The results of the current study demonstrate that although total CH4 emissions were unaffected by increasing concentrate feed levels, CH4 emissions per kilogram of milk produced declined with concentrate feeding.
Thus, provided it is accompanied by an increase in milk production, offering increasing concentrate levels to grazing cows provides a strategy to reduce emissions per kilogram of milk produced.
However, from a climate change perspective, the impact of concentrate feeding on total GHG (CO2, CH4, and N2O) emissions associated with the entire milk production system must be considered.
This includes GHG emissions arising from growing, processing, and transporting the individual
concentrate ingredients; the effect of higher milk yields on herd fertility and health, and their effects on herd survival; and possible savings in GHG emissions that may arise due to lower forage intakes (and associated low inputs for grass production) associated with increased
concentrate feeding.
These factors demonstrate the need to examine the effect of any change in a single component of a system, not just in terms of emissions of a single GHG at the local farm level, but via a full
life-cycle-analysis approach.