in this study was to use a deterministic model (using cattle nutrition, metabolism, and herd population demographics collected from data from U.S. dairy farms and national databases) to update estimates of the environmental impacts of U.S. dairy production systems between 2007 and 2017. The deterministic model system estimated resource inputs, GHG emissions, and nutrient excretion of U.S. dairy cows, from manufacture to milk at the farm gate, between the years of 2007 and 2017, and did not include impacts of any transport or processing done outside of the farm gate.
The 2017 environmental impact was significantly reduced compared to the year 2007 values. The GHG emission per 1.0x106 MMT (one million metric ton) of energy corrected milk (ECM) was calculated, and the 2017 amount was only 80.8% of 2007 GHG emissions, compared to a similar production of milk in the year 2007. The 2017 production systems also used 74.8% of the cattle, 82.7% of the feed, 79.2% of the land, and 69.5% of the water resources, compared to 2007. Manure, nitrogen, and phosphorus waste were 79.4%, 82.5%, and 85.7%, respectively, of the 2007 values. Methane gas and nitrous oxide were also reduced by approximately 20% (to 80.9% and 81.5% per 1.0 MMT ECM of the 2007 values, respectively). The GHG emissions of U.S. dairy cows increased by only 1.0% despite a substantial ECM increase of 24.9% between 2007 and 2017, indicating better efficiency of 2017 productive systems.
Overall, this study suggests that improvements in the productivity of livestock systems can have positive impacts on GHG emissions and environmental impacts. There is a need for both scientific and technological advancements and up-to-date whole-system environmental impact analyses to keep data on GHG emissions and environmental impacts current. More studies to determine the current environmental impacts of other livestock production systems are well justified.
Infographic - https://doi.org/10.1093/jas/skaa017