Present in blood, urine, and milk, the chemical compound urea is the primary form of nitrogen excretion in mammals. Testing for urea levels in dairy cows helps scientists and farmers understand how effectively nitrogen from feed is used in cows' bodies, with important economic implications for farmers in terms of feed costs, physiological effects for cows such as reproductive performance, and environmental impacts from excretion of nitrogen in dairy cow waste. Thus, accuracy in testing dairy cow urea levels is essential.