Main comment is that additional sentence(s) in methods is needed so reader understands how the U+DCD treatment differed from U+DCDf, and how they were achieved. A few minor typos are noted below
  In Main Results - consider revising middle sentence to -
The DCD excreted in the cow urine was effective at reducing nitrous oxide emissions from urine patches by between 34 and 64%. Larger reductions were observed from urine patches with DCD at a rates of 10 and 30 kg ha-1, respectively. 
    In section 4, revise 2nd and 3rd to last sentences to - 
The This also reduced the milk nitrogen foot print from 12.9 to 10.4 kg N per ton milk, compared to the control. There was a cost of using inhibitors was low and reduced farm net profit from 1,574 to 1,500 € ha-1.
