Metabolism studies often require collection of urine for accurate determination of excreted products. Total collection of urine over a period of 24 h or more can be stressful to the animal and is often impractical, especially in grazing situations and when large numbers of animals are involved. Urine spot-sampling, while not as accurate as total collection of urine, can be useful for assessing the metabolic state of an animal if total daily urine output can be calculated. Creatinine is a waste product of muscle turnover and the creatinine concentration of urine spot-samples has been used to estimate daily urine excretion.