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The effects of rumen degradable protein and urine production on ammonia (NH₃) emission were studied in two experiments. In the first experiment, the urinary concentration of urea and the NH₃ emission from cows that were fed two diets alternately were measured. Diet L contained 0.1 kg rumen protein surplus daily and diet H contained 1.0 kg rumen protein surplus daily. Diet L resulted in a 39% lower emission rate compared with diet H. The urinary concentration of urea was 42% lower when feeding diet L compared with diet H. In the second experiment, three different diets were rotationally fed during seven 3-week periods. The effects of urine volume and urinary concentration of urea on NH₃ emission were studied. A higher urine volume increased not only the number of urinations but also the volume excreted per urination. Both the urinary concentration of urea and the urine volume can be influenced by …