Use of blood urea nitrogen concentration as an indicator of protein status in cattle

Abstract

Measuring blood urea nitrogen (UN) concentration in ruminants has become a common technique for monitoring protein status both in livestock production research and the clinical environment. The technique is used world-wide and although there is a plethora of reports on values obtained under various conditions, caution should be given to interpretation of blood UN data due to the number of variables which can affect blood UN values. This is especially true when factors other than nutrition, such as health of the animal and physiological state or stage of production are involved. The advent of rapid and inexpensive automated analytical procedures, use of UN and other metabolic indicators is expected to continue in the future. Best use of this information can only be made with an understanding and consideration of the various factors that affect these metabolic parameters. The following is intended to be a useful overview of these factors and the practice of using blood UN concentration as an indicator of protein status in cattle.